HOUSTON — Internal studies by Ad Astra Rocket Co. propose key propulsion roles for the company’s Variable Specific Impulse Magnetoplasma Rocket (Vasimr) on formative space missions drawing interest from Washington and abroad.
Those missions include the retrieval of a Near Earth Asteroid (NEA) to prepare for future human deep-space exploration and mitigation of the Earth orbital debris threat, as well as commercial initiatives to reboost and refuel Earth-orbiting spacecraft.
Space tugs powered by one of several Vasimr solar electric propulsion (SEP) options, which rely on magnetic containment and directional control of superheated fuels and their thrust, could potentially lower mission costs and advance or sustain operations longer than alternative strategies, according to company presentations prepared for the investor community.
In December, Ad Astra signed a third extension of its 2005 Space Act Agreement withto place the VF-200-1, a prototype of the Vasimr engine, on the International Space Station in early 2016 for its first in flight characterizations. However, a new series of in-house studies are looking at commercial markets well beyond, including regular resupply of a human lunar orbiting base if U.S. policy makers opt to move in that direction.
“We believe it’s a game changer,” Ad Astra President and CEO Franklin Chang-Diaz told Aviation Week Jan. 7. “But obviously, believing is not good enough. We have to demonstrate our capability with experimental results and well-done studies. We’ve started down that path.”
Chang-Diaz, a plasma physicist and formerastronaut, has worked on Vasimr for more than three decades. Since shepherding the initiative from the Massachusetts Institute of Technology and NASA to the private sector in 2005, the seven-time shuttle mission veteran and his colleagues have developed an argon-fueled, 200-kw prototype, the VX-200, which has undergone more than 10,000 test firings in Ad Astra’s suburban Houston vacuum chamber and demonstrated an efficiency exceeding 70%. The company plans to follow work with its first flight prototype on the ISS with an orbiting free-flyer demonstrator, the VF-200-2, near the end of the decade.
Early flight tests would support the concept of a multimission, commercially partnered reusable space tug, with Ad Astra providing the propulsion.
One ambitious venture addresses retrieval of NEA 2008HU4, the focus of an April 2012 study by the Keck Institute for Space Studies (KISS) and a current topic of discussion in space policy circles. Under the scenario, NASA would lead a robotic mission to capture the asteroid and maneuver it into a high lunar orbit, where it would serve as a test bed for future deep space missions, scientific inquiry and prospecting.
The 10-year mission cost was estimated by KISS participants at $2.6 billion in current year dollars, a figure Ad Astra believes it can lower by replacing the KISS study’s SEP strategy that relies on 40-kw Hall thrusters and Xenon as fuel. A range of Vasimr options carry price tags for the mission ranging from $326 million to $614 million by using lighter and less expensive argon or krypton as the fuel and 100- to 400-kw versions of the solar-powered Ad Astra plasma engine.
Characterizations of the VX-200 with krypton as a fuel for greater thrust began in the company’s vacuum chamber last year.
Mission estimates using a Vasimr option range from 1.8 to 4.6 years, according to Ad Astra.
“We are not trying to put anyone down,” insists Chang-Diaz. “We are happy to compete on a level playing field. We are trying to point out we have a high-power engine with enough muscle to carry out these missions.”
A second Ad Astra study envisions the Vasimr tug as an orbiting space cleaner, addressing concerns raised by NASA’s orbital debris program office, as well as the United Nations and others, that space junk levels have reached a critical point. Collisions between existing debris will inevitably spawn more junk unless some of the most menacing rocket bodies and fragments can be deorbited.
The company’s assessment proposes the use of tugs capable of deorbiting 19 large known threats, primarily spent Russian Zenit rocket upper stages. The study envisions use of the 200-kw, argon-fueled version of the Vasimr to achieve multiple plane changes.
The tug would be launched with a tray holding 20 solid rocket motors (SRMs) and a detachable chemical rocket pod (CRP) to control the tug’s close-proximity operations. Under the scenario, the cleaner would rendezvous with its 8-metric-ton Zenit targets at 800 km altitude, where it would release the more maneuverable CRP to capture and return the Zenit hardware to the tug. Once a spent upper stage is secured, the CRP would install one of the SRMs in the Zenit rocket nozzle. The tug would then descend to 400 km, where it would release the SRM-propelled Zenit for a destructive descent into the Pacific.
The low-orbiting tug would also form the nucleus of higher-altitude versions suitable for removal or refueling of communications satellites, another Ad Astra commercial focus.
A congressional emphasis on fiscal “sustainability” as an underpinning for future NASA missions has not been lost on Ad Astra, especially policy discussions over a habitat in lunar orbit, possibly at a lunar Lagrange point (L-1), which at some juncture might serve as the staging base for human expeditions to Mars.