A13 SM after explosion

After the explosion on the A13 SM, was the SM able to provide any
water, oxygen, or electricity?

In article ,
says...
After the explosion on the A13 SM, was the SM able to provide any
water, oxygen, or electricity?

Short answer -- no.

All of the SM's electrical power generation capability came from its
three fuel cells, which were powered by hydrogen and oxygen. The fuel
cells also generated all the water that the SM provided. One of the two
oxygen tanks was destroyed when it exploded, and the other developed a
slow leak. It was basically empty about two hours after the accident.
So, after that happened, the SM was unable to provide any of the three
items you mention.

The CM had four batteries that were designed to power it through re-
entry; those provided electricity after the final fuel cell failed, in
the half hour or so before they got the LM powered up fully and were able
to completely shut down the CM. But the SM was unable to provide much of
anything (except to cover the CM's heat shield and keep it from suffering
from thermal effects) for the rest of the mission.

Because of this, all SMs after Apollo 13 carried an extra oxygen tank
that was isolatable from the other two, and also a large battery that
could run the CSM for several hours all by itself. A lot of people
thought that this was overkill, since the original SM design was fine, as
long as you didn't damage an oxygen tank to the extent that it
exploded... but it was done to satisfy people that an Apollo 13-type
accident, even if it were to happen, wouldn't force you to shut down the
CSM. It was more of a political move than an engineering solution.

--

Do not meddle in the affairs of dragons, for | Doug Van Dorn
thou art crunchy and taste good with ketchup |

In article ,
Doug... wrote:
Because of this, all SMs after Apollo 13 carried an extra oxygen tank
that was isolatable from the other two, and also a large battery that
could run the CSM for several hours all by itself.

Not just "several hours", but all the way back to Earth, given drastic
power conservation measures. Essentially, those two additions (plus some
more minor stuff) made it possible for a CSM to survive an Apollo-13-class
accident without help from the LM. Which was highly desirable, given that
the Apollo 13 accident *could* have happened while the LM was on the
surface.

A lot of people
thought that this was overkill, since the original SM design was fine, as
long as you didn't damage an oxygen tank to the extent that it
exploded... It was more of a political move than an engineering solution.

No, it was a sensible engineering solution to a previously unrecognized
vulnerability: with all the fuel cells and tankage in one bay of the SM,
anything violent happening in that bay endangered all of the supposedly
redundant systems simultaneously. The new tank and battery were placed in
the same bay later used for the SIM pallet, on the far side of the SM.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

In article , says...
In article ,
Doug... wrote:
Because of this, all SMs after Apollo 13 carried an extra oxygen tank
that was isolatable from the other two, and also a large battery that
could run the CSM for several hours all by itself.

Not just "several hours", but all the way back to Earth, given drastic
power conservation measures. Essentially, those two additions (plus some
more minor stuff) made it possible for a CSM to survive an Apollo-13-class
accident without help from the LM. Which was highly desirable, given that
the Apollo 13 accident *could* have happened while the LM was on the
surface.

A lot of people
thought that this was overkill, since the original SM design was fine, as
long as you didn't damage an oxygen tank to the extent that it
exploded... It was more of a political move than an engineering solution.

No, it was a sensible engineering solution to a previously unrecognized
vulnerability: with all the fuel cells and tankage in one bay of the SM,
anything violent happening in that bay endangered all of the supposedly
redundant systems simultaneously. The new tank and battery were placed in
the same bay later used for the SIM pallet, on the far side of the SM.

I recall reading a discussion of the initial meetings of accident review
board in which several NASA engineers were insisting that, assuming the
oxygen tanks weren't damaged, there was NO reason to make any engineering
changes to the vehicle, and that the Cortright commission was out of line
in suggesting oxygen tank redesigns or additional tankage, etc. The
resolution was that the engineers were told "You're right, it isn't
strictly necessary, but we need to placate the managers and politicians
who are insisting that we HAVE to make some changes to ensure we could
survive such an accident after the LM is no longer available."

One thing I always wondered about and never saw a good answer for -- once
the SIM bay was incorporated, didn't they have to move, or at least re-
arrange, that service module bay to make room for both the extra oxygen
tank and the big battery AND the SIM itself? In other words, the Apollo
14 SM was the only one left to fly which had a completely empty bay in
which to put the extra tank and battery, and the SIM on later flights
seemed to take up pretty much the entire bay. Where did the extra tank
and battery go on the J-mission SMs?

