Apollo 13

It is 77½ hours into the mission of Apollo 13. A little over 20 hours earlier, the explosion of the number 2 oxygen tank in the Service Module not only cancelled their lunar landing mission to Fra Mauro, but has put the lives of the three astronauts in jeopardy. They are now camped out in the Lunar Module Aquarius that is serving as their lifeboat and the Apollo 13 spacecraft stack is making its only pass of the far side of the Moon. They have done a brief burn using the Descent Propulsion System in the Lunar Module, an engine normally used to land on the Moon. They plan to do a larger burn two hours after their closest approach to the Moon. This PC+2 or 'pericynthion + 2' burn is intended to shorten their return by 10 hours and hence give them a more comfortable reserve of electric power, cooling water and breathing oxygen for the return leg of the mission.

Apollo 13 has disappeared behind the Moon and will be out of radio contact for approximately 25 minutes. It is not known if the crew or the people following them in Mission Control realized that their return trajectory would swing them around the Moon in a manner that puts them the furthest away from Earth than any other manned space mission, a record still to be broken to this day. This is Jim Lovell's second time breaking that record, having done so for the first time in 1968 during Apollo 8 when he was part of the crew that was the first to depart Earth orbit and head for the Moon.

AS13-62-8923 shows Mare Moscoviense as the dark feature. This picture is looking towards the North pole of the Moon, with east to the left. Named for Moscow. Craters around the mare are named for Russian cosmonauts. Prominent is the crater Komarov, named for the cosmonaut Vladimir Komarov (1927-1967) who died during the first test flight of the Soyuz spacecraft.

Lunar surface map showing Mare Moscoviense. It is located on the far side of the Moon around 30° North latitude and 150° East longitude. (NASA/LPI)

The Apollo astronauts are right on time.

The radio signal is not perfect, but workable.

Comm break.

Comm break.

Lovell is observing Mare Smythii on the edge of the near side of the Moon, located roughly about the zero ° latitude (lunar equator) and between 80° and 90° East longitude. It is named for the British astronomer William Henry Smyth (1788-1865).

They are slowly moving away from the Moon, and instead of a flatness that dominates their view, they are already at a distance where the curvature of the lunar surface is evident.

Mare Crisium - the Sea of Crises - is located westwards of Mare Smythii and is on the nearside of the Moon. Its rough location is between 10° and 25° North in latitude and between 50 to 70° East in longitude.

Jim is referring to the 250mm objective they have available for their Hasselblad electric camera carried onboard.

The lunar far side looks very different from the near side because it lacks the huge, dark basalt plains known as maria that characterise the near side. Instead it is dominated by heavily impacted, light-toned highland landscape. One of the most distinctive features therefore is Tsiolkovsky, a 180-km crater with a dark, mare-like floor and impressive light-toned central peak. Being 20° south, it has not been well viewed during earlier missions which have hugged the Moon at only 60 nautical miles (110 km) and stayed close to the equator.

Two photos from Apollo 13 were especially striking, as seen here.

Jim's earlier flight, Apollo 8, did capture good shots of the crater.

In about 15 months, Apollo 15 will pass directly over Tsiolkovsky.

The very dark Crater Tsiolkovsky is located on the far side with its center around 20° South latitude and 127° East longitude. It is named for Konstantin Tsiolkovsky (1857-1935), the Russian physicist and rocket theory pioneer.

It is likely they are referring to the fact that that the cold temperature of the cabin is causing condensation to form on the windows, fogging them up. They have electric heaters that can be used to clear them, but they obviously will not dare to spend any of their battery power to operate them. Each of the heaters consumes as much power 2.5 amps - same as the guidance computer!

Jim recalled his compatriots' photographic enthusiasm later on as well.

Lovell, from Apollo Expeditions to the Moon (NASA SP-350, 1975): "Suddenly, I noticed that Swigert and Haise had their cameras out and were busy photographing the lunar surface. I looked at them incredulously and said, "If we don't make this next maneuver correctly, you won't get your pictures developed!" They said, 'Well, you've been here before and we haven't.' Actually, some of the pictures these tourists took turned out to be very useful."

