[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Right-sizing a sat [was: Antennas on the bird]

Robert Oler wrote:

> Absent the really Dark Star (great movie BTW)...

Very much a creature of it's time: bespoke the Vietnam-War era astronautics
experience for some of us: nothing about space could be divorced from the
Gummint and the Forces of Darkness (not to be confused with the Evil Empire
(tm)) And if you liked "Dark Star", "Silent Running" was every bit as grim but
without the humor. "Congratulations! You've decided to clean the elevator!" 

> ...the folks who made the decision that we were going this big in the first 
> place....

Now being a relatve newbie to the scene, I'm speaking from inference, but I get
the impression that P3D got to be as complex as it did *starting* from being a
reasonable upgrade from what AO-10 and AO-13 had been. 

But as the development cycle dragged on, the modular nature of the spacecraft
seemed to invite additions. It looks from here like it wasn't quite so much a
concious decision to "go big" as a gradual accretion of complexity. Now I wasn't
in the scene at the time, so this is inference and archeology rather than
history. ("Elephant: Mouse designed by a committee") Still...it seems to me that
the complexity was reasonably modularized and structured. 

It's been the dickens to get anybody to give us a free ride on a launch vehicle.
These opportunities are rare enough and difficult enough to come by that there
is a natural desire to want to get as much as possible out of each

The other side of that coin is that we end up with a lot riding on each
opportunity, and the bigger the opportunity the more risk there is involved.
This is a trade off: when you place your bet, how much can you afford to lose if
things go sour? And if you win, will you wish you'd bet more in the first place? 

If we could put a sat on-orbit by kicking it out the door of my Cessna at an
altitude of 3 km, the "let a thousand flowers bloom" engineering philosophy
would be a no-brainer. But we can't.

Do we really feel better about the outcome of the picosats launched from OPAL?
Because they were smaller/faster/cheaper/simpler? It's not a guarentee of

I suppose one could argue that P3D sapped resources from these projects and
starved them out. But gee, somewhere along the line they would have gone from
"too small" to "too big"; the "sweet spot" that Goldilocks was looking for is
usually somebody's gut-based judgement call. It's really easy to say "too
big/complex" *after* something has turned up dicey, and the retrospectroscope is
an instrument on *every* sat op's workbench.     

There isn't a "right answer" here. Any spacecraft complex enough to be worth
launching is quite likely to have *something* crap out. The engineering genius
is to design in enough flexibility and redundancy that you can work around what

And while the flight of P3D/AO-40 *has* been a real rollercoaster ride since
launch, in the words of the plague victim from Monty Python's Holy Grail, "I'm
not dead yet! I don't *want* to go on the cart!". I'll take that over "uh, we
know it separated from the launch vehicle, and we think we tracked a beacon for
a while" any day. There's no rollercoster in that. 

I'm still not convinced that the Oscar-40 spacecraft is inherently "too
complex". It *is* true that it is generations more complex than anything done
before. If it zombies-up on us, that will hurt a lot. But I think the very
complexity of the bird has given it an amazing amount of survivability. And if
some of the systems that still appear salvagable *are* eventually comissioned,
the result will be a real asset and a noteworthy accomplishment.  

And all the more so for having been conducted in a fishbowl. Anybody who thinks
there's no politics in engineering hasn't ever really done engineering.

 73 de Maggie K3XS

-----/___.   _)   Margaret Stephanie Leber    / "The art of progress  /
----/(, /|  /| http://voicenet.com/~maggie   / consists of preserving/
---/   / | / |  _   _   _    `  _AOPA 925383/ order amid change and /
--/ ) /  |/  |_(_(_(_/_(_/__(__(/_  FN20hd / change amid order."   /
-/ (_/   '  K3XS  .-/ .-/    ARRL 39280   /___ --A.N.Whitehead ___/
/____ICQ 7161096_(_/_(_/__AMSAT 32844____/ <maggie@voicenet.com>
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org