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Dream Chaser: what now for Sierra Nevada Corp's space plans?
Nasa’s recent announcement that Sierra Nevada Corp’s Dream Chaser was not among the winners in the agency’s commercial crew transport competition is an obvious blow to the company, but the mini-shuttle may yet fly into space.
The last time an American-built spacecraft delivered astronauts to the International Space Station was July 2011. The following month, the Space Shuttle fleet was officially retired and the orbiters now reside in museums across the US. Since then, the only option for Nasa has been to fly its astronauts on the Russian Soyuz at a cost of some $70m per round trip.
Lack of forward planning and limited political support have placed Nasa between the ‘rock’ of paying its former space-race adversary to ferry its astronauts and the ‘hard place’ of developing some sort of Shuttle replacement with severely limited funds. Its solution has been to seed-fund budding US commercial operators – by way of its Commercial Crew Development programme – in the hope that one or more of them will develop a vehicle safe and reliable enough to fly crews to the ISS by 2017, by which time Nasa will have been outsourcing to Russia for six years.
The leading contenders were Boeing, with its long heritage in the space business; SpaceX, upcoming rocket and space capsule manufacturer; and Sierra Nevada Corp (SNC), a small satellite builder with roots in avionics and communications systems. On 16 September 2014, NASA announced that it had selected Boeing and SpaceX to develop its vehicles under the so-called Commercial Crew Transportation Capabilities (CCtCap) programme and awarded contracts worth $4.2bn and $2.6bn, respectively, to Boeing and SpaceX. Sierra Nevada was left out in the cold.
So where does that leave Dream Chaser? Sierra Nevada’s brief statement following the announcement said that it was “disappointed” but would await the results of a debrief with Nasa before announcing its future plans. These plans are as difficult to second guess as the Agency’s decision to sideline Dream Chaser, but there is still a chance that the mini-shuttle could fly.
Even those with a cursory knowledge of American manned spaceflight will recognise the step-change in design represented by the Space Shuttle: until its development began in the 1970s, Nasa’s astronauts were delivered to orbit and despatched to the Moon in cone-shaped capsules with heat-resistant shields on their blunt, rotund bases. By contrast, the Shuttle was an aircraft-like vehicle with wings, tail and a large cargo bay.
In the post-Shuttle era, crew vehicle design appears to have returned to the age of the space capsule and a form reminiscent of the 1960s’ Apollo. While Lockheed Martin is building the Orion Multi-Purpose Crew Vehicle (MPCV) to meet Nasa’s exploration needs, in the commercial crew delivery sector Boeing and SpaceX have also chosen the tried-and-tested capsule solution, mostly for reasons of cost and relative ease of implementation. SNC, however, bucked the trend with its design for Dream Chaser, which owes its heritage to Nasa’s HL-20 Personnel Launch System lifting body of the late 1980s.
A lifting body is usually defined as a craft that produces aerodynamic lift using its body or fuselage rather than wings. According to Giorgio Tumino, project manager for the European Space Agency’s IXV experimental re-entry vehicle, “lifting bodies have the advantages of capsules and winged bodies, without their disadvantages”. Although capsules are simple and efficient, he says, they have “problems in manoeuvrability, controllability and comfort”, especially if re-entering from orbit at a steep angle. Winged bodies tend to be more complex and expensive, but they are more controllable and have a larger ‘cross range’, which enables emergency landings to either side of the nominal re-entry flight path.
In 2012, Boeing and SpaceX each received approximately $450m from Nasa under special ‘Space Act Agreement’ contracts, while SNC received just over $200m. Nasa associate administrator William Gerstenmaier said at the time that Nasa could not afford to support three commercial entities all the way to critical design review (CDR), but that SNC’s contract would “remove a large amount of technical risk”. In other words, what most of us would describe as Nasa hedging its bets.
All three contenders fielded designs capable of transporting up to seven passengers and crew, along with cargo, to the ISS. As long as they could prove that their designs met the Agency’s rigorous safety standards, the shape and overall appearance of the vehicle was not that important. It was clear, however, that SNC was an outsider in the race: it was the least experienced of the three and its lower level of Nasa funding suggested a ranking of ‘also ran’. The recent announcement appears to have confirmed the surmise.
The road ahead
So what progress have the chosen companies made towards Nasa’s 2017 goal of transporting its own astronauts to the ISS?
Boeing’s capsule – the unimaginatively named Crew Space Transportation-100 (CST-100) – was originally designed for Nasa’s defunct Constellation programme to send astronauts ‘to the Moon, Mars and beyond’, as the hype had it. The capsule is currently under test and, back in February, passed a development milestone termed ‘pilot in the loop’ when former astronaut Chris Ferguson flew a virtual mission to the ISS. According to Boeing, this was the final milestone before the spacecraft’s CDR this summer. Indeed, Keith Reiley, Boeing’s deputy programme manager for commercial crew, has been quoted as saying the capsule could fly as early as 2015.
