Spacecraft and cars, Thrifty and efficient vs. wasteful and risky Options

[karolp]

I was just thinking: if we buy an expensive car, we do not use it to drive to one destination and then throw it away. Also, car companies do not develop a brand new car for each new customer. I guess a large portion of the cost involved in each mission (and hence a limiting factor to the number of missions we are able to send there) is not launch or the materials but actually developing the spacecraft itself. We have already started recycling - Stardust and Deep Impact are bound to new destinations and meanwhile ESA sent identical spacecraft to Venus and Mars (MEX and Venus Express). What if instead of dumping scarce funds into starting from scratch each time, we actually reused designs and developed derivatives? Consider the following possibilities:

- sending 2 more MERs to other destinations on Mars, carefully selected based on MRO photos (which did not exist yet when Oppy and Spirit arrived), possibly outfitted with new instruments and protective mechanisms based on what we learnt using the first two :-)
- sending a MER or a Sojourner to Phobos
- adapting the MER design for lunar rover missions
- using existing Mars spacecraft designs for Mars sample return mission

What do you think?

[nprev]

The general idea of mass production/standardization of UMSF hardware has come up here several times before (in fact, I did so myself a couple years back), but the sad fact of the matter is that it really isn't feasible, at least at the top level of design.

Couple of reasons for this:

-Given the rapid evolution of technology, it can become quite difficult and expensive to reprocure many items several years after the fact, esp. for unique design items. I run into this phenomenon all the time in my job; we call it "vanishing vendors". And, frankly, who would have wanted to commit to building a dozen MERs before Spirit proved the design? That's a lot of assumed risk, and remember that budgets for UMSF are always tight as a drum.

-The way the mission selection process seems to work is by filtering down through a sheaf of proposals to (ideally) find new & significant science objectives. Generally, this requires unique payload design attributes, which in turn will affect bus design.

So, given the long lead time for planetary missions & the usual gap of at least several years between same, we're probably never going to see assembly-line production of MERs, for example. All that said, though, there are a lot of components that build on lessons learned and continuously evolve (the phrase usually used is "heritage design").

Mass production seemingly works a lot better for non-exploratory Earth-orbit applications, probably because they're built to perform very specific, well-defined functions. Soyuz is a good example, and a lot of companies manufacture standard spacecraft busses for comsats.

[AndyG]

- sending a MER or a Sojourner to Phobos

A solar-powered rover on Phobos raises some interesting issues.

While the MERs can't go fast enough (by a factor of about 200) to accidently enter Phobos orbit, they might get into serious difficulty with dust kicked up by moving. But they would, at least, be able to jump boulders (well, ones about a foot tall) at the low-gravity end of the moon.

Would planners prefer operations around the poles of near-constant illumination, or would they adopt working cycles to make use of the 230 minute "day"? Or would they send a rover that could keep up with the sunshine - need to go about quarter of the escape velocity (~9km/hr) - to do that?

Andy

[djellison]

Sending lots of MER's doesn't make a lot of sense. THey have a tiny, comparatively, payload and a VERY tough limitation on Landing Sites. I've seen people saying they should be stacking 3 of them together, launching them on Atlas V's etc. I doubt you could find 6 safe, scientifically interesting place to land an MER on Mars.

And VEX was not identical to MEX by a LONG way. Different solar panels, different comms, different MLI, different instruments. It was identical at two levels - the structure and the boxes inside. Mike Caplinger has often said, very wisely, on UMSF that heritage works well at the 'box' level. As an example, flying copies of Pancam would clearly be good, ditto the UHF comms on MER, or the batterys on MER. But as a complete system, MER is totally wrong for Phobos or the Moon.

Doug