🚀 go-pugleaf

Henry Spencer in response to a question from Richard A. Schumacher:
>>Uhhh... why didn't NASA just reuse the Skylab toilet on Shuttle?
>Good question.  I haven't seen a detailed explanation.
> I think the excuse was that the Skylab toilet wasn't suited to use
>by women, because it assumed anatomy that could urinate and
>defecate separately.  This has always struck me as the sort of
>problem a good engineer could solve easily in any of several ways.
  
    Actually, I think the primary reason was because the Skylab
toilet used the old empty Saturn tank to dump the wastes into (like
the Skylab trash disposal did).  On shuttle, you couldn't dump the
wastes overboard without the possibility of contaminating anything
in the payload bay, and you didn't have the large empty tank to use.
(The shuttle dumps waste water overboard, but is very careful about
when and how it dumps the water from the holding tanks).  Also, the
Skylab toilet was rather large and heavy, and on shuttle they tried
to reduce it down into a "closet" size.  The male/female stuff was
something that wasn't that hard to design for (which is obvious if
you look at the design).
   According to some the ECLSS designers I talked with, the reason
the baseline shuttle toilet wasn't suitable for EDO shuttle missions
was
  1) It couldn't hold enough
  2) It didn't work well, anyway  (had a tendency to backup into the
atmosphere, and sounded like a jet turbine loaded with BB's while
running).
  To get the longer duration, the best description I've heard is
that the EDO toilet is a "compactor" which compresses the waste into
"cans" which can be sealed and changed out, whereas the old shuttle
toilet was a "flinger" which would rapidly fill up and couldn't be
changed out.
  
Edward V. Wright writes in response to Allen W. Sherzer:
>>The GAO report concluded that the 'extended duration toilet' costs
>>about ten times more than it needed to because of NASA procurement
>>practices.
> Not only did it cost ten times more than it needed to, it cost ten
>times more than it was budgeted for.  Seems the contractor kept
>tacking on features, and no one at NASA thought to say, "no."  This
>despite the fact that NASA probably has more beancounters than a
>Big Eight accounting firm.
   Actually, from my reading of the GAO report, it states the reason
was that NASA kept making changes to the toilet design without ever
pricing the impact those design changes were making. And from what I
heard, everybody at NASA directed changes constantly.  And then when
the contractor presented the bill for those changes, it was
substantially (!!) over budget.   Again, talking with some ECLSS
designers I know, they confirm this.  For example, NASA tacked on
the new NASA-STD-3000 "Man-machine interface" requirement on the EDO
toilet (which was not imposed on the old one), which required the
subcontractor to find a "5th percentile oriental female" and a "95th
percentile caucasian male" and _verify_ the system worked with
people of those sizes and plumbing.  Another was the infamous
"coffee can".  It's a small receptacle (about the size and shape of
a coffee can) attached to the toilet which uses the toilet vacuum
system to capture small items and hold them.  It was used on the old
toilet to hold "wet wipes" and miscellaneous stuff.  The EDO design
didn't include it since it wasn't required, but the astronaut office
insisted it be put back in (the rumor I heard was the astronauts had
gotten used to using it to hold their toothbrushes) at about a $250
K design change.  I really got my ear bent about these changes...
   Probably the most insightful thing I heard from one designer was:
"Well, if we're modifying something like a hydrazine propulsion
system, we typically don't get a lot of "help" from everybody at
NASA, since they know they aren't an expert on hydrazine propulsion
systems.  But everyone's an expert on going to the bathroom and
using the toilet....."
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 Wales Larrison                          Space Technology Investor

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