In a major step towards the commercial delivery of astronauts to the International Space Station, hopefully by the middle of this decade, United Launch Alliance (ULA) has completed the fifth – and perhaps the most publicly visible – milestone in certifying its Atlas V booster for human occupants. Under the Commercial Crew Development Round 2 (CCDev 2) with NASA, the company has finalised its Hazard, System Safety and Probabilistic Risk Assessment, which precisely outlines how the Atlas V hardware will ensure astronaut safety throughout the launch and ascent phases of future flights.
The year-long, unfunded partnership featured five reviews from ULA and NASA experts, which explored design implementation plans, detailed system and subsystem analyses, qualification, certification and actual flight data. “We commend ULA for taking on the challenge of human spaceflight,” said Ed Mango, manager of NASA’s Commercial Crew Program, “and we look forward to learning more about their innovative and cost-saving solutions as we continue to move forward in developing a crew transportation capability for America.”
‘Human-rating’ the Atlas V – a vehicle with a history of 33 launches since August 2002, of which 32 have been wholly successful and the other classed as a ‘partial failure’ due to the premature shutdown of its Centaur upper stage – has been ongoing for several years and an early agreement was reached with Bigelow Aerospace for private flights into low-Earth orbit. However, it was not until 2010 that ULA received its first small contract for $6.7 million under NASA’s Commercial Crew Development Program to build an emergency detection system as a first step toward human-rating the Atlas V. Other than the inclusion of this system, it would appear that few other major changes to the booster are necessary, aside from ground infrastructure modifications. Michael Gass, ULA’s President and CEO, has expressed his desire to execute a three-mission test programme, the last flight of which may carry a pair of Boeing pilots into space in late 2015.
The ‘capability’ of launching American astronauts once more from their home soil has turned into something of a political – as well as technical – hot potato since last year’s retirement of the Space Shuttle fleet. When Atlantis’ wheels kissed the runway at the Kennedy Space Center in the pre-dawn hours of 21 July 2011, they effectively left the United States without the means to fly its own astronauts from its own turf for the first time in three decades. Although Commercial Crew was already well advanced by the time of the final Shuttle mission, questions were asked about the rationale of creating such a wide gap in capability and allowing it to endure for half a decade or more. Blame was variously heaped at the respective doors of the Bush and Obama administrations, with supporters of each side accusing the other of poor management, unsustainable funding and an inadequate political will to pursue space exploration with the intensity demanded of it.
At length, in early August of this year, NASA selected three finalists for its Commercial Crew integrated Capability (CCiCap), with contracts totalling more than $1.2 billion, shared between Sierra Nevada Corporation, SpaceX – the company whose first Dragon Commercial Resupply Services (CRS-1) craft is presently docked at the International Space Station – and Boeing. As part of the CCiCap contract, which runs until May 2014, the three finalists will be required to provide NASA with complete end-to-end design of their crew-ferrying spacecraft, including the vehicle itself, its booster and associated launch services, ground-support and mission operations and recovery systems.
Although SpaceX plans to use an upgraded variant of its home-grown Falcon 9 rocket to launch the ‘DragonRider’ craft, both Sierra Nevada and Boeing have announced their intent to employ the Atlas V. Sierra Nevada proposes to loft its ‘DreamChaser’ spaceplane – not dissimilar in physical shape to a miniaturised Space Shuttle orbiter – with a crew of between two and seven astronauts. Drop tests are planned at Edwards Air Force Base in California later this year and in June ULA, NASA and Sierra Nevada performed buffeting evaluations of the combined DreamChaser/Atlas V stack. Meanwhile, a mock-up of Boeing’s CST-100 capsule (also capable of flying up to seven astronauts) underwent an altitude drop test over the Delamar Dry Lake, near Alamo, Nevada, in April 2012, successfully demonstrating the performance of its three main parachutes from 11,000 feet. Although designed to be compatible with the ULA’s Delta IV and SpaceX’s Falcon 9, it is the intent of Boeing to use the Atlas V as its “initial” launch vehicle.
Current planning envisages that the crew-carrying Atlas V will be configured as the yet-unflown ’402′ variant, with a 4-metre-wide payload fairing, no strap-on solid rocket motors and a dual-engine Centaur upper stage. Both Sierra Nevada and Boeing expect to launch their first crew-carrying vehicles into orbit sometime late in 2015 or early in 2016 and the baseline data provided by ULA’s successful Atlas V milestone offers a strong and tantalising indicator that these dates may be achievable. “This has been a tremendous team effort between NASA, ULA and our commercial crew partners,” said George Sowers, ULA’s vice president of human launch services, “and we have made a great deal of progress toward safe, affordable human spaceflight.”
Missions » ISS »