Wall·E, Disney Pixar's depiction of the prototypical planetary rover. (Credit: Disney/Pixar)

Anyone who hasn’t been living under a rock for the past five years of continuous success from NASA’s two Martian surface probes, Spirit and Opportunity, can tell you what a planetary rover looks like: there’s a compartment with electronics, a few solar panels, and maybe some instruments, all carried forward by a set of wheels underneath. This design has served the two Mars Exploration Rovers exceptionally well, but after more than 1750 sols (Martian days) of traverses through the sandy dunes of the Red Planet, the familiar ‘miniaturized car’ concept is beginning to show its weaknesses. On Spirit, for instance, the right wheel ceased functioning on sol 779 after having driven 7 kilometers on the Martian surface and ever since then, its operators back on Earth have had to drive the rover around on the planet in reverse, dragging the dead wheel along.

Perhaps in response to issues such as these, a few weeks ago, a novel concept for a planetary exploration vehicle that quite literally is a thought outside of the proverbial box that the two Mars rovers resemble, surfaced on the web log of open source Google Lunar X PRIZE contestant Team FREDNET: a ball. Instead of a meticulous assembly of little wheels, gears and other delicate and fault-prone moving parts, why not enclose all the electronics safely inside a sealed spherical container and roll it around on the Moon? The concept was originally proposed in the team’s online forums almost a year ago, but had been largely abandoned in favor of more traditional wheeled concepts then making progress. But in late January, a new member came across the idea when going through the archives. His interest was piqued and he decided to have a fresh look at it.

“It is just a rigid ball, designed to move over the surface of the Moon,” explains the new designer, Joshua Tristancho, an aerospace engineer teaching digital electronics engineering at the Universitat Politècnica de Catalunya (Polytechnical University of Catalonia) in Spain. Where Team FREDNET’s other rover concepts are based on conventional wheel drives, Tristancho’s spherical rover moves by continually displacing its center of mass with a motorized weight moving on the interior of the ball, causing the ball to roll. “The ball is half empty, with the rover’s core systems in the other half,” he says. “When the ball is rolling, inertia is controlled by the main drive wheel, allowing the rover to achieve great speeds. The exterior surface of the ball is rough in order to minimize slipping.” He explains that if the rover spins too fast, it will slip like the wheels of a car on a wet surface – only not because of water, but due to the granularity of the fine dust on the lunar surface.

Tristancho was drawn by the simplicity of the ball concept. “The ball is a well-confined thermal system with optimal geometry with respect to incoming solar radiation,” he claims. He explains that a sphere like his rover is subject to the same amount of solar radiation, or insolation, at any given time regardless of its orientation, whereas in more rectangular rovers such as the Mars Exploration Rovers, the insolation depends on the angle of incidence of the sunlight. The uniform insolation of the spherical rover makes it easier to design the vehicle’s internals to cope with the Moon’s highly variable surface temperatures. Furthermore, the ball has no risk of rolling over and getting stuck on one side as the rectangular rovers do.

Once Tristancho rediscovered the concept, it didn’t take him more than a few days to get the ball rolling for his new design, which he dubbed “Picorover”, in reference to its small size. “I was looking for ideas for a rover, and as I was watching my cat play, I began to get an impression of how balance in two dimensions works,” he says. Tristancho’s cat, which reportedly is fat like a ball, throws its weight around in order to keep its balance when playing. “I bought a toy ball and built in the hardware from my old radio-controlled model airplane, and – there it was! The ball concept worked,” he exclaims. “I designed, built, and recorded the first test movie of the Picorover in just three days, mainly because the concept is so simple.”

Since then, Tristancho has been hard at work to refine the concept and scale it to meet the harsh conditions of the lunar surface. He originally envisioned an opaque ball, enclosed in a heat reflective shield, that would be able to stop and open to take pictures of the lunar surface, but concerns over dust ingestion issues as the vehicle opened, as well as competition rules requiring the rover to shoot video while in motion, led him to a yet simpler, fully sealed design in which pictures could be taken through a window in the ball. Due to its sealed design, the Picorover may in principle reach unlimited speeds, unlike wheeled rovers, which must keep their speeds as low as a few meters per minute to avoid accumulation of dust that could otherwise quickly damage or wear down the machinery by abrasion.

To take advantage of this capability, Tristancho intends to integrate a small radar – a so-called nano-SAR – in the rover. Due to the communications delay to mission controllers back on Earth, preventing the team from intervening in moments of high risk, the Picorover will need a clear overview of its vicinity in order to plan operations at the high speeds without driving over ridges or into craters. The software on-board the rover will be designed to exhibit high degrees of autonomy – essentially, mission controllers will supply only a target destination, and the rover will then self-adjust its course as new terrain information becomes available to it during its tumble across the lunar soil. “I hope the nano-radar will give us a range of about 30 meters,” Tristancho says. “We can send directions to the rover, but navigation must be completely autonomous.”

One of the aspects that will be of particular importance in the evaluation of the Picorover is its performance on slopes. Due to its reliance on effectively ‘falling over’ to move, no forces other than the ball’s weight act directly on the ground, and therefore no reactionary force is generated to push the ball forward, as there is in wheeled rovers. This may prove to limit the Picorover’s traction significantly. Tristancho has conducted analyses indicating that apart from the exterior surface’s adherence to the ground, the rover’s performance on slopes depends not only on its weight, but also on how the mass is distributed in the vehicle. In the ideal case in which the center of mass is located on the periphery of the vehicle, the rover would theoretically be able to traverse slopes of up to 30 degrees. “When you go over a slope of more than 30 degrees, your main problem is traction; wheels will slip,” he asserts.

However, Tristancho hopes that the rover’s high maximum speeds can make up for this drawback: “The faster it goes, the steeper slopes could be overcome,” he says. “The most demanding operation is initiating the motion. Once running, the main drive wheel can add some inertia every second, in order to reach a high cruise speed. For this reason, it is important to have a good long-term navigation algorithm, so the inertia can be put to full use,” he explains. “Our two wheeled rovers have a better approach to climbing than the Picorover. They can take their time in order to decide the best strategy of movement. But, on the other hand, the Picorover might make quick decisions which are not as conservative as those of our two other rovers. The ball concept is good for plain regolith, but not for rocky and irregular terrain.”

Regolith is a loose, heterogeneous rock material, blanketing the lunar surface to a depth of several meters, that was formed over the last several billion years’ steady meteoroid bombardment of the lunar surface. Especially the super-fine, highly fragmented top fraction of the regolith, the so-called lunar dust, poses a great challenge to any mission visiting the lunar surface. Apollo astronauts, for instance, reported that once the dust got onto their spacesuits, it clung so tightly to them that it was impossible to wipe off again. One might wonder if a ball rolling carelessly around in this material would not very quickly get coated in a thick layer of dust, much like a cartoon snowball rolling down-hill growing bigger and bigger as it picks up more snow? But Tristancho says he will address this problem by covering the exterior surface of the Picorover in a coating of very thin steel wires that will act similarly to the tread pattern of a car tire. When the rover is rolling at high speeds, the coating will allow any lunar dust that it picks up to be more easily expelled as the rover spins around. Furthermore, the coating will increase the rover’s surface grip as well.

Tristancho has now assembled a small team of student volunteers from his home town of Barcelona, who will help him develop and construct the next prototype as fast as possible. “We are a little late,” he explains. “WRV1 and Jaluro, our team’s two other rover concepts, are in a very advanced state. We have just begun so we must approach this project with fast prototyping techniques to get up to speed,” he adds. “We will develop and test each component separately. Finally, we will assemble the components, do an integration test and then Picorover will be ready for launch; all this has to be done in six months.”

Staying true to its name, Tristancho aims to keep the size of the Picorover equivalent to the size of a so-called CubeSat pico-satellite. CubeSat is a standard for small research payloads weighing no more than 1 kg that is particularly popular in the academic community. Some launch vehicles and larger satellites have payload compartments specifically for CubeSats built-in, allowing the small satellites to ‘piggyback’ into orbit on the launch of a larger payload at relatively low cost. “Our students could compete for one of these opportunities, to prove the Picorover’s reliability in Low Earth Orbit (LEO), in order to qualify the rover’s internal systems, communication links, materials, and so on,” Tristancho says. “Once qualified, these components can also be used in our other rovers,” he adds. Because the surface environment on the Moon is nearly identical to the space environment in LEO in terms of pressure, temperatures and radiation levels, having the team’s systems qualified like this would be a major milestone for the project.

