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Anonymous Poster

Shuttle to the Moon?

12/20/2006 7:31 AM

With NASA's unimaginative approach to landing on the moon with an approach almost to the letter to the moon landings over 35 years ago makes me beg the question.

Why could they not have used the shuttle to go to the moon? With its payload capacity surely they could have carried the equipment and means to make this possible? Or am I missing something really obvious

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#1

Re: Shuttle to the moon

12/20/2006 8:00 AM

Good question. Anyone?

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#2
In reply to #1

Re: Shuttle to the moon

12/20/2006 8:17 AM

How much fuel and oxygen would they need? Landing on the moon, I imagine, would be quite a different scenario; no runway, less gravity, zero atmosphere..

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#3

Re: Shuttle to the moon

12/20/2006 8:22 AM

The biggest problem is getting the beast, which weighs 240,000 pounds (almost 120 tons!) into lunar orbit. Right now we use two SRBs (Solid Rocket Boosters) and a huge payload of hydrogen/oxygen mix for the three main engines just to get to low Earth orbit.

To get to a translunar injection is going to take a whole lot more energy than what we have available for the Shuttle. The payload area can only hold another 50,000 pounds of cargo or fuel if you like.

The SRBs are the most efficient way to get thrust for the mass. They weigh 1,300,000 lbs each! The main fuel tank is another 1,700,000 lbs full, and the total system weighs in at 4,500,000 lbs as it sits on the pad! Total weight for boosters and fuel is 4,250,000 lbs, so an additional payload of 50,000 possible for fuel is not even worth considering.

The Shuttle can't land on the Moon, so you need payload for some form of LEM. All in all, the Shuttle doesn't have the fuel budget to get beyond low Earth orbit and there is a long way to go before you reach Earth's escape velocity of 25,000 mph. Right now the Shuttle orbits at about 200 miles up with an orbital speed of just over 17,000 mph. To get the extra velocity required for escape requires a lot more energy as the "energy slope" gets steeper as you increase velocity.

However, Hollywood does seem to know how to get the Shuttle to the Moon and a few asteroids. Maybe NASA should be talking to Alex Baldwin or Bruce Willis?

Meanwhile, NASA is hard at work with the CEV (Crew Exploration Vehicle), which is much better suited to the task and will contain the latest technology. The Shuttle is a very old technology that is long overdue for retirement. The CEV can be launched from a standard booster (albeit a BIG one), which saves a lot of launch costs and the booster can be tailored for the job at hand (i.e., Earth orbit, Lunar trajectory, or even Martian trajectory).

The only other hope was Scotty getting the transporter working again. Scotty could always get things fixed in just under an hour. Sadly, he passed away years ago and no one knows how the fangled thing works! In the meantime, we are left with rudimentary technology that may not be very glitzy, but is proven to be fairly reliable and cost effective. Throw in 30 years of technological advances for NASA since the last Lunar mission and we should have a pretty good system!

Sorry, I didn't have time to write a short answer.

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#4

Re: Shuttle to the Moon?

12/20/2006 10:16 AM

The shuttle is designed for low earth orbit, only. It is not capable of getting to the moon, or anywhere else.

The "unimaginative approach to landing on the moon with an approach almost to the letter to the moon landings over 35 years ago" is due to the physics involved in getting to the moon, which, amazingly, have not changed in 35 years.

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#5
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Re: Shuttle to the Moon?

12/20/2006 10:21 AM

But the technology should be alot better, unless microsoft is on board.. Uh-Oh.

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#6
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Re: Shuttle to the Moon?

12/20/2006 10:23 AM

Now I am worried!

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#7
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Re: Shuttle to the Moon?

12/20/2006 10:24 AM

Oh sure, the tech will be state of the art, as it was in 1969. Fortunately the state of that art has changed.

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#8

Re: Shuttle to the Moon?

12/21/2006 5:13 AM

One of the problems with the space shuttle is those solid fuel rocket boosters SRB that it uses to get off the pad and high enough for the main motors to take over. Whilst they produce enormous thrust they are basically uncontrollable. Its a light the blue touch paper and hang on like grim death sort of system. As a result there is a no abort period of the launch during which the failure of just about anything means you are history.

One of the main parameters that the new system need was there was not to be a no abort period during the launch. Put simply that means no solid rocket boosters and the end of the space shuttle.

Whilst there are similarities with the Apollo, Saturn V system and the new Orion concept there are some major differences. Firstly the Luna Lander and departure stage are launched separately and without personnel on board. Since the system is at this stage unmanned it can use solid rocket boosters to launch. Once in orbit the crew launch on a separate rocket in the Crew Exploration Vehicle CEV and dock with the as yet unmanned part of the spacecraft. They then use the departure stage to send them on their way to the Moon. The rest is much the same as the Apollo missions except that nobody stays with the CEV in lunar orbit. That means some poor schmuck doesn't get left behind twiddling his thumbs in lunar orbit while his mates get to have all the fun and glory.

