Tuesday, November 17, 2009

Ten Questions for HSF Committee - Question 6

What are the implications of astronaut servicing of Lagrange point observatories?

The Committee outlines “Flexible Path” Lagrange point destinations where one objective is to service deep space observatories. It may make sense, if we actually do go to the trouble to develop astronaut satellite servicing and repair capabilities again, to do so on a larger scale, rather than to go to such trouble just for 1 or 2 Lagrange point satellites. In fact, if such servicing is productive for Lagrange point satellites, it may very well be more productive for Earth-orbiting satellites of comparable value. Earth-orbiting satellites can be easier to reach, and specific servicing procedures could be applied to lines of identical satellites in Earth orbit.

If satellite servicing capabilities are developed for exploration, will they only be used for exploration, or will they be used for Earth-orbiting satellites, too? Is there a role for NASA to encourage widespread commercial satellite servicing by providing an initial market for this type of service, developing standards, or developing technology? These seem to be important questions. Satellite servicing in the context of NASA exploration could be a way for exploration to deliver major benefits to the nation if it results in widespread use of servicing, upgrade, and repair capabilities on nationally-important satellites, and if it results in a thriving commercial space industry developing the serviceable satellites and performing the servicing.

All of this, of course, depends on satellite servicing and repair capabilities being justifiable in an economic sense. Can we improve upon heritage satellite servicing costs enough to make them commercially viable? Some possible improvements might come through:
  • lower-cost launch
  • lower-cost in-space operations
  • servicing multiple satellites per mission
  • performing other useful work during satellite servicing missions
  • using common servicing techniques on multiple identical satellites
  • using permanent "servicing nodes" rather than repeatedly launching and retrieving the same servicing hardware

I don't know if these or other approaches are enough to make satellite servicing worthwhile, but if we do engage in Lagrange point servicing, it would make sense to consider the capability in a broader light.

Can we do satellite servicing safely enough to apply it to dozens of satellites?

There are many variations on how Lagrange point observatory servicing could be done.

The mindset driving servicing may vary:
  • The servicing could be done as a "box to check" in an exploration path that seeks to go farther from Earth. This mindset places a high value on ground-breaking exploration for its own sake.
  • The servicing could be done with the intention to repeatedly service a number of Lagrange point observatories. This mindset places a high value on the satellite servicing capability and/or the satellites being serviced.

Different servicing concepts could result from the two approaches. For example, a more permanent servicing capability may justify long-duration servicing node(s) that may only be occupied occasionally.

The plan for responsibility for the capability can vary:

  • Servicing may be seen as a strictly government responsibility.
  • Servicing may be seen as a government responsibility that is transferred to commercial space to allow government to explore more.
  • Servicing could include commercial participation from the beginning.

The scope of servicing can vary greatly:

  • Servicing could be limited to Lagrange point satellites.
  • Servicing could be developed for Lagrange point satellites as part of an exploration plan, and then these capabilities could be applied to Earth-orbiting satellites.
  • Servicing could be applied to Earth-orbiting satellites with an eye towards later applying it to Lagrange point satellites as part of the exploration plan.

Serviced Earth-orbiting satellites might be owned by NASA, other government agencies, or private industry.

The specific type of servicing and repair could also vary:

  • Servicing could be limited to satellite inspection.
  • Servicing could include refueling.
  • Servicing could include replacement or upgrade of major components such as instruments.
  • Servicing could be done by robots, astronauts, or combinations of robots and astronauts.

The destinations for the astronauts performing Lagrange point servicing can vary:

  • Astronauts could go to Earth-Moon Lagrange points, and service Earth-Sun Lagrange point satellites there (requiring the satellites to move themselves between Lagrange points, or tugs to move them).
  • Astronauts could go to Earth-Sun Lagrange points to service satellites there.

The diversity of destinations for astronauts would become even richer if the capability is applied to the satellites in various Earth orbits.

If it is done in the first place, a great deal of thought should go into how to develop Lagrange point servicing in such a way that similar capabilities become useful in Earth orbit:

  • If tugs are designed to move Earth-Sun Lagrange point observatories to and from Earth-Moon Lagrange points, would this architecture work well if applied in Earth orbit to move satellites to astronauts in LEO?
  • Would an architecture where the observatories and satellites move themselves work well in Earth orbit?
  • Could a Lagrange point servicing node be duplicated in a useful way in Earth orbit for servicing satellites there?
  • Is there any synergy with the exploration refueling capability described by the Augustine Comittee report and the ability to refuel satellites? If so, is there any synergy with the propellant ISRU capability described by the report and refueled satellites?
  • Could commercial satellite servicing in Earth orbit have any synergy with the ISS commercial crew transport services in most of the report's options?
  • Could exploration vehicles or depots be serviced in a similar manner to satellites?

Many similar questions need to be considered.

It is beyond the scope of the Augustine Committee to fully delve into all of the possibilities and decisions surrounding satellite servicing, but it would be useful for the report to point in a direction that helps start the conversation. We may not be able to get astronauts to Lagrange points any time soon, but we should be able to get them to LEO where they could do servicing sooner. We need to think well in advance of actual servicing missions about making observatories serviceable, too.

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