The Picorover will compete against other concepts submitted in the team’s rover design competition, possibly as early as later this year. The best features of all the proposed designs will then be combined into one rover, which will be built and tested, and then hopefully finally sent towards the Moon aboard the team’s lunar transit vehicle. No firm dates are set, but the team aims for a launch before the Google Lunar X PRIZE expires in 2014.

Thanks to ms. Sonia P. Mansilla for her corrections to this article.

The team – which uniquely conducts all its work under the same full-disclosure, Open Source terms that made software projects such as Linux and Firefox what they are today – is inviting members of the public to submit their best ideas for a rover that can be deployed onto the lunar surface and assist the team’s mission in meeting its objectives of driving hundreds of meters in the vast, otherworldly and unexplored fields of lunar soil – the so-called regolith – and sending live video of the trek back down to Earth, for everyone to enjoy, at the same time. The best ideas will be thoroughly tested and evaluated by Team FREDNET’s interdisciplinary and international team of volunteers, and eventually, one final design is to emerge from the submitted proposals, to hopefully one day be sent on a journey towards the Earth’s distant natural satellite by the team’s lunar transfer vehicle, also currently under development.

The intricate Soviet rover Lunokhod 2, which rolled through the lunar soil in 1973, is to date the last human artifact to have operated actively on the Moon. In 1993, twenty years after communications from the rover ceased due to a failure, ownership rights for Lunokhod 2 were purchased by computer gaming entrepreneur Richard Garriott, making him the world's only private owner of an object on a celestial body. Garriott is also noted for visiting the orbiting International Space Station in October 2008 - at a time when several teams are competing in the Google Lunar X PRIZE competition to land the next privately owned spacecraft on a celestial body, but this time without the governmental backing that ensured Lunokhod's success. One of these teams, Team FREDNET, is already so far ahead in development that they were able to intercept image and voice communications transmitted from the ISS over the course of Garriott's visit. (Source: Wikipedia)

The coordination of Team FREDNET’s parallel rover development effort is informally led by Jörg Schnyder, an electrical and mechanical engineer from Switzerland, currently working at RWMS, a defense contractor based in Ochsenboden, Switzerland.

Schnyder is more than aware that the challenge of driving a robotic vehicle across the surface of the Moon is not an ordinary one, nor one that is easy. The lunar surface is covered in a thin veneer of dust prone to clinging to machinery, and wearing down motors and wheel systems by abrasion. And after 14 terrestrial days of being exposed to intense, burning hot sunlight under the weatherless sky during lunar day, anything left on the lunar surface suddenly falls prey to another 14 days of freezing cold darkness when lunar night sets in – big temperature swings putting all the materials and electronics making up a robotic system to the test. “The dust and the extreme temperatures are the biggest challenge for the rover,” Schnyder says, “but shock and vibration during start, flight and landing are also important,” he continues, referring to the extreme forces exerted upon a spacecraft when being lifted off the Earth by a heavy launch vehicle such as the Ariane 5 that the team intend to use, and when it thrusts through the subsequent stages to first gain enough momentum to leave the Earth’s strong gravitational grip, and since to all but negate it again, in order to finally land slowly and elegantly on the lunar surface.

Weighing in at nearly 800 tonnes – all of which will either burn up or be too damaged to recycle after just a single launch – a non-reusable Ariane 5 rocket is not cheap: one launch is estimated to cost some 180 million US dollars in total. For a small non-profit such as Team FREDNET, the only conceivable way of matching such a price tag is to leave as much room aboard the rocket as possible to other customers, and relying on them to pay most of the bill. For the team’s rover, this implies that the vehicle must be kept as light as possible – at the expense of conveniences such as big power supplies and heavy, throughly hardened structural materials.

Thus, Team FREDNET’s rover designers are faced with two wildly diametric requirements of, on the one hand, having to increase the mass of the vehicle to survive the harsh lunar environment, while on the other having to decrease it, to keep launch costs low enough to allow the team to land the rover on the surface of the Moon in first place. “The way to solve this challenge,” Schnyder muses, in homage to Albert Einstein, “is to design a rover as simple as possible, but not simpler.”

Another challenge for the team is the software programs controlling the small rover as it rolls over the lunar surface. Due to the latency involved in communicating with the equivalent of a remote-controlled car, not in the backyard of your home, but on the surface of a celestial body hundreds of thousands of kilometers away, there is a need for the rover to be able to operate semi-autonomously, without relying on exact instructions from mission controllers back on Earth. Even if the few seconds it takes a command to reach the Moon is relatively little compared to the several minutes at play when space agencies communicate with spacecraft at Mars and beyond, the delay is still too long for mission controllers to be able to intervene in critical moments like if, for instance, the rover is about to drive off the rim of an unforeseen crater. In situations like this, or when radio communications with Earth, for whatever reason, are obscured altogether, the rover has to be able to take matters into its own hands and take the actions most appropriate to meet mission goals. The software – which likely will need to be based on some form of Artificial Intelligence (AI) technology – will be developed by the team’s software group in cooperation with the rover designers.

The small, two-wheeled Jaluro rover is one example of a design currently under development by one of the groups within Team FREDNET. By keeping the number of components at a minimum, this design seeks to keep mass as low as conceivably possible. (Source: Tobias Krieger)

Jörg Schnyder invites everyone – members of the team and of the public alike – who think they may have an idea for a rover design that can help the mission meet its tough requirements, to join one of the existing rover development teams or create a project of their own and begin working. “If all of the teams are developing components that can be shared by the other ‘parallel developers’, and of course integrate components designed by the other teams, we can finally create a rover picking up the best of them”, Schnyder says, echoing the rationale behind the ‘bazaar’ development methodology driving popular Open Source projects such as Linux, the fastest evolving software project in the world. Concluding his invitation with a word of advice to any would-be Open Source lunar rover designers out there, Schnyder notes: “Existing components created for ‘earth-use’ mostly will fail in space, so as I said before: keep it simple, but think of the rough environment and stress the components have to withstand as well.”

Development of Team FREDNET’s rovers are conducted in the team’s online forum and wiki, where all team members have a chance to review the proposed designs, and share whatever insights they may have from their respective fields of knowledge. Once a good mass of proposals have been put forward, the team will test the most qualified candidate designs to evaluate which one to finally send to the Moon.

Schnyder hopes that the parallel development process will reach a point where each design will inspire and drive forward the others, but he also knows that, traditionally, Open Source hardware projects tend to be more challenging than their software counterparts. “The fact that hardware always has additional costs, and needs some special skills for production, could be the hardest thing to overcome,” Schnyder says. “I would like to integrate a construction kit such as Stokys in the development process, so the groups can create mock-ups without big investments, and so they can build their designs with own and shared components,” he continues.

Asked what the deadline for rover proposals will be, Schnyder says that there most likely won’t be one, opting instead to let the team evaluate the incoming rover designs continually, and adjust the mission parameters accordingly. “Just do something,” he urges prospective Team FREDNET rover designers. “Doing is always better than talking!”

The TVRX daughterboard is a complete VHF and UHF receiver system based on a TV tuner module. It can receive a 6 MHz wide block of spectrum from anywhere in the 50-860 MHz range. All tuning can be controlled from software. (Source: Alexandru Csete)

‘Open source’ Google Lunar X Prize contestant Team FREDNET is putting the final touches on the team’s ‘open source communications lab’, which will be used for upcoming prototyping and testing of the radio technologies that will be utilized on the team’s robotic mission to the Moon.

In accordance with the project’s open nature, all schematics and specifications for the hardware used in the lab are freely available on the Internet, allowing anyone with basic electrical engineering knowledge to set up their own lab at home. The software used in the lab, GNU Radio, is available under the open source GPL license and is being developed under the auspices of the Free Software Foundation, which first defined some of the crucial principles that underlie today’s open source community two decades ago.

GNU Radio implements a relatively new technology called software-defined radio. Unlike in traditional ‘hardware radios’, where a number of important signal processing functions are hardwired into the receiver and transmitter with components such as mixers, filters, amplifiers and modulators, in software-defined radio these functions are instead implemented in computer software programs.

