Six companies are developing different concepts for the station
The six US companies designing ground-based prototypes for NASA’s Deep Space Gateway (DSG) station — Boeing, Lockheed Martin, Bigelow Aerospace, Sierra Nevada Corporation, Orbital ATK, and a consortium called Ixion —are to receive grants totalling $65 million up to the end of this year as part of a programme NASA calls NextSTEP (Next Space Technologies for Exploration Partnership), with a decision taken on which designs will go on to become flight modules in 2018 or 2019.
The DSG could potentially acclimatise crew for the long durations in space required for deep-space missions, and to develop and test systems for long-duration spaceflight and the conditions distant from Earth. It will be a space station positioned in lunar orbit, around a quarter of a million miles from Earth and well outside the protection of the magnetosphere.
Each of the six companies is developing different concepts for the station. Bigelow, whose 3m-diameter BEAM (Bigelow Expandable Activity Module) chamber is part-way through a two-year trial on the ISS, is developing another expandable structure, known as B330, as a habitat module for the DSG. Projected to be 13.7m long and 6.7m in diameter, the module is a made of a multi-layer material capable of withstanding micrometeorite strikes, and, although designed to be inflated with compressed air, should be regarded as more similar to a steel radial tyre than a balloon.
Sierra Nevada is a space industry veteran, currently working with NASA to develop Dream Chaser, a lifting-body reusable spaceplane concept intended to ferry crew and supplies to the ISS. Like Sierra Nevada, Orbital ATK is basing its concept on features of an existing spacecraft, the Cygnus capsule. “This award allows us to mature plans to develop an Exploration Augmentation Module [EAM] based on the Cygnus product line and a new docking node concept,” said Frank DeMauro, head of human spaceflight systems. “Cygnus modules can be added to increase pressurised volume for the crew and outfitted to increase the associated functionality of the EAM.
Ixion includes satellite and space hardware specialist Nanoracks, which has worked extensively on ISS projects, along with Space Systems/Loral, another satellite builder, and United Launch Alliance (ULA). Ixion is studying the feasibility of converting ULA Centaur rocket upper stages into habitat modules. NASA’s first space station, Skylab, was originally proposed to be made from converted upper stages, and Nanoracks explains this is “more affordable and involves less risk than fabricating modules on the ground and subsequently launching them into orbit.”
Lockheed Martin is developing a multipurpose habitat module that it is converting from an ISS logistics module, a container originally developed to be carried in the Space Shuttle’s cargo bay, explained programme manager Bill Pratt. “These modules were made in Italy, and the one we’re converting for our ground-based prototype never actually flew,” he said.
The prototype module will include ECLSS and avionics systems, included for ‘form-and-fit’ testing, Pratt said. However, he added, Lockheed Martin anticipates that in use, the DSG will use an Orion module, which would always be docked to the station when it is crewed, as a ‘flight deck’ for the station. “It’s rated for deep space, and it has all the necessary functionality, including avionics, communications, a toilet, galley and its own ECLSS that could augment any system on the DSG,” he said.
The DSG will have to use a different internal architecture from the ISS, Pratt said. “We just won’t have the space for the large racks that house equipment in the ISS; most things will have to be on pallets, and ideally reconfigurable.” An example of this might be a shielded area for crew to shelter from the radiation of solar storms. “We don’t want to have a permanent refuge, we’d just want to be able to put one up when it’s needed.” One possibility might be to use the docked Orion’s shelter, he said.
Other radiation such as energetic cosmic rays could be more of a problem, Pratt added. “We really don’t know much about them. We might use the DSG in autonomous mode, with no crew on board, to study them so we can come up with a protective system when crew go on board.”
Boeing is using its experience as prime contractor for the US portions of the ISS and in designing SEP systems, and has unveiled concept designs both for the DSG and a SEP-equipped deep-space transit vehicle. Much of the hardware it is developing uses technology developed for the ion-driven Dawn spacecraft, which visited the asteroid belt last year, and the 702 series of high-power communication satellites.