As anyone who's seen the movies The Right Stuff and Apollo 13 knows, a spacecraft must reenter Earth's atmosphere at a precise angle to avoid burning up or skipping back out into space. Well before the space program, astronomers were aware that meteorites burned up when they fell into our atmosphere.
The astronauts and mission control were faced with enormous logistical problems in stabilizing the spacecraft and its oxygen supply, as well as running on batteries due to the loss of the fuel cells to allow successful reentry into Earth's atmosphere.
Because they were a little shallow on their re-entry angle, so took a longer flight path into the atmosphere.
With the electrical systems turned off, the temperature approached about 34 degrees Fahrenheit prior to entering the atmosphere.
They must plan to hit the atmosphere at the precise angle and speed for a safe landing. If they hit too steeply or too fast, they risk making a big “splash,” which would mean a fiery end. If their impact is too shallow, they may literally skip off the atmosphere and back into the cold of space.
If they skipped out the first time, they would reencounter Earth's atmosphere on the next pass, since orbits are closed, and enter a final time. That would eliminate the possibility of a lunar gravity assist (which might result in an escape), since the moon wouldn't be there on the next orbit.
Due to a shallower re-entry path, Apollo 13's blackout was calculated to last about 4.5 minutes. Flight director Gene Kranz's logs show that it took about 6 minutes to re-establish contact with Apollo 13. Telemetry was usually the first signal received after the blackout.
You're inside the air that's being ripped apart as you're re-entering the atmosphere. Very little feeling, no shaking, no vibration, but you just see the heat that's being generated by the space shuttle entering the atmosphere.
During re-entry, the shuttle is going so fast, it compresses the air ahead of it. The compression of the air layers near the leading edges of the shuttle is quick, causing the temperature of the air to rise to as high as 3000 degrees Fahrenheit!
It is heavy when it takes off, but during the landing, having used up most of its fuel, it is low density and so slows down much higher in the atmosphere than the Space Shuttle. As a result, it will reach lower temperatures than the Space Shuttle on re-entry though higher than a supersonic jet at Mach 3.
The command module was dying, quickly. But the lunar lander, docked to the command module, was intact. Under the direction of Glynn Lunney, the flight director whose shift followed Mr. Kranz's, the Apollo 13 astronauts scrambled into the lunar module, which served as their lifeboat.
Spacecraft reentry
The ionized air interferes with radio signals. For the Mercury, Gemini, and Apollo spacecraft, such communications blackouts lasted for several minutes. Gemini 2, for example, endured such a blackout for four minutes, beginning at 9 minutes 5 seconds into the descent.
Apollo 13 presently 4,075 nautical miles out from Earth. Velocity now showing 24,619 feet per second. We're less than 27 minutes now from time of entry into the Earth's atmosphere. With less than half an hour to go, they are now at 7,547 km away and speeding in at 7,504 m/s.
When astronauts come back to earth, their otolith organs need to readjust to the force of gravity, which can take a few days. In the meantime, they may experience balance issues and problems with coordination.
The Apollo 13 malfunction was caused by an explosion and rupture of oxygen tank no. 2 in the service module. The explosion ruptured a line or damaged a valve in the no. 1 oxygen tank, causing it to lose oxygen rapidly.
It's the story of the engine that brought those astronauts home, and the chemist who invented it. On April 13, 1970, Gerard Elverum's pintle injector rocket engine fired for 34 seconds to put the damaged Apollo 13 spacecraft on a safe path back to Earth.
Re-entry is a technologically challenging thing to survive, and even the smallest problem can escalate quickly, as the Columbia disaster taught us only too well. The main source of the problems with re-entry is that if you're orbiting the earth, you're going extremely fast.
“The Shuttle used ceramic tiles to reradiate heat outwards, with a layer of insulation between the tiles and the vehicle,” says Anderson. The two principle factors that ensure a spacecraft can safely traverse the reentry corridor are the shape of the vehicle and its angle of reentry.
The atmosphere starts to make noise. You can hear that rumble outside the vehicle, and as the vehicle tries to control, you feel that little bit of shimmy in your body. And our bodies were much better attuned to the environment, so we could feel those small rolls, pitches, and yaws.
In space, there is no gravity to pull things straight down, so the gas and liquids in the astronauts' stomachs don't seperate. This means the gas can't come back up to create a burp! Or, at least, a burp like we would known on Earth.
Did You Know? Astronauts need to sleep next to a ventilator fan while they're in weightless orbit; otherwise, they might suffocate in their sleep.
Back pain is highly prevalent in astronauts and space travelers, with most cases being transient and self-limiting (space adaptation back pain). Pathophysiologic changes that affect the spine occur during space travel and may be attributed to microgravity, rapid acceleration and deceleration, and increased radiation.
3.5 Apollo 13
During the second period, the Commander, Command Module Pilot, and Lunar Module Pilot slept 5, 6, and 9 hours, respectively. The third sleep period was scheduled for 61 hours, but the orygen tank incident at 56 hours precluded sleep by any of the crew until approximately 80 hours.
An explosion 56 hours into the mission happened before the command module and lunar module had separated, so the crew were able to use the intact lunar module as a lifeboat with its own power sources, rockets and oxygen supply.
The command module, with the astronauts inside, continued onward, entered Earth's atmosphere, and splashed down on target on April 17 at 1:07 pm Eastern Standard Time, 142 hours 54 minutes 41 seconds from the time the huge Saturn V had roared to life. The astronauts had no lasting ill effects from their ordeal.