Keep in mind the space shuttle has now been around for over half the time man has been traveling in space so while it is an impressive machine it pretty old technology. It also has the problem that from the time the SRB are lit till they exhaust their fuel there is no way to abort the mission. If you ask the astronauts that fly in the shuttle they will tell you that the most nerve wracking part is while those SRB are burning.

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#9

Re: Shuttle to the Moon?

12/21/2006 8:10 AM

If the shuttle weighs 120 tons on Earth it would be just short of 20 tons on the moon. I'd guess it would be more like flying an 18 wheeler. If I were in charge of NASA, I'd be thinking about evolving the shuttle. Maybe launching an unmanned rocket full of additional fuel and oxygen that can mate with the shuttle once in orbit.

Maybe Burt Rutan and Richard Branson will develop such a vehicle.

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#11
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Re: Shuttle to the Moon?

12/21/2006 9:00 AM

The Shuttle, or more correctly, the Orbiter, has virtually zero capacity for carrying fuel. What fuel it does carry is for orbital corrections and reentry burn.

The main engines feed exclusively off of the main tank, which is jettisoned long before attaining orbit. The tank actually breaks up upon reentry.

The Saturn V rocket was about 50% more massive than the Space Shuttle with the SRBs and Main Tank filled. The Saturn V had a payload capacity of about 100,000 lbs to get to lunar orbit. To date the Saturn Y is still the uncontested heavyweight. However, NASA has plans for a new rocket that has about the same diameter as the Saturn V and two Shuttle-like SRBs. It is called Ares V and will be used for future lunar missions.

I think the Ares V is the right choice because the operational costs will be far cheaper than the Shuttle could ever hope to be even if it had the thrust capacity to reach lunar orbit.

The Shuttle was a great idea that never achieved its design goals. NASA had planned to launch almost 50 flights per year, but the program came to a screeching halt with the loss of the Shuttle in the 1980s. After that, reality was forced upon NASA and they had to retreat from the ambitious goals for the Shuttle and the cost savings that were promised never materialized. It still is a technological feat that is well worthy of praise and the program has helped us learn a lot over the years. Still, it is yesterday's technology and it is time to move on to better things.

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#25
In reply to #9

Re: Shuttle to the Moon?

12/21/2006 12:29 PM

Bear in mind that weight is meaningless. It is mass that counts. Even in a weightless environment it still takes the same energy (fuel) to move mass around.

Escaping a gravity well such as the Earth versus the Moon is a different story.

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#10

Re: Shuttle to the Moon?

12/21/2006 8:21 AM

This would involve 2 shuttles; one already docked, fueled and ready to go at the ISS. The astronauts would leave the earth and get to the ISS the conventional way with shuttle1. Then they could rest up, have a meal and get ready for the long-haul. Shuttle2 would have the LEM on board as well as O2 and supplies/food. It wouldn't take much thrust or fuel to get from the ISS to the moon (I suppose). Orbiting around the moon, shuttle2 would dispatch the LEM and land. The return trip would be the opposite of the arrival trip.

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#12
In reply to #10

Re: Shuttle to the Moon?

12/21/2006 9:34 AM

Lets look at the concept of using a shuttle as the spacecraft to go to the moon. Firstly it doesn't fulfill the requirement off not having a no-abort period during launch. The removal of the no-abort period is something NASA and the astronauts are have stated is not negotiable so that alone kills the shuttle.

Lets go on and look at the logistics of using it as the spacecraft that travels to the moon. In theory I suppose it would be possible to use it for the outbound trip but trying to attack a whopping great tank of liquid O2 and H2 to it in orbit isn't going to be easy.

Lets assume for the moment that we solved all the problems, got to the Moon and were on the way back to Earth. Now once you leave the moon and are headed back to earth you will start to accelerate as soon as you pass the LaGrange point. This steady acceleration has you arriving back at Earth traveling as something like 16Kms-1. The shuttle however is already close to is limit reentering the atmosphere at 7.6Kms-1.You have two options, you either slow down enough to go into orbit or you slow down enough so you don't burn up on reentry. Strangely both procedures would need roughly the same amount of fuel, fuel that you havn't got because you didn't take it with you when you left orbit. It's not just a matter of taking a little extra fuel it's a matter of taking roughly the same amount of fuel that you used to go to the Moon in the first place. When you translate this back it means you now need at least 3 times as much fuel to leave earth and head for the moon than you would if the spacecraft just entered the atmosphere directly.

