Did the LEM only use RCS during the Ascent?

[gta-man]

After looking at this photo and the LEM specifications, I only see a really tiny engine cover on the ascent stage of the LEM.

https://en.wikipedia.org/wiki/Apollo_Lunar_Module#Ascent_stage

Did it only use RCS?

Thanks.

Edited July 20, 2013 by gta-man

[Nikolai]

No, it had an engine.

http://en.wikipedia.org/wiki/Ascent_Propulsion_System

[brooksy125]

No it had a small solid fuel engine if I remember correctly.

[deadshot462]

It had a small engine. Also cool fact - the fuel was picked in a manner than no "sparkplug" was required, the simple combination of two chemicals would instantly ignite the fuel, to avoid engine ignition failure.

[DragonRoco]

And the engine didn't use pumps but used helium to force the fuel out of the tanks. That was just to make the engine simpler.

You can just see the engine bell in this photo: https://en.wikipedia.org/wiki/File:Apollo_17_LM_Ascent_Stage.jpg

[stupid_chris]

It had a small engine. Also cool fact - the fuel was picked in a manner than no "sparkplug" was required, the simple combination of two chemicals would instantly ignite the fuel, to avoid engine ignition failure.

Indeed, the joy of hypergolics.

[PakledHostage]

After looking at this photo and the LEM specifications, I only see a really tiny engine cover on the ascent stage of the LEM. Did it only use RCS?

There's a good description of the lunar module's ascent stage at Robert Braeunig's braenig.us website. He did a numerical simulation of the ascent of Apollo 17's Challenger module from the lunar surface and compared his results to the actual NASA data. He estimates that Challenger had an attainable delta-V of 1985 m/s but used only 1868 m/s.

[philly_idle]

Yes it had an engine that used hypergolic propellants. I heard the propellants were so corrosive they couldn't test the actual flight engine on the ground and the engineers had a good time up until they ascended back to the Service Module

[Pulstar]

Man those RCS thrusters are huge, and here I was thinking the ones in KSP are a bit too big on small landers.

[Nibb31]

As you can see on the diagram, there was an ascent engine cover that protruded inside the cabin, so that the nozzle came flush with the top of the descent stage. This is why you don't see it underneath the LM on the video. The cover could actually be removed so that they could attempt to fix it or bang on things if it failed to start.

The ascent stage engine was primarily designed to be robust, with as less moving parts as possible, which is why they use hypergolics and helium instead of mechanical pumps, because it was the only engine in the Apollo-Saturn vehicle that would cause an unrecoverable loss of crew if it failed to fire.

[Brotoro]

The service module propulsion system would also lead to loss of the crew if it failed to fire for Trans-Earth Injection.

[PakledHostage]

I think nibb's point is that it would lead to loss of the crew if it failed to fire the first time. The service module's engine would have already been fired several times prior to TEI. If it had failed to ignite the first time, they'd still have had alternatives.

And I recall reading somewhere that they could even manually control the fuel valves from within the ascent stage if they had to.

[Brotoro]

The fact that your service module propulsion system already worked to do mid course corrections and Lunar Orbit Insertion would not make you any happier about it not working when it comes time for Trans-Earth Injection.

Yes...they could start the LM ascent engine by manually opening the valves.

[Flixxbeatz]

Man those RCS thrusters are huge, and here I was thinking the ones in KSP are a bit too big on small landers.

I think that's where they've got the design for the Yawmaster 2500 RCS block.

[PakledHostage]

The fact that your service module propulsion system already worked to do mid course corrections and Lunar Orbit Insertion would not make you any happier about it not working when it comes time for Trans-Earth Injection.

No, I guess it wouldn't... But it would give me (and I am sure many others) more confidence knowing it had worked once already. That, ultimately, is the point.

[magnemoe]

Yes it had an engine that used hypergolic propellants. I heard the propellants were so corrosive they couldn't test the actual flight engine on the ground and the engineers had a good time up until they ascended back to the Service Module

Lots of the old ICBM and even some current Russians used hypergolic, its nasty in multiple ways, as in it does not matter if its very poisonous and corrosive as it explodes with contact with air.

However they are tested regularly on ground, pollution from an launch is small in the overall perspective so you just has to find an decent location.

However I guess the lander had to low TWR to be tested as it is on earth.

And you see the lander has RCS, it does not appear that they have separate ones on the decent stage.

[nyrath]

Lots of the old ICBM and even some current Russians used hypergolic, its nasty in multiple ways, as in it does not matter if its very poisonous and corrosive as it explodes with contact with air.

That's putting it mildly. Some hypergolics were quite good at rapidly dissolving human flesh, so poisoning was only an academic risk. In World War II, the German Komet rocket planes had a few crashes while in development. All that would be left of the pilot was a skeleton.