To many apollo lunar lander was the epitome of the moon missions and one of the oddest looking spacecraft that have ever been built, with some saying that it looked like some weird robotized insect or fake and just too flimsy to be used as a space craft. But the lunar Lander was very much a case of form following function and with that in mind why did the lunar Lander look so odd?
When President Kennedy announced the moon missions in 1962, no one at NASA even knew how they would get men to the moon let alone land them on the surface and then return back to the earth.
Many of the principles that were initially thought of came from the realm of science fiction and usually had a rocket landing vertically and then taking off in the reverse fashion much like SpaceX Falcon rockets and the Starship.
But in reality, many at NASA and some of their contractors who would go on to do the work such as Grumman who won the contract to build the lunar Landers thought it should be done with a dedicated spacecraft specifically designed to land on the moon, rather than using a general purpose rocket that might be too heavy or too tall and would be at risk of tipping over on an uneven surface.
The other problem was that they still knew very little about the moon’s surface, some thought that it was lunar dust that could be up to 10 metres deep and if you tried to land a heavy spacecraft on it, it would just sink into it like quicksand.
The surveyor missions of the mid 60’s were sent to find out what the lunar surface was like at the prospective Apollo landing sites.
The results from this showed that whilst there was dust, rocks and craters, the dust it was not as deep as some had expected.
Grumman was chosen from a shortlist of contractors to build the lunar Landers because they had already done quite a bit of design work themselves and come up with an idea which expanded on NASA’s design creating a two-stage spacecraft which would descend to the surface and then a smaller ascent stage would take off when the mission had ended and return to rendezvous with the command service module in lunar orbit.
All this was done to reduce weight, if you have less weight to lift off the moons surface you need smaller engines and less fuel, all of which reduced weight that would have to be lifted from earth.
Both NASA and Grumman had to try and figure out what would happen if landing wasn’t quite so straightforward, if for example it was still travelling laterally instead of straight down.
How easy would it be able to tip over if the landing legs dug into the lunar surface? Many tests were done landing Models on different types of surfaces and on inclines. Initially, five legs were considered but to help save weight four legs were found to be perfectly adequate and stable.
The legs also required some form of shock absorbing to cushion the landing once the descent engine was turned off.
Even though there was only one-sixth gravity on the moon it would still need a shock absorber of some type for the landing. However, there were concerns that heavy duty shock absorbers used on earth which were hydraulic or pneumatic in nature might have problems in the cold and vacuum of space. They would also be very heavy, the amount of travel which NASA anticipated was up to 32 inches or 87cm.
Because the Landers would only be landing on the moon once, they came up with a single-use dry shock absorber which used an aluminium honeycomb material made by Hexcel that was compressed in the cylinder of the shock absorber when the lander touched down. This would allow for a single compression stroke and maybe one extra bounce but still being very light weight.
Although the compression rate for the honeycomb material was 10 feet per second, the actual landing only exerted about four feet per second, so the length of the legs was longer than expected After landing. This meant that Neil Armstrong’s small step was a couple of feet longer than anticipated. On Apollo 12 when Pete Conrad took his giant leap from the bottom of the ladder to the landing pad his first words were “Whoopie man, that may have been a small one for Neil but it was a long one for me”.
Weight would be the key issue for the lander, for every 1kg of weight it would take 4 kg of fuel to lift it from the earth. In the original Grumman design the crew cabin was a hemispherical shape with large glass windows but the glass would be heavy so this was reduced down to just two small triangular shaped windows with the rest of the cabin being made from lightweight aluminium hull with Titanium fasteners which can be seen here without the thermal insulation and exterior skin.
After the first revision of the Lander was made it was found to be too heavy, so NASA went through the entire structure shaving off a kilogramme here, maybe a 100 grammes there.
The hull itself was redesigned to be as thin as possible but still have structural integrity in space and the 1/6 gravity of the moon.
As the lander progressed the astronauts were brought in to try out the design and use it as they would do during a mission, However, once they did this, they found that there were various things which on the drawing board looked fine but in reality just wouldn’t work with a man in a bulky spacesuit.
The Grumman design included seats in the cabin which added extra weight, but after the astronauts stood up to use the controls, they realised that in the 1/6 gravity on the moon, standing up would be much less of a problem and the seats would not be required.