It sounds like Jim is ushering his crewmates on by suggesting that their unaltered return time of 152 hours GET is unacceptable.

Comm break.

Long comm break.

They are modifying this page of the checklist. Instead of using the fuel quantity as their cue to turn off the fuel pressurization helium, they are using the elapsed time of the burn.

Fred has punched in the power amplifier on the S-Band radio to get a better signal for this important talk.

The PAD is interpreted as follows:
Purpose: This PAD is the final version for a burn of the LM's main engine approximately two hours after pericynthion (their closest approach to the Moon) in order to return them to a specific place on Earth; in this case the Mid-Pacific Landing site or MPL, and to do so faster than would have been the case with just a unmodified free-return trajectory.
Time of ignition (Noun 33): 79 hours, 27 minutes, 38.3 seconds.
Change in velocity (Noun 81), fps (m/s): x, +833.0 (+253.9); y, -50.9 (-15.5); z, -213.9 (-65.2). The change in velocity is resolved into three components which are quoted relative to the LVLH (Local Vertical/Local Horizontal).
H_A, expected apogee of resulting orbit (Noun 42): Not applicable. This burn is to place Apollo 13 on a, Earth-bound trajectory, the apogee of which would be over 9999.9 nautical miles, beyond the limit of the computer's display.
H_P, expected perigee of resulting orbit (Noun 42): 20.5 nautical miles (38.0 km). The perigee distance is so low, it will take the spacecraft well into Earth's atmosphere and thereby, the spacecraft will re-enter.
Delta-V_R: 861.5 fps (262.6 m/s). This is the total resultant change in velocity the spacecraft would experience and is a vector sum of the three components given above.
Burn duration or burn time: 4 minutes, 24 seconds.
Spacecraft attitude: Roll, 272°; Pitch, 81°. The desired spacecraft attitude is measured relative to the alignment of the guidance platform and is therefore set using the FDAI display in its inertial mode. Unlike a CSM PAD, yaw is not stated for the LM. Procedures for a lunar landing allowed the spacecraft to yaw around the thrust axis as required for operational reasons.
CSM mass: 62,480 pounds (28,340 kg). LM mass: 33,452 pounds (15,174 kg).

Additional notes include a so-called 'ullage' burn to settle the propellants at the bottom of their tanks by burning two of their RCS thrusters for ten seconds. The throttle settings that should be used during the burn are; 5 seconds at 10 per cent thrust to give the computer time to sense if the GDA angles ought to be trimmed. The next 21 seconds will be at a 40 per cent setting with the rest at full throttle. Retro expects that this burn should result in a splashdown time of 142:47 GET.

Expected splashdown point (Noun 61): 21.65° south, 165.0° west; in the mid-Pacific. This would later be decremented based on data from the EMS' own accelerometer.
Range to go: 1,163.5 nautical miles (2,154.8 km). To set up their EMS (Entry Monitor System) before re-entry, the crew need to know the expected distance the CM would travel after Entry Interface. This would later be decremented based on the data from the accelerometer.
Expected velocity at Entry Interface: 36,292 fps (11,062 m/s).
Time of Entry Interface: 142 hours, 39 minutes and 22 seconds GET. This is the predicted time at which the spacecraft would be at 400,000 feet (121.92 km) altitude.
GDC align stars: The stars to be used for GDC align purposes are the north set, Deneb and Vega. The align angles are roll, 7°; pitch, 144°; yaw, 68°.

As planned, the previously troublesome S-IVB stage has impacted the Moon and the effect of the impact is being detected by the Apollo 12 seismometer. This is the first time this had been attempted during the Apollo program.

Seismologists usually characterised the Moon's response to these impacts as 'ringing like a bell'.

Nunki is the navigation star 37, also known as Sigma Sagittarii.

Long comm break.

By 'posigrade', the PAO means that the burn will be used to add velocity, instead of slowing them down.

They plan to power down the spacecraft immediately after the PC+2 burn to prepare for the long coast home, using as little of their power and water as posible.

Long comm break.

The Pre Amps warning light indicates an issue with the power supply to the control electronics, but they know the issue and are not worried about it. They simply haven't put the circuit breaker in.

Long comm break.