All this needs to be done in an aircraft that is over a quarter of a century old, is past its use by date and was never meant to go more than a few hundred kilometers from earth. Some how I just can't see it being a cost effective let alone practical solution. With our current propulsion technology a reusable spacecraft for Earth-Moon travel just isn't a realistic solution. Maybe when we get fusion reactors and ion drives going and make them small and light enough it will be feasible but that's in the future.

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#13
In reply to #12

Re: Shuttle to the Moon?

12/21/2006 9:43 AM

OK, OK, I'm shutting up here!

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#14
In reply to #12

Re: Shuttle to the Moon?

12/21/2006 10:05 AM

I was talking about 2 separate orbiters or shuttles. One to rendezvous with the space station, and the other for the trip to the moon. We know one orbiter can launch (no there's no abort--but that's a risk that the astronauts and NASA have taken ever since the early Gemini missions, and they seem to live with it (most of the time) -- dock w/ the space station and (usually) return safely. The second craft ( probably a VERY modified shuttle)-(I'm trying to use current technology and equipment-not something that hasn't been built and tested in space); How much fuel do we need? It would seem to me that they could "coast" most of the way, and if the lunar orbit was far enough out, not too much would be used for orbit/ return trip. The bulk of the fuel would be used for slowing down and re-docking at the ISS. The shuttle1 would be there re-fueled and ready for the return trip from the ISS to earth. (Please pardon my bad grammar.) Feasible or not?

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#18
In reply to #14

Re: Shuttle to the Moon?

12/21/2006 11:22 AM

Okay, let's run some numbers! We can use data from the Apollo era to get a rough figure. First, Apollo used up three stages just to get to low earth orbit (LEO). What was left was the Command Module and the Service Module with the LEM. Apollo would park in LEO for two orbits to determine if they were a go/no-go for Trans Lunar Insertion (TLI). So, all I needed was mass of the remaining spacecraft and mass of the propellant to get the cost to get to and back from the Moon.

Here's the numbers. The Service Module weighs in at 6,800 lbs without fuel. The Command Module weighs 13,000 lbs. The Lunar Excursion Module (LEM) weighs 13,000 lbs with fuel. We need to consider the LEM's fuel weigh as part of the package. That's 32,800 lbs. More if you count the weight of the astronauts.

The weight of just the fuel for TLI is 40,000 lbs. So, for every 33,000 lbs of spacecraft we need 40,000 lbs of fuel.

The Shuttle Orbiter weighs 240,000 lbs dry (no fuel). We still need to add the LEM at 13,000 lbs and supplies for the trip. Let's round that to a total package of 255,000 lbs.

Using our ratio above we need 309,090 lbs of fuel to do a return trip to/from the Moon in the Shuttle with the Shuttle already starting from LEO! Okay, let's use the scenario you proposed and park a Shuttle in orbit. Now, all we need to do is fill her up at the orbiting Sunoco station in the sky. We will imagine that the orbiter's lunar tank is already there somehow.

Well, let's make a special tank that fits in a Shuttle bay to carry our fuel and load her up. The actual service weight that the Shuttle can get to LEO is about 60,000 lbs. If we say that the tank weighs 10,000 lbs then we can manage 50,000 lbs of fuel per launch. Okay, that is just 7 Shuttle missions to LEO. At the current rate we fly that would be just shy of two years worth of missions just to get one Moon shot! That assumes we would be able to store that fuel for two years when we get it up there!

As I said before a loaded Shuttle on the pad weighs in at 4,500,000 lbs. A loaded Saturn V is about 6,600,000 lbs. It takes 7 + 1 Shuttle launches to accomplish what we did in one Saturn V launch. That would be real progress!

So, that is why we can't take the Shuttle to the Moon.

The above source for masses is from Wikipedia.

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#21
In reply to #18

Re: Shuttle to the Moon?

12/21/2006 11:56 AM

You didn't allow for the fuel that the shuttle needs to slow down again when it gets back to Earth so that bumps up the total weight for trans lunar injection from earth to

Shuttle + Lunar Module + Deceleration Fuel = 240,000 + 13,000 + 309,090 = 562,090 pounds

And now applying the trans lunar injection fuel ratio we get another 681,319 pounds so that means the all up weight of the craft prior to trans lunar burn is 1,243,409 pounds which means it just isn't going to work.

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#22
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Re: Shuttle to the Moon?

12/21/2006 12:23 PM

Yes, I did. The fuel for the Apollo mission included that in the 40,000 lb fuel budget.

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#23
In reply to #14

Re: Shuttle to the Moon?

12/21/2006 12:24 PM

Bhankii you stated

"There is an abort period during every shuttle launch - although it is after separation from the SRBs. If you listen to radio chatter you'll hear the call outs of when it's safe to return (to Spain), and when it's safe to abort to orbit on two engines, then one engine. There's never been an SRB failure where abort would be an issue anyway - they don't fail, they blow up."

