Could the Space Shuttle be flown to the moon?

I realize that the shuttle wouldn't be too useful as a lunar lander, but if one of the pilots decided to, could he/she loop the craft around the moon and return to earth orbit? Any input from JPL would be helpful.

You need an awful lot of fuel to change from a simple earth orbit to head off to the moon, and a similar amount to slow down when you get back. My gues is that the shuttle is not designed to carry that much fuel. Hey, it doesn't even have enough to get into earth orbit to begin with; that's what the boosters are for. The shuttle has enough for minor course corrections and a safe landing. That's probably it.

Absolutely. They would need to make some serious modifications and increase the main tank capacity, configure it to carry much more O2 and life support systems, but the orbiter could definately make the trip. If your discussing the entire luanch system including the boosters and tank as is, then no, chances are there wouldn't be enough thrust. I would wager that JPL, and NASA have plans drawn up in case they ever wanted to do it. Chances are it is just more efficient to build a new transport from scratch than to retrofit anything using the precision neccessary for a space vehicle.

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The facts expressed here belong to everybody, the opinions to me. The distinction is
yours to draw...

Omniscient; BAG

Well, I'm not in JPL but I can answer the question for you. It can't be flown to the moon. It is designed as a vehicle for LEO (low earth orbit) only. It can't even be flown to geosynchronous orbit.

There are zillions, and I'm using that number conservatively :-) of problems that would prevent this. The shuttle, for instance, can't produce enough delta-V to get to the moon. The SSME's can't be started in earth orbit. The craft isn't stressed for atmospheric entry at the sorts of velocities that would be involved from a trip around the moon and back. The shuttle is not radiation hardened outside of LEO, where the radiation environment can be harsher (outside the van-allen belts). Etc etc etc - there are hundreds more issues.

I rather suspect it would be much, much cheaper to design an entirely new vehicle for the purpose than to try to modify a shuttle.

The basic thing to know here, I guess, is that manned spacecraft aren't like cars that you can just point somewhere, press the accelerator, and go there. They are designed to a very specific set of requirements, and it's very complex to run them even within those parameters.

Hope this answers your question :-)

k0myers

Omniscient writes, "Absolutely. They would need to make some serious modifications and increase the main tank capacity, configure it to carry much more O2 and life support systems"

Rather: absolutely not. First, the original question was whether a shuttle commander could just "decide to do it", and the answer to that is "not even remotely possible in his wildest dreams". But even in the "serious modifications" category, the answer is "in theory, with an unlimited budget, yes, in the same sense that in theory I can convert my car into an ocean going vessel and sail to England, but it reality it makes little sense." It's just the wrong tool for the job.

It's actually far more involved than just increasing the available expendibles, making some tweaks, and flying away to the moon. There are hundreds, more likely thousands, of technical problems, some of which would take literally years to address and have huge impacts on the rest of the system. The shuttle is an enourmously complicated system. It has been called the most complex thing created by humans; I don't know if that's really true, but it's certainly right up there!

Off the top of my head I can think of: guidance and software issues (a great deal of software would have to be re-written from scratch, and in a man-rated system this is no trivial thing), structural issues when you get back want to aerobrake (presumably you want to get the astronauts back alive, and the current shuttle isn't stressed for re-entry from the necessary speeds - doing so would make it heaver, and propegate yet more changes all throughout the system, as would adding yet more fuel for non-aero type braking), radiation-hardening issues for the shuttle's onboard systems, cooling issues, etc etc etc - this is just barely scratching the surface, and it doesn't get into the procedural changes, the necessary changes in ground equipment, people training, and so on.

It'd be a really hard thing to do.

k0myers

Alright how about an answer from JLP.
Yes, you can take the shuttle to the moon. You just point it where you want to go and say "Engage"

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no matter where you go...there you are

JLPicard writes, "You just point it where you want to go and say 'Engage'"

Now that's funny :-). I wonder if the real space shuttler commanders are ever tempted to do that.

k0myers

Just for kicks, let's say you did point it in the right direction and fired the engines. Wouldn't it go there? (Forget the crew)
Maybe to the Sun?
Peace,
mangeorge

mangeorge ponders, "Just for kicks, let's say you did point it in the right direction and fired the engines. Wouldn't it go there?"?

