writes:

I was just watching the DVD of Apollo 17. During launch, I heard Gene
Cernan tell the other two guys to get ready for staging and to hold
on. shortly after, Evans and/or Schmidt was saying how rough the
event was.

How violent was it, really? Was it shown accurately in the movie
Apollo 13? Did they really get thrown out of the seat then slammed
back into it?

We can reason it out, given that the couches have to be holding
the astronauts pretty much like a mass on a spring in equilibrium and
we know shortly before engine cutoff the force is about four times the
force of gravity on the surface of the earth, which is rather abruptly
reduced. But the direct experience is probably more convincing. From
Frank Borman, describing Apollo 8:
http://history.nasa.gov/ap08fj/01launch_ascent.htm
[Borman, from the 1969 Technical Debrief - "The
S-IC/S-II separation was nominal; the crew was thrown forward
in their seat, as you would expect in a staging. Then the g
load was shifted from 4 to about 1. Consequently, you noticed
the change in thrust quite distinctly.]

And from David Scott in Apollo 15:
http://www.hq.nasa.gov/office/pao/Hi...arth_orbit.htm

[Scott, from the 1971 Technical Debrief - "The staging
was as we expected, I guess. It was what I'd call violent when
the S-IC shuts down and everything recoils there, and that was
almost identical to Apollo 9. It was really just a big bang. We
saw the fireball come up to the BPC [Boost Protective Cover];
I saw it in my left side window. I saw the fireball out the
front window, too."]

... though there's room for different expectations:

[Worden, from the 1971 Technical Debrief - "After being
briefed several times of what to expect at separation, it didn't
seem as violent as I was really expecting it to be."]

[Scott, from the 1971 Technical Debrief - [speaking to
Worden] "Which one?"]

[Worden, from the 1971 Technical Debrief - "The first
one."]

[Scott, from the 1971 Technical Debrief - "I thought
you agreed that it was pretty violent."]

[Worden, from the 1971 Technical Debrief - "It was pretty
violent, but I guess I was expecting something even more than
that."]

[Irwin, from the 1971 Technical Debrief - [speaking to
Scott] "You had us so well briefed, Dave, that we were expecting
it."]


For the other staging event:
[Scott, from the 1971 Technical Debrief - "The S-II to
S-IVB staging was about a quarter to a fifth the force of the
S-IC staging. It was again a positive kind of feeling, but it
wasn't a violent crash like we felt on the S-IC; I didn't think.
We had the same light 10- to 12-cps vibration on the S-IVB all
the way into orbit. The shutdown was smooth. All the sequences
throughout the launch were nominal and as expected. All the
lights worked good; controls and displays were good; comfortable."]

[Irwin, from the 1971 Technical Debrief - "The noise
and the vibration were less than I was expecting; it was much
less. I was impressed about the lateral vibration on launch. It
was much greater on the S-IC than it was on the S-II. Just a
shaking, back and forth, lateral vibration all the way through
the launch. It was a pretty smooth ride."]


--
Joseph Nebus
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