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At the end of June 2014, a spacecraft will launch at Cape Canaveral in Florida for NASA’s Commercial Crew Program, which will see the US space agency buy seats for its astronauts for orbital trips from 2017. The purchase of US spacecraft has come into sharp focus with the Ukraine crisis because, for now, NASA has to buy seats on Russian spaceships to get its astronauts to the International Space Station (ISS) as the agency has no transportation system of its own since the space shuttle fleet was retired in 2011. The aim of the program is to utilize private companies to ferry astronauts to and from the ISS as part of the stepping stone to the human exploration of Mars.

The June launch will test Space Exploration Technologies (SpaceX) Dragon Version 2 (V2) spacecraft’s SuperDraco thrusters, which will propel a capsule from the top of the Falcon 9 rocket, which was also built by SpaceX. Based in California, SpaceX is one of three US companies that were selected in August 2012 for the final stages of NASA’s Commercial Crew Program. The other two companies are: Boeing, a company with a long space flight history; and Sierra Nevada Corporation (SNC), which is based in the state of Nevada, USA. Two of the companies have a conventional rocket and capsule type system, while Sierra Nevada has a space plane it calls Dream Chaser. This space plane is launched on top of the Atlas V rocket, which is manufactured by Lockheed Martin and launched by the Lockheed/Boeing joint venture United Launch Alliance (ULA). Boeing also uses the Atlas V for its capsule spacecraft, the Commercial Space Transportation (CST)-100.

Launch abort testing

The SpaceX June launch abort is one of the Commercial Crew Program milestones agreed between the firm and NASA. All of the companies have milestones against which NASA links funding. According to a presentation given in April by the crew program’s manager Kathy Lueders, who was appointed to the position that month, SpaceX will also have an inflight launch abort test in August. This means the Dragon will separate from the Falcon 9 rocket 73 seconds into its ascent into space.

According to an October 2013 NASA statement, SpaceX’s Dragon will be outfitted with about 270 sensors for the launch abort test to measure a wide variety of stresses and acceleration effects on the spacecraft. An instrumented mannequin, similar to a crash test dummy, will be inside. The spacecraft’s parachutes will deploy for a splashdown in the Atlantic, where a ship will be pre-positioned for simulated rescue operations. The test spacecraft will be returned to Port Canaveral by barge so data can be retrieved and incorporated into the system’s design.

The SuperDraco rocket engines that are being tested in the on-pad and inflight aborts passed their qualifying firing testing in May at SpaceX’s Rocket Development Facility in McGregor, Texas. That testing involved multiple starts, extended firing durations, and what SpaceX calls “extreme off-nominal propellant flow and temperatures”.

The SuperDraco is a development of the Draco engine of the Dragon spacecraft being used for ISS cargo transportation. The SuperDraco has much higher thrust at 16,000 lb and features a 3D printed combustion chamber made from Inconel, a high-performance nickel chromium superalloy.

Like SpaceX, Boeing has a pusher escape system for its CST-100 and, like SpaceX, a launch abort will mean a sea landing in the Atlantic Ocean. So that the CST-100 can cope with this, Boeing has been working with Bigelow Aerospace, a US company that has developed an inflatable space habitat that can act as a space station or be part of such an orbital outpost. Boeing explains, “There has already been robust testing conducted at Bigelow Aerospace of our airbag system in case of a water landing.” The airbag is for flotation and keeping the capsule upright in the water.

Boeing’s most recent important test was its February flight control software system design review. This demonstrated spacecraft control with a pilot in the loop. Boeing says, “The CST-100 is fully autonomous; the pilot serves almost as a backup system for the spacecraft, so developing robust flight control software is critical.”

The CST-100 may be fully autonomous, but it is yet to fly. Sierra Nevada has flight tested its Dream Chaser, but it was only a low-speed landing approach test with a prototype. In October 2013, Sierra conducted its first free-flight test of the Dream Chaser spacecraft at Armstrong Flight Research Center, formerly Dryden Flight Research Center, in California. During the test, the company says it demonstrated “excellent performance of our flight software in the controlled descent and landing phase of flight”. It also confirmed that “flight software development is continuing and will be further demonstrated as part of the future flight tests”, and assured that flight software development is “on schedule”.

However, that flight test saw the Dream Chaser prototype’s left landing gear fail and the spacecraft skidded to a halt on the Armstrong Center runway.

Wind tunnel testing

Sierra’s most recent milestone test was its April wind tunnel testing of a Dream Chaser scale model. Three major wind tunnel tests were used to evaluate the integrated Atlas V and Dream Chaser dynamics during their ascent through the transonic and supersonic flight regimes. This was for Sierra’s agreement with NASA for its Commercial Crew integrated capability (CCiCap) phase of the crew program. On April 15, 2014, Sierra presented data from those tests to NASA. Mark Sirangelo, corporate vice president and head of Sierra’s Space Systems, says the data confirmed “that the integrated launch vehicle and spacecraft stack performs very well”.

The next step for Boeing for its CCiCap agreement is a critical design review and a safety review in July. For Sierra, the next important area of testing is for the Dream Chaser’s main propulsion system and its reaction control system, which consists of small rocket engines that enable the spacecraft to maneuver in orbit.

Sierra has agreements with many NASA research centers. The US space agency is made up of one headquarters building in Washington DC and nine research centers and other facilities dotted around the USA. As well as the Armstrong Center, Sierra has worked with five other NASA centers: Ames Research Center in Moffett Field, California; Langley Research Center in Hampton, Virginia; Marshall Space Flight Center in Huntsville, Alabama; Johnson Space Center in Houston, Texas; and Kennedy Space Center in Cape Canaveral, Florida. Langley is where the Dream Chaser wind tunnel testing took place.

Boeing is also using four of the centers – Langley, Ames, Kennedy and Johnson – as well as the NASA facility at White Sands, New Mexico.

The bottom line

All of this testing costs hundreds of millions of dollars – SpaceX declined to answer any questions, but Boeing revealed it has been awarded US$580.2m so far, and Sierra has been given about US$330m.

For Sierra Nevada’s Dream Chaser, it won two CCDev awards, totaling US$100m; a CCiCAP award worth US$212.5m; and a Certification Products Contract for US$10m. NASA also awarded Sierra Nevada an additional milestone funding, totaling US$15m. Neither company will reveal how much funding they have put into the Commercial Crew Program.

With only three years before NASA will make its decision on what will ferry its astronauts from the USA, and other countries, to the ISS, it should become clear in the next 18 months whether it is space flight veteran Boeing, cargo resupply winner SpaceX, or Sierra’s reusable shuttle that will maintain human access to outer space, and with that ultimate goal to allow humans to live on other planets. 

Rob Coppinger is a UK-based postgraduate engineer and spaceflight writer.

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