Moon landing denied. Stephen hawking - Page 3

Jeff Root · #61 (**permalink**) 14-November-2008, 08:44 AM

The word "possible" has an awfully wide range of meanings.

-- Jeff, in Minneapolis

PhantomWolf · #62 (**permalink**) 14-November-2008, 09:18 AM

Quote:

Originally Posted by Obviousman

Jay is right. It is possible, but it is simply not practical.

And he didn't even go into the issues of the fact the SSME is designed to be fired once and then has to be retooled. To get the to the moon and back, even just as an Orbiter it'd have to fire at least 4 times, 5 if it was to attempt to re-enter Earth orbit on the way back. He didn't specifically cover the issues of docking and attaching a fuel tank in space or issues with keeping the cryogenic fuels cold during the mission either.

NASA itself looked at the possibility in the mid 1980's under Reagan, but scrapped it as unfeasible without a near total redesign of the shuttle. There is a NASA paper on it somewhere. It appears that the idea was raised again in 1996 where it was suggested that Columbia be refitted for attempts at lunar orbit. Again it proved unfeasible.

Jason Thompson · #63 (**permalink**) 14-November-2008, 09:59 AM

Quote:

Originally Posted by Vallkynn

The re-entry speeds from a mission from moon, as the ones used in Apollo program were a compromise on the available technology/payload.

The re-entry speed from the Moon is a consequence of physics. If you coast back from the Moon you will be doing roughly 25,000mph when you hit the atmosphere, whatever technology and payload you happen to have.

Quote:

Of course the Shuttle could enter in an earth orbit before the reentry.

It could? How? The translunar speed is 25,000mph, while Earth orbit is 17,500mph. How would you slow the shuttle by 7,500mph? Additional fuel of course. But then where would you carry that fuel? How would you get it up in the first place?

Quote:

Plus, the shuttle could carry a lander on it's cargo bay and after moon orbit, the lander could descent by itself.

A reasonable suggestion, but you still have the get the shuttle to the Moon in the first place.

Quote:

Still, I have doubts about radiation shielding of space-shuttle in outer space.

I don't have figures for this, but I suspect that, if anything, the shuttle is actually better shielded than the Apollo spacecraft, since it is intended for Earth orbit and will often be on orbital paths that take it through a region of the inner van Allen belt known as the Southern Magnetic Anomaly every orbit, resulting in a cumulatively higher radiation does than the two rapid dashes through the belts needed on a lunar mission.

Quote:

Another requirement is fuel. An additional fuel tank would required for the trip to the moon. Maybe the cargo bay was enough, I don't know

That's the key problem. The shuttle uses all the fuel in the external tank plus the two SRBs plus a small kick from the manoeuvring engines just to get the orbiter to the 17,500mph needed to orbit the Earth. The Apollo spacecrfat needed about 70% of the fuel in the S-IVB stage to get a considerably smaller and lighter vehicle to the Moon. How much extra fuel would you need for something the size and weight of the orbiter? And then you need more fuel to brake into lunar orbit, then more fuel to break out of it again. Then you have the problem of slowing to an acceptable re-entry speed because the shuttle orbiter isn't designed for re-entry at translunar speed. Where does all that extra fuel come from? And where does it go if you have a lander in the cargo bay?

Modifying a shuttle to go to the Moon is like trying to modify a Robin Reliant 3-wheeled van to make a Pacific cruise: so absurdly complex and expensive that you'd be better off designing and building a boat from scratch.

pzkpfw · #64 (**permalink**) 14-November-2008, 10:37 AM

Quote:

Originally Posted by Jason Thompson

...like trying to modify a Robin Reliant 3-wheeled van to make a Pacific cruise: so absurdly complex and expensive that you'd be better off designing and building a boat from scratch.

Though you might get a better van by putting wheels on a boat...

Jeff Root · #65 (**permalink**) 14-November-2008, 11:03 AM

Very nice analysis, Jason. I'm a bit discombobulated by your absolutely
correct use of the words "brake" and "break" in the same sentence, though.

-- Jeff, in Minneapolis

Jason Thompson · #66 (**permalink**) 14-November-2008, 11:51 AM

Quote:

Originally Posted by Jeff Root

I'm a bit discombobulated by your absolutely
correct use of the words "brake" and "break" in the same sentence, though.

Oh, I'm sorry. I'm anaspeptic, thrasmotic, even compunctuous to have caused you such pericombobulations.

May I offer my contrafibularities?

Jason Thompson · #67 (**permalink**) 14-November-2008, 11:53 AM

Quote:

Originally Posted by pzkpfw

Though you might get a better van by putting wheels on a boat...

