G’day Jupiter2
You’ve raised a number of questions which suggest you’ve got an incomplete knowledge of how rockets work. Others have addressed them, but I’d like to deal with just a few.
You mean like the Surveyor spacecraft which soft-landed on the Moon?
Heck of a complex question, there.
The Apollo astronauts got some of their information by looking out the windows, to see the ground beneath them. But the LM also had a radar, and the Lunar Module Pilot was able to tell how fast the LM was descending, and how fast it was moving forwards/backwards and left/right.
In addition, NASA had calculated a flight path, meaning that everyone knew how fast the LM would be descending at any altitude. If they were descending at the wrong rate, they could change their angle of descent to get it back on course.
And, as others have explained, three of the LM’s legs had six foot probes protruding underneath, and as soon as one of them touched the ground, the Commander shut off the engine to ensure it wasn’t firing at touchdown.
If you think that’s the only proof that Apollo was real, you’re sorely mistaken. There are plenty of other pieces of evidence which all point in the one direction.
What’s wrong with using radar to determine altitude?
No. Six times the gravity means six times the thrust needed to accelerate a given mass. That’s a whole different basket of fish.
Why is the time from undocking important? At the time it undocked, the LM was in a sustainable orbit. After that, it entered the descent orbit, which was also sustainable. Once it fired the Descent Engine to descend to the surface, it could still abort the landing at any time. As it happens, the Descent Engine fired for 12 minutes and 32 seconds from the start of Powered Descent to Touchdown. The fuel load was calculated to include some hover time so the Commander could check out the landing site with his own eyes. In the case of Apollo 11, Armstrong changed the landing site because the intended landing site was full of rocks.
What do you mean “no help from Mission Control”? The descent path was plotted out well in advance, and everyone in the LM and in Mission Control knew what that path was. They also knew, thanks to radar and other instruments, the actual speed and position of the LM. Comparing the plan with the actuality allowed initially the LM computer and later the astronauts to adjust the trajectory in real time.
And others have pointed out that the LM was inherently stable, with most of its mass low in its structure, and in any case had an automatic correction system in the form of gyroscopes and the Reaction Control System.
And why doesn’t this happen with other rockets? Like the Surveyor spacecraft which landed on the Moon, or the Viking spacecraft which landed on Mars? And in general, if rocket exhaust is so hot, how do other rockets survive?
If you really know what the pogo effect was, you’d know whether it was relevant.
Think about this, Jupiter2. In order for a rocket to ascend, its thrust must exceed its weight. If the thrust equals the rocket’s weight, the rocket will hover. But if the thrust is less than the rocket’s weight, it will descend. At its most basic, that’s all that’s involved in landing the LM.
It’s fairly straightforward to come up with a thrust profile which takes account of weight, thrust, speed and altitude to ensure that a descending spacecraft achieves zero speed at zero altitude, with some fuel left. You can even try a simple lunar landing simulator at
www.apolloarchive.com.
Remember, acceleration is proportional to thrust divided by weight. Do the calculations and see if it’s wrong.
Here’s a counter-example. In the movie “Moonraker”, the Shuttles crawl off the launch pads. In reality, the Shuttles clear the tower in half the time it takes in the movie. But the movie was produced before any Shuttles had lifted off, and the producers didn’t know how fast they’d climb in reality. Instead, they modelled the lift-off on the only large rocket they knew – the Saturn 5.
Reality doesn’t always match our expectations.
What’s wrong with the idea of practicing the camera panning? The guy operating the camera knew where the countdown was, knew the delay, and knew when he had to start panning. Even then, he messed it up on Apollo 16.
The Ascent Engine fired into the Descent Stage. No exhaust directly hit the ground, so you wouldn’t expect dust to be blasted. Instead, what gets blasted is the stuff the exhaust actually hit – insulation material on the Descent Stage.
Most rocket exhausts in a vacuum are invisible. Look at the rocket exhaust on a Delta rocket launch. Look at the exhaust of the Space Shuttle Main Engines. In fact, the fuel on the LM was also used on the Titan rockets used in the Gemini program. Have a look at their exhausts, and you’ll see they’re virtually invisible, even in the Earth’s atmosphere.
So why do the Gemini launches have big clouds of smoke? Because when the engines are being started, the fuel/oxidiser ratios aren’t perfect, and so either spare fuel or spare oxidiser reacts with the air. This can’t happen on the Moon.