Moving in 1/6th gravity.

[margamatix]

On the moon, where gravity is only a sixth of that on Earth, a man should be able to jump 10 feet vertically, yet the highest jump made by any astronaut was 19 inches, and horizontally, steps taken were no longer than those on Earth. is there a reason for this?

[Bob B.]

The astronauts needed to maintain their balance and control. Just because you can do something doesn't means you should. What if an astronaut did something ill-advised and damaged his equipment or hurt himself. This would be a very serious problem. The astronauts limited their movements to those that could be safely controlled. You have to also consider that the bulky pressurized spacesuits limited their mobility. They just couldn't get into the deep crouch needed to jump exceedingly high. Furthermore, the 19 inch figure I don't believe is accurate. The astronauts jumped considerably higher than this to get up to the first rung of the LM's ladder. Of course in doing so they could grab hold of the side rails of the ladder to steady themselves.

[margamatix]

Is it true that if you double the speed of the film, the astronauts look *exactly* as they would look running around on Earth in a clumpy suit?

I also heard that no country claims to have sent any man, woman or animal more than 400 miles away from Earth in the last 30 years, but the moon is 240,000 miles away. Is that true?

Finally, is it true that the daytime temperature on the moon is 250 degrees celsius?

[JayUtah]

The highest jump made by an astronaut was 5 feet.

The astronauts themselves discussed mobility extensively. Neil Armstrong said he made several attempts at high jumps, but stopped when he nearly fell over backward. Balance is more difficult to judge in lower gravity. The suits had a center of gravity higher and to the rear compared with a normally-clad human being, so they had a tendency to rotate backwards.

The major limiting factor was the flexibility of the suit. You get only as much thrust as you can generate in your contact with the ground on departure. It's not a matter simply of thinking of how little resistance there is from gravity. If you were to jump on Earth bending your legs only as much as the astronauts could, you would only rise a few inches. It takes quite a bit of work to bend your legs further: you have to fight the pressure of the suit and (in the case of the earlier models) the inability to bend at the waist. Further, the suits have a mobility assistance system that attempts to help bent limbs stay bent. It's a system of cables, pulleys, and friction sleeves that means when you finally got your legs bent against the pressure of the suit, you could not extend them as rapidly as without the suit.

Neil Armstrong, in describing his five-foot leap up to the LM ladder (which is on the TV coverage), said he had to work hard to bend enough to get a good launch, and then wasn't able to push with his legs as hard as he might without the suit.

Most astronauts, by their own admission, simply didn't want to try gymnastic moves, simply out of fear of falling down and hurting themselves or their equipment. They weren't balanced enough for it.

[JayUtah]

Is it true that if you double the speed of the film, the astronauts look *exactly* as they would look running around on Earth in a clumpy suit?

No. The conspiracy theorists show you five seconds of carefully chosen film that looks like that might work, but if you speed up any randomly-chosen other bit of film, it looks like sped-up film.

I also heard that no country claims to have sent any man, woman or animal more than 400 miles away from Earth in the last 30 years, but the moon is 240,000 miles away. Is that true?

True, but irrelevant. Bart Sibrel, who originated this claim, sets an arbitrary limit of 30 years because he knows that earlier than this the Soviets sent Zond 5 around the moon and back with biological samples aboard that were recovered alive and safe. This is what we call a "rail-split". He's concocted what sounds like a meaningful test, but it carefully and arbitrarily avoids the answers that prove his general point wrong.

Finally, is it true that the daytime temperature on the moon is 250 degrees celsius?

The temperature of what?

[margamatix]

jayutah said:

Finally, is it true that the daytime temperature on the moon is 250 degrees celsius?

The temperature of what?

Well, everything. You get a cold day, you get a hot day. It was hot here today (London, England) at around 30 degrees celsius. 45 is the highest I have ever experienced, in the Middle East.

I would have thought that 250 degrees celsius is very hot and I would be too tired for playing golf or driving around. In fact, I imagine I would be dead within a few seconds of being in it.

There is no type of spacesuit-cooling system which is pysically plausible so what's the story here?

[Bob B.]

margamatix said:

Well, everything. You get a cold day, you get a hot day. It was hot here today (London, England) at around 30 degrees celsius. 45 is the highest I have ever experienced, in the Middle East.

Of course the temperatures you are referring to are air temperatures. There is no air on the Moon so the only thing that can heat up is the ground. The 250-degree figure that is so often quoted is the maximum temperature that can be achieved. The Apollo landings all occurred during lunar morning when the Sun was low in the sky and the ground had not yet heated up to those kinds of temperatures.

margamatix said:

There is no type of spacesuit-cooling system which is pysically plausible so what's the story here?

This is entirely untrue. The Apollo spacesuits did have a cooling system and those who claim the cooling system wouldn't work are largely ignorant about heat transfer. Quite simply, they don't know what they're talking about. Here is a link describing the Portable Life Support System (PLSS) and how it worked:

history.nasa.gov/alsj/plss.html

[margamatix]

bob said:

[ The Apollo landings all occurred during lunar morning when the Sun was low in the sky and the ground had not yet heated up to those kinds of temperatures.