I know that was meant in jest, but it is also applicable to the discussion at hand. A craft designed for a lunar mission works quite easily with minor modifications in an Earth orbit mission, as the Skylab and Soyuz flights showed. Not so the other way round.

Laguna · #68 (**permalink**) 14-November-2008, 02:43 PM

Quote:

Originally Posted by Jason Thompson

Oh, I'm sorry. I'm anaspeptic, thrasmotic, even compunctuous to have caused you such pericombobulations.

May I offer my contrafibularities?

Hmmm, for some reason my english translator capitulates to this sentence.

gwiz · #69 (**permalink**) 15-November-2008, 02:52 PM

Quote:

Originally Posted by PhantomWolf

NASA itself looked at the possibility in the mid 1980's under Reagan, but scrapped it as unfeasible without a near total redesign of the shuttle. There is a NASA paper on it somewhere. It appears that the idea was raised again in 1996 where it was suggested that [/FONT][/COLOR]Columbia be refitted for attempts at lunar orbit. Again it proved unfeasible.

As originally intended, the STS system would have included a Space Tug, a high-performance cryogenically fuelled upper stage that would be carried in the Shuttle payload bay and used to carry payloads beyond low earth orbit - much easier than trying to get the Shuttle itself into higher orbit. In the event, the Tug was never funded and a variety of lower-performance solid-fuelled upper stages were developed instead.

This failure to develop the Tug is the reason manned missions beyond low earth orbit have not been seen in the Shuttle era.

captain swoop · #70 (**permalink**) 15-November-2008, 09:05 PM

Quote:

Originally Posted by Laguna2

Hmmm, for some reason my english translator capitulates to this sentence.

It's what Blackadder said to Dr Johnson.

classic · #71 (**permalink**) 16-November-2008, 01:39 AM

The space shutttle could hold tons of moon rocks in that shuttle bay. That's a lot of H3 for fuel.

JonClarke · #72 (**permalink**) 16-November-2008, 07:48 AM

Quote:

Originally Posted by Jason Thompson

I don't have figures for this, but I suspect that, if anything, the shuttle is actually better shielded than the Apollo spacecraft, since it is intended for Earth orbit and will often be on orbital paths that take it through a region of the inner van Allen belt known as the Southern Magnetic Anomaly every orbit, resulting in a cumulatively higher radiation does than the two rapid dashes through the belts needed on a lunar mission.

I think this is correct. The Apollo CM had 8g/cm2 of shielding, the Oribter 11 g/cm2.

Jon

Skyfire · #73 (**permalink**) 16-November-2008, 04:50 PM

Quote:

Originally Posted by classic

The space shutttle could hold tons of moon rocks in that shuttle bay. That's a lot of H3 for fuel.

Interesting comment. However, as has already been pointed out, there are so many problems with trying to get the shuttle to the moon, and possibly more importantly, back in one piece without burning up, that this is just not a possiblity!

Laguna · #74 (**permalink**) 16-November-2008, 05:15 PM

Quote:

Originally Posted by classic

The space shutttle could hold tons of moon rocks in that shuttle bay. That's a lot of H3 for fuel.

How much per ton?

Kelfazin · #75 (**permalink**) 16-November-2008, 06:48 PM

Quote:

Originally Posted by classic

The space shutttle could hold tons of moon rocks in that shuttle bay. That's a lot of H3 for fuel.

So now it would need to carry the equipment to extract the H3 from the rock too, increasing the mass, requiring more fuel to slow it down for entry into earth orbit.

Van Rijn · #76 (**permalink**) 16-November-2008, 09:38 PM

H3? Do you mean 3He or Helium 3? Which, by the way, we can't use today.

Nowhere Man · #77 (**permalink**) 17-November-2008, 12:34 AM

Or tritium (³H)?

Fred

DogB · #78 (**permalink**) 17-November-2008, 01:30 AM

Quote:

Originally Posted by Jason Thompson

Modifying a shuttle to go to the Moon is like trying to modify a Robin Reliant 3-wheeled van to make a Pacific cruise: so absurdly complex and expensive that you'd be better off designing and building a boat from scratch.

Or you could make it into a space shuttle.

Quote:

In the February 18, 2007 episode of Top Gear, a Reliant Robin was used by Richard Hammond and James May in an attempt to modify a normal K-reg Robin into a reusable space shuttle. Steve Holland, a professional radio-controlled aircraft pilot, helped Hammond to work out how to land a Robin safely. The craft achieved a successful launch, flew for several seconds into the air and managed to successfully jettison the solid fuel rocket boosters on time. This was the largest rocket launched by a non-government organisation in Europe. It used 6 x 40960 NS O hybrid rocket motors giving a maximum thrust of 8 metric tons. However the car failed to separate from the large external fuel tank due to a faulty alignment between the Robin and the external tank (10 thousandths of an inch out), the Robin subsequently crashed and exploded.

