beowulf in space

Robert G. Brown rgb at phy.duke.edu
Thu Apr 17 08:14:38 EDT 2003


On Wed, 16 Apr 2003, Art Edwards wrote:

> I think I'm jumping into the middle of a conversation here, but our
> branch is the shop through which most of the DoD processor programs are
> managed. For real space applications there are radiation issues like
> total dose hardness and single even upset that require special design
> and, still, special processing. That is, you can't make these parts at
> any foundry (yet). There are currently two hardened foundries through
> which the most tolerant parts  are fabricated. Where the commercial
> market is ~100's of Billions/year, the space electronics industry is
> ~200million/year. So parts are expensive, as Jim Lux says. But more
> importantly, the current state-of-the-art for space processors is
> several generations back. Now, with a 200 million market/year, who is
> going to spend the money to build a new foundry? (anyone?) It's a huge
> problem, and beowulfs in space will not give the economies of scale
> necessary to move us forward. 
> 
> I don't know if this has been discussed here, but have you thought about
> launch costs? They're huge. Weight, power, and mission lifetime are the 
> crucial factors for space. These are the reasons that so much R&D goes
> into space electronics. I apologize if I have gone over old ground.

Actually, this is the sort of thing that makes (as Eray pointed out) the
idea of a cluster (leaving aside the COTS issue, the single-headed
issue, and whether or not it could be a true "beowulf" cluster)
attractive in space applications.  What you (and Gerry) are saying is
that the space and DoD market is stuck using specially engineered,
radiation hard, not-so-bleeding-VLSI processors from what amounts to
several VLSI generations ago.  The parts are expensive, but the cost of
building a newer better foundry for such a small and inelastic market
are prohibitive, so they are the only game in town.

If you have an orbital project or application that needs considerably
more speed than the undoubtedly pedestrian clock of these devices can
provide, you have a HUGE cost barrier to developing a faster processor,
and that barrier is largely out of your (DoD) or Nasa's control -- you
can only ask/hope for an industrial partner to make the investment
required to up the chip generation in hardened technology with the
promise of at least some guaranteed sales.  You also have a known per
kilogram per liter cost for lifting stuff into space, and this is at
least modestly under your own control.  So (presuming an efficiently
parallelizable task) instead of effectively financing a couple of
billion dollars in developing the nextgen hard chips to get a speedup of
ten or so, you can engineer twelve systems based on the current,
relatively cheap chips into a robust and fault tolerant cluster and pay
the known immediate costs of lifting those twelve systems into orbit.

Again presuming that it is for some reason not feasible to simply
establish a link to earth and do the processing here -- an application
for which the latency would be bad, an application that requires
immediate response in a changing environment when downlink
communications may not be robust.

A question that you or Gerry or Jim may or may not be able to answer
(with which Chip started this discussion):  Are there any specific
non-classified instances that you know of where an actual "cluster"
(defined loosely as multiple identical CPUs interconnected with some
sort of communications bus or network and running a specific parallel
numerical task, not e.g.  task-specific processors in several parts of a
military jet) has been engineered, built, and shot into space?

This has been interesting enough that if there are any, I may indeed add
a chapter to the book, if/when I next actually work on it.  I got dem
end of semester blues, at the moment...:-)

  rgb

-- 
Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu




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