Apollo Lunar Module Abort

[viper101]

Theoretical Question: <br /><br />Let's say Neil ran out of gas - what was the procedure for an abort? Specifically: What would have happened in the event of an abort - I understand this is something of an automated function given the Abort Mode scare on Apollo 14's lunar landing - but I'm just wondering - if an abort was done, would the LM automatically right itself, drop the descent stage and fire the ascent...or what?<br /><br />

 

[drwayne]

The manuever would look, I believe, similar to the planned Apollo 10 staging. (Things went a little weirder than planned, due to a switch error)<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[vogon13]

IIRC, it would get real tricky near the surface.<br /><br />Maybe the abort range overlapped the safe free fall height of the LM, and maybe it didn't.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[dobbins]

IIRC there was a point where you "went over the cliff". Where you were committed to a landing because you were too low for a safe abort.<br /><br />

 

[viper101]

Yeah that's kind of what I am wondering about: How would ths have played out near the surface. Eagle landed with under 20 seconds of fuel remaining (although it has been said there was likely more available in the tank).<br />If the clock hit zero with 200 feet to go - if someone hit the abort switch - What happens? Does the descent stage pop off, does the LM right itself and shoot for orbit? <br /><br />I tried googling this, but you can imagaine what kind of results 'apollo' 'lunar' 'abort' (etc...) return.

 

[viper101]

One other thing: While searching for an answer - I came across this line on astronautix. I found myself nodding in agreement:<br />"Apollo was one of the great technical endeavours of the 20th Century. In the United States, it left remarkably little legacy. The spacecraft and launch vehicles developed at such enormous expense were abandoned and replaced by pursuit of a chimera - a fully reusable space shuttle. For the hundreds of thousands of industry and government workers that contributed to the project, it was one of the greatest periods of their lives. The generation that had learned how to get things done quickly in World War II were again called to action in the prime of their lives. Compare the schedule of Apollo - seven months from the decision to go ahead to issuance of all major contracts for the spacecraft, rocket stages, and launch site - to NASA's current performance. There were giants in those days - we shall not see their like again. "<br /><br />-Too True. <br /><br />http://www.astronautix.com/craft/aponding.htm

 

[drwayne]

I recall reading in Ben Rich's writings about how the governmental procurement process had changed from Kelly Johnson's heyday, when he could walk in with an idea for an aircraft and walk out hours later with a contract to build it - to days extended procurement cycle (or at least into the '90's for Ben Rich)<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[viper101]

Some days I think that if that pace has continued through the 70's and 80's and 90's - right now we could be tapping away on this forum, from our comfortable domes at Utopia Planetia - wondering how much longer we would have to wait to see a manned return to Titan...<br /><br /><img src="/images/icons/wink.gif" />

 

[henryhallam]

<font color="yellow">If the clock hit zero with 200 feet to go - if someone hit the abort switch - What happens? Does the descent stage pop off, does the LM right itself and shoot for orbit?<br /></font><br /><br />Yes, I think so. I'm not sure if the entire process was automated or if a couple of switches had to be flicked, but regardless the crew would have trained to do this in a second or two. The ascent engine was unthrottled so it would come on at full power, nulling any downward velocity and then the crew would probably have initiated a PGNS program to pitchover and establish an orbit.<br /><br />In fact judging by the "Orbiter" simulator it is pretty easy to fly an ascent or abort manually, all the way to rendezvous and docking (without autopilot, though the computer still does the transformations necessary to make the thing handle sensibly).<br /><br />The tricky part is doing a manual <b>descent</b> without any autopilot. It is possible if you have the computer give you some numbers that indicate your current state vector and the acceleration/velocity components needed to meet each target gate. Without even that, you could probably fly a survivable manual descent but don't even think about a precision landing.

 

[krrr]

If a bad thing happened during the ascent of a future LM - shouldn't the astronauts deserve a second chance?<br /><br />I'm thinking about an emergency system which would, in the case of a mishap, lift the crew cabin (and just that) into lunar orbit. Alternatively, if the problem occurred in the first half of ascent, abort to lunar surface, else abort to orbit. Of course, in the first case, a rescue LM should be ready.<br /><br />Assuming my bare-bones crew cabin weights 1 tonnes (including astronauts), another 1+ tonnes (engine plus propellant) would be required for the abort-to-orbit option. Maybe not totally unfeasible...

