So I was, coincidentally, watching Apollo 13 last night. Good stuff. But the final outcome left me with a few questions, which I’m sure you guys can answer.
Their trajectory was low, and came in too steep. However, they lost radio contact with them for much longer than NASA expected. Since their trajectory was shorter than normal, why would they be out of contact longer? Dramatic license?
The one thing that Ron Howard did not show was the cockpit during re-entry, and probably for good reason. It probably got hotter than <insert something Dan Rather would say here>. How hot did it get? 200[sup]o[/sup] F?
The radio black-out is caused by plasma surrounding the spacecraft. If its angle was too steep, its speed would have been high enough to pile up plasma around the capsule for a longer time. In fact, radio blackout lasted a full minute longer than expected.
The heat during reentry was not excessively high, as the heat shielding was not damaged (as had been feared) . . . and remember that, because they were conserving every watt of power, the temperature inside the cabin had dropped to just 3[sup]o[/sup]C.
Interesting, thanks Podkayne. Also, if their trajectory was off enough to alter their re-entry schedule, how were they so accurate as to the landing site? Was there really a ship that close in real life?
The radio blackout is always a variable thing, so I wouldn’t read too much into it. It’s possible that the expected radio blackout time wasn’t altered to account for their trajectory, though I can’t find a reference that says, one way or the other.
They came down within 4 miles of the recovery ship, which is about pretty close. They’re usually within about 20 miles. (On the open ocean, the horizon is a couple of miles away, for compairson.)
Keep in mind that they have no control over the capsule as it decends–it’s basically a rock falling through the atmosphere until the parachutes open–and then it’s a rock with parachutes falling through the atmosphere. So they compute a landing location based on the reentry trajectory and put the boat about where they think it’ll come down. Sometimes it’s closer, sometimes it’s farther away.
As the space program progressed Mission Control was able to calculate, with precision, the target spash down point.
During the Apollo 8 mission, the spacecraft landed only 2.8 miles from the carrier. This prompted Mission Control to send a memo to the Recovery Division asking them to relocate the recovery forces 5-10 miles from the target point to avoid the possibility of the space craft hitting the carrier.
Actually the trajectory was too shallow, not too steep. They had to keep making course corrections because the re-entry angle kept moving towards the shallow end of 2 degree arc (roughly between 5.5 to 7.5 degrees).
Other way around, Munch - the spacecraft’s path was in the “window”, but near the too-close-to-parallel-with-the-ground side. That extended the duration of re-entry (and lengthened the blackout period), although it reduced maximum heat shield temperatures, and led to a slight overshoot of the target point. If the approach had been too shallow, it would have bounced off the atmosphere and been unrecoverable. A too-steep approach would decelerate the spacecraft too quickly and overheat the shields.
I do recall a brief scene in the movie of the frost on the instrument panel melting and dripping on the astronaut’s faces, obscuring their view of the colors of the hot gases outside the windows. The command module had been powered down to save enough power for re-entry control, although they had been partially recharged from the lunar module just prior to its jettisoning.
Sorry to keep hammering this, but I specifically remember a scene in the movie that mentioned that the module was coming in too shallow, and they were going to recompensate. The official said that if they recompensate too much, they’d skip off the atmosphere. I.e. the opposite of shallow = skipping off the atmosphere.
The reason there was a longer blackout period was covered by Podkayne - a steeper angle of entry caused more plasma build-up, which created a longer radio blackout period.
No, too shallow = skipping off, too steep = burning up. For a reference, please watch a DVD of the movie, use the commentary by Jim Lovell, and specifically watch chapter 53. He will explain this quite well. (Or read the book)
The longer blackout was because it took longer to re-enter the atmosphere because the angle was a bit shallow.
Question: Your book, as well as the movie, Apollo 13, both show a delay in re-establishing radio contact with your Apollo 13 crew and mission control after re-entry blackout. Why was there such a long delay, especially when it was only supposed to last 4 or 5 minutes?
Jim Lovell: The blackout period was longer because we entered the atmosphere at the **shallow end of our entry corridor. **
Anyone even remotely interested in the Apollo missions or the early space program would do well to pick up the book Convict quoted from, “Failure Is Not An Option” by Gene Kranz (for you movie buffs, he was played by Ed Harris in the movie).
It is a fun read, and he is a very interesting man. I got the chance to meet him a couple of years ago when he spoke at a conference my company was putting on, and he signed books to my dad, husband, brother and son. He is quite a guy. To hear him walk you through the events of the Apollo 13 mission is mesmerizing.
So they compute a landing location based on the reentry trajectory and put the boat about where they think it’ll come down. Sometimes it’s closer, sometimes it’s farther away.