I said there is a NO-ABORT period while the SRB burn. In other words they cant abort while the boosters are burning and if anything goes wrong they are history. Even if they noticed the leaking SRB on the Challenger there was nothing they could do. Once those SRB light they were doomed as there was no way to abort the launch or escape.

Steve-o you stated

"no there's no abort--but that's a risk that the astronauts and NASA have taken ever since the early Gemini missions, and they seem to live with it"

Well actually no! All the launch system prior to the space shuttle had an escape rocket attached to the top of the capsule. In the event of a emergency at any time up to and during the launch this escape rocket can be fired. It lifts the capsule clear of the lunch vehicle and allows it to return via the descent parachutes. The Russians have the same system on their capsules. They have used it at least once to save the crew when the launch vehicle caught fire and exploded on the pad.

They also came close to using it during one of the Apollo missions when the entire Saturn V stack was struck by lightning, shortly after launch, crashing all the guidance computers.

So during all launches till the space shuttle there was no period were they couldn't abort the mission and escape.

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#24
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Re: Shuttle to the Moon?

12/21/2006 12:28 PM

I stand corrected.

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#15
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Re: Shuttle to the Moon?

12/21/2006 10:18 AM

I'm not sure where you're getting this from. There is an abort period during every shuttle launch - although it is after separation from the SRBs. If you listen to radio chatter you'll hear the call outs of when it's safe to return (to Spain), and when it's safe to abort to orbit on two engines, then one engine. There's never been an SRB failure where abort would be an issue anyway - they don't fail, they blow up.

Ares I is an SRB. It's the same SRB that's used on the shuttle - except with 5 segments instead of 4. SBRs are preferable to liquids for safety and cost - they're simple, once they're lit they burn until they're empty - this is why a lot of the big liquid launchers aren't man-rated, although Bigelow and Lockheed are trying to get one upgraded now. Ares-5 uses both SRB's and the shuttle's main tank and engines.

The CEV will be a reusable earth - lunar vehicle. Except for the docking interface and heat shield, they will be recycled. The landers won't be coming back, of course.

But, yeah, the shuttle is completely ill-suited to a moon mission.

For a lot of great presentation material of the future of space flight, the AIAA '06 space explorationconference has posted it's stuff:

http://www.nasa.gov/mission_pages/exploration/main/2nd_exploration_conf.html

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#16
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Re: Shuttle to the Moon?

12/21/2006 11:10 AM

I don't think an SRB failure equals explosion - when the Challenger exploded, it was because of the segmented SRB sections leaking exhaust gases through the side of the SRB, into the big orange tank of liquid. Upon catastrohpic failure of the big orange tank and then the orbiter itself, the SRB's were intact and still flying, albeit unguided. The SRB's were then self-destructed when it was decided that they were possibly heading for population. To seld-destruct the SRB's, you basically break the solid propellent into lots of little pieces (explosively) so it burns out rapidly instead of the usual controlled manner - it's very effective, yet quite messy! I think as demonstrated by the accident at Thiokol and by the Pershing accident in Germany back in the 80's, solid fueled motors don't fail if lit, they typically perform as designed which makes them great for space use.

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#17
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Re: Shuttle to the Moon?

12/21/2006 11:18 AM

You are correct. Do you really drive a sled? Does it have reindeer?

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#40
In reply to #17

Re: Shuttle to the Moon?

12/22/2006 9:18 AM

I do call my ride "the Sled"; sorry, no reindeer!

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#19
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Re: Shuttle to the Moon?

12/21/2006 11:24 AM

The ARES-5 looks great, but it won't be ready until the year 2020, right? I was thinking of (just for the sake of discussion) of using present day technology to get us there a lot sooner than that. I mean, we made it to the moon in 1969, surely we could do it now..

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#20
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Re: Shuttle to the Moon?

12/21/2006 11:31 AM

We could do it now, if we still had any Saturn 5's (the most powerful machine ever built) around.

Space flight is a very specific business. Craft are designed for particular missions, and aren't much good for anything else.


2020 is just around the corner.

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#32
In reply to #20

Re: Shuttle to the Moon?

12/21/2006 3:36 PM

Bhankiii,

I just finished writing an article for CR4 about the first use of a Saturn V with a manned space mission. According to Wiki (which is sometimes a source of questionable information), each of the rocket's F-1 engines had "more thurst than all three space shuttle main engines combined". Does that sound right to you?

Moose

P.S. Would you terms the Saturn V "one of the greatest engineering accomplishments of the 20th century". I read that claim on one of the web sites I visited.

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#34
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Re: Shuttle to the Moon?

