The Lunar Module earns its legs


Fifty years ago today, SA-204 finally flies



Fifty years ago today, January 22nd, the first lunar module was tested, without a crew aboard, in earth orbit.  We are the crew, we the controllers in the trenches of Mission Control, ushering the Lunar Module LM-1 through it’s paces.  First up, four hours after launch, a test firing of the DPS, the Descent Propulsion System, the engine that will land the vehicle on the moon.  It will fire for 26 seconds at 10 percent thrust and then 7 seconds at full throttle.

“DPS on — 10 percent.”

“We’ve got a [computer] caution.”  Shutdown, shutdown after only four seconds.  We’ve only got a few orbits to figure this out before the LM’s shifting orbit takes it out of communication range of the tracking network, ending the mission in failure.

What has already been a long day is getting longer and hotter.   Launch didn’t occur until 5:48 p.m., after four hours of delays from pad 37B.  There were ghosts aboard the Saturn IB launch vehicle, number 204.  Two-oh-four, a year earlier had sat at Pad 34, a Block One Apollo capsule mounted atop it, the spacecraft in which Grissom, White and Chaffee died.

If the launch helped exorcise those ghosts — and of course it couldn’t — now we’re chasing the ghosts of the Lunar Module’s trouble-plagued history.  LM-1, a developmental craft, does not have windows or its four leg-like landing gear.  We need this first flight of the Lunar Module, unmanned as it is, to prove not just the Descent Propulsion System and the Ascent Propulsion System that will lift it back into orbit.  Part of the flight plan involves a “fire in the hole” test of a landing abort where the descent engine shuts down just as the ascent engine fires to lift the crew module back to a safe orbit.  Such an abort will be needed if something goes wrong during a landed and needs to be tested before astronauts fly aboard the LM.

We quickly figure out why the computer killed the engine burn.  Thrust did not build up to 10 percent in the programmed allowable time.  Due to calculation errors, the time was set too short.

Now we work quickly to devise a work around.  Instead of letting the computer control the burn, we’ll do it through a simple autopilot system.  But we need to be over a tracking station.  And we’re also dealing with com dropouts.

. . . Running out of time, now six hours after launch, finally all is set.  DPS on.  “We are burning.  The rates are good.  We are go.”

Perfect.  Now for the vital “fire in the hole” abort test, just 32 seconds later.  We’ll fire 26 seconds at 10 percent, then just 2 seconds at full throttle.  Then shut down the DPS and fire the APS, Ascent Propulsion System, for 60 seconds.

DPS firing . . .  Shutdown and staging.  APS on.  “It’s solid.  We are go.”

The test comes off perfectly.  The LM has earned its legs.  Indeed the day proves the LM so well that it is deemed ready to carry a human cargo when it next flies.   A second unmanned test, LM-2, is cancelled.   LM-2 now resides in the Smithsonian, dressed up for display to appear like the Apollo 11 lunar module, Eagle.


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