Apollo 13 "Houston, we're got a problem."

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(Below left) Aquarius points the way to distant Earth. The visible
rocket nozzle is part of the Aquarius Reaction Control System.

(Above right) Flight controllers view prototype of the "do-it-yourself" lithium hydroxide unit that Apollo 13 astronauts constructed following directions from the ground. The apparatus enabled Aquarius to utilize lithium hydroxide canisters from the crippled Odyssey.

Time was at hand for the burn. two hours after closest approach to the Moon. The descent engine would fire five seconds at 10 percent throttle, 21 seconds at 40 percent, and nearly four minutes at full blast.

This burn would add 585 miles per hour to the velocity of the spacecraft, bringing it to Earth 10 hours sooner, and would make the target for splashdown a spot in the Pacific Ocean south of American Samoa. The carrier Iwo Jima already was enroute to that pin-pointed spot.

CAPCOM--Three minutes--counting down ...Mark...

SC--We're burning 40 percent...

CAPCOM--Looking good at two minutes.

SC--Two minutes, Roger...

CAPCOM--Aquarius you're go at three minutes...

SC--Shutdown. CAPCOM--I say that was a good burn.

SC--Now we want to power down as soon as possible.

CAPCOM--We have a procedure ready...

Aquarius had been designed as a two-man spacecraft and, in the original flight plan, would have been used less than 60 hours. Could her consumables--oxygen, water, batteries--be stretched to keep three men alive nearly 90 hours, from the loss of CSM power the evening before, to just before reentry two and a half days ahead ?

After some early false alarms, the outlook by Wednesday morning was reassuring. Plenty of drinking water could be brought Plenty of drinking water could be brought over from the Command Module. Oxygen stores showed a margin of 95 hours. With power kept up only on the life-support, telemetry, and communications equipment, except during critical maneuvers, cooling water would last 23 hours beyond reentry, batteries 60 hours--ample to recharge the Command Module's batteries before separation.

One item could be a problem: the cartridges of lithium hydroxide that remove carbon dioxide from the spacecraft atmosphere. The LM'S cartridges would last only 50 hours, and the CM'S wouldn't fit the LM.

Bob Smylie and Jim Correale, of the Crew Systems Division at Houston, devised a makeshift adapter, and Astronaut Tony England tested the design by putting one together from oral instructions alone. As Mission Control voiced these up to Aquarius, Swigert and Lovell built adapters using cardboard cue cards from unneeded lunar surface procedures, plastic storage bags, and adhesive tape to attach cartridges from the CM to LM hoses that sucked cabin air through them.

CAPCOM--The next step is to cut a diagonal hole...

SC--Okay, our do-it yourself lithium hydroxide unit is complete.

Earth stations continued to track the spacecraft. Within four hours after the big burn, just this side of the Moon, their data was showing that because the automatic guidance system had drifted out of alignment, the resuits hadn't been as precise as first thought.