Sidebar: The Lunar Escape Device

study-for-a-lunar-escape-device

The frontispiece for General Dynamics’ 1964 proposal “Study for a Lunar Escape Device”. Click for a larger view.

The LESS was far from the only suggestion for how Apollo astronauts could rescue themselves from the surface of the Moon—it was merely the best worked out. For example, in 1964 General Dynamics sent a report into NASA entitled “Study of a Lunar Escape Device”.

This was sufficiently far back in the past that the LEM (as it was still called at the time) hadn’t been fully designed yet; in the picture above it’s clearly still the first Grumman design rather than the one finally built. Even so the basic arrangement still held, and General Dynamics hit on the idea that when on the Moon even a wrecked LEM represented the best resource pool for astronauts trying to recover from a survivable crash. This approach also dove-tailed nicely with the major difference between the Apollo missions that would use the LED and the later missions for which the LESS was designed: there was no second lander to carry the escape craft and so it had to fit in the tiny weight allowance of the lander which was to carry the astronauts.

constructing-the-led

The world’s scariest IKEA instructions. How to dismantle a stricken LEM and turn it into an escape craft.

Accordingly, what General Dynamics designed was a kit of necessary extra components which would complement a number of much heavier parts cannibalized from the stricken LEM. Two of the lander’s legs would be removed and turned into a launch cradle. The LEM’s fuel and oxidizer tanks, its pressure tanks, the life support and comms equipment, and even a seat would be reclaimed too. Only support brackets for the tanks and seat, the main engine and small attitude controls, a star tracker, and a control panel would be unique to the rescue craft. Altogether the kit would come in at 49.5 kilograms and take up less than 60 liters of volume (2 cubic feet). General Dynamics’ pride at coming in at less than 0.4% of the entire LEM weight shines through the dry technical language of their proposal. Even once the cannibalized components are included the LED would have rung in at 460 kilograms (including propellant but not counting anyone on-board), which to best of the author’s knowledge makes it the smallest fully functional spaceship ever seriously proposed.

led-one-and-two-man-concepts

Literally flying by the seat of your pants. The crew arrangement for one and two astronauts aboard the LED.

The one-man version perched the astronaut at the end of what can only be described as some kind of high-tech witch’s broom, while the two-man version looks even more precarious. Under those circumstances, the seat was moved forward just enough for the second astronaut to stand behind the seat with his feet in stirrups attached to the bottom of its frame.

While quite clever, the concept suffers from two flaws. For one, it assumes that all the components of the LEM would be available for re-purposing, which seems optimistic when you consider that the LED would only be used if the LEM had crashed; it’s also unclear how the astronauts were supposed to remove two legs from the lander without causing further damage to it.

More subtly, the LED’s designers missed something that North American Rockwell picked up on when designing the LESS. The hard part of escaping from the lunar surface would not have been building a rocket that could do the trick—the Moon’s weak gravity and lack of air lets surprisingly dinky-looking craft make the journey to orbital heights. Rather the problem would be getting the escape craft into close proximity to the Command Module with a vector similar enough to allow the astronauts to transfer over. The later proposal spends many pages discussing how this could be accomplished, while the General Dynamics presentation merely states what the astronauts would need to do and then moves on in silence without discussing how they could possibly do it.

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5 thoughts on “Sidebar: The Lunar Escape Device

  1. I don’t know enough about the normal LM-CSM rendezvous procedure to think about how hard it would be to replicate it with less hardware – and my usual sources don’t go into anything like adequate detail. I’d think that with careful timing of the launch it ought to be possible, though a crashed LM might well mean no surface-to-CSM communication…

    • I think the relevant number here is 1600 m/s, which is the mean orbital speed of the CSM around the Moon. Not only does the LED have to be fired in a way that produces and intersection with the CSM’s orbit, it has to have the same speed and direction to within about ±1 m/s or risk the LED barreling through the rendezvous point too quickly for the astronauts to transfer (unlike the LESS, there was no docking adapter to forgive somewhat higher speeds so long as you hit the CSM’s nose)

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