The story of the impossible lunar lift-off...
Another iconic scene that has fired up the paranoid imagination of conspiracy theorists is the TV footage of the Lunar Module ascent stage lifting off from the surface of our satellite. Faced with these images, deniers usually ask two triumphant questions, convinced that they have exposed the whole charade: who was operating the camera if both astronauts were inside the departing cabin? And why does not even the slightest flame or column of smoke, typical of every rocket launch, come out of the engine?
The Apollo 17 lunar rover parked in its final position before the crew lifted off from the Moon. The GCTA camera, remotely controlled by radio from Earth by Ed Fendell at Houston's MCC, appears on the left, gold-colored, above the rover's right front wheel. Photo courtesy of NASA.Both objections, as usual, do not prove the existence of a film set, only the deniers' profound ignorance of 1960s aerospace technology and of the chemistry of propulsion in a vacuum. The answer to the first question bears the name of Ed Fendell, the NASA flight controller sitting at the INCO console (Integrated Communications Officer) of the Mission Control Center (MCC) in Houston. From the Apollo 15 mission onward, the color TV camera was not mounted on a simple tripod, but on the Lunar Roving Vehicle (LRV), the electric rover that the astronauts parked about a hundred meters from the Lunar Module before leaving. This camera was fitted with a motorized system called GCTA (Ground Controlled Television Assembly), which allowed the MCC to remotely control its pan,
Ed Fendell at the INCO console of Houston's MCC. He was responsible for remotely controlling the GCTA camera mounted on the lunar rovers of Apollo 15, 16 and 17. Photo courtesy of NASA. tilt and zoom. The feat of filming the ascent, which culminated in the geometrically perfect footage of Apollo 17, was a masterpiece of timing and orbital calculation. Since the radio signal took about 1.3 seconds to reach the Moon, and the images took just as long to come back to Earth, Fendell had to send the movement commands to the camera almost three seconds before the action actually appeared on the screen. The operator had to anticipate the engine ignition and calculate the vehicle's vertical acceleration blindly, moving a joystick on Earth to follow an object 384,000 kilometers away. There was no fake cameraman hidden behind a sand dune on Earth, just an absolute triumph of telemetry and telecommunications engineering. The second conspiracy riddle, namely the absence of flames and smoke from the ascent engine (APS - Ascent Propulsion System), is solved simply by opening any chemical propulsion textbook. Our collective imagination has been shaped by the launches of the Space Shuttle or of the gigantic Saturn V rockets, where solid propellants or mixtures of kerosene and liquid oxygen produce blinding flames and colossal clouds of smoke, shaped and compressed by the surrounding atmospheric pressure. The Lunar Module, however, used a completely different technology, dictated by the need for absolute reliability and survival. The ascent engine used hypergolic propellants: a mixture of hydrazine and unsymmetrical dimethylhydrazine (Aerozine 50) as fuel and nitrogen tetroxide as oxidizer. The fundamental, life-saving property of these substances is that they ignite spontaneously as soon as they come into contact with each other, eliminating the need for a spark ignition system that could have failed at the most critical moment, turning the Moon into a tomb for the crew. The combustion of these particular hypergolic propellants is extremely efficient and produces exhaust gases that are almost completely transparent to visible light!
Moreover, and this is the crucial factor that laypeople constantly miss, the event took place in the hard vacuum of space. On Earth, the massive atmospheric pressure forces the hot exhaust gases into a narrow visible column that stretches out beneath the rocket. In the lunar vacuum, with no air to contain and shape the jet, the gases leaving the engine nozzle instantly expand into a very low-density spherical bubble, cooling in fractions of a second and spreading their already faint glow over an enormous volume. The visual result is exactly what the rover's camera recorded: a quick, seemingly silent separation, with no Hollywood glare or smoke trails, accompanied only by an invisible but extremely violent expulsion of gas that scatters in all directions the fragments of thermal insulation (the gold Kapton) torn from the Descent Stage below, which stayed on the Moon as the launch pad for the Ascent Stage carrying the crew. Expecting to see the flames of an Earth rocket in the lunar vacuum with hypergolic engines is like expecting to hear the roar of an engine in a vacuum: it is a childish projection of our everyday experience onto an environment that obeys diametrically opposite chemical and physical laws! Once again, the absence of flames does not in any way prove that the video is fake; on the contrary, it certifies its absolute and rigorous scientific authenticity.