 

[drwayne]

Note that there was a good deal of flexibility in Apollo to have the Command Service module go to a quite low orbit to perform the docking with the lunar module.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[henryhallam]

Well, that's more or less what the ascent stage of the Apollo LM did - there isn't a lot more to it than the crew cabin, and enough propellant, engine and navigation equipment to get into lunar orbit.<br /><br />I'm not sure how much about the future LM has been decided, it will be interesting to see whether they go with a separate ascent and descent stage or just use a single engine, perhaps with drop tanks. From what I recall this is quite possible without much mass penalty at all; the principal advantage in having a separate ascent stage is that if there's a malfunction in the descent stage then you have a whole 'nother engine to abort with.

 

[drwayne]

Interesting parallel thought:<br /><br />http://yarchive.net/space/apollo/lunar_module.html<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[henryhallam]

hehe, another Henry thinking alike <img src="/images/icons/wink.gif" />

 

[krrr]

Indeed a descent-plus-ascent stage system protects from *descent* failures. However, the ascent stage must be 100% reliable.<br /><br />If the ascent stage fails, RIP. Therefore my suggestion. It is analogous to a terrestrial abort system but obviously harder to implement in the absence of an atmosphere with parachute landing.

 

[drwayne]

"If the ascent stage fails, RIP."<br /><br />Not neccessarily. As I stated earlier, there were modes in which the LM could assume a very low orbit, and the CSM could go low to get it.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[henryhallam]

<font color="yellow">If the ascent stage fails, RIP. Therefore my suggestion. It is analogous to a terrestrial abort system but obviously harder to implement in the absence of an atmosphere with parachute landing.</font><br /><br />I see what you're saying now, but this is basically sticking another ascent stage on as a backup. For it to have enough dV capability to abort at any time, I think the mass penalty would be a bit too high. You're looking at adding propellant weighing about 1.5*the mass of whatever you want to orbit, and I fear the crew cabin, ECS, engine, RCS and necessary avionics would come to quite a bit over 1 tonne. Plus added complexity of quick-disconnects etc.

 

[krrr]

<font color="yellow">"If the ascent stage fails, RIP."<br /><br />Not neccessarily. As I stated earlier, there were modes in which the LM could assume a very low orbit, and the CSM could go low to get it.</font><br /><br />That would have been the case if the LM ascent stage would have performed 90 or 95% of its duty. Otherwise, a parabolic trajectory with impact at 1500+ m/sec.

 

[henryhallam]

The trajectory is still elliptical <img src="/images/icons/wink.gif" /> But yes... not pretty... I think the key is to make the ascent engine as simple, foolproof and reliable as possible (hypergolics, quadruply-redundant valves etc). As was done with Apollo.

 

[josh_simonson]

The descent stage aught to be more reliable since it's up and running once they leave the orbital modules. If it fails outright, they can just re-dock with the orbital module and go home. In order to need an abort to the ascent engine, the descent engine would have to fail at some point during the flight down after running fine for a while. Any failure in the ascent engine is disaster though. Best bet is probably one cluster of engines for both jobs - with engine out capability. That way if they all aren't working, you can abort in orbit, and several would have to fail to cause a serious problem in getting back.

 

[drwayne]

I recall needing less than that, but I do not have the reference - I'll see what I can dig up...<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[henryhallam]

There was some cross-plumbing, though I forget whether the RCS could be cross-fed from the descent or ascent tanks (it wasn't both)

 

[viper101]

Thanks S_G! I kind of figured that, but could not find anything on it out there - surprising since I feel, as far as in-space emergencies, this was one of the more commonly envisioned ones. <br /><br />

 

[jammers]

The RCS was linked to the Ascent tanks

 

[viper101]

I'm going back to the game now - <br /><br />http://www.games.com/playgames/arcade/lunarlander/lunarlander_600.jsp