Apr 112015


Today in 1970 at 13:13 CST Apollo 13 was launched from the Kennedy Space Center in Florida. It was the seventh manned mission in the Apollo space program and the third intended to land on the Moon. The lunar landing was aborted after an oxygen tank exploded two days later, crippling the Service Module (SM) upon which the Command Module (CM) depended. Despite great hardship caused by limited power, loss of cabin heat, shortage of potable water, and the critical need to jury-rig the carbon dioxide removal system, the crew returned safely to Earth on April 17. I remember the incident very well. I was a sixth former in England at the time. I, like much of the general public, had largely lost interest in the space program and was not watching the televised programs until the explosion happened (originally believed to be a meteoroid strike). Then I was glued to the screen.


The flight was commanded by James A. Lovell with John L. “Jack” Swigert as Command Module Pilot and Fred W. Haise as Lunar Module Pilot. Swigert was a late replacement for the original CM pilot Ken Mattingly, who was grounded by the flight surgeon after exposure to German measles. Seven days before launch, the backup Lunar Module pilot, Charlie Duke, contracted rubella from one of his children. This exposed both the prime and backup crews, who trained together. Mattingly was found to be the only one of the other five who had not had rubella as a child and thus was not immune. Three days before launch, at the insistence of the flight surgeon, Swigert was moved to the prime crew. Mattingly never contracted rubella, and was assigned after the flight as Command Module pilot to another crew, which later flew Apollo 16, the fifth mission to land on the Moon. By that time I was in university and had lost interest yet again.

The Apollo 13 mission was to explore the Fra Mauro formation, or Fra Mauro highlands, named after the 80-kilometer-diameter Fra Mauro crater located within it. It is a widespread, hilly selenological area thought to be composed of ejecta from the impact that formed Mare Imbrium. The next Apollo mission, Apollo 14, eventually made a successful flight to Fra Mauro.

The mission was launched at the planned time, 02:13:00 PM EST (19:13:00 UTC) on April 11. An anomaly occurred when the second-stage, center (inboard) engine shut down about two minutes early. The four outboard engines and the third-stage engine burned longer to compensate, and the vehicle achieved very close to the planned circular 100 nautical miles (190 km) parking orbit, followed by a normal translunar injection about two hours later.

The crew performed the separation and transposition maneuver to dock the Command Module Odyssey to the Lunar Module (LM) Aquarius, and pulled away from the spent third stage, which ground controllers then sent on a course to impact the Moon in range of a seismometer placed on surface by Apollo 12. They then settled in for the three-day trip to Fra Mauro.


Approaching 56 hours into the mission, Apollo 13 was approximately 205,000 miles (330,000 km) from Earth en route to the Moon. Approximately six and a half minutes after the end of a live TV broadcast from the spacecraft, Haise was in the process of powering down the LM, while Lovell was stowing the TV camera, and Houston flight controllers asked Swigert to turn on the hydrogen and oxygen tank stirring fans in the Service Module, which were designed to mix the cryogenic contents and increase the accuracy of their quantity readings. Almost two minutes later, the astronauts heard a “loud bang,” accompanied by fluctuations in electrical power and firing of the attitude control thrusters. The crew initially thought that a meteoroid might have struck the Lunar Module.

It was later determined that the number-2 oxygen tank, one of two in the Service Module, had exploded. Damaged Teflon insulation on the wires to the stirring fan inside oxygen tank 2 allowed the wires to short-circuit and ignite this insulation. The resulting fire rapidly increased pressure beyond its 1,000-pound-per-square-inch (6.9 MPa) limit and the tank dome failed, filling the fuel cell bay (Sector 4) with rapidly expanding gaseous oxygen and combustion products. The resulting pressure inside the compartment popped the bolts attaching the 13-foot (4.0 m) Sector 4 outer aluminum skin panel, which as it blew off probably caused minor damage to the nearby high-gain S-band antenna used for translunar communications. Communications and telemetry to Earth were lost for 1.8 seconds, until the system automatically corrected by switching the antenna from narrow-band to wide-band mode.

Mechanical shock forced the oxygen valves closed on the number 1 and number 3 fuel cells, leaving them operating for only about three minutes on the oxygen in the feed lines. The shock also either partially ruptured a line from the number 1 oxygen tank, or caused its check or relief valve to leak, causing its contents to leak out into space over the next 130 minutes, entirely depleting the SM’s oxygen supply.

Because the fuel cells generated the Command/Service Module’s electrical power by combining hydrogen and oxygen into water, when oxygen tank 1 ran dry, the remaining fuel cell finally shut down, leaving the craft on the Command Module’s limited-duration battery power and water. The crew was forced to shut down the CM completely to save this for re-entry, and to power up the LM to use as a “lifeboat.” This situation had been suggested during an earlier training simulation, but had not been considered a likely scenario. Without the LM, the accident would certainly have been fatal.


