Tomorrow is the anniversary of the Apollo 11 moon landing. For most of the followers of this blog, it is part of history. I saw it happen, on a grainy black and white TV in the lounge of a college dorm. (see 27. That Was My Childhood)
You can’t land on the moon by parachute, nor by wings. No air. The only choice the Apollo program had was to land tail first, by rockets, something that had been a science fiction staple for decades, but was nothing like easy to manage. (see yesterday’s post)
Designing a craft to do the work was within the limits of the technology of the day. Vertical landings on Earth had been successfully accomplished. Pilot control on Apollo was expedited by having the astronauts stand to fly the Lunar Lander; the problem with VTOL planes had been that the pilots were strapped into a seat that kept them facing the wrong way when they landed.
The craft could be built, the astronauts were the best test pilots America had to offer. But how do you train?
Simulators? Maybe. Resurrect Pogo or Vertijet? Perhaps. Build a new craft just to use as a trainer? Better. But how do you build a trainer to react as if it were in a 1/6 gee field while landing in on Earth? You can’t just make gravity go away – or can you.
The answer is almost, more-or-less, and good enough to do the job. The first iteration of the trainer was the Lunar Landing Research Vehicle, nicknamed the flying bedstead. You may have seen it. Neil Armstrong ejected from one of them after the controls failed; the footage of the crash is both exciting and brief, which gets it a lot of air play in retrospective specials, especially on anniversaries like tomorrow.
If you see footage of the LLRV not crashing, or of the advanced version LLTV (Lunar Landing Training Vehicle), you can easily see what it is all about. The vehicle consists of an open framework of tubing with the pilot sitting upright in the front (in an ejection seat, thank goodness) with a batch of somewhat shrouded equipment balancing the rear. In the middle, attached vertically, pointing downward and clearly throwing flames, is a jet engine. The craft is uneasily hovering.
Note, I didn’t say hovering on its jet. That is what it looks like, but that is not what is happening. Not quite. When the jet is fired up at takeoff, the LLRV or LLTV simply sits there. The jet has 5/6 of the thrust needed to lift the craft. While hovering, the rest of the thrust is provided by a separate set of hydrogen peroxide thrusters which are controlled by the pilot. If the pilot were to simply turn off his thrusters, the LLTV would crash to the ground at the same speed it would crash to the moon.
The jet subtracts enough of the LLTV’s mass to make it react as if it were in a 1/6 gee gravity field, allowing the pilot to maneuver his craft as if he were coming in for a lunar landing. Armstrong made over fifty LLTV landings before he landed on the moon.
If you want to know more about this craft, there is a half hour special full of information, old footage, and interviews with retired LLRV pilot and an engineer from the project. Huell Howser is the host. If you live in California, and you watch PBS, you know Huell. He is an acquired taste that I have never quite been able to acquire, but sometimes what he covers makes up for his idiosyncrasies. This is one of those cases. The program is California’s Gold #13003 – LUNAR LANDING. Try your local PBS station or check with the Huell Howser Archives at Chapman University.