No such thing as a free launch
This article inaugurates our series of articles on spacecraft propulsion. We begin with a bit of background and an introduction to rocketry and the state of orbital spaceflight.
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.
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- September 15, 2008 / 6:09 pm