Well, it's sort of more involved than that. Here's a brief synopsis - I'm sure there's more detailed info on the web if you're interested - this is just from memory here. But briefly: the shuttle has a number of different types of engines. Some of them, like the SRB's (solid rocket boosters) are part of the shuttle stack but separate on the way up. The SSME's (space shuttle main engines) are part of the shuttle proper, but their fuel is contained in the big external tank you see affixed to the stack when it's on the pad; that drops off before the shuttle enters orbit as well. And then there are the OMS thrusters, which stands for "Orbital Maneovering System", and the RCS (reaction control system) thrusters. Both of those are fairly small, and run of internal fuel stored within the shuttle.

Ok, with the definitions out of the way, let's consider the question. Neither the RCS nor OMS thrusters can produce enough delta-V to send the shuttle to the moon - they're not even in the right ballpark. The SRB's drop off on the way up, which leaves the SSME's. The SSMEs, in theory, could produce enough delta-V, but in practice they can't do it either because, (1) they don't have any fuel when the shuttle is in orbit, and (2) they can't be started in orbit, only on the ground. (Starting those suckers up is a pretty complicated series of steps; it's a lot more involved than, say, starting your car).

So even if you didn't care about all the other issues and just wanted to send the shuttle on a one-way trip to the moon, you couldn't do it without other physical modifications to the system, to allow another fuel source for the SSME's and to allow them to be started in orbit. The problem with starting the SSME's in orbit is that it requires a lot of equipment that's only present on the pad. For instance, before you can fire them up, you need to cool certain parts of the engines to specific temperatures, for one thing. There are probably other issues, but that's getting beyond what I know about the system.

Sorry for the long-winded answer, but at least it might give you some idea of what's involved.

k0myers

>The shuttle, for instance, can't produce
>enough delta-V to get to the moon.
Ok,I'm not used to this spacecraft lingo, but at my first guess would be that Delta-V is change in the ships speed or thrust. I seem to remember from physics that moving to higher orbit requires incrementally less thrust, so if it has enough thrust to make a higer orbit, which it does or it would never dock with anything, then it has enough thrust to break orbit. This is of course not to say that it has enough fuel to break orbit, it seem the common consensus is that fuel is the biggest problem.

Hi Falcon2,

Yeppers, you'rre absolutely correct that the higher you go (i.e, the further out of the earth's gravity well), the less oomph it takes to go higher yet.

But the shuttle doesn't (relatively speaking) get very high - this is again just from memory, but I believe it's standard orbit is in the ballpark of 160 miles, and it can go somewhat higher at the cost of reduced payload. From LEO, it takes about +4 km/sec to get to the moon, which is less than from the surface to LEO, but still not trivial. You're out of the worst part of the gravity well in LEO, but there's still some, and then there's just the shuttle's mass to be accelerated.

I can probably work out the numbers if you're interested, but it'll take me a while because I don't remember the thrust of the various shuttle engines, nor the mass of the shuttle, so I have to go look a bunch of stuff up before I can figure out how much fuel it would take. Anyway, fuel is only one of the problems. My gut feel (without having done the math, so I could easily be wrong here) is that you could probably carry enough fuel in the cargo bay to send the shuttle around the moon, as long as you didn't care about slowing down on the way back, and assuming you had worked out all the details of feeding the engines from that fuel supply and starting them in orbit and so on.

k0myers

Most of the answers dealing with delta-v here are neglecting the possibility of in-flight refueling. Suppose we have a station in orbit that's been stuffed with fuel?

It'd take even more than two "full tanks" to get the shuttle to the moon, but with enough refueling stops, you would eventually get there. Of course, if you had enough time and enough refueling stations, you could theoretically fly to Andromeda. Whether it's realistically possible is a different question entirely.

jens ponders, "Suppose we have a station in orbit that's been stuffed with fuel?"

Then it becomes easier for (our hypothetical, ultra-modified) shuttle, because it doesn't have to cart all of it's fuel up from the surface. And you spend most of your fuel, lifting the rest of your fuel :-), so it can help quite a lot to have some already up there. Of course, that's neglecting the 47 zillion other problems with this whole scenario, but we'll ignore those, since we're quite far into fantasy here anyway!

