The Hidden Challenges NASA Overcame to Achieve the Impossible Moon Landing
Meanwhile, the ascent stage was powered by a 16,000 Newton thrust Bell Aerospace rocket engine, also fuelled by Aerozine 50 and Nitrogen Tetroxide. These propellants also fuelled the reaction control system or RCS thruster quads that allowed the LM to be manoeuvred in the vacuum of space. Due to the corrosive nature of these propellants, the ascent engine could only be ignited once before having to be rebuilt, meaning the first time a production engine was fired was when the LM lifted off from the lunar surface. If it failed, the astronauts would be stranded with no hope of rescue. Understandably, a huge amount of effort was devoted to ensuring the ascent engine would fire the first time, every time; failure, as they say, was not an option.
In addition to the ascent engines and thrusters, the LM also contained the pressurized cabin for the Commander and Lunar Module pilot, flight controls, batteries, oxygen tanks for the life-support system, navigation and communications systems, and everything else needed to land on the lunar surface, keep the astronauts alive for the duration of their mission, lift off again, and rendezvous and dock with the orbiting CSM. This included a hatch and docking ring at the top of the module, which allowed the LM to dock with the CSM and the crew to transfer from one vehicle to another through a short tunnel. Originally, a second docking port was integrated into the forward ingress/egress hatch to allow the LM crew to take an active role in docking. However, this was eventually deleted in the name of weight savings and responsibility for docking given to the Command Module Pilot. Early on, it was unknown whether the crew would be easily able to perform the procedure of pulling away from the SIVB rocket stage, turning around, docking with the LM, and extracting it from its adapter. Therefore, various rigid and flexible tether mechanisms were devised to assist this process. However, the ten 2-man Gemini missions flown between 1965 and 1966 demonstrated that orbital manoeuvres – including the dreaded rendezvous and docking – were far easier than expected to perform, so these features were deemed unnecessary. Meanwhile, the Ranger and Surveyor unmanned probes, launched between 1961 and 1968, determining that the lunar surface was mostly solid with only a thin coating of dust. The LM and the astronauts inside would be in no danger of sinking into oblivion.
Without aerodynamic forces to provide resistance and damping, the LM was an extremely difficult and unforgiving machine to fly. As a result, Bell Aerospace was contracted to construct three strange, spider-like aircraft known as the Lunar Landing Training Vehicles or LLTVs. Nicknamed the “flying bedstead” by the astronauts, the LLTVs were powered by a downwards-facing 19 Kilonewton thrust General Electric CF700 jet engine and controlled by hydrogen peroxide thrusters, allowing the unusual handling characteristics of the LM to be replicated on earth. The unusual vehicle proved tricky and even dangerous to fly – so much so that on May 6, 1968, astronaut Neil Armstrong was forced to eject from his LLTV when it suddenly flew out of control, barely escaping with his life. His quick reaction and overall skill at piloting the “flying bedstead” were among the many factors behind Armstrong’s eventual selection as the commander of Apollo 11. Hardly remembered today, the unorthodox-looking LLTV was considered by many astronauts to be the “unsung hero” of Apollo, without which a successful lunar landing would have been impossible.
With most of the major unknowns regarding Lunar Orbit Rendezvous now resolved, NASA was finally ready to test the Apollo hardware in the harsh environment of outer space. The first flight of a production Block 1 Apollo CSM took place during the February 26, 1966 launch of AS-201, the spacecraft being lofted on a suborbital trajectory by a Saturn IB rocket. The test was partially successful, the spacecraft suffering serious – but easily corrected – failures in its engine and guidance system. AS-201 was followed on August 25, 1966 by AS-202, which was entirely successful and convinced NASA that the CSM was ready for manned flight. However, the tragic deaths of the Apollo 1 astronauts in a pad fire on January 27, 1967 revealed a laundry list of faults with the Block 1 spacecraft, requiring it to be completely redesigned. Meanwhile, development work continued on the larger Saturn V rocket and the Lunar Module, with the first unmanned launch of the former, Apollo 4, taking place on November 9, 1967. The flight, which completed 3 orbits of the earth, was a complete success, reassuring NASA that achieving a manned lunar landing by the end of the decade just might be possible.
A pre-production Lunar Module was supposed to have been flown aboard Apollo 4, but when the vehicle arrived at Cape Canaveral, NASA engineers discovered hundreds of design and construction flaws. NASA was unwilling to delay its launch schedule, and so Apollo 4 flew without a Lunar Module. The first unmanned LM test flight instead took place on January 22, 1968 during the Apollo 5 mission, the spacecraft being boosted into orbit by a Saturn IB. The main objectives of the flight were to confirm that the LM’s descent engine could be reliably fired multliple times, to test the vehicle’s control and manoeuvring systems, and conduct a “fire in the hole” test where the ascent engine was fired while still attached to the descent stage – the procedure that would be used to lift off from the moon or during an aborted descent. Due to a fault in the second SIVB stage guidance computer, the spacecraft achieved a lower orbit than expected. However, flight director Gene Kranz – who would later famously direct the Apollo 11 and 13 missions – quickly improvised an alternate test procedure and succeeded in carrying out all the mission objectives. This success led to the cancellation of a second unmanned LM test, greatly advancing the Apollo Programme timetable. However, an incomplete “boilerplate” LM test article was flown aboard Apollo 6, the second and last unmanned test flight of the Saturn V rocket. This flight also carried a Block I CSM with a number of Block II modifications developed in the wake of the Apollo I fire – including a new, easier-to-open crew hatch. Interestingly, Apollo 6 carried a large number of cameras, the footage from which is often used in documentaries to represent the launch of Apollo 11 and other manned missions. However, the footage is easily distinguished by the fact that the CSM is painted white; on manned missions the spacecraft were left their natural silver colour.
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