The Lunar Landing Training Vehicle was used during the Apollo missions to simulate flying the lunar lander at 1/6th the force of Earth's gravity:

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Many sources have indicated a conflict between astronauts and management about the trainer - with the management deeming it dangerous and trying to get rid of it, and the astronauts wanting to keep it, calling it a vital training device.

It seems that astronauts had to bail out of failing LLTVs more than once - which would certainly cause me to think it's slightly dangerous.

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Stuart Present ejecting from a failing LLTV

However, I've never seen anything which mentions the exact reason the trainer was unreliable - was it simply designed or built too quickly? Was there a vital design flaw? A certain piece of hardware that continually failed?


2 Answers 2


There were 3 LLTV crashes. One was caused by running out of the helium that pressurized the attitude control system, in the second crash the LLTV was flying in more wind than it was designed for, the third was a malfunction in the flight control system, while testing a major modification to the LLTV's computer system.
Like the Harrier, it was rather unforgiving. If the aircraft's attitude goes too far off the horizontal, you end up not having enough thrust in the manauvering thrusters to get it upright again. You basically fall off the thrust column and will crash.
Cernan called it a "very unstable vehicle". So, 3 crashes in a couple hundred flights. It sounds like a lot, but the LLTV was a very experimental vehicle, in a flight regime where any malfunction would lead to a crash. With 3 different causes, I don't see much evidence for bad design or build quality.

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    $\begingroup$ It would be interesting to find out how the LLTV fared in comparison to other hover-type aerial vehicles, like the Harrier, Osprey, and various rotorcraft, especially in their development stages. $\endgroup$
    – Tristan
    Dec 9, 2013 at 16:51
  • $\begingroup$ What does "fall off the thrust column" mean? Does it just mean that you can't re-orient the thrust vector vertical in time to avoid crashing? $\endgroup$
    – ikrase
    Mar 25, 2020 at 2:44
  • $\begingroup$ it's just a manner of speaking. The main engine has limited deflection, on the LLTV the engine was gimbaled IIRC. If the craft's attitude is at a larger angle than the deflection limit plus whatever assistance you can get from the maneuvering thrusters, you're going to crash. I was picturing the LLTV as an unstable object sitting on a vertical stick, and you have to balance the combination by moving the stick around. This is doable as long as the object remains in a certain attitude range, but if it wobbles too much it'll fall off. $\endgroup$
    – Hobbes
    Mar 25, 2020 at 20:25

Only one astronaut ejected from an LLTV--Neil Armstrong, in May 1968; the other two ejections were by training pilots. Armstrong's ejection was caused by a roll to one side late in a flight, when the hydrogen peroxide levels were already low: after a certain degree of roll the pickup port in each saddle tank was now uncovered (low $\text{H}_2\text{O}_2$ level) meaning only high pressure helium came out the thruster nozzles for roll and translation control. He had no control at that point. Armstrong recognized the situation and had ejected before from a fighter so he knew what to do: pull the black-and-yellow strap and leave in a hurry.

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    $\begingroup$ Do you have a reference for this? I mean, it looks great, but it would be nice to know your source. Welcome to Space Exploration :) $\endgroup$
    – kim holder
    May 7, 2015 at 22:44
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    $\begingroup$ Will totally upvote this if you provide a reference, or convince me you were there . . . $\endgroup$ May 8, 2015 at 4:40

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