“The idea of software-defined radio has been around for many years now, but it is only recently with the availability of cheap high performance AD/DA converters, and fast CPUs that it has become easily accessible,” says Alexandru Csete, team lead of Team FREDNET’s Communications Group, who in the daytime works as a software engineer at Rovsing, an aerospace and defense company based in Denmark. Csete explains that software-defined radios have priceless benefits for space use: first of all, the reduction of hardware means reduced weight, lower manufacturing costs and lower power consumption. Furthermore, the team can do extensive reconfiguration and modification of their communication systems in flight simply by uploading new software to the spacecraft – a great advantage if mission requirements change while the radio is on its way to the Moon and replacing the component physically is just out of the question. Finally, the software-defined radios delivers much better performance for the processing of weak signals – exactly the kind of signals a spacecraft will need to be able to receive when traveling in outer space, hundreds of thousands of kilometers away from transmitters on Earth. “In my opinion, software-defined radio is the only sensible option today,” Csete says when asked if the technology will be employed on the actual mission to the Moon.

And Csete’s team intend to use the open source GNU Radio software not just in the lab, but for the radio platform on board the spacecraft as well. “The GNU Radio library and framework is a really impressive piece of work,” Csete says. “There is a wide range of applications it has already been used for, ranging from simple FM radios to radio astronomy and space applications.” GNU Radio gives the programmer a set of small program chunks called ‘blocks’ which can be combined in a multitude of ways to form a signal processing system fitting the programmer’s exact needs. “While we most certainly won’t use the whole library on-board, we can take the pieces that we need and create our own libraries optimized for the target processor,” Csete says. He also notes that his team is free to extend the framework in areas lacking functionality needed for their mission, thanks to the GPL license which the software is distributed under.

The hardware that Team FREDNET has recently acquired for its communications lab is solely intended for prototyping and testing, however. Although the current setup provides the functionality that will be needed for the actual mission, “the performance is not quite adequate for long range communications and weak signal processing,” Csete says. Individual components of the setup may be reused in the team’s ground stations if they are supplemented with custom-made hardware of the required performance, however, and because the schematics for the hardware are publicly available, the team can in any event use the design as a starting point for the hardware to be built for the actual mission, if deemed worthwhile. Much of the software developed with the lab can most likely be used in the team’s production systems with small optimizations.

An example assembly consisting of the USRP, the RFX2400 and the TVRX mounted in an enclosure. (Source: Alexandru Csete)

The lab currently consists of four components, purchased from Ettus Research LLC, a company which also contributes directly to the development of the GNU Radio software, at a price of around 1,800 US dollars. “A lot of money for the private budget, but I expect it will have a good return on investment,” says Csete. The central component is the Universal Software Radio Peripheral (USRP), which connects with a standard host PC through a regular USB 2.0 interface and performs a number of general purpose operations on the incoming and outgoing radio signals, such as conversion between analog and digital representations, allowing the host CPU to operate directly on a radio band. The USRP in turn connects to one of a range of so-called RF frontend components which connects the USRP to the desired radio band. Team FREDNET’s lab currently includes three such frontends – the RFX1200, the RFX2400 and the TVRX – which each covers one segment of the radio spectrum. Both receivers, transmitters and transceivers (a combined receiver and transmitter) can be set up with these components.

“Now we have some building blocks, both hardware and software – think of them as Lego bricks,” Csete says. “Next step is to build a few example configurations and use them in some realistic scenarios. We have a few experiments in mind that we expect to carry out by the end of this year,” he says. The experiments will be announced on the team’s internet forum once finalized.

Csete explains that the lab will support his team in learning about the technologies used in state of the art space communications and evaluating various design options for things such as modulation, forward error coding and signal processing. Furthermore, the lab will be used for testing the team’s own hardware and software implementations for the various communication subsystems to be used on its mission and for defining and documenting a reference ‘lab system’ that can be easily reproduced by other members of the worldwide team or by interested third parties.

“Prototyping, experimentation, and simulations are key elements in a successful space mission,” Csete says. “Some people think it is a waste of time to play around and that we should be focusing on building the ‘real thing’ instead, but believe me, we learn many important lessons during these activities,” he continues and says that this is something that applies to all subsystems, not just communications. The upcoming experiments will help Csete’s team catch up on recent advancements in radio technology and he also intends to create some instructive material and reference documentation on the subject such that some of the experiments can later be repeated as real-time demonstrations during various events.

“I only had some very basic theoretical knowledge of software radios before I started in Team FREDNET – so there was a lot to learn and there is still a lot to explore,” Csete says. “I have used hardware radios since 1990 and I find the software radio world extremely exciting. This is one of the reasons why I’d like our ‘open source communications lab’ to also serve as an educational and experimentation platform,” he continues. “I’d like people with no prior experience or knowledge about the subject to have a chance to learn about space communications. Education is one of our primary missions in this endeavor.”

Since the design documentation for the lab hardware components is freely available in the GNU Radio source repository, interested team members can in principle duplicate the lab at home. “Anyone who has experience with electronics and has access to the required equipment – production of printed circuit boards, soldering equipment, etc. – can build it,” Csete says. “However, it is hardly feasible to build an exact copy of it yourself if you take the cost of raw materials, parts, and required time into account. The advantage of open source in this case is that the schematics is publicly available and you can freely modify it to suit your own needs or optimize it for a specific application.”

Csete has purchased the equipment in the lab for money of his own to get work on the project started: “Until we get sponsorship agreements in place we have to do it like this. It is the same with many other things – servers, network bandwidth, travel expenses,” he says. “For now, I consider the whole project as a hobby and as an investment in the future.” However, he also notes that while the team relies on individual contributions to the extent possible until agreements with sponsors can be arranged, the project has never been intended to be self-financed by team members, nor does the team expect that team members spend their own money on the project.

Should anyone out there be interested in getting involved in Team FREDNET’s communication systems work, Csete advises them instead to get in touch with him directly by e-mail or on Team FREDNET’s forums. “Officially, we are in the initial phase where we capture requirements and do high level analysis,” he says. “One of my top priorities now is to finish a draft system requirements document. This is the beast we will use to validate our final communication system against, so it is very important to get it right and unambiguous if we want to have a chance for space qualification,” Csete explains, referring to the process of ensuring that his team’s spacecraft can stand up to the special requirements of use in a space environment, be allowed on board a launch vehicle, fulfil radio regulation requirements and so on.

“However, I realize the need for ‘activating’ some people who haven’t had a chance to get involved yet and therefore I am about to kick off some software projects that do not require extensive knowledge about space and communications systems,” Csete continues, and states that work packages will be published on the team’s forum as they are finalized. “Finally, those who want to learn about digital signal processing and software radios can follow the instructions on the wiki and install GNU Radio on their PC. They can have a lot of fun without any hardware,” he says.

The particular escape maneuver to send a spacecraft on a trajectory from Earth orbit to an orbit around the Moon is called a Trans Lunar Injection (TLI). During the Space Race, TLI’s were typically performed by the launch vehicle itself. On Apollo 8, the first manned mission to leave Earth orbit, for instance, the third stage of the rocket assisted in driving the craft into Earth orbit but remained attached to later perform the TLI.

The S-IVB third stage of the Apollo 8 Saturn V, shortly after separation from the Command/Service Module. (Source: NASA)

But since the days of Apollo, interest in the Earth’s distant natural satellite has waned, and few rockets built today have upper stages powerful enough to perform TLI: the telecommunications and television broadcast satellites, which constitute the majority of payloads launched into space today and act as a relay for radio communication between sites on the ground, have no need to leave Earth orbit. Thus any probes headed towards the Moon will generally be required to carry kick motors and fuel to perform TLI themselves. Conventional kick motors rely on the same chemical propulsive principles as rockets – obtaining thrust from the expulsion of gases produced by the combustion of fuel – but recent years has seen an increase in the development of so-called electric propulsion technologies.

Electric propulsion (EP) engines generate thrust by expelling electrically charged particles (ions) accelerated to very high speeds by electrostatic or electromagnetic fields. Typically, electric thrusters have much better fuel efficiency, or specific impulse, than comparable conventional chemical thrusters. This make them ideal for interplanetary flights; on the enormous distances between astronomical bodies, every gallon of propellant counts.

EP engines has been used on a number of probes and satellites since the 1970′s, including the European Space Agency‘s first Moon probe, SMART-1. During its 3 years long mission, SMART-1′s Hall effect thruster – an engine in which ions are accelerated by an electric field – produced a total increase in speed of about 4 km/s (14,000 km/h or 8,948 mph). That’s 45 m/s (162 km/h or 101 mph) per kilogram of propellant.

Early mission plans from ‘open source’ Google Lunar X Prize contestant Team FREDNET, which intend to land a robotic rover on the surface of the Moon, also considered the feasibility of using electric thrusters for their mission’s lunar transfer, but the team eventually decided against it:

“It not that it’s infeasible,” says Team FREDNET’s Lunar Bus Subsystem Manager, Michael Barrucco, who works with astrodynamics at the Naval Research Laboratory in the daytime. “It can certainly be done. In the spacecraft industry, however, we look for methods with heritage, meaning a system that has shown it can handle all needs of space travel,” he explains. “Electric propulsion has been used, but not often. Chemical engines have been taking us to the Moon for 50 years. I argue – especially with this mission being a race to the finish – that we stick with what we know works well.”