They have powered up the electronics for receiving the data update on their computer. It contains the state vector as derived by the ground-based tracking - their exact position information.

It is extremely important for Mission Control to get good ranging data at this moment, to ensure that they can support the upcoming burn and make it as accurate as possible to get them home.

Long comm break.

Comm break.

The crew had a procedure read to them earlier on how to pressurize the water tank in the Command Module by using the surge tank oxygen pressure. Mission Control has no way to measure how much water is being used by the crew, and needs the crew to keep them up to date on their drinking so that they can estimate how much water they have left.

80 ounces is about 2.3 litres of water. If this is all the water they've had access to since the accident happened about 22 hours previously, each of them has consumed only 0.7 litres or so, which is very little daily intake for a healthy adult male. It is not known exactly how much they were drinking at this point, but they would soon be suffering from dehydration as a result of drinking too little water out of fear of running out.

Long comm break.

This is 1,563 metres per second. After passing the Moon, the lunar gravity is now slowing them down as it tries to pull them back towards itself.

Long comm break.

The 'flashing 99' being discussed refers to Verb 99 (Enable Engine Ignition) which would be displayed on the DSKY, and requires them to press the Pro button to permit the engine to start under automatic computer control.

Fred's question shows that the poor radio quality is affecting their communication to a degree that misunderstandings are a real possiblity and a danger they have to take into account.

Long comm break.

Very long comm break.

With Jim at his station on the left side of the LM so that the two sets of LPD lines line up, the full Moon appears to be centred on the 14-degree mark, a useful check of their attitude

Brand suggests that to give them a rough reference on whether their attitude is correct, they can look at how the Moon is lined up on the targeting lines on his window.

Long comm break.

To be more specific, Jim named the mountain after his wife, Marilyn Lovell.

This photograph was taken during Apollo 10. It shows the CSM Charlie Brown in lunar orbit as seen from the LM Snoopy. Beyond the CSM in the upper right of this picture is a triangular feature. This is Mount Marilyn and it is 110 kilometres east of the crater Secchi.

Mt Marilyn is located on the Secchi ridge that separates The Sea of Tranquility from the Sea of Fertility, to the southeast. In 2017, the International Astronomical Union (IAU) approved this as the official name of this lunar landmark. They cite AFJ creator W. David Woods' book 'How Apollo Flew to the Moon' as a reference for the naming.

Marilyn Lovell and Mary Haise were present in Mission Control to view the last TV broadcast, just before the accident. They'd just left for home and only learned of it later.

Long comm break.

It's 8:36 pm in Houston. Many astronauts have once again come to Mission Control to be at the center of action for the crucial PC+2 burn. Frank Borman, mentioned here as Jim Lovell's Commander for two of his past missions, would have been working as a special White House representative at the moment, informing President Nixon of the progress of the mission.

At this distance they have to take the speed of light - and their radio waves - into account, besides the speed of human fingers!

Long comm break.

Comm break.

It is a quiet time on the radio, with the crew concentrated on their final actions before the burn. Things that will happen before ignition are the Engine Arm selection, the ullage to settle the propellants in the DPS tanks, and prepare for giving the computer the clearance to fire the engine by pressing the Pro button.

Comm break.

The DPS engine has reached 100 per cent power, delivering 10,500 pounds or 46.7 kilonewtons in thrust. The DPS' ability to have its thrust level smoothly controlled or throttled was unique in the Apollo program - no other engine used during the mission had this capacity. It was a big technical challenge to design an engine capable of having its performance adjusted while in operation. The solution reached was a series of flow constrictors in the fuel injector system that could be used to meter the amount of propellant allowed into the engine to be burnt.

While innovative in design and sufficient for the purposes of the lunar landing mission, the DPS throttle is not withouts its limitations. The allowed engine operation zones are 10 per cent to 60 per cent, and 90 per cent or up, with the levels between 60 and 90 per cent considered to be unusable. At this power level, the engine was known to erode the ablative lining inside the engine nozzle at a higher than acceptable rate, which would result in the engine eventually destroying itself.

What the PAO means is that they can read the Program 40 DSKY displays in Mission Control via the telemetry.