Here is the voice recording of the critical moments. Note the actual words used “Houston we’ve had a problem (repeat message). Not “Houston we have a problem.” The tense is very important. “Had” means it is in the past while “have” means it’s ongoing. Grammar police take note. “Have” is the quote that has survived.


The damage to the Service Module made safe return from a lunar landing impossible, so Lead Flight Director Gene Kranz ordered an abort of the mission. The existing abort plans, first drawn up in 1966, were evaluated; the quickest was a Direct Abort trajectory, which required using the Service Module Propulsion System (SPS) engine to achieve a 6,079-foot-per-second (1,853 m/s) delta-v (change in velocity). Although a successful SPS firing at 60 hours ground elapsed time (GET) would land the crew one day earlier (at 118 hours GET, or 58 hours later), the large delta-v was possible only if the LM were jettisoned first, and since crew survival depended on the LM’s presence during the coast back to Earth, that option was out of the question. An alternative would have been to burn the SPS fuel to depletion, then jettison the Service Module and make a second burn with the LM Descent Propulsion System (DPS) engine. It was desirable to keep the Service Module attached for as long as possible because of the thermal protection it afforded the Command Module’s heat shield. Apollo 13 was close to entering the lunar sphere of influence (at 61 hours GET), which was the break-even point between direct and circumlunar aborts, and the latter allowed more time for evaluation and planning before a major rocket burn. There was also concern about the structural integrity of the Service Module, so mission planners were instructed that the SPS engine would not be used “except as a last-ditch effort.”


[Click for clear, enlarged image. BACK returns you here.]

For these reasons, Kranz chose the alternative circumlunar option, using the Moon’s gravity to return the ship to Earth. Apollo 13 had left its initial free-return trajectory earlier in the mission, as required for the lunar landing at Fra Mauro. Therefore, the first order of business was to re-establish the free-return trajectory with a 30.7-sec. burn of the DPS. The descent engine was used again two hours after pericynthion, the closest approach to the Moon, to speed the return to Earth by 10 hours and move the landing spot from the Indian Ocean to the Pacific Ocean. A more aggressive burn could have been performed at PC+2 by first jettisoning the Service Module, returning the crew in about the same amount of time as a direct abort, but this was deemed unnecessary given the rates at which consumables were being used. The 4-min. 24-sec. burn was so accurate that only two more small course corrections were subsequently needed.


Considerable ingenuity under extreme pressure was required from the crew, flight controllers, and support personnel for the safe return. The developing drama was shown on television. Because electrical power was severely limited, no more live TV broadcasts were made; TV commentators used models and animated footage as illustrations. Low power levels made even voice communications difficult. The Lunar Module consumables were intended to sustain two people for a day and a half, not three people for four days. Oxygen was the least critical consumable because the LM carried enough to repressurize the LM after each surface EVA. Unlike the Command/Service Module (CSM), which was powered by fuel cells that produced water as a byproduct, the LM was powered by silver-zinc batteries, so electrical power and water (used for equipment cooling as well as drinking) were critical consumables. To keep the LM life-support and communication systems operational until re-entry, the LM was powered down to the lowest levels possible. In particular, the LM’s Abort Guidance System was used for most of the coast back to Earth instead of the primary guidance system, as it used less power and water.


Availability of lithium hydroxide (LiOH) for removing carbon dioxide presented a serious problem. The LM’s internal stock of LiOH canisters was not sufficient to support the crew until return, and the remainder was stored in the descent stage, out of reach. The CM had an adequate supply of canisters, but these were incompatible with the LM. Engineers on the ground improvised a way to join the cube-shaped CM canisters to the LM’s cylindrical canister-sockets by drawing air through them with a suit return hose. The astronauts called the jury-rigged device “the mailbox.”


Another problem to be solved for a safe return was accomplishing a complete power-up from scratch of the completely shut-down Command Module, something never intended to be done in-flight. Flight controller John Aaron, with the support of grounded astronaut Mattingly and many engineers and designers, had to invent a new procedure to do this with the ship’s limited power supply and time factor. This was further complicated by the fact that the reduced power levels in the LM caused internal temperatures to drop to as low as 40 °F (4 °C). The unpowered CM got so cold that water began to condense on solid surfaces, causing concern that this might short out electrical systems when it was reactivated. This turned out not to be a problem, partly because of the extensive electrical insulation improvements instituted after the Apollo 1 fire.