12/21/2006 4:00 PM

It's 1.5 million pounds for each F-1 vs. just under .5 million pounds for each shuttle main engine, so that's about right. The Saturn 5 can lift almost 5 times the mass (into low earth orbit) as the shuttle.

One thing I remember from one of my profs in school was that the fuel for the F-1's came through a 6 foot diameter line - that's a lot of fuel.

I've also heard that the Saturn-5 taking off was the loudest man made sound ever created.

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#35
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Re: Shuttle to the Moon?

12/21/2006 6:17 PM

Shook the ground for something like a 50 mile radius. ;-)

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#36
In reply to #34

Re: Shuttle to the Moon?

12/22/2006 2:59 AM

'I've also heard that the Saturn-5 taking off was the loudest man made sound ever created.'

Really? That's pretty loud then. But was it? I'd have thought it was the loudest sustained noise, but surely there's been louder man made sounds? I'm thinking of our predilection for big bangs etc.

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#37
In reply to #34

Re: Shuttle to the Moon?

12/22/2006 3:59 AM

"I've also heard that the Saturn-5 taking off was the loudest man made sound ever created."

I believe this is true with the exception of thermo nuclear devices like hydrogen bombs etc.

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#26

Re: Shuttle to the Moon?

12/21/2006 1:25 PM

We know that the orbiter (with SRBs) can make a round trip to the ISS and back without refueling. So the trip to and from the ISS is a done deal.' Nuff said. Now we have to get the crew to and safely back from the lunar surface. This is a round trip from the ISS to the moon and back to the ISS --not Earth--This should not require that much fuel. Numbers anyone? That is where we send another shuttle up to the ISS carrying a LEM in the cargo bay and strip this shuttle down (wont need wings in space etc) to save weight. Send the "stripped" shuttle carrying crew and LEM to the moon and back to the ISS where the docked orbiter (wont need the LEO Sunoco because it's only 1/2 way through its mission), and back to earth using the first orbiter (shuttle #1), leaving the stripped shuttle (or redesigned deep space ship whatever you want to call it) at the ISS for its next mission to the moon. The modified ship would be an ISS to Lunar-and-back ship only which alleviates much of its fuel-consuming duties of achieving Earth escape velocity. Working with what you have can be as much of a challenge as designing from the ground up. (And less time-consuming.)

Plus I'll be 64 in 2020:/

As a kid I saw the movie 2001 A Space Odyssey and couldn't wait. Now we're here but the future's not )-:!

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#27
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Re: Shuttle to the Moon?

12/21/2006 1:58 PM

Plus I'll be 64 in 2020:/

So will I. That's why I'm spending the next 14 years of my career working on the CEV and lunar lander.


I know that big ol' black monolith is out there somewhere!

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#28
In reply to #27

Re: Shuttle to the Moon?

12/21/2006 2:16 PM

Do you work for JPL?

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#29
In reply to #28

Re: Shuttle to the Moon?

12/21/2006 2:21 PM

No, I'm a contractor at JSC. Currently designing the CEV docking system.

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#30
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Re: Shuttle to the Moon?

12/21/2006 2:28 PM

Cool job!

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#31
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Re: Shuttle to the Moon?

12/21/2006 2:32 PM

Coolest ever - I'm gonna ride this baby until I retire!

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#33
In reply to #26

Re: Shuttle to the Moon?

12/21/2006 3:56 PM

Well, I will disagree with you on fuel. The difference of fuel required between return from lunar orbit to Earth orbit, versus a return from lunar orbit to reentry to Earth is so tiny that it does not matter.

Remember, there is a tiny portion of fuel retained in the Orbiter just for that purpose. They don't use the main engines, but small thrusters to deorbit from LEO (where the Space Station is).

The big fuel burning expense is the TLI and then the TEI (Trans Earth Injection). You must slow the space vehicle down to reach orbital velocity and speed it up to break orbit and that costs fuel. The difference is so trivial that it would be less than 1%.

I know we go through this again, and again, but I tried to make it painfully obvious that when you compare the two masses of the spacecrafts (Apollo vs. Orbiter) and the fuel required for each, that you are bringing along are almost an order of magnitude more hardware with a Shuttle Orbiter than an Apollo-like space craft. Stripping parts off an Orbiter is a dead end prospect and will never match the parity of a Saturn V-like approach. Quite frankly, when you consider the cost of the Orbiter and the huge amount of extravehicular activity involved to reconfigure a space craft into something it was never designed to be, it just won't work.

Think of it as starting with a Ford F-150, parking it outside at the North Pole (in winter), then attempt to reconfigure it into a Formulae 1 racecar!

When you are done, give me a call and we will see how it does on the track!

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#38
In reply to #33

Re: Shuttle to the Moon?