They are about halfway through the 4-minute, 24-second burn and have achieved more than half of their desired 861.5 feet per second [262.6 m/s] Delta-V.

Verb 16, Noun 40 means the DSKY is displaying the velocity still to be gained (hopefully a small and decreasing number) and their accumulated Delta-V, both of which Houston can see via telemetry.

Upon pressing the Pro button again, the DSKY displays the contents of Noun 85. The three numbers in the displays represent the velocity to be gained in each of the three cartesian coordinates. If the reading is negative, it means the engine burn overshot the desired velocity change along that axis. These numbers are known as the residuals. Depending on the situation, further small burns may be made using the spacecraft's RCS thrusters to bring these residuals to zero, which was known as 'nulling the residuals'. In this case, because they are not manoeuvring very close to the Moon, they will leave the residuals alone. The values on the DKSY are +1 fps in X, +0.3 in Y and zero in Z. These are extremely small values, of only centimeters per second.

Jim understands that after the high power use during the PC+2 maneuver, their power load needs to come down so that they can save as much battery charge as possible. Their electric load peaked around 50 amps during the DPS burn, with all the high power equipment running.

Comm break.

Fred's question is another show that precision in terminology can be crucial in their communication.

Long comm break.

Although the crew is ready to proceed, Mission Control is holding back while they ruminate on what to do next.

They have a pre-existing plan for powering down the LM systems, but modifications are made that mostly reflect their current situation and equipment being used. They will not use the VHF and will leave it off as well as the power amplifier, a configuration that they already are using. The interior lights will stay off. They will also not switch their attitude control to 'Direct' which would mean manually firing the RCS jets, but let them remain under the control of the computer for now.

The Contingency Checklist has diagrams of the circuit breaker panels that can be used as a quick reference on how to configure all the 178 breakers to the requested state. They are doing several modifications again however. They want to keep the RCS thrusters and the guidance system powered for the moment.

Fred thinks that since they are not using the Ascent Stage batteries, they should not have the associated ECA control electronics box powered.

These breakers keep the other half of the RCS jets powered.

Power 7 shows the LMP's side of the circuit breaker panels, and its desired configuration.

This will remove power from the radio signal amplifier from the electrical distribution point of view instead of just using the power switch.

Jim removing the inverters from the power bus means that they are turning off the AC power needed by the FDAI 8-ball.

They are reverting back to using the computer screen for their attitude reference by having it display the gimbal angles.

The cabin fan is mostly used for cooling the LM cockpit, and is not crucial, especially when they want to save power and their temperature is already low. It is the suit fans inside the life support system that circulate the cabin air through the lithium hydroxide canister to scrub the atmosphere.

With Mission Control monitoring them via telemetry, Fred thinks they can save that power as well.

Turning off power to the ASA, or the Abort Sensor Assembly, would effectively write it off. Losing temperature control in the ASA will likely either degrade their performance, or disable the system completely.

This maneuver effectively tips them 90 degrees backwards, thinking in terrestrial terms.

They wish to use the computer to maintain their position after their maneuver by configuring for the Digital Autopilot again.

To disable the plus-X RCS thrusters, Brand offers the crew a procedure that works via the computer. To do so, they input Verb 25 Noun 07 (Load Component - Channel/Flag Word Operator) in order to access the computer’s routine for automatic control of the RCS thrusters. By identifying to location of the instruction they want to modify, they are able to set the individual bit that controls the status of the RCS thrusters. Since binary language has only two states, 1 and 0, it is most logical that something like the status of a rocket engine can be indicated by the state of an individual bit, considering such a piece of equipment too only has two states, on or off. For this particular action, they access location 1257 and the 'CH5MASK' routine there.

This is another show of the remarkable nature of the Apollo Guidance Computer, in that the crew could at times be asked to manipulate individual bits in the computer memory to have the desired effect on the operation of the spacecraft.

Brand is reminding Jim that, because he won't be able to use the FDAI (8-ball) to see his attitude, he will need to use the attitude numbers as stored in the computer and displayed on the DSKY. The DSKY has three 5-digit displays for outputting values, based on the fact that in spaceflight, such values often come in threes (e.g. X, Y and Z or roll, pitch and yaw). These register displays are known as R1, R2 and R3.