Apart from being a relatively unproven technology, there is also the issue of thrust. Although electric thrusters are very efficient per unit of propellant, their propulsive performance per unit of time is several orders of magnitudes poorer than that of conventional chemical thrusters. This limitation is also the reason that electric thrusters can not be used for launching the spacecraft – the thrust of the EP engine is far too small to make up for Earth’s gravity and atmospheric drag at the ground.

“Space travel is very different from what we see in the text books as homework problems,” Barrucco continues. “Electric propulsion works – we can calculate burn times given engine characteristics, scale fuel needs and such. However, it is less practical in the real world.”

By ‘burn times’  Barrucco refers to the durations of single firings of the engine. Orbital engineers like Barrucco dream of the ‘impulsive burn’ – a firing of the engine that change the velocity of the spacecraft instantly. According to the book Orbital Mechanics for Engineering Students by Howard D. Curtis, an “impulsive maneuver is an idealization by means of which we can avoid having to solve the equations of motion with the rocket thrust included” – or, in short, a simplification of the rocket science involved in changing a spacecraft’s trajectory. Being an idealization, no rocket engine can in fact perform an impulsive maneuver, but it can be approximated:

Ion engine in operation. (Source: NASA)

“If the burn is not impulsive you lose efficiency,” Barrucco explains. “To keep the efficiency as high as possible, we can chop up the necessary burns into smaller burns starting a little before the periapsis point and ending a little after. The more times you chop up the burn, the closer to an impulsive maneuver. The higher the thrust, the less we need to chop up the burns.”

This ‘chopping up’ can be done for electric thruster burns as well as it can be done for chemical thruster burns, but in the case of electric thrusters it requires many more maneuvers in the mission plan, along with high-precision tracking of the position and orientation of the spacecraft to time the individual burns correctly, which typically can only be accomplished with support from several ground stations on the surface of the Earth – capabilities which a smaller private enterprise like Team FREDNET do not possess. Hence, Team FREDNET’s best option, from an operational point-of-view, is a higher-thrust, fewer-burns chemical engine.

Additionally, the electric engine requires a supply of electric power. Space probes like SMART-1, using electric thrusters for propulsion, rely on solar energy as their power source. This combination of solar power and electric propulsion, known as solar electric propulsion, has been studied by NASA for several lunar transfer missions, but for a private, non-profit mission like Team FREDNET’s, solar power is simply not affordable. “Solar electric propulsion requires large solar arrays, producing between 2 to 6 kW of electrical energy,” says Ryan Weed, team lead of Team FREDNET’s Propulsion Systems group. “At more than 1 million US dollars per kW of high efficiency multi-junction solar cells, the cost of these components, in addition to their mass, would be a major barrier for a project of this size.”

Michael Barrucco stresses that “the difference is not only in the price for the solar array, but the extra cost of mass as well. The big reason for using electric propulsion is saving fuel mass, but electric propulsion requires other hardware that adds to the mass,” he explains, and says that although he haven’t looked at the exact numbers in terms of mass, he is “betting that the mass difference, because of the high specific impulse, is all but negated by the extra cost of hardware and mass of the bigger solar arrays.”

Electric propulsion is not suited for the so-called retrothrusters that have to be employed to slow the descending spacecraft down before landing on the lunar surface either. At the low thrust the EP engine delivers, the craft would plunge into the ground. “While electric thrusters are very efficient, the thrust to weight ratios are just too small, and usually less than one,” says Ryan Weed. “For example a typical thruster may weigh 5 kg, but would only give a thrust of 50 mN, which on the lunar surface could only hold up 100 grams.”

Thus, with a lander weighing several kilograms, Team FREDNET has no other options than using chemical retrothrusters for landing. And using separate propulsion methods for TLI and landing is not a good idea either, Barrucco explains: “If you use two types of fuel, you add the mass of the tanks and extra valves and electronics to control the new fuel tank.” If the team instead opts to use chemical propulsion for TLI, the “propellant can be used for not only the attitude control system but also for landing,” says Barrucco. Depending on the mission requirements, the same chemical engine may even be shared for TLI and landing which, as opposed to having two separate engines, “would certainly save mass,” according to Barrucco.

Overall, Michael Barrucco is not in doubt as to which method of propulsion he would recommend his team: “In short, with the well-known heritage of chemical propellants, the fact that most hydrazine combinations in a bipropellant system produce a hypergolic reaction needing no spark for ignition, the decreased operations costs, and the fact that the chemical propellant can be used for the attitude control system and for landing as well, chemical propulsion seems like the best choice,” he says. “I will, however, conduct a trade study once the astrodynamics calculations are done to see what the best propulsion system choice will be”.

A SM-3 missile launches from the USS Lake Erie, impacting a non-functioning spy satellite approximately 247 kilometers over the Pacific Ocean to prevent it from releasing toxic hydrazine fuel. (Source: US Navy)

Hydrazine fueled engines have been used on such high-profile missions as the Viking program Mars landers in the late 1970′s as well as the Phoenix lander which is operating on the northern polar cap of Mars right now, after landing on the planet in May. Hydrazine is also sometimes used for thrusters on board satellites orbiting the Earth – most notably the defunct spy satellite USA 193 which caught some press earlier this year when the American government destroyed it with a sea-launched missile, purportedly due to the potential danger of a hydrazine release if the satellite re-entered the Earth’s atmosphere intact. Hydrazine is dangerously unstable and highly toxic – so toxic that the workers fueling hydrazine propelled spacecraft are required to wear big, protective suits when handling the substance. Can such a dangerous chemical even be considered for use in a spacecraft built by amateurs?

“The fueling will most likely need to be contracted out,” says Michael Barrucco. “I have not looked at prices or possible contractors as of yet, but it is definitely possible for a team of our caliber to design a craft to meet all the specifications required for a hydrazine propelled spacecraft,” he affirmed.

Liftoff of the SpaceX Falcon 1 Flight 4 vehicle from Omelek Island in the Kwajalein Atoll, at 4:15 p.m. PDT / 23:15 UTC. (Source: SpaceX.com)

The partially reusable Falcon 1 is designed and manufactured by PayPal co-founder Elon Musk’s space-transportation startup, SpaceX. And although the Falcon 1 itself is capable of transferring payloads of up to 670 kg into orbit, it’s greatest importance lies perhaps in its role as a testbed for designs that will be reused in SpaceX’s much larger Falcon 9.

The Falcon 9, in its lightest version, will be capable of transferring no less than nearly 10,000 kg of payload into orbit and is being considered for NASA‘s COTS program for transporting cargo to and from the International Space Station when the Space Shuttle is decommissioned in a few years. With prices significantly lower than competing launch vehicles, the Falcon series of rockets also for the first time offers a whole new range of small businesses and organizations access to orbit.

One of these organizations is the non-profit foundation Team FREDNET which is putting together a mission for sending a robot rover to the surface of Moon in the hope of claiming the 20 million US dollar Google Lunar X Prize. According to plans released by the organization in July, Team FREDNET estimates that sending their spacecraft to the Moon on a Falcon 1 would cost around 5 million U.S. dollars. A relatively high price, which is in part due to Team FREDNET’s special requirements – not many spacefarers are going to the Earth’s distant and desolate natural satellite as Team FREDNET is.

Most scientific payloads headed into space are left by their launch vehicle in Low Earth Orbit (LEO, 160 km to 2000 km above the mean sea level of the Earth), some communications satellites are left in Geostationary Transfer Orbit (GTO, same altitude as LEO but at a higher velocity), and nearly all the remaining payloads are left somewhere in between. The only payloads to escape the Earth’s gravitational sphere of influence entirely are probes sent into interplanetary space by governmental agencies such as NASA and ESA. Therefore, most launch vehicles are designed for LEO or GTO trajectories, with the Falcon 1 falling into the former category.

If left in LEO by a rocket such as Falcon 1, Team FREDNET’s spacecraft would need to propel itself towards the Moon, which in turn would require it to carry much more fuel on-board: “From LEO, we will need a heavier spacecraft to get to lunar orbit, as compared to GTO – probably most of a Falcon 1 payload,” says Ryan Weed, team lead of Team FREDNET’s Propulsion Systems group. The added weight means that Team FREDNET would have to pay most or all of the launch themselves as it would leave little room for other customer’s payloads aboard the rocket.