12/22/2006 8:18 AM

Well, I was going to jump off of this thread, because (and I hate this cliche) I thought that there was not enough "thinking outside the box," and inventiveness (word?) present, and I'm not a rocket scientist, but here I go again.. one more thought. Forget modifying the shuttle. Build a brand new ship. How much fuel would it take to get from the space station to the moon, orbit 2 days and back to the space station? I don't think that you would need a Saturn V rocket for that. The main point here, that I'm trying to make, is by using the Orbiter for the trip from Earth to the space station and back to Earth, you'd be saving a s***-load of fuel. Pardon-my-***s. I admit that I probably haven't thought through the logistics and details as well as some of you all, but what about the basic idea? It's hard to think that the next trip to the moon is 14 years away. I know that the politics involved are partially to blame. Like I said before, we did it in 1969; I wouldn't think that it should take FIFTY YEARS to do it again..

Thanx,

Steve

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#39
In reply to #38

Re: Shuttle to the Moon?

12/22/2006 8:58 AM

Steve_O you asked

"This is a round trip from the ISS to the moon and back to the ISS --not Earth--This should not require that much fuel. Numbers anyone?"

Ok here are the numbers

The orbital part of the shuttle weighs about 110Mg and needs to be traveling at around 7.5Kms-1 to get to a 300Km high orbit so the energy involved is

KE = ½ mv2 = ½ x 110 x 103Kg x 7.5Km/s23 Tj

PE = mgh = 110 x 103Kg x 9.81 x 300 x 103 ≈ 234 Gj

Total Energy = 3.234 Tj

Now we need to find out how much fuel it takes using the shuttles engines to generate this much energy. The shuttle is fueled by liquid H2 and O2 plus the solid fuel and for the trans lunar injection burns we cant use the SRB we can only use the liquid H2 and O2 so we need to find out how much each of the fuels contributes to the final energy of the shuttle in orbit. So

v = f/m x t ………………………………Equation 1

KE = ½ mv2 ………………………….…Equation 2

So by substituting Equation 1 into Equation 2 we end up with something like this

KE = ½ mv2 = ½ m (t f/m)2 = ½ t2f2/m …Equation 3

Now the solid rocket boosters provide 83% of the thrust for around 120 seconds and the liquid engines provide the remaining 17% for around 600 seconds so if we use Equation 3 and these figures we get

KESRB = ½ 1202/m .832/m = 5,202/m

KELiquid = ½ 6002/m x .172/m = 5,202/m

So that means that 50% of the final energy comes from the solid fuel and 50% from the liquid fuel. At launch the volume of liquid fuel is 2.025Ml so we can now calculate the amount of fuel required per init of energy as follows

FuelRatio = 2.025Ml / (50% x 3.234Tj) = 1.2523 μlj-1

To convert the volume of fuel required to mass we need to know the density of the fuel and since at launch the mass of the liquid fuel is 730,441Kg the density works out as

FuelDensity = FuelMass / FuelVolume = (730,441Kg / 2.205 Ml ≈ 0.3313 Kgl-1

We now have a factor that we can use to convert energy into fuel so to calculate the amount of fuel we need we need to work backwards from the time the shuttle ends up back in Earth orbit the its departure from Earth orbit to the Moon.

As we approach Earth on the return journey we need to slow the shuttle down from around 16Kms-1 to the LEO velocity of 7.6Km-1 therefore

KEApproach = ½ mv2 = ½ 110 x 103Kg x (16 x 103)2 ≈ 14.080 Tj

KELEO = ½ mv2 = ½ 110 x 103Kg x (7.6 x 103)2 ≈ 3.176 Tj

KEEarth Orbit Injection= KEApproach – KELEO = 14.080 Tj – 3.176 Tj = 10.904 Tj

And the amount of fuel needed to carry out the LEO Deceleration burn is

FuelLEOD = 1.2523 μl x 10.904 Tj = 13.6551 Ml

We can now calculate the return mass of the spacecraft and fuel prior to the EOD burn as

MassReturn = ShitttleMass + FuelMass

MassReturn = 110 x 103 Kg + 13.6551 Ml x 0.3313 Kgl-1

MassReturn = 4.633 x 106 Kg

We now have the weight of the spacecraft and fuel immediately prior to EOD burn, which is for all practical purposes it the same mass that will need to be accelerated by the Trans Earth Injection burn that is carried out in lunar orbit. The escape velocity for the moon is 2.4Ks-1 and this burn need to accelerate the craft from the orbital velocity of around 1.3Kms-1 so if we do the calculations the same way as with the EOD burn we get