But surely they were there for three days?

[echnaton]

margamatix said:

There is no type of spacesuit-cooling system which is pysically plausible so what's the story here?

Welcome to the board, margamatix

How would cooling a space suit differ from cooling a space capsule?

If you are contending that space suits can’t be cooled then you are also in essence saying that space ships can’t be cooled either and that the whole space program is a hoax.

[twinstead]

margamatix said:

bob said:

[ The Apollo landings all occurred during lunar morning when the Sun was low in the sky and the ground had not yet heated up to those kinds of temperatures.

But surely they were there for three days?

The lunar day lasts 2 weeks, IIRC.

[Bob B.]

twinstead said:

The lunar day lasts 2 weeks, IIRC.

That's correct. In one day on the Moon the Sun moves only about as far as it moves in 50 mintues on Earth. The Earthly equivalent to staying three days on the Moon is like arriving 7:00 AM and leaving at 9:30 AM.

[JayUtah]

It was hot here today (London, England) at around 30 degrees celsius.

What was hot in London? The air? The ground? The buildings? The water of the Thames?

I'm not being obtuse: you need to thoroughly understand what you're saying and/or asking before the answers will make sense. When we say "it" is hot outside (on Earth) we generally mean the air temperature. That has no meaning on the moon. So when we say "it" is hot on the moon, we mean the only thing on the moon that's capable of having a temperature: the surface.

But why does it get hot/cold? Because the sun shines on it. The degree to which the sun warms things depends on how much sunlight is absorbed, and that's different for different kinds of materials. So at lunar noon the temperature of some parts of the ground may indeed be 250 F, but that doesn't mean that another object -- say, one made of aluminum -- will reach the same temperature. Aluminum absorbs far less solar energy than lunar rocks, so it may get to only 100 F.

There is no type of spacesuit-cooling system which is pysically plausible so what's the story here?

A lot of us here are professional engineers. I happen to design thermal control systems for supercomputers, so I can tell you with quite a lot of confidence that the cooling system described by NASA for the space suits is entirely plausible. In fact, the system is sold as a commercial product.
xnwp021.utc.com/ssi/ssi/Applications/SpaceVehicles/crv_sublim.html

The space suit reflects away about 80% of the solar energy that strikes it. And half of it is in shade at any given instant. And it's heavily insulated so that although the outer layer may heat up, it doesn't conduct heat to the inside. Conversely, it doesn't conduct the astronaut's metabolic heat to any place where it can be radiated or otherwise rejected. Hence the sublimator: the astronaut's metabolic heat is drawn away by a liquid-cooling garment, and that coolant is in turn chilled by sublimating ice. As long as you have a perfect vacuum in which to set up the sublimation condition, you can reject heat quite effectively this way.

[JayUtah]

I might add that cooling an astronaut on the lunar surface is little different than cooling him in low Earth orbit or anywhere else in space. On the moon you do tend to get a little more heat through re-radiated thermal energy from the surface, but the primary external heat load will still be direct radiation from the sun, and that's the same whether you're standing on the lunar surface or floating about in Earth orbit. As with all space suits, the primary thermal problem is rejecting the astronaut's metabolic heat.

The thermal systems for the Apollo astronauts are no different than the thermal systems for the space shuttle astronauts, the Soviet cosmonauts, or the ISS crew. They all use systems that differ little in design and operation from the Apollo suits. So contrary to what the conspiracy theorists tell you, this is common technology. It's not something that was invented only for Apollo and never used elsewhere.

[papageno]

margamatix said:

There is no type of spacesuit-cooling system which is pysically plausible so what's the story here?

Have you ever watched Rough Science on BBC2?
In the series set in Death Valley, they made a cooling system for a suit which was not much bulkier than modern space-suits.

[gwiz]

margamatix said:

On the moon, where gravity is only a sixth of that on Earth, a man should be able to jump 10 feet vertically, yet the highest jump made by any astronaut was 19 inches, and horizontally, steps taken were no longer than those on Earth. is there a reason for this?

OK, Margamatix, as you claim no-one has answered you on this, what don't you understand about the following?

19 inches is not true, the maximum that they jumped was some 5 ft. The bottom step of the LM was at least 3 ft up. Look for video of the crew entering the LM at the end of each EVA.

They were wearing spacesuits which, including the backpack, about doubled their weight. The suits also restricted their agility. Were these factors included in your 10 ft estimate?

If all that stands between you and vacuum is a space suit, you're not going to risk a fall that damages it. A high jump in 1/6 g means a long time off the surface with no means to control your attitude and keep pointing head up/feet down. These factors combine to suggest that going for the maximum high jump is unwise.

To my eyes, the loping run that was the favoured way of getting about on the Moon certainly looked to have a longer stride that an Earth equivalent. Again, have you looked at the video?

This seems to cover all your points, so what's your answer?