How did Apollo separate the lunar ascent/descent modules?

[Astrosag]

Hi all, hope everyone's doing well.<br /><br />I had a question regarding the Apollo mission and how the lunar ascent module it separated from the lunar descent module and how it fired its take-off engine. Did the missions use small solids or explosive measures before firing the main engines or were the engines fired with ducts to vent exhaust and prevent any damage done to the engines? I hope I'm being clear enough. I appreciate the help...it will help the propulsion team in my senior design class- its a lunar return sample (ice) mission.

 

[drwayne]

I'll see if I can find the sequence somewhere. My dominant memory of the process as there was a guiatine type of arrangement for cutting the wiring between the two module prior to liftoff.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[nolirogari]

If you have a high-speed connection, go here:<br /><br />http://www.geocities.com/bobandrepont/lmpdf.htm<br /><br />He has links to all sorts of documents, most of which are stored on the NASA server. Some take a long time to download as the are huge .PDFs, but once you have them you can spend hours reading the very fine details and learn a ton. I usulally tell it to save a document, then go away for a few minutes and while it hunts and saves. The NASA server for historic documents is VERY slow. If you are on dial-up... just start stabbing yourself in the forehead with a fork now, rather than try and load one of these. It'll be less painful.

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>If you are on dial-up... just start stabbing yourself in the forehead with a fork now, rather than try and load one of these. It'll be less painful.<p><hr /></p></p></blockquote><br /><br />*laughs* Their images are the same way. They've got a lot of people downloading stuff, and often at very high quality, so it can get slow. Another option is to try to find an off-peak time for downloading, although that usually means a time that'll be inconvenient for you.<br /><br />But it's worth the wait. There's some priceless stuff out there for the patient. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[gofortli]

Hi,<br /><br />I just got finished reading a book called "Chariots for Apollo" that covered this in pretty good detail. Yes, there was a large "guillotine"-like device that sliced through "miles" of cables and wiring that connected the ascent and descent stage. Milliseconds after this, the single ascent engine fired and launched the astros back into lunar orbit.<br />-dk-

 

[Astrosag]

Thanks all for the help and that website link- great source. So the engine fired while the ascent module was still on the descent module correct? The issue we are having is ducting the exhaust from our retrun vehicle. We looked into placing solids on the sides to give us some altitude (roughly a 1 meter or more) before the ascent engine fires. Problem is that multiple solids isn't a great idea - they MUST fire at the same time and burn at the same rate and stop at the same time- and also, solids do not perform as well in cold temperatures....and our thermal subsystem is telling us that it'll be damn hard to keep those relatively warm. With our current config (which is still in its early stages), the ascent engine is resting on the descent (lander) body...which means that if it fired, it'd blow up ....lol. Thanks for the help, as usual...its well appreciated.

 

[no_way]

<blockquote><font class="small">In reply to:</font><hr /><p>They've got a lot of people downloading stuff, and often at very high quality, so it can get slow<p><hr /></p></p></blockquote><br />somebody, tell them about bittorrent

 

[Astrosag]

Exactly my question. I don't think an engine that is flush against a surface (at its nozzle end), can ignite and burn...so if Apollo's ascent and descent modules' engines were one ontop of the other, how did they fire the ascent engine...was there a boost to add altitude between the two craft or did it have blowdown panels to create an escape route for the exhaust? Thanks.

 

[CalliArcale]

For convenience, here is the relevant part:<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>The ascent stage engine had it's on exhaust hole theough the descent stage.<p><hr /></p></p></blockquote> <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[Astrosag]

Lol I completely missed that, thank you. I'm still having trouble picturing this....I'm visualizing the ascent engine sitting directly ontop of the descent engine. Maybe I'm just being dumb lol...

 

[trailrider]

"The descent stage was used as the ascent stage launch pad. The ascent stage engine had it's on exhaust hole theough the descent stage. Pyro genic cutters cut all connectios with the descent stage at ascent stage ignition."<br /><br />While this is NOT the detailed design, IF the ascent nozzle was a good bit wider than the descent stage engining and associated plumbing, and presuming (and probably correct) there were no bulkheads (for weight saving) forward of the descent engine, then the ascent engine's exhaust could flow around the descent engine plumbing so that pressure didn't build up to any significant degree. As I recall, the ascent engine used hypergolics, which means all they had to do was fire the pyro-valves in the propellant lines. Simultaneously, the firing circuits fired the linear shaped charge that cut the skin between the two stages, and most likely a pyrotechnic guillotine cutter severed the wiring. If you notice the T.V. of Apollo 17, there is a lot of debris flying from around the cut line between stages and the ascent stage litterally pops off its "launch pad". This may be due to the acceleration of the ascent stage from the engine alone, or from any pressure buildup in the internal spaces.<br /><br />I'm not familiar with what you are doing, but you need to be sure that all your pyrotechnics fire on command in the order they are supposed to. I didn't get involved with the actual Pyro Initiator Controllers (PIC), but know a bit about the principles and realities.<br /><br />Ad Luna! Ad Ares! Ad Astra!