However, the Falcon 1′s big brother may still be an option: “The Falcon 9 is enticing because it does lunar transfer orbits, with something like 2000 kg of payload,” says Weed. The greater lifting power of the EELV class Falcon 9 allows it to perform direct Trans Lunar Injection, eliminating the need for a heavy kick motor with fuel on the payload itself. Weed estimates that the total mass of Team FREDNET’s payload on a Falcon 9 would be less than 100 kg, or a twentieth of the Falcon 9′s total trans-lunar lifting capability. “And at 50 million US dollars per launch, one twentieth of that is looking cheaper than a full Falcon 1,” he says, and concludes: “In the end its all about the money.”

Another man keeping an eye on the launch business these years is Tom Hill of the Mars Society, an international space advocacy non-profit organization dedicated to encouraging the exploration and settlement of Mars. Hill recently had an experiment he had proposed, called TEMPO³, approved for funding by the Mars Society. TEMPO³ intends to show the feasibility of using tethers to generate artificial gravity in space, in the hope of convincing space agencies that the technology can be used to counter the negative health effects of weightlessness on long manned voyages in space to e.g. Mars.

The TEMPO³ experiment is to be launched as a CubeSat mission by the California Polytechnic State University, but planning has only just begun and as of yet no launch vehicles have been chosen for consideration. The rocket that has flown the most CubeSats so far is the Russian Dnepr, and although Tom Hill would not rule out SpaceX as a possible carrier, his team has not started any direct negotiations with the company either. The CubeSat project considers many launch providers of which SpaceX is just one.

“Directly, there’s no real impact to the TEMPO³ mission of Falcon 1’s launch success,” says Tom Hill. “Indirectly, however, there’s a huge boost for private space efforts. Elon Musk showing what a small company can do is great, and it will point out the fact that other groups, and not necessarily just government-run space agencies, can be active in space.”

Musk, who became a dotcom-multimillionaire through his sale of PayPal to eBay, founded SpaceX to fulfil childhood dreams of one day sending missions towards other planets and is not at all a stranger to the non-governmental movement to further human presence in space:

“Elon got an early introduction to space efforts through The Mars Society, and he’s been a general supporter as well as funding specific projects, so any success on Elon’s part has the potential of translating to future Mars Society success,” says Hill. “Elon has expressed an interest in using his Falcon 9 Heavy boosters and their progeny for Humans-to-Mars missions, which is incredibly exciting”.

AMSAT, an international non-profit organization dedicated to building and operating amateur radio satellites, is also assessing the capabilities of the new launch market entrant. On October 9, representatives of SpaceX and AMSAT-DL, the German chapter of the AMSAT organization, met in Marburg, Germany to discuss possibilities for cooperation. The AMSAT representatives, whose organization is currently developing a first-of-its-kind amateur mission to Mars named P5-A, were interested to learn details on Elon Musk’s own ideas and plans concerning the Red Planet:

“Bottom line is that SpaceX and AMSAT-DL share common philosophies regarding access to space,” says P5-A mission manager Achim Vollhardt. But Vollhardt echoes the sentiment of Ryan Weed and Tom Hill that, ultimately, it’s the best offer that wins: “In general, we only require a geostationary transfer orbit for any of our missions, so any commercial satellite launcher can serve our needs,” he says, and explains that reducing launch price is critical to minimizing overall mission costs.

The next Falcon 1 is set to launch in January 2009, with a payload from SpaceDev, another important space startup. The highly anticipated maiden flight of the Falcon 9 is also scheduled for launch sometime in the first quarter of 2009.

A spaceflight is generally divided into several discrete stages, in order to break the challenge of planning the voyage into smaller, more manageable tasks, which may in turn be divided into even smaller sub-stages. Due to the physics involved in spaceflight, a trip from one astronomical body to another will always consist of at least three such stages: leaving body A, moving from body A to body B, and arriving at body B. Each stage is defined by its physical characteristics, and their difference from those of the next. Since the vast majority of spaceflights conducted today originates from our home planet, body A will generally be the Earth.

The great mass, and thus gravitational attraction, of the Earth entails that leaving the planet requires a tremendous amount of power, compared to the power delivered by propulsion systems used in cars, ships and planes closer to the ground. The only systems capable of delivering such power today are rockets – vehicles obtaining thrust from the continuous ejection of exhaust gases produced by the combustion of special fuel stored in a large container on-board the vehicle itself.

Historically, constructing and operating rockets powerful enough to reach space were the domain of governments and big, established aerospace contractors like Boeing and Lockheed Martin, and the cost of access to space were counted in many tens of thousands of dollars per kilogram of payload. But as the new Space Age begins – marked by SpaceShipOne‘s first privately-funded manned spaceflight in 2004 – new launch options are becoming available and are driving costs down.

With the Space Shuttle to be retired in a matter of years, NASA has called for reliance on so-called Commercial Orbital Transportation Services (COTS) – private spaceflight vendors transporting cargo to and from, for instance, the International Space Station (ISS) – which offers the private aerospace sector a solid window of opportunity for the development of commercial space cargo services. Essentially, NASA is establishing the procurement-bureaucracy equivalent of an X Prize for inexpensive, privately-funded heavy-lift capabilities.

Although Scaled Composites’ SpaceShipTwo, the newest descendant of the spacecraft which won the Ansari X Prize, will be able to freight passengers and cargo across the 100-kilometers-altitude Kármán line, and thus officially into space, it will not be one of the vehicles shipping supplies to the astronauts aboard the ISS, once the spaceplane is put into service by Richard Branson‘s Virgin Galatic ‘spaceline’. The velocities that the craft is capable of attaining are simply not high enough to put payloads into orbit around Earth, similar to how a spinning top not spun fast enough can not stay upright.

Dotcom millionaires and hotel magnates

Thus, while the Virgin Group’s adventure into space tourism is an exciting step from a consumer point-of-view, its service is, for now, only of peripheral interest to the space industry at large, which generate its main revenue from things such as communications and television broadcast satellites, and of even less interest to NASA’s COTS program in particular.

Instead, NASA is contracting ‘real rockets’ from private companies. One of the most notable entrants is Space Exploration Technologies Corporation (SpaceX), founded by PayPal co-founder Elon Musk. Since its inception in 2002, prompted by Musk’s childhood dreams of one day launching missions to other planets, SpaceX has developed several vehicles to support their launch business. SpaceX Falcon 1 is a relatively small rocket, ideal for putting small satellites (up to 670 kg) into Low Earth Orbit (LEO). SpaceX Falcon 9 is a so-called EELV class rocket, capable of transferring much larger payloads (up to 27,500 kg) to LEO (e.g. destined for the ISS), geostationary transfer orbit (GTO) or, should the need arise, even towards the Moon.

While all three launches of SpaceX so far (two of them test flights) have failed, Musk remains confident that his company will succeed in establishing a reliable lift, once the first few expensive lessons have been learned. And with prices of as little as a few thousands of dollars per kilogram of payload, a large audience of space enthusiasts and prospective consumers of the service are holding their breath as well, as a reliable launch provider in this price range will offer even the ‘long tail’ of small start-ups and research initiatives a realistically affordable gateway to space – and maybe revitalize the burgeoning space industry as a whole in the process.

Ryan Weed, team lead of the Propulsion System group of the OSEJ’s favorite Google Lunar X Prize team, Team FREDNET, is not one of them, however. “Personally, I very much doubt that SpaceX’s Falcon 9 will be ready in time for a lunar transfer launch”, he says. His team is racing to land their rover on the face of the Moon before Google’s prize is cut in half on December 31, 2012, about four years from now, and, of course, before any of the competing teams beat them to it. “Right now”, Weed continues, “it looks like Team FREDNET’s best option is an auxiliary payload on an Ariane 5″. The Ariane rocket was developed in the early 1990′s for the European Space Agency (ESA) and is being operated by the French company Arianespace – the most used and most reliable launch provider in the world, but at prices comparable to those of other established aerospace companies in e.g. the U.S.

SpaceX is not the only mover in the field for low-cost launches, however, and nor is NASA the only customer willing to put big money on the table for the development of commercial orbital services. In 1999, Robert Bigelow, an entrepreneur who made his fortune through the hotel chain Budget Suites of America, founded the company Bigelow Aerospace which is pioneering work on expandable space station modules, or in lay terms: an inflatable space hotel. The initial design work for the modules were done by NASA under its Transhab program. Facing budget cuts, NASA had to slash the program and subsequently awarded the rights to commercialize the Transhab designs to Bigelow.