KETEI = ½ mvTLE2 = ½ x 4.633 x 106 Kg x (2.4 x 103)2 = 13.334 Tj

KELO = ½ mvLO2 = ½ x 4.633 x 106 Kg x (1.3 x 103)2 = 3.915 Tj

KETEI Burn = KETEI – KELO = 13.334 Tj – 3.915 5Tj = 9.428 Tj

Which we can now use to calculate the amount of fuel for the TEI burn as

FuelTEI = KETEI Burn x FuelRatio = 9.428 Tj x 1.2523 μlj-1= 11.864 Kl

Which allows us to calculate the mass of the spacecraft and fuel prior to the TEI burn as

MassTEI = FuelTEI x FuelDensity + MassReturn

MassTEI = 11.864 Kl x 0.3313 Kgl-1+ 4.633 x 106 Kg

MassTEI = 4.677 x 106 Kg

Now we need to calculate the fuel required for the Lunar Orbit Deceleration burn that slow the craft down from the Trans Lunar Velocity of 2.4 Kms-1 to the Lunar Orbit Velocity of 1.3 Kms-1 bue we now need to include the 6,000 Kg Lunar Exploration module so

MassLOD = MassTEI + MassLE = 4,677 x 106 Kg + 6.0 x 103 Kg = 4.683 x 106 Kg

And calculating the kinetic energies before and after the LOD burn give us

KELO = ½ MassLOD x vLO2 = ½ x 4.683 x 106 Kg x (1.3 x 103)2 = 3.957 Tj

KETL = ½ MassLOD x vTL2 = ½ x 4.683 x 106 Kg x (2.4 x 103)2 = 13.487 Tj

KELOD Burn = KETL – KELO = 9.530 Tj

Which allows us to calculate the fuel for the burn as

FuelLOD = KELOD x FuelRatio = 9.530 Tj x 1.2523 μlj-1= 11.934 Kl

MassFuel LOD = FuelLOD x FuelDensity = 11.934 Kl x 0.3313 Kgl-1 = 3.934 x 103 Kg

Now adding the mass of the fuel burnt during Lunar Orbit Deceleration burn to the mass of the craft in lunar orbit gives us the mass of the spacecraft for the Trans Lunar Injection Burn as

MassTLI = MassLOD + MassFuel LOD

MassTLI = 4.683 x 106 Kg + 3.934 x 103 Kg

MassTLI = 4.686 x 106 Kg

This leave us with the final set of calculations for the amount of fuel that is required to accelerate the spacecraft from the Earth Orbital Velocity of 7.6 Kms-1 to the Trans Lunar injection Velocity of 16 Kms-1 in the now familiar was so

KETLI = ½ MassTLI x VTLI2 = ½ 4.686 x 106 Kg x (16 x 103)2 = 599.808 Tj

KEEO = ½ MassTLI x VEO2 = ½ 4.686 x 106 Kg x (7.6 x 103)2 = 135.331 Tj

KETLI Burn = KETLI – KEEO = 599.808 Tj – 135.331 Tj = 464.477 Tj

And calculating the amount of fuel to carry out this burn gives us

FuelTLI = KETLI Burn x FuelRatio = 464.477 Tj x 1.2523 μlj-1= 558.055 Ml

MassFuel TLI = FuelTLI x FuelDensity = 558.055 Ml x 0.3313 Kgl-1 = 186.196 x 106Kg

And going back to calculate how much fuel was in the spacecraft that is needed for the Luna orbit and Earth orbit deceleration burns we have

MassTotal Fuel = MassTLI – MassCraft + MassFuel TLI

MassTotal Fuel = 4.686 x 106 Kg – 116 x 103 Kg + 186 x 106 Kg

MassTotal Fuel = 192.767 x 106 Kg

Which gives us the volume of the fuel

VolumeTotal Fuel = MassTotal Fuel / FuelDensity

VolumeTotal Fuel = 591.85 Ml

So if we now take the volume of the fuel and compare it with the existing tank we can get some idea how big the tank would be

NewTank = VolumeTotal Fuel / VolumeExisting Tank = 591.85 Ml / 2.025 Ml

NewTank = 292.27

This gives us the mission profile as follows

  • Shuttle launches to orbit as it dose now with lunar module in cargo bay
  • Shuttle docks with fuel tank that is already in orbit and full of fuel
  • Shuttle uses main engines to leave earth orbit and head to the moon
  • Shuttle uses main engines to decelerate and enter orbit around the room
  • Luna module is use to descend to the moon
  • Luna module ascends to lunar orbit and docks with shuttle
  • Shuttle uses main engines to leave lunar orbit and head back to earth
  • Shuttle uses main engines to decelerate and enter orbit around earth

To do this a new fuel tank need to be constructed with the following dimensions

  • Length 311.24 metres
  • Diameter 55.75 metres
  • Volume 592 Ml

That's one mind bogglingly colossally hefty tank that would contain around three times the amount of full that all the shuttles have used in all the missions to date This tank is only for the trip to the moon and back and from the size of it it's not worth even thinking about how to get the monstrosity into orbit in the first place.

