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Forum:	Mercury - Gemini - Apollo
Topic:	Apollo 15: LM Falcon landing skirt buckled

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Your Reply: HTML is ON UBB Code is ON Smilies Legend	[QUOTE]Originally posted by David C: [B]Very old news, it’s in the Mission Report.[/B][/QUOTE]
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<table border=0 cellpadding=0 cellspacing=0 width="600"><TR><td bgcolor="#000000"><TABLE BORDER=0 cellpadding=4 border=0 cellspacing=1 WIDTH="100%"><TR bgcolor="#660000"><TD COLSPAN=2><CENTER>T O P I C     R E V I E W</CENTER></TD></TR><TR bgcolor="#494949"><TD valign=top>Buel</TD><TD>Didn't know this until today — the landing skirt on the Apollo 15 lunar module Falcon buckled on landing?From Andy Sanders ("Apollo Remastered") <A HREF="https://twitter.com/AndySaunders_1/status/1421026110826061824" TARGET=_blank>on Twitter</A>: <BLOCKQUOTE>Here I've produced for you, from 16mm film frames (HD source Stephen Slater), an enhanced view from Jim Irwin's window as they approach the landing spot (red dot). The landing buckled the engine skirt.</BLOCKQUOTE> <center><a href="http://www.collectspace.com/review/buel/apollo15_buckled_landing_skirt01-lg.jpg" target="AirLock"><img src="http://www.collectspace.com/review/buel/apollo15_buckled_landing_skirt01.jpg" width="400" height="450" border="0"></a></center></TD></TR><TR bgcolor="#333333"><TD valign=top>David C</TD><TD>Very old news, it’s in the Mission Report.</TD></TR><TR bgcolor="#494949"><TD valign=top>Robert Pearlman</TD><TD>The buckling is briefly discussed (and additional photos shared) in this 2010 thread: <A HREF="http://www.collectspace.com/ubb/Forum29/HTML/001189.html">Height above surface at engine shutdown</A>.</TD></TR><TR bgcolor="#333333"><TD valign=top>MarylandSpace</TD><TD>Very interesting reading the older thread.</TD></TR><TR bgcolor="#494949"><TD valign=top>Blackarrow</TD><TD>The issue was also addressed in some technical detail in the thread <A HREF="http://www.collectspace.com/ubb/Forum29/HTML/001582.html">Apollo lunar module touchdown dynamics</A> and I recommend the book "Digital Apollo" by David A. Mindell.</TD></TR><TR bgcolor="#333333"><TD valign=top>AlanLawrie</TD><TD>The possibility of the nozzle extension impacting the lunar surface was specifically designed for and tested by the engine supplier TRW. They built a "crushing test fixture" and subjected a columbium (niobium) nozzle extension to a simulated 10 ft/sec landing impact by compressing the nozzle extension 28 inches in less than half a second.</TD></TR><TR bgcolor="#494949"><TD valign=top>oly</TD><TD>The lunar module descent engine nozzle contacting the lunar surface was a design factor of both the spacecraft and the flight plan.A reason that the landing probes and the contact light were incorporated into the spacecraft design was to provide a proximity alert for when the vehicle was considered close enough to the lunar surface that the descent engine could be shut down, and the vehicle could settle to the surface as a safe velocity. The reason that the flight plan was designed, and practiced in simulation, for the engine to be shut down before surface contact was to avoid a situation whereby a rock or lunar soil could potentially plug the descent engine nozzle and cause a catastrophic failure. This scenario is also why astronauts inspected and photographed the gear, nozzle, and underlying lunar surface, and gave feedback during the EVA.The realigned landing footage of Apollo 14 details the surface rocks, craters, and surface undulations that were potential hazards, and also shows that the vehicle could withstand a gentle landing with the engine still running.<center><iframe width="400" height="225" src="https://www.youtube.com/embed/1tG3YCLNp6Q" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen>

From what I understand, one of the biggest lunar module engineering surprises was how little amount the landing gear was compressing during the landing, as engineers had expected and designed for a greater gear compression.

With the gear legs not compressing as far as was anticipated, the distance from the lower ladder rung to the gear footpad was greater than expected, one of the reasons Armstrong made sure that he could get back up the ladder (however, I suspect that in a pinch, a lunar surface experiment package or rock box could be used as a step).

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