By 'going in', Fred is referring to programming the computer to not to use the plus-X (downwards-pointing) RCS thrusters for the moment. He mentions masking, too, in reference to the CH5MASK flag in the computer in the procedure that was read up to them a moment earlier.

For most of the time, only one of the crewmembers onboard the LM is wearing a headset hooked up to the radio. They are not all in the loop, as usual, but have to share information among themselves onboard.

Comm break.

Fred is lamenting the brief time they used the AGS so far.

Comm break.

It is 9:30 pm in Houston, which is the time that the crew is using as well. References to terrestial time are relatively rare during the Apollo missions, with the crews living Ground Elapsed Time, rather.

Comm break.

The Ron Howard movie substituted Jim's line here with a "We just put Sir Isaac Newton in the driver's seat," most likely for the more dramatic effect to imply that their journey is now controlled by the laws of physics, rather than their computer.

It is likely that the scriptwriters were looking back at a comment made by Apollo 8's LMP William Anders during their return from the Moon, when he quipped to CapCom Michael Collins that "I think Isaac Newton is doing most of the driving right now."

Fred is referring to Program 37, which is the CSM computer program that will calculate their entry trajectory. The Lunar Module's guidance computer understandably does not have such programming installed.

The craters they are observing are those located near to their planned landing area of Fra Mauro. They would be familiar landmarks for them to spot while coming along their lunar orbit, heading west while coming from behind the Moon. Ptolemaeus is named after the Greek astronomer and polymath Claudius Ptolemaeus (Ptolemy, c. 87-150 CE). Alphonsus is named for Alfonso X of Castile (1221-1284), the Spanish ruler and astronomer. Herschel is named after Sir William Herschel (1738-1822), the German-born British astronomer who is best known for his discovery of Uranus. His sister Caroline and his son John also have lunar craters named after them.

This map shows the intended landing site of Apollo 13 in Fra Mauro as well as the landing sites of Apollo 12 and Apollo 11. This highlights quite well the narrow area on the lunar surface that could be targeted by the Apollo landings.

In the Manned Spacecraft Center in Houston, engineers in various departments and especially at the Crew Systems Division have been working on solving the carbon dioxide issue. Some of the key people involved were Crew Systems Division Chief Ed Smylie, Deputy Chief Jim Correale, and Test Director Jim LeBlanc who each played a key role in the process of creating the famous solution to the 'square peg in the round hole' problem.

Ed Smylie, from 1999 JSC Oral History: "About one o'clock on the 14th, 1am on the 14th, we had realized that we had to do something about CO₂. My first baseline solution, and I think the one that Mission Control was carrying, was to continue to operate the Command Module suit loop thing, had the hoses extended into the Lunar Module to absorb CO₂. That probably would have been a power problem in the Command Module, because we're the ones who shut the Command Module down. I think me and Jim Correale and probably Dick [Richard E.] Mayo concluded that there was a way we could probably use the Command Module canisters in the LM, and our first thought was to use the liquid-cooled garment and the tape, liquid-cooled garment bag, plastic bag and the tape, to tape the Command Module canister on the suit outlet hose in the LM, just blow the air through. That was what we were working towards. Somebody, I'm not sure who, suggested that it would be better to put it on the suit inlet hose because you get warmer air and moister air, which makes the chemical work better. That was a better solution, They said that would suck the bag down against the canister and block the flow, and that's when we came up with the EVA cue card from the Flight Plan to form an arch. So that's what we began to work toward."

Jim LeBlanc, from 2019 correspondence: "Our Deputy Division Chief, Jim Correale had our technician set up two long conference room tables in the Bldg. 7 high bay just adjacent to the 11 ft. chamber. He then had us gather up example of materials the existing (sic) within the Apollo 13 Command Module and LEM and set them up on the tables. These included plastic bags, duct tape, flight data files, etc. While this activity was taking place, I was assigned as the Test Director to perform any test required to verify whatever reconfigured LiOH canister that his team came up with."

Ed Smylie, from 1999 JSC Oral History: "Early that morning I called both Downey and Kennedy and asked for some canisters to be sent so we could test that. We found them at the Cape, chartered an airplane. Grumman chartered an airplane, I guess, or North American did, and flew them up, and we had them that afternoon. I got Art [H.] Hinners, who ran our test division, to begin to set up a test to test that."