In fact, it's interesting you thought of this, because a lot of thought is being given by the aerospace community to cheaper ways to lift expendibles like water and fuel to orbit. Putting them on a man-qualified rocket is horribly expensive, and also, supplies are much more rugged than people, so it's OK to slam them around on the way up in a way that would damage humans. People are looking into cheap ways to lift sturdy things into LEO, so you are right on the mark about the advantage of it!

AuraSeer writes, "It'd take even more than two "full tanks" to get the shuttle to the moon, but with enough refueling stops, you would eventually get there"

Wait, hold the bus :-). I'm not sure exactly what you mean by "a full tank", or which thruster system you're talking about specifically, but this is a misleading thing to say. Generally, spacecraft don't just thrust all the way to their destination; there's no way to carry that much fuel (I'm just talking about hypergolic propulsion here, not exotica like ion engines), and they can't refuel along the way because even if there was something to refuel from on the way, they've done so much work to speed up that it wouldn't be worth while to slow down until they get where they're going. Basically, they thrust at the very beginning of the journey to give themselves enough delta-V to get where they're going, and then coast for almost the entire distance (it's a little more complex than that, but that's a good 1st order approximation). Sometimes, they can even use other planets' gravity to help boost their speed. If they need to slow down at the end, then they must thrust again to slow down, or aerobrake if the destination has an atmosphere (the moon has almost none), or both.

But whichever, you can't really think of it like a car that goes for 400 miles, fills up the tank, goes for 400 more miles, and so on. The physics of space travel is very much different than we're used to here on earth. And getting from LEO to the moon is actually easier (IIRC) than getting from the earth's surface to LEO.

I'm glad to see that people are interested in space travel. I believe it is one of the most important things for our species to do, just for our own long term survival as well as for the knowledge we gain in the process.

k0myers

Pardon me, I'm short on sleep and my post was worded fuzzily. What I mean is that the Shuttle, minus its external tank, has a relatively small fuel supply. One full load of fuel can't even bring the ship to geosynchronous orbit; even more fuel would be required for a moon shot. To make the round trip, it would certainly have to refuel more than once.

If you truely want to understand the dimensions of the fuel problem, simply take a scale model of a Saturn V rocket and place it next to a scale model of the shuttle launch configuration (shuttle, exterior LO2 tank, and 2 solid fuel boosters). Then compare the sizes of the payloads.

The gigantic Saturn V is needed just to send a tiny capsule and LEM to the moon. The relatively tiny shuttle tanks and rockets have a payload that is thousands of times heavier, but then they are only required to take their payload 0.012 the distance!

Has any one thought of a space elevator? I know it sounds strange, but it has at least been thought of. Basically all you do is take a long segment of A
super-light super-dense cable and attach it to a platform in a low earth geo-synchronous orbit. Attach the other end to the ground and ride a magnetic elevator into orbit. This doesn't help your space shuttle to the moon, but what it does do is give you an easy way to refuel your "Acme all purpose space shuttle" Has any one else herd of this? I know that it's been done in books but any real plans?

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no matter where you go...there you are

Soul., the idea of a nuclear powered engine is being developed, but on a different scale than you are using. First you must understand that a nuclear engine in a space travel evironment doesn't worklike a sub or carrier. Basically the nuclear engine just creates electricity that turns a electric motor which turns the screws on the ship. In space a mechanical engine doesn't work because in a vacuum there is nothing for the mechanical engine to push off. Now the electric engines in development are being designed for use on very small interstellar and interplanetary explorers. The way a electric engine works in space is amazingly complicated, and there are a variety of competeing ideas on how to make it work. One method basically creates a charge and sends electrons in an Arcjet from a plate into a collector at the back of the module. This creates a thrust because of the momentum created by the impact of the electroms. Knowing how small the electrons are you can imagine how small these forces are. No matter what type of engine wins the "race" it will be used on a scale where the thrust is of the magnitude .01-.1 Newtons at a specific impulse of 1000 seconds. My professor was working on a 50W Helium pulsed Arcjet for installation on orbital satilites for orbital manuvering. The specifics of this type of engine baffle me to this day, its a shame he class was at 9 am or I may have learned how it worked. All that being said not even the most ambitious proffessor has thought a nuclear/electric engine could be used to reach escape velocities and even alter orbit altitudes. The magnitudes of thrust are just way to small compared to the necessary forces.