More details - http://www.bbc.co.uk/topgear/show/ep...episode4.shtml

Sam5 · #79 (**permalink**) 17-November-2008, 03:29 AM

I think English might not be sjunky's native language, so give him a break regarding some words and phrases.

Vallkynn · #80 (**permalink**) 17-November-2008, 09:44 AM

Quote:

Originally Posted by Jason Thompson

The re-entry speed from the Moon is a consequence of physics. If you coast back from the Moon you will be doing roughly 25,000mph when you hit the atmosphere, whatever technology and payload you happen to have.

--->Wrong, you just need fuel to reduce speed

It could? How? The translunar speed is 25,000mph, while Earth orbit is 17,500mph. How would you slow the shuttle by 7,500mph? Additional fuel of course. But then where would you carry that fuel? How would you get it up in the first place?

--->Easy, it could be with an additional launch

A reasonable suggestion, but you still have the get the shuttle to the Moon in the first place.

I don't have figures for this, but I suspect that, if anything, the shuttle is actually better shielded than the Apollo spacecraft, since it is intended for Earth orbit and will often be on orbital paths that take it through a region of the inner van Allen belt known as the Southern Magnetic Anomaly every orbit, resulting in a cumulatively higher radiation does than the two rapid dashes through the belts needed on a lunar mission.

--->I don't think so. Actually the Southern Magnetic Anomaly is avoided in orbital paths. You're saying that 4 days outside the earth magnetic shield is safer than 7 days in orbit? Bull****.

That's the key problem. The shuttle uses all the fuel in the external tank plus the two SRBs plus a small kick from the manoeuvring engines just to get the orbiter to the 17,500mph needed to orbit the Earth. The Apollo spacecrfat needed about 70% of the fuel in the S-IVB stage to get a considerably smaller and lighter vehicle to the Moon. How much extra fuel would you need for something the size and weight of the orbiter? And then you need more fuel to brake into lunar orbit, then more fuel to break out of it again. Then you have the problem of slowing to an acceptable re-entry speed because the shuttle orbiter isn't designed for re-entry at translunar speed. Where does all that extra fuel come from? And where does it go if you have a lander in the cargo bay?

--->I though it was clear that a lunar lander will not fill the cargo to full capacity. Obviously the remaining space could be used to carry fuel. Also the trip could take a little big longer than the 4 days of apollo program.

Modifying a shuttle to go to the Moon is like trying to modify a Robin Reliant 3-wheeled van to make a Pacific cruise: so absurdly complex and expensive that you'd be better off designing and building a boat from scratch.

--->I don't agree, the absurd thing here is that after 40 years, NASA is still planning to go to the moon using the same concept and the same technology, with some improved computers in the middle. There's nothing new.

Laguna · #81 (**permalink**) 17-November-2008, 10:20 AM

Quote:

Originally Posted by Vallkynn

--->I don't agree, the absurd thing here is that after 40 years, NASA is still planning to go to the moon using the same concept and the same technology, with some improved computers in the middle. There's nothing new.

Nothing new? What do you excpect them to use?

Nicolas · #82 (**permalink**) 17-November-2008, 10:37 AM

Quote:

However the car failed to separate from the large external fuel tank due to a faulty alignment between the Robin and the external tank (10 thousandths of an inch out), the Robin subsequently crashed and exploded.

I don't have all the information, but reading this, I'd say don't blame the misalignment. Blame whatever system they came up with that requires such a ridiculously precise alignment. A quarter mm on a car during a violent launch...come on.

Quote:

--->I don't agree, the absurd thing here is that after 40 years, NASA is still planning to go to the moon using the same concept and the same technology, with some improved computers in the middle. There's nothing new.

100 years after the ford T, we still drive 4 wheeled cars with front placed combustion engines and air-filled rubber tires to get to places. Just some computer technology and improved design in the middle. Same for aircraft: still a fuselage with some wings, tails and engines here and there, just a bit improved. Don't even get me started about still eating with a spoon.

Why would you want to step away from the rocket-with-capsule concept to go the moon? How else would you do it? The fact that we used this technology and concept for a long time doesn't mean it's bad. In contrary, it might be a clear sign that it's good.

Tog_ · #83 (**permalink**) 17-November-2008, 11:21 AM

For that matter, can you believe people still hunt with a bow and arrow?

The simple fact is: It worked then, so it's a pretty safe bet it will work now.

Make it more efficient. Make it more safe. Change what needs to be chanced to accommodate the new mission goals, but to come up with a radically different method just to have something radically different sort of defies the whole common sense thing.