Jim LeBlanc, from 2019 correspondence: "I assembled a team experienced in operating the chamber, the support systems as well as the LEM ECS. I prepared a test procedure to operate the LEM ECS at a 5 psia reduced pressure exactly the same pressure as the Apollo 13 spacecraft. We already had a system in place to inject a controlled amount of CO₂ into the 11-foot cabin so we functionally checked all of our chamber and support system as we awaited a modified LiOH canister configuration. Jim Correalle worked tirelessly and came up with the plastic bag, flight data file and duct tape Command Module LiOH canisters. Each astronaut goes through a metabolic calibration on a treadmill prior to flight so that monitoring instrumentation installed on each crewmember, the medical doctors and engineers can determined each crewman’s metabolic rate and also the rate at which each crew member expires CO₂ back into the cabin. With this information we set up our test to inject a CO₂ rate equivalent to the three Apollo 13 crew members. We also had real time cabin gas analyzer that monitored the 11 ft. cabin atmosphere to assess when the canister had to be changed out."

Jim LeBlanc, from 2019 correspondence: "Our testing in the 11 ft. chamber continued so that we could fine tune the change out times in order to maximize each canister usage since the total usage appeared to be very close. I continued as test director for 36 hours straight until Mr. Correale realized I had been there the whole duration of the test and sent me home. The test continued with an Assistant Test Director until I returned and only stopped once Apollo 13 was near reentry into the Earth's atmosphere."

As a bit of extra redundancy, the LiOH cartridges in the PLSS backpacks are compatible with the LM's ARS - Atmospheric Rejuvenation System. Fred is reminding Brand that they could take them out of the PLSS packs and use them on the LM's life support system instead.

Fred's question is a very good one. It was also a major concern for the people involved in designing and testing the canister adapter.

Ed Smylie, from 1999 JSC Oral History: "In the meantime, we began to work procedures. I think Correale and I built one. We began to develop procedures, and we got hold of T.K. [Mattingly]. T.K. was busy doing other things, and he assigned Tony [Anthony W.] England to work with us on developing procedures to send up to the crew on how to build this thing."

It sounds like Jim saw pieces of the foil-like insulation glittering in the sunlight, before they disappeared behind the Moon.

Comm break.

Conventionally, a spacecraft's manoeuvring thrusters are arranged around its centre of mass and their operation has well-understood results. The situation Jim now finds himself in is that he needs to manoeuvre a stack which has a 28-ton mass hanging off one end and such manoeuvres had not been practiced. The centre of mass of the stack is well away from the thrusters and therefore, their operation does not produce the expected result. Jim and Fred are working it together.

They have two ways of changing their attitude, the ACA hand controller and the TTCA hand controller. The latter produces thrust in a way that can alter their trajectory, and they want to be sparing on that. Too much, and they could be off course.

The top of the LMP's console has a bank of caution and warning lights, including those for the Environmental Control System. The ECS light goes on if various parts of the system fails. Now it has lit up due to the increased carbon dioxide level.

There is a separate warning light at the bottom of the right side of the main console. This CO₂ is known as the component light and is designed to light when the amount of carbon dioxide exceeds 7.6 mmHg.

Brand is using the full name of the measurement, 'partial pressure carbon dioxide'.

Jim is referring to the sun visor that is slipped on top of his helmet. His comment could be interpreted that something was placed in or on the LEVA for him to find.

Fred is bidding farewell to their mission objective, now slowly slipping away from them.

The crew is anxious to get the adapter started, but Brand is holding back. They know that while important, it is not something they have to - or should - do in a hurry. The CO₂ situation is not immediately critical.

Comm break.

Comm break.

Comm break.

Comm break.

Comm break.

Long comm break.

Long comm break.

It sounds like Jim is starting to feel his exhaustion after the excitement of the PC+2 burn.

Long comm break.

Comm break.

Comm break.

This is the procedure to program the computer to stop the downwards-facing RCS jets from firing.