Bigelow Aerospace has successfully tested two of their modules, Genesis I and Genesis II, in space, and on October 3, 2006, the company received the Innovator Award from the Arthur C. Clarke Foundation, and later, on January 26, 2007, joined the list of distinguished winners of the Space Foundation’s Space Achievement Award. In other words, their efforts looks very real – and while Bigelow expects its first operational modules to be used for things such as microgravity research and space manufacturing, the company does have greater plans. By 2010 it wants to launch a so-called orbital resort, tentatively named the CSS (Commercial Space Station) Skywalker.

As NASA scrambles to find launches cheap enough to keep the ISS supplied with mission-critical cargo and trained personnel, how exactly does Bigelow Aerospace intend to send tourists aboard a hotel floating in space? While SpaceX’s man-rated Falcon 9 launch vehicle together with their manned Dragon capsule can not be ruled out as one possible option, Bigelow is not afraid to push the envelope here either. The hotel magnate has established a prize of 50 million US dollars – or five times the previously discussed Ansari X Prize – to be awarded to the first US-based privately-funded team to design, build and fly a reusable manned capsule capable of carrying 5 astronauts to a Bigelow Aerospace inflatable space module twice in 60 days.

The prize, titled America’s Space Prize, expires in 2010. Among the contestants are Interorbital Systems, founded in 1996 by Roderick and Randa Milliron, and based in Mojave, California. Interorbital design so-called amphibious launch vehicles, meaning rockets that can be launched from sea, thus reducing the risk that a failed launch could do damage to people or property on land, which in turn gives the company a bigger safety margin to play with.

Two of Interorbital’s low-cost, rapid-response vehicles has orbital capabilities. The smallest of these, the Sea Star MSLV, which can carry small satellite payloads (20.4 kg to 26.3 kg) into space, is planned to be launched as early as this year, which according to Interorbital, if successful, would make it the world’s first satellite-launching rocket developed completely without government funding.

The larger of Interorbital’s launch vehicles, the Neptune, were designed with everything from space tourism to space mining and cargo launches in mind. Among the Neptune‘s most interesting features is its pressurant tank which, once depleted after having launched the craft into orbit, can be used as a recreational area by the rocket’s crew. The recreational area, or habitat, thus incur no additional payload weight or volume on the launch vehicle.

“The rocket is a ‘pressure-fed’ system – there are no turbopumps”, Interorbital CEO Randa Milliron explains. In most conventional rocket designs, turbopumps are used to feed the rocket fuel, or propellants, into the combustion chamber where the fuel is ignited. But in the Neptune, “the propellants are forced toward the combustion chambers by pressurized gas, in this case helium“, Milliron continues. Once in orbit, “the large volume of the pressurant gas container becomes the on-orbit habitat, the OSM (Orbital Station Module) – the Neptune essentially brings its orbiting hotel with it, in the form of a re-used empty pressurant gas container”, she says. Launch cost of both the Sea Star and the Neptune is likely to be minimal, and it will be interesting to see if Interorbital Systems succeed in achieving their goals.

An adventure 65 years in the making

And, once more, somewhere in the background of all this, in another dusty hangar in the Mojave Desert, we find Burt Rhutan’s famed Scaled Composites and their line of spaceplanes developed for Richard Branson’s Virgin Galactic spaceline. If Virgin’s suborbital service, based on Scaled Composites’ SpaceShipTwo design, is successful, Richard Branson intends to order the development of another vehicle, SpaceShipThree, capable of carrying a crew into orbit.

While Rhutan spoke about an orbital version of his plane at an UK Royal Aeronautical Society lecture in London as early as 2004, details about the project remain sparse – except of course from the fact that Rhutan’s wits and Branson’s capital holdings seems just the right pair to make commodity access to orbit a reality.

The idea of an ‘orbital spaceplane’ has been explored on and off by many agencies for several decades. The concept can be traced back to the pre-Apollo X-20 Dyna-Soar developed by the US Air Force as a platform for military operations from space. The X-20 itself was eventually canceled over concerns that the project were lacking direction, but, by a peculiar turn of events, may prove to become among the forefathers of the spacecraft that will take a new generation of civilian spacefarers into orbit.

In response to the development of the X-20, the Soviet Union began development of an orbital spaceplane known as the MiG-105 “Spiral” in 1965. Like the X-20, the Spiral were never actually flown in space before the program was canceled. But a few years later, the Soviet Union decided to construct a scaled-down (1:2) version of the Spiral, known as the BOR-4, to test materials to be used for the Soviet Union’s Buran space shuttle, then under development.

After completing one of these tests and parachuting to an ocean splashdown in June 1982, the BOR-4 was captured on images taken by a reconnaissance aircraft from the Australian air force as the Soviet Navy were recovering the spacecraft from the sea near the Cocos Islands. The photographs were presented by the Australians to NASA, who in turn initiated an investigation of the spacecraft’s design that would later conclude that the craft had good aerodynamic characteristics for orbital flight.

The Challenger disaster in 1986 sparked interest in a smaller, safer alternative to the heavy-duty Space Shuttle, and NASA began looking to the BOR-4 shape for a personnel spaceplane concept designated HL-20. The concept progressed well but eventually stranded when the Russian Soyuz spacecraft were selected as the initial emergency rescue vehicle for the International Space Station around 1991. Later, in 1997, NASA initiated a program unrelated to the HL-20, called the ‘Orbital Space Plane‘ program, which would eventually evolve into the Orion spacecraft that is currently planned to send humans back to the Moon by 2020.

But in November 2005, nearly 50 years after the first outlines of the X-20 Dyna-Soar were being drafted, a Poway, California company known as SpaceDev announced a concept known as Dream Chaser for a six passenger orbital spacecraft based on NASA’s HL-20 and using rocket motors the company developed for Burt Rhutan’s successful SpaceShipOne.

Like its ancestors, Dream Chaser is to be launched horizontally by a conventional expendable rocket, enter orbit, and then return to Earth, landing softly like an aircraft at almost any runway in the world, much like the American Space Shuttle. The spacecraft had been mentioned as a possible contender for Bigelow’s America’s Space Prize, but SpaceDev later opted to fund the project under NASA’s COTS program, disqualifying the Dream Chaser from the prize.

SpaceDev intends to offer a sub-orbital version of their service within years. Pricing information for both the sub-orbital and orbital service is yet to be disclosed, but would depend greatly on the launch vehicle being used.

N for nano, nine and nearly impossible

Manned spaceflight, however, is just one leg of mankind’s leap into space. The safety and payload weight requirements for a mission sending humans, as demanded by America’s Space Prize, into orbit incur a high price on the launch vehicle – and satisfying exploration of space can be done with much less.

Thus the smaller, and somewhat more obscure, N-Prize calls for entrants to launch a satellite weighing between 9.99 and 19.99 grams into Earth orbit, and to track it for a minimum of nine orbits. Most importantly, though, the launch budget must be within £999.99 (about $2000) – and must include all of the required non-reusable hardware and fuels. The winning team will be awarded the prize sum of £9,999.99 (about $20,000).

While, as the organizers of the N-Prize openly admits, the prize sum is “ludicrously small”, several teams have already registered for the contest, many employing some form of ‘rockoon‘-design – rockets carried by a balloon into atmospherically more favorable altitudes and then ignited. And although the prize may stimulate some creativity in amateur rocketry and launch platforms that can be deployed in the backyard, thus saving the shipping costs of transferring a payload to a launch provider, lead organizer of the N-Prize, Paul Dear, also admits that there is no immediate sensible economic reason for the N-Prize: for a sum equivalent to the prize’s launch budget, companies like SpaceX offers to put 5 times the payload mass stipulated by the N-Prize into orbit.

“It’s purpose is just to have fun, and to inspire other people to think creatively. As long as everyone enjoys themselves and nobody important blows themselves up, I’ll be happy”, concludes Paul Dear. Still, it will be interesting to see if the teams come upon designs which may be suitable for developing viable ‘nano’ alternatives to expensive, full-blown launch platforms that could send very small payloads into orbit – something that has been sought by amateurs and small research institutions for decades (‘nano’, in the context of orbital payloads, means, and has always meant, small payloads, weighing maximally a few kilograms).