The Grumman design also had no ladder from the door and attached to the leg. It was thought that it would be easier to have a winch and a harness to lower the astronauts onto the surface but when they tried it out on a full-scale mock-up, the astronauts couldn’t get back up using the hand-operated rope winch, so the ladder was put back.
The door on the Grumman design was also a round hatch, but when the astronauts tried to get in and out with their large rectangular backpacks on, they found it very difficult if not impossible to get in and out, so the door was changed to a square shape for easy access.
Because of the small space there would be no airlock, the crew would have to get into their full space suits before the cabin would be depressurized when they could then exit the Lander. When they came back into the cabin, they would have to seal the door and then repressurise the inside of the Lander before they could take off their suits.
During pressure testing in a vacuum chamber of the finished design, one of the triangular-shaped windows shattered spraying bits of glass all over the inside of the cabin, cutting wires and even puncturing the structure.
Technicians had to go in and try and find every last shard and piece of glass no matter how small because in the weightlessness of space, anything that was on the floor on earth would be floating around during the voyage and could get into the astronaut’s ears, eyes or be breathed in during the mission. The cause of the broken window was never satisfactorily resolved but on the off chance they changed all the existing windows of the other landers and rechecked all the new ones just in case.
The Landers were made in one of the first clean rooms, assembly areas cleaner than an operating theatre where the technicians assembling the craft would wear face masks, gown, gloves, hair nets to try and stop flakes of skin and hair getting into the controls and wiring.
This also applied to anything which had been left behind during the manufacture and that might have fallen behind the control panels or into cracks and crevices inside the cabin. Any small bits of wire, nuts, bolts, rivets etc possibly even tools could short out electrical equipment and if they were very small they could be breathed in by the astronauts once in space.
To help try and get every last piece of debris out of the Lander during manufacture and after any modification work had been done, the ascent module was put onto a tumbling rig where it would be turned upside down and shaken and any pieces that had fallen out were counted and checked, only when nothing else fell out was it deemed to be clean enough for mission use.
But by the time the Landers got to the moon surface the inside of them we’re no longer pristine and new with wear marks on the controls and surfaces being easily visible.
This was because everything that would happen on the moon was practised and tried out on earth before hand. Every switch, lever and control was tested by the astronauts wearing full space suits to make sure but they could operate all the controls and they knew where everything was.
Because of the time pressure to get everything done before the 1970 deadline the worn-out paint on controls, scratches and scuffs, were just left as they were because technicians had more important things to do than make it look pretty inside.
They even had a simulator that would project an artificial image of the moon surface which was controlled by the astronaut and different scenarios could be played out which might include equipment faults, computer malfunctions and landing difficulties.
But there was another issue that would affect the lander before they even got to the surface and that was the temperature range that the craft would have to endure once in space and on the moon.
In the sunlight it could be up to 150° Celsius and in the shade -170°. With this huge temperature range the worry was that the aluminium hull could buckle and many critical structures were glued together with resin, this included the Hexcel shock absorber core of the landing legs, if this got too hot it could affect its structural integrity.
So a new material that had been recently developed by DuPont was used. This was an aluminium covered mylar film with a gold colour and was used to wrap the exterior including the legs. Multiple layers of this were used which was found to be a very good insulator against extreme temperature changes.
Around the hull, 3 layers of Inconel, a nickel-chromium-based superalloy with resistance to high temperatures and corrosive environments were used. Then 25 layers of the mylar film were sandwiched together to create a thermal layer along with an aluminium structural skin layer.
This not only provided an excellent thermal layer but also protection against micrometeorites. Although these layers were only a few millimetres thick, in the vacuum of space there was no air resistance and even travelling at up to 25,000 mph or 39,000km/h on their way to the moon, this was easily capable of doing the job whilst being lightweight but it did look like it was made out of tinfoil which many of the conspiracy theorists jumped on board and said that it was just a stage prop without taking the time to understand how and why it was created this way.
On the inside many of the walls we’re covered with control panels and those that weren’t had plastic to cover the structural hull, only around the windows was where you could see the hull of the craft.
Although the Apollo lunar Landers looked incredibly flimsy, they were designed to do just one job and do it extremely well without being overly engineered. For the time this was cutting edge stuff that had never been done before, if we were to do the same again the new generation of Landers, they will not look the same and take advantage of huge leaps in material science over the last 60 years.
They might well have been one of the oddest looking spacecraft ever designed but they are now an icon of how we overcame the challenge of getting to the moons surface and back home again, with a can do attitude that seems to be sorely lacking these days.
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