Verb 16, Noun 20 brings up the current gimbal angles on the DSKY's three register displays. In this mode, R1 shows the outer gimbal angle, R2 is the inner gimbal angle and R3 is the middle gimbal angle. The angles are displayed to an accuracy of two decimal places.

Jim is concerned about their supply of drinking water and food. The water is a precarious balance between what they are drinking and what the spacecraft’s cooling system requires. Although the Command Module water is not currently being used to cool the LM, Jim is taking into account the possibility that at some point they will have to use the drinking water supply for that purpose. He is loathe to spend too much of it until he knows that they will get back on what they have onboard.

Jim expresses additional worries about the food. He thinks that at their current situation, only the ready to eat and snack-type foods are really suitable for consumption. The rehydratable foods require water to be added before eating, and although they could use part of their drinking water for this purpose and consume that water as part of the meal, reconstituting the food with just cold water would make eating it an unpleasant experience. Even if they had the power to spare to run the water heater, it is located in the Command Module. The Lunar Module has always been designed to cater only cold foods to its crew.

Lovell also mentions 'wet packs' - these were foil-sealed TV-meal type ready to eat portions that were kept in a cold box inside the Command Module and heated in an electric heater before being eaten. He thinks that they are good to eat, but does not elaborate on how they would prepare them without power.

The spoon bowl package was a development on the original freeze dried food bags designed for Apollo. The port on the bottom of the bag was used to introduce hot water into the bag, which was then kneaded and allowed to set for a few minutes. Afterwards the top could be opened and the contents eaten rather conventionally with a spoon, rather than squeezed out. The moisture of the food serves as a natural glue to stick the food into the spoon and stop it from floating into the cabin.

To supplement the other food, some of the provisions were packaged in a ready to eat form. Various foodstuffs were carefully treated - chemically, biologically, even radiologically! - and then sealed in plastic to prevent spoiling at normal room temperature in the cabin. They required no preparation and could be eaten simply by opening the package. The crew usually enjoyed them, due to the texture and flavour being relatively well preserved, compared to the freeze dried food. Still, it is no surprise that a lot of them were confectionaries, such as cake, to make them more palatable.

Jim is likely referring to the Oxygen Purge System (OPS), a unit that was to be attached to the top of a PLSS before an EVA on the lunar surface. The PLSS had its own tank of oxygen to keep a crewman supplied with breathable air during an EVA. But if there were to be a breach in the suit, the OPS could be activated to flood the suit with additional oxygen. If the breach wasn't too large, this could maintain suit pressure while the crew got back into the safety of the LM.

The OPS package contained two storage spheres that held a total of 2.3 kg of oxygen at a pressure of nearly 6,000 psi. This extremely high pressure was likely why Jim referred to the PLSS being a bomb. The PLSS's own oxygen supply also came from a high-pressure tank but this was only at a quarter of the OPS spheres and carried only about a third of the mass of oxygen.

Long comm break.

Comm break.

Comm break.

A situation of confusion exists between the crew and Mission Control over dumping waste water. Mission Control thinks the crew is doing so, while the crew thinks that the order not to dump is a permanent one.

Comm break.

Brand is referring to science astronaut Tony England, who has been supporting the mission, as well as the familiar CapCom astronaut Jack Lousma.

It was important for Lousma to be involved, considering that it was hoped that someone who had built one of the adapters would be the one to tell the crew of Apollo 13 how to build one onboard the Aquarius!

Albeit the LiOH situation is a concern, they still have plenty of capacity left in the LM system before they are forced to switch over to their self-built backup.

It sounds like Fred is observing Earth weather.

This scan from Apollo 13 LM Contingency Checklist shows the amperages of the PGNS components. Turning off the platform and the computer saves them 10 amps, essentially halving their power consumption.

Comm break.

Ptolemaeus and Alphonsus are two large dominant craters near the centre of the Moon's nearside disk. The fact that the crew can see them indicates that they are seeing more of the near side.

Alphonsus is notable because it has three distinctive dark patches around the edge of the crater floor, thought to be volcanic in origin.

Fred is peering around with the AOT, but has been caught with the Command Module blocking his view.

A table produced after the mission shows a listing of the critical LM consumables and their usage during each hour of operation, and the expected time they are to last. These varied according to their present use, of course.

