# Foil on Lunar Modules **URL:** \ **Category:** Factual Questions\ **Created:** [October 17, 2011, 7:15pm UTC](https://boards.straightdope.com/t/foil-on-lunar-modules/599944 "2011-10-17T19:15:06Z")\ **Posts on this page:** 4\ **Page:** 2
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [October 20, 2011, 8:17pm UTC](https://boards.straightdope.com/t/foil-on-lunar-modules/599944/21 "2011-10-20T20:17:42Z")
Well, Armstrong and Aldrin would play all kinds of practical jokes, and Collins would just express frustrated annoyance… ---
**Author:** ![user\_hostile](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/user_hostile/32/474_2.png) [@user\_hostile](https://boards.straightdope.com/u/user_hostile)\ **Post date:** [October 20, 2011, 8:35pm UTC](https://boards.straightdope.com/t/foil-on-lunar-modules/599944/22 "2011-10-20T20:35:58Z")
> [@scr4](#): > > It’s just the nature of the material - it’s not an elastic (stretchy) film. And there’s no reason to try to make it perfectly smooth and flat; and some reason it may be undesirable (e.g. if it’s stretched taut, it’s more likely to rip due to mechanical stresses, vibration, thermal expansion/contraction, etc). On the contrary, there are _flat_ applications. A few of the GEOs I worked on, had a single layer installed on the “top” deck of the spacecraft. It was taunt as a drum; they were mounted like volleyball net on the non-solar panel sides. During vibration tests, you’d watch film transition through several modes (1st order, second order, etc…). ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [November 1, 2011, 8:47pm UTC](https://boards.straightdope.com/t/foil-on-lunar-modules/599944/23 "2011-11-01T20:47:07Z")
> [@arnesw](#): > > **Kevbo** [this](http://www.airfix.com/airfix-products/space/a50106-one-small-step-for-man-a50106/) is the set. Ring any bells? I’m pretty sure mine was different. Thinking back it also had a command module. There was a base (with craters and stuff) that the LEM sat on, and it had an arm that held the command module above it. There were also a couple of astronauts and an american flag that stood on the base. Wow, I was really little when I had this. My dad and big brother had to help me put it together. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [November 2, 2011, 2:48am UTC](https://boards.straightdope.com/t/foil-on-lunar-modules/599944/24 "2011-11-02T02:48:56Z")
> [@arnesw](#): > > I don’t doubt that at all - I was thinking about what purpose the wrinkling of the material would serve. It doesn’t serve any purpose. The wrinkling is an artifact of how the material is applied, i.e. it is wrapped, bonded, or otherwise attached to irregular surfaces (like the LM) that it is not feasible to apply a solid reflecting layer, just as when you wrap foil around a plate of food it is not smooth. The wrinkling makes it slightly less efficient (as some radiation is re-radiated onto adjacent surfaces) but not dramatically so, and for protection against incident radiation it is superior to cork, RTV, and other forms of passive thermal protection. The wrinkling is not necessary to prevent layers from touching, as the scrim between layers that provides tensile strength against thermal stresses also provides thermal separation, and the layers of metal mesh underneath the outer reflective layer are typically coated with plastic to minimize conduction. In some situations, as **user\_hostile** states, the material can be stretched taut, and it is in fact quite tough, but that generally isn’t needed or desired, and could result in undesired acoustics during the boost phase. MLI is generally just reflective on the outward facing side, and in fact is used to cool (by differential radiation) the vehicle. Although solar heating is sometimes used as a thermal source (using a maneuver called a “barbeque roll” for assuring that volatiles are boiled off before uncovering optics or normalizing thermal stresses before deploying mechanisms), for heating propellant or instruments internal thermal sources are almost always employed to assure positive control. Also, it is the Apollo Lunar Module (LM, or sometimes ALM). Lunar Excursion Module (LEM) was employed in some trade study documentation but was never the official nomenclature for the Apollo lander. The lander/habitat for the Constellation program was known as the Lunar Surface Access Module (LSAM) despite space journalists and enthusiasts consistently referring to it as the LM, LEM, CLEM, et cetera. Stranger [Previous page](https://boards.straightdope.com/t/foil-on-lunar-modules/599944.md?page=1)