Nicolas · #84 (**permalink**) 17-November-2008, 12:30 PM

btw I just googled it, and it appears I'm spot on with my "100 years after the Ford T", which was a wild guess

.

Jeff Root · #85 (**permalink**) 17-November-2008, 01:23 PM

The idea of trying to modify a Space Shuttle orbiter to orbit the Moon just
seems intensely silly to me. It's a little kid's idea, not an idea from anyone
who knows anything about engineering, celestial mechanics, or project
management. The one big advantage of the orbiters is that they exist.
Everything else is a disadvantage. They are completely the wrong design
of vehicle for the task, and very obviously so.

Having said that, I do think the Shuttle 'Churchill' in the movie 'Lifeforce'
was pretty nifty, with its nuclear engine in the payload bay.

-- Jeff, in Minneapolis

Vallkynn · #86 (**permalink**) 17-November-2008, 02:06 PM

Quote:

Originally Posted by Laguna2

Nothing new? What do you excpect them to use?

A government space program is supposed to do research because private companies don't have the huge resources required for fundamental research, so it's expected that major achievements come from NASA.
Sooner or later the technology from space programs will enter the life of common citizens and there's lots of examples on this. Sadly the present approach is conservative. 50 year old multi-stage rocket designs, ballistic capsules and Launch Tower escape systems are not exactly high technology demonstrations, but only approaches from someone only interested in keeping his job by not taking chances.

It wasn't that approach that took the men to the moon.

The aerospike engine, the rotary engine, the peroxide engine, the SSTO are concepts currently shelved. Not one of them is to be used. So what's the purpose of getting back to the moon with the same basic hardware? To say that "See, we still can do this"..... 50 years later..........

Nicolas · #87 (**permalink**) 17-November-2008, 02:11 PM

So Vallkynn, you do have quite clear opinions about what a government space agency should do. On what do you base that opinion; do you have knowledge or experience in space engineering?

Do you know what the governmental space agencies are and are not researching at the moment? You name a few concepts and say they are shelved. These concepts are not being implemented in a lunar craft, that is true. But does that mean the governmental space agencies did not research them at all?

Is Ares the same basic hardware as Apollo? Is there a better alternative for the money available that serves our space needs in LEO and beyond? to name one example you put in your post: why should they not use an escape tower; in your wildest dreams, what better alternative can you think of; what is wrong with an escape tower?

I appreciate all opinions when they have solid arguments to back them up, but no armchair engineering or armchair managing please.

Especially with your escape tower argument, you come accross to me as if expecting NASA to innovate always and everywhere for the sake of innovation, because it's government rather than private. You don't want them to use an escape tower because that's already been done in the past. Where does this stop, are the astronauts allowed to sit in chairs or should they invent some magneto-body-lifter gizmo to float in on the ride up?

Vallkynn · #88 (**permalink**) 17-November-2008, 02:13 PM

Quote:

Originally Posted by Jeff Root

The idea of trying to modify a Space Shuttle orbiter to orbit the Moon just
seems intensely silly to me. It's a little kid's idea, not an idea from anyone
who knows anything about engineering, celestial mechanics, or project
management. The one big advantage of the orbiters is that they exist.
Everything else is a disadvantage. They are completely the wrong design
of vehicle for the task, and very obviously so.

Having said that, I do think the Shuttle 'Churchill' in the movie 'Lifeforce'
was pretty nifty, with its nuclear engine in the payload bay.

-- Jeff, in Minneapolis

Little kids ideas originated space programs, rockets and ultimately the space shuttle. The problem here is that nobody is really understanding why so many years later we're going to use the same old basic hardware. If no basic breakthrough was achieved then maybe it's worthless to return to the moon.

Nicolas · #89 (**permalink**) 17-November-2008, 02:18 PM

Quote:

Little kids ideas originated space programs, rockets and ultimately the space shuttle.

Little kids ideas originated an awful lot of concepts. Solid engineering and science is what sifts fantasy from achievable idea. What do you have in mind for NASA to do?

Quote:

The problem here is that nobody is really understanding why so many years later we're going to use the same old basic hardware.

I understand it. Don't generalise.

Quote:

If no basic breakthrough was achieved then maybe it's worthless to return to the moon.

Is it? I thought that in '69, the travel an sich was the mission. This time, the destination is the mission, the travel just the means. We're building better means to go to the moon using the same basic concepts. What's wrong with that when no better alternative is available within budget or even necessary?

Donnie B. · #90 (**permalink**) 17-November-2008, 02:22 PM

Quote:

Originally Posted by Vallkynn

The problem here is that nobody is really understanding why so many years later we're going to use the same old basic hardware.

Well, at least one person here isn't understanding why we're going to use the same old basic hardware.

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