As for the space elevator, the idea is so absurd I won't get into the physics of it. First the wieght of such a cable would be so great the nothing could even lift it to get it to the launch platform let alone get it of the ground. Second, what would hold it up? Do you think that space is some magic place that holds things in it? Anything in space is constantly falling, and the entire length of the cord would fall very quickly because of the segments that are close to the earth.

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The facts expressed here belong to everybody, the opinions to me. The distinction is
yours to draw...

Omniscient; BAG

Omniscient, Actually, the physics do work out in a beanstalk design. It has been shown that modern carbon fibers have the tensile strength to resist the pull on them, and buckytubes are even better. As for what holds the beanstalk up? Centripital force does. The stalk is long enough that the tangental force on the space end is great enough to pull the entire stalk taut. Think of it as a yoyo that you are spinning over your head. (Just hope the stalk don't break, cause if it does...well thats a lot of stuff going on a long trip.)


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>>while contemplating the navel of the universe, I wondered, is it an innie or outie?<<

---The dragon observes

Oh, and most proponents of the beanstalk, feel that you wouldn't lift the entire structure at once, you would lift your end mass and a couple of cables, then start spinning the rest of the stalk, working downwards rather than upwards. (Move cables up into orbit normally at first, connect them to the stalk and then spin them downwards.)

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>>while contemplating the navel of the universe, I wondered, is it an innie or outie?<<

---The dragon observes

Omniscient writes, "As for the space elevator, the idea is so absurd I won't get into the physics of it."

Well, it may be counterintuitive, and building one from the ground to orbit may be impossibile, but the concept itself is definately not absurd. The idea has been looked at quite seriously (by no less than NASA). There's nothing wrong with "the physics of it" in the general case, just in certain specific cases.

> Second, what would hold it up?

Depends on the specific form the system would take. In some, the tether's center of mass would be in geosynchronous orbit. There are many other possible designs, including tension tethers between two orbiting objects at different heights. It turns out that when you use a tether to constrain the movement of such objects, orbital dynamics cause the tether to be in tension.

The really big ones are beyond both our current materials technology and our ability to lift that much mass. But they're not so far beyond that we should ridicule the idea.

k0myers

It won't work. First, you would need the anchor to be in Goestationary orbit. Thats 250-300 miles for a satilite, depending on how much greater this mass is it could double the needed height. Then you'll be putting that anchor in a goestationary orbit at a certain speed (height) that allows the correct centripital force to keep that mass in orbit. Now you add a mass of a few cables, to maintain geostationary orbit, you'll need to increase speed (ergo centripital force) and to maintain geostationary orbit then you'll need to increase alttude. You see the coming problem? Everytime you add mass of new cables you need to add altitude and speed. Given this the total length of the cable gets longer and longer, a Catch 22. Now unfoutunately I can't recall the equation that would dictate the increase in height with respect to the increase in mass for geostationary orbit, but i suspect that it is great enough to make this mathmatically impossible if not just practically impossible. Also recall that as mass increases the launch cost increases, and as needed altitude increases the availible mass potential decreases so the pieces of cable will need to get infinately short not only because they need to get thicker, but because they need to reach an ever increasing height. I don't see how this could ever become cheaper than just launching to space even if it were possible, and any cost saving technology created to facilitate this would also bring the cost of launches down and negate the supposed cost benefit of the elevator.

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The facts expressed here belong to everybody, the opinions to me. The distinction is
yours to draw...

Omniscient; BAG

There are many other possible designs, including tension tethers between two orbiting objects at different heights. It turns out that when you use a tether to constrain the movement of such objects, orbital dynamics cause the tether to be in tension. Yeah, two objects would be in tension, but what two objects and what orbits that could possibly facilitate any benefit in the beanstalk?

I'd also like you guys to explain the beanstalk a bit. Do you mean one end is thicker and the stalk get exponentially smaller? If so where would you put the thick end and where would you put the thin end? If the thick end is at the top because it needs to support he mass of the rest of the cable, ok, but the mass of the operative payload is heavier near the surface of the earth.

One final contradiction, when you send up a payload the mass of the system will increase and the station would need to reach a higher altitude. So everytime you deployed a payload you would need to expend more thrust to increase and then decrease the altitude (assuming you sent that payload away from the elevator).

The entire concept is foolish.