The last problem to be solved was how to separate the Lunar Module a safe distance away from the Command Module just before re-entry. The normal procedure was to use the Service Module’s reaction control system (RCS) to pull the CSM away after releasing the LM along with the Command Module’s docking ring, but this RCS was inoperative because of the power failure, and the useless SM would be released before the LM. To solve the problem, Grumman called on the engineering expertise of the University of Toronto. A team of six UT engineers was formed, led by senior scientist Bernard Etkin, to solve the problem in one day. The team concluded that pressurizing the tunnel connecting the Lunar Module to the Command Module just before separation would provide the force necessary to push the two modules a safe distance away from each other just prior to re-entry. The team had 6 hours to compute the pressure required, using slide rules. They needed an accurate calculation, as too high a pressure might damage the hatch and its seal, causing the astronauts to burn up; too low a pressure would fail to provide sufficient separation of the LM. Grumman relayed their calculation to NASA, and from there in turn to the astronauts, who used it successfully.

As Apollo 13 neared Earth, the crew first jettisoned the Service Module, using the LM’s reaction control system to pull themselves a safe distance from it, instead of the normal procedure which used automatic firing of the SM’s RCS. They photographed it for later analysis of the accident’s cause. It was then that the crew were surprised to see for the first time that the entire Sector 4 panel had been blown off. According to the analysts, these pictures also showed the antenna damage and possibly an upward tilt to the fuel cell shelf above the oxygen tank compartment.

Finally, the crew jettisoned the Lunar Module Aquarius using the above procedure worked out at the University of Toronto, leaving the Command Module Odyssey to begin its lone re-entry through the atmosphere. The re-entry on a lunar mission normally was accompanied by about four minutes of typical communications blackout caused by ionization of the air around the Command Module. The blackout in Apollo 13’s reentry lasted six minutes, which was 87 seconds longer than had been expected. The possibility of heat-shield damage from the O2 tank rupture heightened the tension of the blackout period. I don’t think I was as nervous as Houston during that extra two minutes of blackout but probably close as I watched the re-entry live.

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Odyssey regained radio contact and splashed down safely in the South Pacific Ocean, 21°38′24″S 165°21′42″W, southwest of American Samoa and 6.5 km (4.0 mi) from the recovery ship, USS Iwo Jima. The crew was generally in good condition although Haise was suffering from a serious urinary tract infection because of insufficient water intake.


Here’s an excellent documentary about Apollo 13 based on interviews with the main players:


Astronaut food and diet was a problem from the very outset of space flight. There was no previous experience; nobody knew whether the astronauts could eat solid food or liquids in weightlessness or what it would taste like. During early space flights the diet consisted of a small selection of liquids and pastes. The taste of this food left much to be desired.


Of course, very much has changed since then. Today the astronauts’ diet includes hundreds of dishes: soups, served in tubes, canned meat and fish, juices, coffee, tea etc. Some of the space food is dehydrated in a special way. If water is added to such food, its original properties are restored. The use of cargo spacecraft has made it possible to add variety to the diet. Fresh fruit, and vegetables and even mustard are most delicious after dehydrated food and the usual canned foods. I remember at that time there was a craze back on earth for freeze dried ice cream.


Astronauts have four meals a day: first breakfast, second breakfast, lunch and supper. The doctors say this is best for the assimilation of food by the body. The daily consumption in terms of calories is 3,200.


Here is a sample astronaut menu for one day.

Astronaut first breakfast: cold roast pork, mashed potatoes, rich wheat bread, quince sticks and coffee.

Astronaut second breakfast: cheese, ship biscuits and apple juice.

Astronaut lunch: jellied sturgeon, sorrel soup, stewed beef, bread, grape and plum juice, prunes.

Astronaut supper: pork hamburger with egg, cottage cheese with nuts, rye bread, sweets and tea.

The space foods are selected to provide a balanced diet in terms of calories and vitamin content. For quite some time the astronauts could choose only a complete ration. The doctors didn’t permit them to make up menus by themselves. The dieticians feared that personal tastes for certain dishes might result in an unbalanced diet. But finally permission was granted to the astronauts to eat what they liked. Today every member of the spaceship crew chooses what he wants most. It does not take an astro-physician to figure out that you are most content when you are eating what you want under stressful conditions.

After 60 to 80 days in space many astronauts have felt their appetites diminishing and the taste of food changing. This is due to shifts in metabolism and changes occurring in the body. In addition, they get tired of some dishes. Any traveler who has been on tinned food will say the same. Thus, both space and Earth travelers face the same problem. I’ll go along with that.

Living in a hostel in China with no cooking facilities – not even a microwave – I feel for the astronauts. I often eat out, but that can sometimes get to me, and I want a change from the sameness. So, I buy dried and vacuum-packed foods and use the hot water at the hostel to make soups of various sorts, spiced up with Chinese sauces. Here’s today’s breakfast stash . . .


. . . and the resulting noodle soup (quail eggs, spicy pork, noodles, broth, dried veggies, seaweed, and black bean sauce). Pretty tasty . . . and cheap.


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