SpaceX has experience with its unmanned Dragon capsule, designed to deliver supplies to the ISS, in its favour: its third mission was successfully completed in April with its fourth planned for September. Although it is one thing to demonstrate a cargo carrier and quite another to transport live crew, the Dragon is pressurised by design and has an in-built capability to return cargo to Earth, as opposed to incinerating itself on re-entry. Indeed, the intention to qualify the capsule for crew delivery has been clear for some time: at the 2012 Space Expo in Los Angeles, Dragon programme manager Garrett Reisman said: “Dragon has a window. I don’t know of any cargo that needs a window!”
So how does progress with Sierra Nevada’s Dream Chaser compare? According to Mark Sirangelo, corporate vice president and head of SNC’s Space Systems, the current development programme is “over 75 per cent complete”. On 26 October 2013, a full-scale engineering test vehicle, having been dropped from a height of 4km, glided to a runway landing at Edwards’s Air Force Base in California, thus demonstrating flight control systems for autonomous flight. In January 2014, SNC completed “a major milestone” when Nasa approved “critical design” elements, including the spacecraft, launch vehicle and ground systems.
The composite structure for the first flight model was delivered to SNC by Lockheed Martin in August and a first orbital flight was scheduled for November 2016 on an Atlas V launch vehicle. The mission is designed to “fully test all functions of the vehicle” with the aim of “flight certification for Dream Chaser”, says Sirangelo, who confidently predicts that “the first crewed flight will be in 2017”.
Asked before Nasa’s recent contract announcement how he would characterise SNC’s position relative to its competitors, Sirangelo was pragmatic. “There are two views to this: an objective view based on what stage of development all the competitors are at, and a subjective view that is more driven by hype and media. Objectively, we are the only company that has actually done a flight test of a vehicle. Others have done parachute drops of mock-ups, but we had a real vehicle with all flight actuation systems operating and avionics and autonomous flight software performing to enable controlled flight and runway landing.”
Addressing the fact that Nasa’s requirements and funding have driven progress to date, Sirangelo recognised that contractual performance is also an important metric. “In terms of per cent complete on the current Nasa programme we are all about equal,” he said. “In terms of design documentation, we are all approaching CDR levels, so there’s not much difference.”
But what about SpaceX’s experience with ISS supply capsules? “Realistically,” said Sirangelo, “a crew-capable vehicle is very different from a cargo-only vehicle, so flight history on one system does not necessarily carry over to another.”
While SpaceX would undoubtedly take a different view, what happens in the next year or so is arguably more important than history, and funding is a key part of that. Despite the characterisation of Dream Chaser as an outsider, Sirangelo was optimistic: “Given the advantages of our lifting-body vehicle over capsules, including the option for pilot control, low-g re-entry, runway landing, use of non-toxic propulsion systems, immediate access to crew and cargo, and Nasa’s stated desire to have a diversity of vehicles for this mission, we believe that Nasa will continue funding for Dream Chaser.”
Asked what would happen if Dream Chaser failed to get funding under CCtCap, Sirangelo was clear on the matter: “SNC is committed to the orbital launch in November 2016.” Of course, it remains to be seen whether this commitment will hold in the light of Nasa’s decision not to fund Dream Chaser.
Building the dream
In the wake of its failure to secure a Nasa contract for ISS crew transport services, it is possible that Sierra Nevada could attract other clients for its Dream Chaser shuttle. Bigelow Aerospace, for example, is an entrepreneurial company with plans to build commercial space stations, but has waited years for the development of a craft to service its proposed stations. Asked whether Dream Chaser would be able to deliver crews to a Bigelow station, Sirangelo confirmed that although no agreements were in place, there was “no reason why we could not deliver crews to a Bigelow space station”.
So for SNC and the other commercial providers, could it be a case of ‘build it and they will come’? Sirangelo has an answer: “Although we all feel like we are somewhat ‘living the dream’ of developing the next space shuttle that will carry the US space programme to orbit, we are a very pragmatic company and not depending on customers to just show up once the vehicle is flying. We have been working very hard the last few years to identify real markets for Dream Chaser that include various commercial and government customers and markets.”
Indeed, SNC already has a number of agreements relating to “both crewed and uncrewed missions”, including some with companies and space agencies outside the US. “We are building the dream,” confirms Sirangelo, “but the market for our vehicle is very much a reality.”
The advantage of composites: no burn-up on re-entry
The structure for the first Dream Chaser flight model is manufactured under contract to Sierra Nevada Corporation by Lockheed Martin at Nasa’s Michoud facility in Louisiana. According to Mark Sirangelo, composites offer several advantages over other materials: they have high specific strengths and low coefficients of thermal expansion well-suited to spacecraft; contours are more easily formed and/or fabricated; and the tooling concept produces long-term cost reduction as it allows multiple copies.
Sirangelo explained that Lockheed Martin is using experience in composite manufacturing developed for the Joint Strike Fighter and other programmes to provide “a lighter weight, affordable, and robust integrated airframe concept”.
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