On March 21st (2014) NASA released a Broad Agency Announcement (BAA) calling for technology concepts and strategies for implementing an Asteroid Redirect Mission (ARM). Visiting an asteroid with human astronaut explorers is the next major goal for NASA’s human exploration program. The agency intends to accomplish this goal sometime in the mid-2020’s.
The Orion spacecraft, under development at Lockheed Martin’s Waterton campus, promises to keep astronauts alive during the ~180 day mission to visit an asteroid. The Space Launch System (SLS) will provide NASA the ideal rocket to send Orion there. So NASA appears to have its ducks in a row for their cornerstone human exploration mission.
Alas, the realities of this mission are far more complicated, and therefore more risky and expensive. Several significant issues must be accounted for, including:
- Orbital dynamics and size-frequency distributions of near-Earth asteroids guarantee a very low probability that any large target can be found and characterized soon enough for an Orion/SLS mission to reach it.
- Smaller asteroids may be more numerous, but they are also more difficult to visit, lack public relations appeal, and may be more diverse in origin and composition than the larger bodies.
- NASA claims an asteroid visit must be accomplished as a stepping stone to their next, ultimate goal for human exploration, sending human explorers to the planet Mars… yet it is unclear exactly how a humans-to-asteroid mission enables the greater goal within the context of NASA budgets and timelines for future exploration.
- Budget pressure at NASA and technical difficulties with the SLS rocket could easily eat into the mission margins, limiting key parameters like the mass or volume of cargo for human explorers - which could limit the length of the mission, the energy available on the mission, or the equipment that can be taken on the mission.
ARM to the rescue!
Partly to address these concerns, NASA announced the ARM mission concept one year ago. The basic idea was simple: if sending an astronaut to an asteroid is difficult and unpredictable, let’s bring the asteroid to the astronaut. ARM will grab an asteroid-like object and park it in a known orbit (i.e. a 71,000 km altitude lunar orbit) where astronauts can visit it whenever NASA can put an Orion/SLS mission together.
Since its unveiling last year, ARM has withered a bit under the close scrutiny of Congress and the scientific community. Naysayers abound, but the dream continues and better ideas have emerged. The new BAA intends to kick the mission into high gear before critics can scuttle it.
The BAA invites industry partners and academia to submit ideas for deployable structures or other spacecraft components that could allow an ARM to capture an small 4-10 meter diameter asteroid or snag a 1-5 meter diameter boulder off a larger one. The specific wording in the BAA states: “This Announcement solicits proposals for system concept studies, technology development activities, and partnership opportunities to support the goals of the Asteroid Initiative.”
Proposers must meet a May 5th deadline. Then NASA will study the submitted ideas for 180 days before issuing an interim report sometime in October or November.
Characterization, the gorilla in the room
The wording of the BAA seems clear and straightforward, yet proposers must still read between the lines in a few places. For example, NASA assumes the asteroid will end up in a lunar orbit, thereby giving assumed preference to low-energy mission profiles for grabbing asteroids already in close proximity to lunar orbit (from an orbital energy perspective). Such mission assumptions may strongly favor a “Mini-Moons” target proposed for ARM last year by Bill Bottke of the Southwest Research Institute and Robert Jedicke of the University of Hawaii.
Other assumptions and interpretations have to do with the characterization issue. NASA’s ARM efforts suffer from a fundamental problem: they won’t know much about the asteroid they intend to snag before they launch an expensive and complex mission to go snag it. The Announcement mentions asteroid characterization as an up-front agency objective but doesn’t include characterization as an ARM precursor. Appendix B of the BAA even states characterization will happen after rendezvous (when it is far too late to abort the mission). Given this mission timeline, will ideas for a characterization precursor mission be accepted?
A useful characterization precursor mission could be the ultra-low-cost Hummingbirds-Charm mission proposed long ago by Golden-based N-Science Corporation. Deep Space Industries recently announced their own intention to conduct a series of “Firefly” missions with similar goals.
Looking toward the future
Another key interpretation in the BAA involves the prominent mention of NASA’s SLS rocket. Since astronauts will visit the retrieved asteroid using the SLS and Orion, the BAA mostly assumes the precursor ARM mission should also use SLS. Yet other options are already possible, and more should be available from vendors like SpaceX by the time ARM launches.
The BAA mentions the potential of “commercial spacecraft design, manufacture, and test capabilities.” Appendix C extends this theme to the launch vehicles, stating the Asteroid Redirect Vehicle must be capable of “being launched on a single launch vehicle, including Atlas V, Delta IVH, Falcon Heavy, or SLS.” This leaves proposers with a dilemma in cases where they need to make assumptions about the launch vehicle. Will generic solutions will be preferred over ones that rely upon a specific launch vehicle?
Appendix C also mentions Solar Electric Propulsion (SEP) prominently, leaving little doubt that the agency’s real intent is to create a SEP “tugboat” with wider capabilities and generic launch capability. Though such a vehicle could prove extremely useful for a wide range of endeavors in space, should initial proposals remain focused on the limited problem of asteroid retrieval? Sometimes too much information leads to more questions.
Likewise, Appendix E mentions exciting but sketchy details about a later Asteroid Redirect Crewed Mission (ARCM). The appendix acknowledges that the ARM vehicle and the ARCM must be compatible in order for the ultimate mission to succeed, so proposers will undoubtedly need more detail on the ARCM.
To address these questions and others, NASA will offer an Asteroid Initiative Opportunities Forum at NASA-HQ on March 26th. This forum will allow potential proposers to ask questions about the mission assumptions and scope.
So… stay tuned. Things are starting to get interesting!
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