Tailkinker

14th Jun 2009

Apollo 13 (1995)

Question: I've always wondered about one scene in the movie. It happens when Tom Hanks says, "prepare for a little jolt, fellas." We see the astronauts being propelled forward in their seats as the spacecraft accelerates very quickly. But the only time you'd be going forward was if you were riding in a car and the brakes were suddenly slammed on, right? Can someone explain this to me?

Answer: While this did actually happen on Apollo 13 it was completely unexpected, the "get ready for a little jolt" line was made up for the movie. There are retro rockets on the S1-C (first) stage of the Saturn V that are supposed to fire at separation to slow the S1-C and create more separation before the S-2 ignites. The retros fired one second early on this mission so it was before separation and the unexpected reverse thrust is what caused them to get thrown forward. Apparently Jim Lovell even had marks on his helmet from hitting it on the panel when this happened.

Answer: You have to think three-dimensionally. The rocket is travelling upwards under the thrust of the first stage - the moment that thrust cuts off, the only force acting on the ship is gravity, so it's effectively as if the brakes have been slammed on, relatively speaking, as they are no longer moving forwards anywhere near as fast. Then the second-stage engines kick in, propelling them upwards at speed again, pushing them back into their seats.

Tailkinker

24th Nov 2008

Apollo 13 (1995)

Question: When Apollo 13 launches, there is a lot of white stuff that look like shingles (I don't know how else to describe it) that fall off the space craft as it is rising. What is it?

Answer: It's ice that condensed on the side of the rocket. The fuel has to be kept at low temperature, leading to the rocket being extremely cold.

Tailkinker

I get it. The fuel needs to be kept at low temperatures. Otherwise the rocket would overheat, and explode.

The fuel does not have to be kept at low temperatures. The ice "shingles" form on the outside skin of the Saturn V that surrounds the oxidiser tanks. The oxidiser is liquid oxygen, which liquefies at −182.96 °C, cold enough to freeze atmospheric water vapour into ice.

The answer to the question states that the fuel has to be kept at a low temperature.

Then the answer is wrong. The fuel of the Saturn V (kerosene) was kept at ambient temperature whereas the oxidiser (liquid oxygen) was kept at near cryogenic temperatures. Look, this isn't rocket science! No, wait, yes it is.

Then why is the ice there?

It forms the skin of the Saturn V that encloses the oxidiser tanks. The liquid oxygen in the tanks is so cold (−182.96 °C) that atmospheric water freezes into ice and is dislodged when the Saturn V is launched.

Ever noticed a wet can or glass of a cold drink in the summer? That's humidity from the air condensing on the cold surface of the glass. Now imagine if that can or glass were about 300° BELOW 0. That same humidity would condense and freeze. It being Florida in July, very humid, lots of condensation turning to ice. It didn't happen to the Space Shuttle because the tank was covered in that brown foam to insulate it like a styrofoam cooler.

1st Dec 2007

Apollo 13 (1995)

Question: Did anyone play him- or herself in this movie? That seems to be typical for many movies of this kind, but I'm not aware of anyone doing it in Apollo 13 (yes, I know Jim Lovell had a cameo at the end).

Answer: Other than a few individuals who appears in archive footage taken from the era, who could technically be said to be playing themselves, no, there's nobody. Too much time has really passed since the original events for anybody to be convincing as their younger selves.

Tailkinker

Answer: Marilyn Lovell also played herself. She is in the viewing stands clapping.

Marilyn Lovell doesn't play herself, she just has a cameo (the same as Jim Lovell) where she plays on onlooker at the site.

Bishop73

2nd Sep 2005

Apollo 13 (1995)

Question: There's an "abort" dial Tom Hanks looks at once as they are taking off and once when the engine shuts off. What would happen if he turned the abort dial?

Answer: The launch escape system, the 'spike' mounted above the command module, would fire a set of four thrusters designed to pull the command module away from the rest of the launch vehicle. Pitch thrusters fire to move the command module laterally, in order to avoid the possibility of the module being hit by the oncoming launch vehicle, or to prevent the module from landing in a dangerous location in the event of a launchpad fire. Once these thrusters have done their job, the escape system jettisons and the module lands using the onboard parachutes. The above describes what happens when the control is rotated in the counter-clockwise direction indicated by the control's legend. If the control is instead rotated in the clockwise direction then control of the rocket passes from the computers built into the Saturn V rocket (later jettisoned with the stages) to the computers built into the command module proper. This control was never used in an Apollo launch.

Tailkinker

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