Half in jest, and half in grave seriousness, the N-Prize website describes its own challenge as “very nearly” impossible – but just how nearly? In May 2004, only weeks before Mike Melvill completed the first privately funded human spaceflight in Burt Rhutan’s SpaceShipOne, a group of about 30 rocket amateurs, calling themselves Civilian Space eXploration Team (CSXT) successfully launched a rocket reaching an altitude of 116 km, making it the first amateur rocket to exceed the official boundary of space. While the 1.9 km/s velocity achieved by CSXT’s GoFast rocket is less than a fourth of the approximately 8 km/s required to enter LEO, and although they relied on one-off corporate sponsorships for funding, CSXT’s accomplishment does give a rough indication of how close even amateurs are at reaching orbital capabilities.

Looking much further into the horizon than that, the field slowly decays into the realm of science fiction. Although technologies such as beam-powered launches (e.g. the Lightcraft), launch loops and space elevators could potentially make orbital spaceflight as commonplace as microwave-heated meals, they all require very significant investments in research and development before becoming a reality.

Until then, we’ll eagerly monitor the more traditional launch providers, such as SpaceX (whose maiden launch of the Falcon 9 is scheduled for the fourth quarter of 2008), as well as the more innovative start-ups, such as Interorbital Systems and SpaceDev, in their quest to bring the cost of access to orbit down, and to ignite a new era in civilian exploration of space.

But if you do allow yourself to be guided, to some degree, by public policy, and thus make your mission eligible to public funding, you can reach even further – even if you insist to work under the full, unrestrictive disclosure that characterize open space exploration.

AMSAT-DL, the German chapter of the international amateur satellite organization AMSAT, is set to prove this in late 2010 to early 2011, when their P5-A probe is to launch from the Earth to begin a year-long voyage towards our closest planetary neighbor, Mars.

Until now, Mars has exclusively been the destination of national space agencies, and the Martian surface, due to the repeated failure of landing probes sent by Russian and European agencies, the sole territory of NASA.

And while AMSAT-DL’s 30 years of experience with space so far is limited to satellites orbiting the Earth, NASA’s two most stalwart scouts on the Red Planet, the rovers Spirit and Opportunity, as well as NASA’s planned Mars Science Laboratory, should not get too comfortable with the title of being the only Earthen probes operating at the surface of Mars.

AMSAT-DL is considering sending a secondary payload, possibly a lander, along with their primary P5-A satellite to Mars, which could for instance collect images and other data from the Martian surface and relay it through the orbiting P5-A back to Earth.

Deployment and inflation test of a full-scale model of ARCHIMEDES baloon inside the Olympia Hall, Munich. (Source: Mars Society Germany)

In particular, the German branch of the Mars Society has an open proposal for a payload, known as ARCHIMEDES, that would separate from P5-A and initiate a descent towards the Martian surface using a small solid-fuel rocket. A heat shield would decelerate the payload, and at an altitude of about 10 kilometers above the surface, a balloon would unfold and inflate. The balloon would then carry the remaining payload and its scientific instruments around Mars a few times, taken along by the high velocity winds of the upper Martian atmosphere, and send pictures and other data of this flight back to P5-A. The ARCHIMEDES vehicle has already been developed and tested extensively by the Mars Society.

Another, technically simpler, proposal for a secondary or ‘sub-satellite’ payload calls for small satellites with a side length of about 10 cm (pico-sats) to separate from P5-A in Martian orbit, enter their own orbit, and establish radio contact with each other. Using a technique called radio occulation, whereby the propagation time of radio signals sent by the small satellites are measured to construct an exact profile of the atmosphere at a given point, the pico-sats may be able to identify regions on Mars that still hold liquid water. This information would be highly valuable to later manned missions to the Red Planet.

With such sophisticated payloads on AMSAT-DL’s hands, it can seem a somewhat daunting leap to go straight from AMSAT’s core competence of Earth-orbiting satellites, which are thoroughly understood and supported by communications infrastructure on the Earth, to something as exotic as an interplanetary probe – why not try with a celestial body a bit closer to home, such as the Moon, first?

AMSAT-DL argues that any orbit around the Moon is inherently unstable due to the relatively close proximity, and thus gravitational pull, of the Earth. Preventing a hypothetical radio amateur satellite orbiting the Moon from being “sucked” back to Earth by gravity is simply too difficult.

Furthermore, the total change of velocity (the so-called delta-v), and thus resources, required to reach Mars is only minimally different from the velocity required to reach the Moon. For a robotic probe, a Martian voyage is, in other words, not significantly more expensive than one to the Moon.

Rather, the main differences are the duration of the voyage – a typical transfer to the Moon takes about a week, while a transfer to Mars may take up to around a year – and the power required to establish radio links with the probe at its final destination, being much farther away (the Moon is around 0.002 AU away from the Earth, Mars between 0.5 and 2.5 AU away).

P5-A will rely on the structure and propulsion systems developed for P3-D, another satellite designed by AMSAT-DL, and now gone into Earth orbit under the name OSCAR-40 (in short, AO-40). The experience gained by AMSAT from operating AO-40 for the past 8 years will serve as a good basis for sending a similar system towards Mars.

An incident on the AO-40, shortly after launch in 2000, disabled a number of subsystems on the satellite, and for a while threatened to terminate the mission. After several weeks of silence, radio links to the satellite were finally reacquired, and most important subsystems restored. It later turned out that a plugged valve in the satellite’s fuel system had, by a sequence of events, caused a small explosion in the satellite. Experiences like this, and the subsequent recovery from them, will give the AMSAT engineers a better understanding of which challenges they are up against when P5-A is going for Mars. Furthermore, the AO-40 mission will prepare radio amateurs around the world to pick up signals with characteristics similar to those to be sent by P5-A.

AMSAT-DL intend to use a radio observatory in Bochum, Germany as their primary ground station. The station, which is equipped with a 20 meter parabolic antenna, has been in operation since receiving the first signals from Sputnik 1, the world’s first man-made satellite, 50 years ago, and proved it’s Martian capabilities in 2003 when, on behalf of AMSAT-DL, it successfully received signals from ESA‘s Mars Express probe on its way to the Red Planet. Later, in 2006, AMSAT-DL’s team at the station received a signal from NASA’s venerable Voyager 1 probe, the most distant man-made object in the universe ever, at a distance of as much as 98 AU, or 40 times the distance from the Earth to Mars.

Sternwarte Bochum radio observatory in Bochum, Germany.

But don’t let the expensive-looking radome in Bochum scare you off. AMSAT-DL ensures us that, in true radio amateur style, signals from P5-A orbiting Mars will be receivable with an off-the-shelf 1.2 meter dish throughout the mission, and when Mars’ orbit around the Sun comes the closest to Earth’s, with as little as a 30 centimeter dish. AMSAT-DL estimates that for 9 months out of a 26 month period, signals from P5-A will be receivable with simple equipment available to the average radio amateur. The big dish in Bochum will be used for high bandwidth, low noise communications as well as emergency communications when weaker receivers are not sufficient.

Transmitting signals to P5-A requires a somewhat less standard setup, but should be possible, provided that the communications does not interfere with AMSAT-DL’s mission.

AMSAT-DL urges radio amateurs all over the world to prepare to tune into P5-A when it has entered orbit and goes out-of-sight for the primary command stations (e.g. the one in Bochum), and upload received telemetry data to AMSAT-DL’s central servers.

While a true radio amateur satellite, designed under ‘open source’ terms and conditions, P5-A relies indirectly on a great degree of government funding – for instance in the form of labor and hardware contributed by involved universities. It has also been suggested that P5-A can act as a much wanted alternative relay for the many planned government surface missions to Mars in the coming years, such as the already mentioned Mars Science Laboratory rover from NASA, and ESA‘s ExoMars rover, which would be another indicator of the mission’s ties to tax money.

Should the design of the probe turn out to be successful, however, it’s freely available specifications will enable anyone with the necessary funds – including private investors – to attempt the launch of another craft based on P5-A’s design. And AMSAT-DL’s demostration that ‘it can be done’ will obviously make investors much more likely to throw money at such a challenging venture. One might, in other words, hope that AMSAT’s mission could kickstart private development of interplanetary spacecraft – which in turn could have far-reaching implications for human exploration of space in general.

AMSAT-DL’s P5-A is set to enter orbit around Mars in August 2012.

Thus, Team FREDNET is looking at a number of options for establishing communication links with the team back on Earth to support the various stages of their mission. Most generously, the SETI Institute has offered all Google Lunar X PRIZE teams seven Earth days of free time on the institute’s Allen Telescope Array, located 290 miles northeast of San Francisco, California, for reception of data from the lunar surface.