SoulFrost writes, "OK...let's say we refitted our already modified shuttle to be nuclear-powered (say, with more efficient engines than our modern submarines have)."

Well, there are a few different ways to propel spacecraft. Some, like solar sails, only exist in theory and involve light pushing against a large surface. But among the ones we can actually build right now, they all involve shoving reaction mass out the back of our spacecraft at high speed to increase it's velocity in the opposite direction, according to conservation of momentum. You can make this more effecient by ejecting the reaction mass at very high speeds.

A "nuclear powered" spacecraft still has to have some sort of reaction mass, and that's really the issue in the end. Just having a reactor on board won't really buy you anything on that front - reactors don't create mass, and they don't speed mass up. (Well, there are some designs for using this energy to speed up mass, but they're all just theorical and likely to remain that way for quite a long time).

The reason a submarine can use a reactor for power is that is has the luxury of having water to push against, which you can do with a screw. Our spacecraft doesn't have anything like that to shove against!

Some unmanned spacecraft, especially those that need to operate far from the sun, do use what's called a Radioisotope Thermoelectric Generator (RTG) to generate electricity. This is definately not a nuclear reactor, but it does use the heat from the decay of some isotope of plutonium to generate electricity to power the craft's systems. The Voyager probes, for instance, have such a system.

k0myers

Omniscient write, "The entire concept is foolish."

No, it's not foolish, Omniscient. It's been studied quite extensively, in fact. You can probably find NASA's technical papers on the subject if you're really interested in learning about it instead of dismissing it.

A tether in tention between two orbiting masses is useful because you can reel stuff up and down it, and it conserves energy. Say you have a large space station in a high orbit. In normal use, a lot of what you lift to the station (say, people, science experiments, things that turn into garbage after use), gets taken back down. Now, with normal chemical propulsion, you have to expend energy to lift all this stuff up, and then expend yet more energy (albeit less) to get it back down again. With a tether, you get back the energy used to lift the stuff be sending other things back down the pipe, so to speak. It's a major net win, and if it wasn't, nobody would be bothering to study it. Rotating tethers have other, but still useful, applications.

> You see the coming problem? Everytime you add mass of new cables you need to add altitude and speed. Given this the total length of the cable gets longer and longer, a Catch 22.

What I see, is that a little knowledge is a dangerous thing :-).

k0myers

Omniscient,

If you're really interested in this topic, here's a NASA page that has a bunch of papers on the subject, mostly written for a layperson audience, so they're easy to digest.

At the very top of the page: "Tethers are now being seriously considered for use with the Space Shuttle and the Space Station for raising or lowering payloads for various scientific and engineering purposes" ... so, in short, don't dismiss something just because you don't understand how it could work :-)

The page of papers is here:

http://infinity.msfc.nasa.gov/Public/ps01/ps02/space.html

At one point, I also had a page with links to more technical papers on the topic, but I can't seem to find it now :-|. I'll post again if I manage to hunt it down.

k0myers

I seem to remember an article in Discover magazine a few years ago that discussed the possibility of "beanstalk" elevators.

If memory serves (and it often doesn't), not only was the elevator from earth to orbit considered, but also one from orbit to various other paths... usually something near the moon. The conclusion was that it was feasible, as long as certain probable technological advances were made.

OK...let's say we refitted our already modified shuttle to be nuclear-powered (say, with more efficient engines than our modern submarines have). Then, we radiation-shielded the hell out of it. Then, we put in Acme's Magic Life-Support System (all that would really be needed is a scrubber that takes the O2 out of the CO2, and food).

Could we fly a manned mission to the moon? Could we get back?

>OK...let's say we refitted our already
>modified shuttle to be nuclear-powered
>(say, with more efficient engines than our
>modern submarines have).
Well the main problem you would have here is, unlike a submarine, that the space shuttle does not have a PROPELLER. If your talking out a fusion pulse engine, I've only read about them in sci-fi books. Inybody know the status of micro fusion research?

SoulFrost - With the alterations you suggest, you could probably fly a Cessna to the Moon!

I'm afraid you aren't so "omniscient" if you think that orbital periods are dependent on the mass of the orbiting body, or that geosynchronous orbits are anywhere near 250 miles.

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John W. Kennedy
"Compact is becoming contract; man only earns and pays."
-- Charles Williams