# Comparison of space shuttle, command module, and lunar module window sizes

The space shuttles had a viewing window much similar in looks like the windshield of a car, or like the cockpit of a plane. However, neither the Apollo command module (CM) nor the lunar module (LM) had windows that big. If it could be done for shuttle, why not for the CM & LM? Was it merely the technology prevailing at the time of their design or any other consideration?

• Please check for existing tags before adding unnecessary duplicate ones. See space.meta.stackexchange.com/q/1601/6944 – Organic Marble Sep 9 '20 at 12:08
• I don't understand why none of the answer authors bothered to upvote your question. Without it, posting these answers would be impossible. Considering the that work went into the answers, the authors almost certainly think that this is a question worth answering. If so, and to encourage more questions, I think they should consider up voting your question as well! Here's mine at least! +1 – uhoh Sep 10 '20 at 7:01
• @uhoh. I appreciate your up voting and wish to clarify on the "acceptance" part of it. Initially, I was ignorant about accepting an answer, but then I was advised by some gentleman to "accept" the answer, which gives some sort of credit to the answer provider. Thereafter, I started accepting the answers, not only as a token of appreciating the efforts taken by the person, but also because of the fact that every answer does have a view point, some scientific/technical knowledge behind it, which adds to my knowledge base - even if I do not agree with the same. I am open to criticism as well. – Niranjan Sep 11 '20 at 9:21
• @OrganicMarble indeed! The weekend is upon us, it's a good time to review my old posts. Thanks for the reminder! – uhoh Sep 11 '20 at 15:55
• @uhoh thanks for the accept! – Organic Marble Sep 11 '20 at 15:55

## Windows are kept small because they are heavy

Windows need to be thick enough to survive micrometeoroid impacts and the stresses of spaceflight, and to provide radiation protection. They also need cushioning and seals. This makes a window heavier than the equivalent area of sheet metal bulkhead.

The Shuttle needed just the delta-v to get into low Earth orbit. Apollo had to do not only that, but also the additional delta-v of getting to the moon and getting back. The lunar module also had to land and take off from the moon. This made the weight budgets of the Apollo spacecrafts smaller than the Shuttle. So the Apollo windows were made as small as possible while allowing sufficient visibility.

The structural design philosophy for the LM windows was to provide a window of minimum weight with maximum crew visibility, which led to the selection of the single- pane-window concept using chemically tempered glass. The design consisted of a single structural pane and an external pane for micrometeoroid and radiation protection.

Apollo Experience Report: Spacecraft Structural Windows, NASA Tech Note D-7439, p. 8

• +1, the question seems to imply that windows are free and that the only constraint on size is whim. – Organic Marble Sep 10 '20 at 13:24
• @Dr. Sheldon. Thats the most convincing answer. I had read about the philosophy of minimum weight with max. crew visibility in the same document, you also referred to. What I was wondering about, is "if possible for shuttles, why not for CM & LM" - which you have aptly explained. Does this mean micrometeorites' problem is less disastrous at lower orbits (LEO) etc.? Perhaps weight was more crucial considering the overall fuel consumption limitations. Thanks for your response. – Niranjan Sep 11 '20 at 9:32

The CM splashed down in the ocean, the LM landed vertically on the moon, the shuttle landed on a runway.

Requirements drive design.

• FWIW, my USAF Test Pilot School dissertation project (back in 1992) was to evaluate how well we could perform Shuttle-type approaches using only a very small "window" (on the order of about 8" x 8", roughly rectangular in shape IIRC). It was amazing how consistent our approaches were. However, would I ever choose such a small window for such a demanding task if a bigger one were possible? No. Eats into your margin too much... – Digger Sep 9 '20 at 17:40
• @ Digger. You seem to be saying "bigger windows" are better. Obviously, but why could we not provide them on LM & CM? Perhaps as Organic Marble has said, they never had to land in the "line of sight" as the planes / shuttle would do. But it still does not answer the question.. if it was possible, why was it not provided? As you said, bigger is always better... – Niranjan Sep 9 '20 at 19:20

The space shuttles, had a viewing window much similar in looks […] like the cockpit of a plane.

The Space Shuttles were planes. The others weren't. Hence it makes sense to have airplane-like windows, and it makes sense that the others don't need them.

• @Mittag. As far as I know space shuttle was never a plane. It did land like a plane i.e. on a runway, but only visually. It decelerated with the help of parachutes. Most importantly, its take off, and climb was with a "non breathing" reaction engine- rockets. Even otherwise, a better view through a wider window can help pilots and astronauts, equally well. There could be more better justifications for the difference. – Niranjan Sep 9 '20 at 19:12
• The drag chute was not added until the 47th mission. – Organic Marble Sep 9 '20 at 19:31
• @Organic Marble. Drag chute was added in the 47th mission?? I did not know this. So how did the shuttles "decelerated" prior to that? Moreover, did they have air breathing engines (also)?. Only then would they qualify to be called "flights" in the conventional sense. – Niranjan Sep 11 '20 at 9:38
• @Niranjan: They were braking using their brakes, just like any other plane. And I am sure most glider pilots would object to you not allowing to call their flights flights. And are electric airplanes not airplanes because their engines are not air-breathing? – Jörg W Mittag Sep 11 '20 at 10:25
• @Niranjan your objections seem totally irrelevant. The orbiters were flown manually to a landing on a runway; in the 70s when they were designed, that required large windows. What possible relevance could how they were launched or the presence of a chute have to that? You don't get to define what a 'flight' is. If you want more info about the chute, suggest you search for existing questions and ask a new one if required. – Organic Marble Sep 11 '20 at 12:52