Mechanical

1. The Lunar Modules made no blast craters or any sign of dust scatter.

No crater should be expected. The 10,000-pound thrust Descent Propulsion System was throttled very far down during the final landing.[127] The Lunar Module was no longer quickly decelerating, so the descent engine only had to support the lander's own weight, which was lessened by the Moon's gravity and by the near exhaustion of the descent propellants. At landing, the engine thrust divided by the nozzle exit area is only about 10 kilopascals (1.5 PSI).[128] Beyond the engine nozzle, the plume spreads, and the pressure drops very quickly. Rocket exhaust gasses expand much more quickly after leaving the engine nozzle in a vacuum than in an atmosphere. The effect of an atmosphere on rocket plumes can be easily seen in launches from Earth; as the rocket rises through the thinning atmosphere, the exhaust plumes broaden very noticeably. To lessen this, rocket engines made for vacuums have longer bells than those made for use on Earth, but they still cannot stop this spreading. The lander's exhaust gasses, therefore, expanded quickly well beyond the landing site. The descent engines did scatter a lot of very fine surface dust as seen in 16mm movies of each landing, and many mission commanders spoke of its effect on visibility. The landers were generally moving horizontally as well as vertically, and photos do show scouring of the surface along the final descent path. Finally, the lunar regolith is very compact below its surface dust layer, making it impossible for the descent engine to blast out a "crater".[129] A blast crater was measured under the Apollo 11 lander using shadow lengths of the descent engine bell and estimates of the amount that the landing gear had compressed and how deep the lander footpads had pressed into the lunar surface and it was found that the engine had eroded between 4 and 6 inches of regolith out from underneath the engine bell during the final descent and landing.

Under the Apollo 11 Lunar Module

2. The second stage of the launch rocket and/or the Lunar Module ascent stage made no visible flame.

The Lunar Modules used Aerozine 50 (fuel) and dinitrogen tetroxide (oxidizer) propellants, chosen for simplicity and reliability; they ignite hypergolically – upon contact – without the need for a spark. These propellants produce a nearly transparent exhaust.[131] The same fuel was used by the core of the American Titan II rocket. The transparency of their plumes is apparent in many launch photos. The plumes of rocket engines fired in a vacuum spread out very quickly as they leave the engine nozzle (see above), further lessening their visibility. Finally, rocket engines often run "rich" to slow internal corrosion. On Earth, the excess fuel burns in contact with atmospheric oxygen, enhancing the visible flame. This cannot happen in a vacuum.

3. The Lunar Modules weighed 17 tons and made no mark on the Moondust, yet footprints can be seen beside them.

On the surface of the Earth, Apollo 11's fueled and crewed Lunar Module, Eagle, would have weighed approximately 17 short tons (15,300 kg). On the surface of the Moon, however, after expending fuel and oxidizer on her descent from lunar orbit, the lander weighed about 2,698 pounds (1,224 kg).[133] The astronauts were much lighter than the lander, but their boots were much smaller than the lander's approximately 3-foot (91 cm) diameter footpads.[134] Pressure (or force per unit area) rather than mass determines the amount of regolith compression. In some photos, the footpads did press into the regolith, especially when they moved sideways at touchdown. (The bearing pressure under Apollo 11's footpads, with the lander being about 44 times the weight of an EVA-configured astronaut, would have been of similar magnitude to the bearing pressure exerted by the astronauts' boots.)

4. The air conditioning units that were part of the astronauts' spacesuits could not have worked in an environment of no atmosphere.

The cooling units could only work in a vacuum. Water from a tank in the backpack flowed out through tiny pores in a metal sublimator plate where it quickly vaporized into space. The loss of the heat of vaporization froze the remaining water, forming a layer of ice on the outside of the plate that also sublimated into space (turning from a solid directly into a gas). A separate water loop flowed through the LCG (Liquid Cooling Garment) worn by the astronaut, carrying his metabolic waste heat through the sublimator plate where it was cooled and returned to the LCG. Twelve pounds (5.4 kg) of feedwater gave about eight hours of cooling; because of its bulk, it was often the limiting consumable on the length of an EVA.