Similarly, the Universal Space Network (USN) has offered the contestants a 50% discount on communication services (passes) for the spacecraft while in transit to the Moon and for 30 Earth days of operations on the lunar surface. The USN connects a total of 14 ground stations scattered over the surface of the Earth, making for good coverage any time of day for a lunar probe.

Apart from the services available to all contestants, Team FREDNET is also looking into communication options of their own. One such option is the venerable AMSAT organization, which has built and maintained amateur radio satellites for decades – much in the same civic spirit that is now driving Team FREDNET towards the Moon. AMSAT launched their first satellite, OSCAR, just a few years after the Soviet Union put the world’s first man-made satellite, Sputnik, into orbit.

Had Team FREDNET been able to meet the ITU‘s criteria for amateur radio communication, their spacecraft might have been able to depend solely on AMSAT’s satellites or ground station capabilities for radio links to the Earth. But, unfortunately, Team FREDNET can not satisfy ITU’s particular requirement for unencrypted communications – the Google Lunar X Prize rules specifically demand that teams transmit data from the Moon encrypted, in order to prevent unauthorized third-parties from intercepting and releasing data such as footage from the lunar surface prematurely.

Team FREDNET is still in contact with AMSAT, however, and are exploring other possibilities for collaboration:

“Even though we can not use amateur radio frequencies for video downlink, due to restrictions on encryption, it is still an option for telecommand uplink and telemetry downlink,” said Alexandru Csete, leader of Team FREDNET’s Communication Systems group. “The question is what we can give back in return for using amateur radio frequencies?” Csete continues. “In my and many other’s opinion, we shouldn’t use amateur radio frequencies for this purpose just because it is a ‘cheap’ option. We must give something in return to the amateur radio community, for instance having a ham radio payload on board the lunar bus or lander. These are the areas we are currently investigating.”

The Jamesburg Earth Station in Cachagua Valley, California. (Source: www.jamesburgdish.org)

Another interesting offer has come forward from the Jamesburg Earth Station in Carmel Valley, California, a former COMSAT ground station that served for 40 years as the terrestrial link for geostationary INTELSAT satellites over the Pacific Ocean until it went out of service when AT&T replaced it’s capacity with fiber optic cables, and subsequently sold the station to a private investor.

Jamesburg was built by AT&T/COMSAT to handle telephone and television traffic between Asia, Micronesia, and North America, and already got a taste of the Moon when it enabled world-wide, live TV coverage distribution of the Apollo moon landings back in the early 1970′s.

With it’s very high gain antenna (approximately 60 dBi), Jamesburg affirmed its capabilities in lunar communications in 2007 when a group of radio amateurs revived the abandoned station for use in a “moon bouncing” experiment – transmitting a signal from Earth towards the Moon, letting it reflect (bounce) off the lunar surface, and picking it up back on Earth again.

According to Pat Barthelow, who leads the group of volunteers who currently manage the station for its owner, Jamesburg could be an option for any Google Lunar X Prize team, including Team FREDNET, if the interested team or teams can build a business offer or model to pay the costs involved.

With the Earth’s half a century use of satellite communications and radio astronomy, it is likely that there is many more ‘dishes’ out there that could support Team FREDNET in their quest to the Moon. We can only hope that the operators of these systems will also step forward and offer their assistance to Team FREDNET’s great initiative.

The Apollo 15 Laser Ranging Retroreflector (Source: NASA)

When ‘open source’ Google Lunar X PRIZE contestant Team FREDNET attempts, if all goes well, to land a rover on the face of the Moon in a few years time, the mission may ingenuously rely on retroreflector mirrors left by the Apollo missions back in the 1970′s to guide the team’s craft safely to the lunar surface, according to a draft mission plan published by the team in late July. A laser range-finder (LRF) will scan the surface of the Moon until a reflected beam is detected and the craft will then steer towards the source of the reflection.

Using the retroreflector arrays as beacons for a lunar touchdown has so many advantages to Team FREDNET’s mission that one may wonder if the Apollo missions left the arrays those 40 years ago just for the sake of Team FREDNET’s navigational needs (the actual purpose of the arrays is for use in high-precision ranging experiments on Earth measuring the distance between our planet and the Moon).

First of all, because it took a manned mission to put the arrays where they are now, in the first place, Team FREDNET have hard proof that the retroreflectors are situated in areas that are generally suited for landing a lunar spacecraft – the retroreflectors basically designate areas that are good, proven landing sites. Hence, by steering towards and landing near one of the retroreflectors, the team may have a better chance of landing their craft safely than if they were to pick a landing site from the Moon’s 37 million km² surface area by themselves.

Secondly, the team will use data from the LRF to establish how fast the lander is approaching the lunar surface during its descent – a highly critical piece of information when using retrorockets to slow down the lander just sufficiently to make a soft touchdown not crashing the craft into the Moon, nor thrusting it back into space. Laser ranging is a textbook way of determining velocity, also used in, for instance, some ‘speed guns‘ used by law enforcement to detect vehicles traveling over the legal speed limit.

And finally, the Google Lunar X PRIZE contest offers the team a bonus prize if it is able to send back images of remains from the Apollo landings. Landing the rover close enough to an Apollo site for it to capture any such images would likely be impossible without the retroreflector ‘beacon’. For the sake of comparison, NASA’s recent mission to Mars, Phoenix, which touched down in May and did not use any form of beacon, operated with a landing accuracy in the range of hundreds of kilometers.

To minimize the time needed for scanning the lunar surface, Team FREDNET’s spacecraft will enter a lunar orbit particularly favorable for locating the Apollo landing sites this way:

“Since we already have a good idea of where ‘historical’ places like the Apollo 15 landing site are, we can narrow down the scanning range, so we don’t have to scan the entire surface of the Moon searching for retroreflectors. That would take way too long,” said Ryan Weed, team leader of FREDNET’s Propulsion System group.

Other uses of the Apollo program’s remains on the lunar surface are also being explored. For instance, an alternative guidance method relying on the heat signature of the RTG‘s (nuclear power sources) placed on the lunar surface by Apollo missions for power supply, which could be imaged from orbit with a sufficiently high-resolution infrared camera, has been suggested. There has even been proposals for the rover to, once deployed, drive up to one of these RTG’s (which remain the property of NASA according to international treaties) during its mission and use the RTG as an energy source to survive the cold lunar nights. This robotic romance could multiply the lifetime of FREDNET’s rover and give it enough energy to e.g. attempt to take photos with its camera at night.

If the team is successful in building on the Apollo program’s lunar heritage, any other private group with the sufficient resources may, due to Team FREDNET’s unique open approach, attempt to copy FREDNET’s methodology for landing other rovers, or perhaps even equipment which could subsequently facilitate a private manned mission, which in turn could one day lead to private colonization of the Moon.

So who said the Apollo missions were a complete waste of public funds?

Team FREDNET outlined their first basic mission plan in late July. According to the draft plan, FREDNET will rely on commercial launch providers to lift their spacecraft into orbit around the Earth, and then, if the chosen launch vehicle does not support so-called Trans Lunar injection, establish communications with the space craft from ground stations and direct propulsion systems aboard the spacecraft itself to send the craft onwards to the Moon and into lunar orbit.

In lunar orbit, the lander module (named the Lunar Lander) will detach from the rest of the spacecraft (named the Lunar Bus). Once in its own orbit, the lander will  scan the lunar surface with a laser range-finder (LRF) for one of the four retroreflector mirrors left by earlier missions to the Moon (e.g. Apollo), and, once located, ingenuously use the reflector as a waypoint as the lander initiates descent towards the surface.

Projected trajectory of Team FREDNET's spacecraft.

During descent, the lander will keep calibrating its trajectory relative to the retroreflector on the surface and gradually decrease its velocity using on-board thrusters. Vertical altitude and velocity is determined using the LRF, horizontal velocity using cameras and a feature-point detection algoritm, calculating how fast a, say, crater is drifting away on the recorded footage as the lander approaches the surface.

At an altitude of about 30 meters, the lander will profile the landing site with a laser to find a suitable landing spot. At an altitude of less than 1 meter, the lander’s trusters will cut off, to minimize dust accumulation around the landing spacecraft. The lander will then free fall for one second to finally hit the lunar surface at an velocity of about 1.6 m/s. This small amount of momentum will be transferred to impact absorbers on the legs or body of the lander, and the g-force generated will initiate the antenna and rover deployment system.

Once on the surface of the Moon, a number of operations, some of which are driven by contest requirements, are planned for the rover, including recording video as it travels the lunar regolith and sending the world’s first e-mail from the surface of the Moon to ground stations on Earth.