Now I hate to rain on your parade and shoot down a seemingly good idea but its just not going to work. The idea needs something like 300 times the fuel that the existing tank contains and the motors couldn't possibly burn that amount of fuel in the time available. As I said in an earlier post the only way a reusable Earth Moon shuttle could work is with some new sort of engine technology like the ion drive powered by fusion reactor. If you want to do it with chemical propulsion it just isn't going to work.

NOTE If you wish to check my calculations you can get nearly all the information from here.

http://en.wikipedia.org/wiki/Space_shuttle#External_Tank

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#41
In reply to #39

Re: Shuttle to the Moon?

12/22/2006 9:25 AM

Uhhh.. Thanks Masu. That was a lot of work for a stupid question. I'll take myself elsewhere now and leave the rocket science to the rocket scientists. You're one smart fellow.

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#42
In reply to #39

Re: Shuttle to the Moon?

12/22/2006 9:37 AM

I see why your eyes are blood shot in your avitar!

Nice math project!

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#43
In reply to #38

Re: Shuttle to the Moon?

12/22/2006 9:49 AM

Ah! That is a valid question! Let's look at the Apollo mission once again. The first three stages are simply used to get the payload to LEO. It is a little lower than the ISS, but close enough. Remember, Apollo goes into a temporary parking orbit for two orbits before ignition of the Service Module's engine for trans lunar injection.

What is left after the third stage separation is all that is needed to get to and back from the Moon. Apollo required 40,000 lbs of fuel to move 33,000 lbs of space vehicle for the Moon mission.

I would assume that the next mission will probably be a bit larger in mass, but the ratios of fuel to space vehicle probably will be about the same.

It is taking 50 years because people don't care about it like they did in the 60s. People got bored. Had we kept the same excitement level and determination we would probably be paralleling Arthur C Clark's vision laid out in his book 2001 with a small lunar colony, orbiting space station, and on the cusp of planetary missions. That was my dream as a child when the 1st lunar landing took place. Since then it has been a disappointing ride to watch as public apathy all but shut down the national space program.

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#44
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Re: Shuttle to the Moon?

12/22/2006 10:07 AM

Amen to that!

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#45
In reply to #43

Re: Shuttle to the Moon?

12/22/2006 10:23 AM

I guess if we were living in Arthur C.Clark's world, the down side would be that we'd have a HAL 9000 to worry about.

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#47
In reply to #45

Re: Shuttle to the Moon?

12/22/2006 10:45 AM

Hey! HAL was a good computer. It was the stupid government officials that changed his programming just before the mission with the conflicting orders. The first order was always tell the truth. Then someone from the government added a second primary order to withold the truth just before the mission began.

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#48
In reply to #47

Re: Shuttle to the Moon?

12/22/2006 11:24 AM

Thank you A.H. That was very kind. I think we're having a problem with the air-lock mechanism; can you come take a look at it? (hehehe)

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#49
In reply to #47

Re: Shuttle to the Moon?

12/22/2006 12:30 PM

Sorry, Yeah you're right. I guess I'd forgotten that part of the plot. He wasn't created evil and deceptive. Leave it up to the government to screw everything up..

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#46
In reply to #43

Re: Shuttle to the Moon?

12/22/2006 10:43 AM

Anonymous Hero stated;

"What is left after the third stage separation is all that is needed to get to and back from the Moon. Apollo required 40,000 lbs of fuel to move 33,000 lbs of space vehicle for the Moon mission."

With the Saturn V the first two stages are used to get the third stage, Command and Service Modules and Lunar Excursion Module into orbit. The third stage is then used to propel the CSM and LEM to the moon and is not jettisoned till after the craft has left earth orbit. It's actually the third stage that sends them on their way to the moon not the CSM motor. The motor on the service module is only used for mid course corrections and to enter and leave lunar orbit.

Unlike the calculations I did for the shuttle they don't slow down but reenter the atmosphere at the full return speed of around 16 Kms-1. The capsule when it gets back has so much energy that it actually takes two bites at slowing down. It enters the atmosphere initially at an angle that allows them to slow down but the sort of skip back up again out of the atmosphere. This allows the capsule cool of for a short while before it enters the atmosphere for the second and final deceleration and descent.

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#50
In reply to #46

Re: Shuttle to the Moon?

12/22/2006 12:57 PM

Ah! Then I misunderstood the staging, but that makes sense. It also makes the rough calculations far worse than what I originally stated.

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#51
In reply to #50

Re: Shuttle to the Moon?

12/22/2006 1:19 PM

As I showed in my long winded calculation if you wanted to use the shuttle to go to the moon it would need a tank almost 300 times the size of the one it usually has and that just to go from low earth orbit not from the ground.

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