--

Do not meddle in the affairs of dragons, for | Doug Van Dorn
thou art crunchy and taste good with ketchup |

One thing I always wondered about and never saw a good answer for -- once
the SIM bay was incorporated, didn't they have to move, or at least re-
arrange, that service module bay to make room for both the extra oxygen
tank and the big battery AND the SIM itself? In other words, the Apollo
14 SM was the only one left to fly which had a completely empty bay in
which to put the extra tank and battery, and the SIM on later flights
seemed to take up pretty much the entire bay. Where did the extra tank
and battery go on the J-mission SMs?

--

Do not meddle in the affairs of dragons, for | Doug Van Dorn
thou art crunchy and taste good with ketchup |


I think the empty space was there because the service module was originally
designed to do a powered landing on the moon. Later they went to the LM, but
the SM was never downsized.

changes to ensure we could
survive such an accident after the LM is no longer available."

How did they expect to break from Lunar orbit without the LM, if they could not
fire the SM? Or were they assuming the SM would not again be so badly damaged?

In article ,
says...
changes to ensure we could
survive such an accident after the LM is no longer available."

How did they expect to break from Lunar orbit without the LM, if they could not
fire the SM? Or were they assuming the SM would not again be so badly damaged?

There is no way of knowing whether or not the SM's engine (the SPS) would
have been all right -- some people believe that the engine bell was
damaged by flying "shrapnel" from the door as it blew off, others think
it was just stained by the escaping oxygen. The idea, though, was to
allow all CSM systems to continue to function (including the SPS) after
an Apollo 13-type event.

--

Do not meddle in the affairs of dragons, for | Doug Van Dorn
thou art crunchy and taste good with ketchup |

Doug... wrote:

Because of this, all SMs after Apollo 13 carried an extra oxygen tank
that was isolatable from the other two, and also a large battery that
could run the CSM for several hours all by itself. A lot of people
thought that this was overkill, since the original SM design was fine, as
long as you didn't damage an oxygen tank to the extent that it
exploded... but it was done to satisfy people that an Apollo 13-type
accident, even if it were to happen, wouldn't force you to shut down the
CSM. It was more of a political move than an engineering solution.



Alternately, it was a mistake not to have had it in the first place.
Given the other extreme redundancy measures (like prime and backup
systems of different designs like PNGS and AGS), sticking a battery in
the SM, which had plenty of weight margin and space already, seems like
a no-brainer.

Brett

In article ,
Doug... wrote:
No, it was a sensible engineering solution to a previously unrecognized
vulnerability...

I recall reading a discussion of the initial meetings of accident review
board in which several NASA engineers were insisting that, assuming the
oxygen tanks weren't damaged, there was NO reason to make any engineering
changes to the vehicle...

Yes, there were people insisting that the accident was such a total fluke
that nothing needed to be done. They were both right and wrong: right,
in that *exactly that accident* was unlikely to recur; wrong, in that it
pointed out an area where the system lacked robustness and needed
upgrading.

Organizations, like hardware systems, have characteristic failure modes.
One characteristic failure mode of an organization which tries to
anticipate all possible problems is that they come to believe that they
*have* anticipated all possible problems, and that there is no need to
make their equipment and procedures robust and versatile for better
handling of un-anticipated problems. "Nothing like that can happen, so we
don't need to prepare for it. Uh, well, even though it happened once, it
can't happen again."

...the engineers were told "You're right, it isn't
strictly necessary, but we need to placate the managers and politicians
who are insisting that we HAVE to make some changes to ensure we could
survive such an accident after the LM is no longer available."

While that was true, that doesn't change the fact that it was technically
(not just politically) a good idea.

One thing I always wondered about and never saw a good answer for -- once
the SIM bay was incorporated, didn't they have to move, or at least re-
arrange, that service module bay to make room for both the extra oxygen
tank and the big battery AND the SIM itself?

Nope. The extra tank and battery occupied only a small part of the bay
(at the upper end, if memory serves) -- they were heavy but not bulky.
The SIM pallet was built to fit in the available space: the original bay,
minus that portion.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

In article ,
Brett Buck wrote:
Given the other extreme redundancy measures (like prime and backup
systems of different designs like PNGS and AGS), sticking a battery in
the SM, which had plenty of weight margin and space already, seems like
a no-brainer.

Space, yes, but not mass. In fact, the Apollo flightss typically maxed
out available mass, to the point where the LOI burn usually required
violating at least one official mission constraint at least slightly.
(Later in the flight, things weren't so tight -- early in the flight it
was necessary to carry sizable reserves against the possibility of needing
inefficient abort strategies at some point.)

The later flights could accommodate more equipment not because the system
always had lots of mass margin, but because the Saturn V's performance was
steadily improved.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |