Apollo 13

Strange noises in the Descent Stage and battery alarms have been the woe of the crew of Apollo 13 for the past few hours. Now over 100 hours into their mission, another 40 hours in space remain until they are to splash down onto the Pacific Ocean. They have also been provided with instructions on how to perform a mostly manually controlled course correction burn using the AGS backup guidance system and visual references by looking out of the LM window. Plans also exist for charging the somewhat depleted CM reentry batteries from LM power using the cables that would normally supply power from the CM into the LM. Their stores of power, oxygen and water are still Go, but subject to careful rationing. Another worry is the constantly dropping temperature, not only uncomfortable to the crew, but a potential threat to their equipment.

Comm break.

Jack has been mostly unoccupied since the accident, considering he has little expertise in the LM systems or its operation. His workload is about to increase considerably now that the return to the Command Module approaches.

The original procedure is provided from the links below as available. What they want to do is to switch on the Command Module batteries and power up some of the onboard system to see how they have survived since the Command Module was powered down after the accident. This will give everyone involved information on what kind of procedures might be needed for their reentry if there is evidence of the systems degrading from the cold temperature.

The LMP's side of the cabin has several circuit breaker panels that Jack is now about to use to get power from the batteries and into the systems onboard the dormant Odyssey. You can view a version with the panels annotated for clarity from this link.

Jack's first step is to work the LMP's side console in the Command Module and close circuit breakers that supply power into the various sensors in the main systems that they want to check out here. They will also prepare the inverters for producing the AC power required by the telemetry sensors .

The next step starts up the Command Module's communication system and configures it to produce a high power signal for the purpose of transmitting telemetry to Mission Control. They will use the Omni D antenna for this.

Next they close circuit breakers that provide power to the aforementioned communications equipment, as well as the CTE - Central Timing Equipment. The CTE provides timing reference used by many of the onboard systems to synchronize them. While the Command Module Computer usually provides the basic timing reference, the CTE has its own crystal-based oscillator - not unlike a quartz clock - to provide this function when the computer is not available. This separate panel is under the Main Display Console.

Panel 250 connects the Command Module batteries to the power distribution system. Now they're connecting Battery C in.

These switches are used to connect both the battery and Power Inverter 2 to Main Bus B.

After pushing in the breaker on Panel 250 to connect Battery B into the system, they will then power the AC Inverter number 2 from Main Bus B, and connect Inverter 2 to AC Bus 1 to provide AC power for the telemetry sensors.

Jack appeared to assume at first that he will perform the procedure with power being transferred from the LM. A procedure for that was read up earlier to him. This is not the case for now, with the plan to only use internal battery power in the CM for the purpose.

The comms configuration they plan to use only involves the telemetry system to transmit data to Mission Control, no voice radio.

They configure the LM comms mostly to the low power mode they've been using throughout the emergency phase of the mission.

Comm break.

Jim is wondering how to stabilize the ship per the earlier instructions. The visual reference available to him for the procedure is the 8-ball, and it doesn't have the same precision as the computer DSKY would have.

Very long comm break.

The orders are to basically just wait and see, which Jim isn't perfectly happy with.

Comm break.

Jack is unable to verify the Main Bus B voltage from the onboard display, and they go on checking their configuration to make sure that they have actually enabled it.

Comm break.

They are finally receiving the much wanted data from the Command Module.

Comm break.

Very long comm break.

Now back in Earth's sphere of influence, the PAO announcements are made in relation to the distance from Earth. Right now it stands at 296,933 km and their velocity is picking up at 1,309 m/s.

The values Jack reads out can be interpreted as below. The RCS temperatures and the battery manifold pressure are read out from the Systems Test Meter.

Battery C voltage - 37 volts - normal.

Pyro battery A and B - 37 volts - normal

SPS helium pressure - 3,450 psi - this is the helium used to pressurize the SPS tanks, and is normal.

Nitrogen A - 2,300 / Nitrogen B - 2,400 psia - high-pressure nitrogen gas is used to operate valves in the SPS engine. This pressure is normal as well.

Command Module RCS injector temperatures - these range from +30°F to +42°F - or -1.1°C to +5.6°C. They are cold, but have internal heaters that can be used to warm them up before use, hence this is not a critical issue.

Battery manifold pressure - 5.60 psia - pressure in the line that is used to vent the batteries if they produce gas - like the LM batteries have done during the mission.

The majority of the readings are drawn from the telemetry, of course, rather than the onboard displays.

The crew's basic onboard clothing consists of the Constant Wear Garment - a cotton full body underwear, as well as the flight coveralls made of Teflon fabric. Neither provides a lot of comfort against the cold temperatures being experienced onboard the two spacecraft at the moment.

Lovell, from 1970 Technical debrief: "I don't know how to discuss the clothing and related equipment. Obviously, the inflight coveralls we had weren't adequate for the conditions we had. The coveralls are great for a nominal mission. I hate to imply that we should carry liners or something like that with us. I sure think we can improve the footwear, though. I know that Grumman, down at the Cape, has for their checkout people a soft boot that is worn in the LM. An insulated soft boot would have been much more adequate than what we had."

Haise, from 1970 Technical debrief: "With the addition of probably just one set of Nomex thermals, we'd have been in good shape. We needed a set of thermal underwear on."

Slayton, from 1970 Technical debrief: "What did you end up wearing?"

Lovell, from 1970 Technical debrief: "Constant wear garments."

Haise, from 1970 Technical debrief: "Two constant wear garments."

Long comm break.

Very long comm break.

Very long comm break.

Battery 2 has rallied, despite the earlier issues with it. The exact cause of the problems is still unknown both to the crew and to Mission Control.

Long comm break.

This PAD was for the situation that radio contact was lost and the crew would have to perform the burn solo without ground assistance - which is the essence of a PAD, anyway.

Long comm break.

This tantalizing conversation suggests that something was hidden in the LM food locker that the crew has discovered. It is not elaborated on, however. It is possible that the hidden item in question was a number of gifts from Marilyn Lovell and Mary Haise to their moonlanding husbands. It is known that something of the sort was found onboard, but we're not exactly sure what.

Very long comm break.

The Service Module RCS quads have a minimum operational temperature rated at 55°F (12.8°C). Since they will not be used, the low temperature in at least one of the quads is not an issue. The range of temperatures is more indicative of the state of their Passive Thermal Control, and is determined by how much direct sunlight each part of the Service Module might be receiving at the time.

The Command Module RCS engine fuel injectors have a minimum operational temperature rated at 28°F (-2.2°C). This only applies to a dormant system, however, and by activating the RCS heaters later on, they will be able to bring them up to a more comfortable operational temperature.

The Command Module has its own RCS jets for attitude control after SM separation. They are embedded in the structure of the ship and consist of a simple design of a fuel and oxidizer injector as well as a burn chamber with an ablative lining to prevent it from melting. The jets are helium-pressurized and use the same hypergolic propellants as the SPS engine and the SM RCS.

The Apollo heatshield is constructed of a stainless steel plate onto which a fibreglass honeycomb is bonded. Each of the 370,000 cells in the lattice are filled with the Avco ablative resin from heated caulking guns. The shield is then cured in an enormous oven to harden the material. The whole heat shield is then X-rayed to detect any defects in its construction. The final product is filed and sanded to shape and thickness.

The ablative heat shield has four temperature sensors installed. The safe range of operational temperature has been determined to be between -150°F (-101°C) and + 200°F (93°C).

Very long comm break.