Water and power usage are intimately tied. Improving one will improve the other. Less power consumption means less heat will need to be transmitted out of the spacecraft, which requires water.

The Command Module battery status is of utmost interest to all of them. Their return to Earth is dependent on how much power they have left for use during reentry.

Oxygen is not a crucial item at the moment. The LM has an ample supply, due to the reserve carried for repressurizing the cabin after two lunar surface EVAs. Since this is not to be done, they have plenty of oxygen to last the return home, three people in the LM or not.

Since the crash of Main Bus B was the first sign of the trouble onboard the ship, they are concerned that this half of the power distribution system might be permanently damaged.

This is the first, and only extended description of the accident heard on the air to ground loop. Neither Mission Control nor the crew is eager to dwell.

Jack is wondering whether they plan to perform Earth atmospheric reentry under Command Module Computer control, or with the crew manually guiding them with information derived from the EMS display.

Jack is surprised to hear their chief on the comm loop.

They have a lasting concern that the oxygen being drained to get the water out of the Command Module tank will limit their oxygen supply usable for the Earth landing.

If we assume that the 22 water bags are 8 ounces each, as mentioned before, this makes about 5.2 liters of water currently for the crew to drink.

Joking or not, Jack is not wrong. He is the first CMP to spend a considerable time in the Lunar Module, let alone be command of it. He also makes a reference to the barrel-like shape of the Ascent Engine cover, which served as his station during the times all three crewmembers were in Aquarius.

The comment about the DPS burn was heard on the air to ground loop by reporters, who later asked Flight Director Gene Kranz about it during his post-shift press conference. Kranz claimed that since the burn had been computed with two crewmen in the LM and one in the CM, the Descent Engine gimbals had to compensate for the change in the two spacecraft's center of gravity due to Swigert's presence, to a degree that it was noticeable in the burn telemetry. Upon being asked to speculate why Swigert joined his two crewmates in the LM for the burn, Kranz suggested that "I think the third man just wanted to see what was going on."

It sounds like Jack is wondering about the plan for the Earth re-entry using the Command Module Computer for guidance control. He is wondering how they can get the CM's guidance platform set up properly.

They are removing power from the RCS jet quads as well as the control electronics.

IMU Operate breaker supplies power into the inertial platform. Once they remove that power they will lose their carefully preserved gimbal attitude reference. As a result, with the power out to the IMU, Houston can't see the Coupling Data Unit information. The CDU interfaces between the IMU and the LM computer, and their attitude information is derived from it in Mission Control as well. They've been using this data to determine when to ask them to switch antennas, too, but now it will be up to the crew to do the switching.

This pulls the power from the RCS quad heaters. They leave the IMU heater on to preserve the platform for further use.

To save a little bit of power, they will only leave one comm panel operational.

They have been making sure that the displays are unpowered throughout the emergency phase of the mission, and Jim doesn't want to repeat the whole list.

The 'hardover' mode refers to an emergency mode on the RCS thrusters, where turning the TTCA hand controller to the max position fires the RCS jets. This could damage the units if the RCS quads are not at their normal operational temperatures. A minimum of 15 minutes of RCS heaters running is required.

POWER-8 page of the Contingency checklist gives a rundown on the systems that remain operational during emergency powered down conditions. Their configurations is similar to this except that the VHF radio and the onboard readouts are eliminated - the VHF due to being useless at this range, and the cabin displays since Mission Control is taking care of monitoring the systems via telemetry.

Lousma assures Jim that their plans for a non-computer-guided maneuver are sound.

Comm break.

The LM was launched with one faulty circuit breaker that was left in the closed position, as it was needed.

They plan to keep controlling the RCS heaters with the switches instead of the power circuit breakers.

Jim's concern is not unwarranted. A major symptom of carbon dioxide poisoning is sedation and loss of consciousness. They might fall asleep and not wake up anymore.

Their carbon dioxide levels are usually kept close to zero. They are pushing the limits of safety, but are alright so far.

The top of the LM's console has the displays for the ECS, including the current CO₂ level.

Very long comm break.

For once it's Jack who gets the jokes from Mission Control, instead of Fred.