Replacement for the shuttle?

[Chaos]

I had an idea some time ago while planning for a SF story. Might be crazy, but anyway:

You strap a disposable jet engine or jet aircraft frame (like a 747 without passenger/cargo space) to the shuttle, get it up as high as possible with a jet engine, then release the jet engine (which, ideally, would be constructed in a way that it can land as a remote-controlled glider after the release) and get into orbit on rocket engines. The shuttle landing works the way it used to.

 

[xouper]

Chaos: I had an idea some time ago while planning for a SF story. Might be crazy, but anyway: You strap a disposable jet engine or jet aircraft frame (like a 747 without passenger/cargo space) to the shuttle, get it up as high as possible with a jet engine, then release the jet engine ... and get into orbit on rocket engines.

Did you miss my earlier reply about this exact question? I'll repeat it here:

A reasonable orbit is an altitude of 300 to 400 miles at a speed of about 17,000 miles per hour. At most, a 747 can get the shuttle 10 miles up and 600 mph.

Instead of using a 747, a specially designed jet platform could get you perhaps another 10 miles closer to orbit. By comparison, the solid rocket boosters get the shuttle to an altitude of 30 miles and a speed of about 3500 mph. No jet propelled platform could do that.

 

[Jon_in_london]

Go with the rotation. You get a free boost from the tangential velocity.

--Terry.

I disagree.

The tangenital (sounds dodgy!) velocity gain is negated because you are going at the same speed as the earth to begin with. Eg: The speed at which the horizon and therefore space approaches is solely equal to the speed you attain (relative to the earth of course)

If you go counter to the rotation, the horizon, and therefore space is coming towards you at the speed of the earths rotation + whatever speed you lauch at.

Think about jumping straight up, jumping 'forwards' and jumping 'backwards' and I think you will see what I mean.

The one disadvantage of a horizontal launch of course is that you have to go through a lot more of the pesky atmosphere sh-t.

Perhaps a ski-jump type thingy with a few klicks of horizontal and then a vertical?

 

[Michael Redman]

I think that's wrong. Orbital speed isn't a matter of speed relative to the surface of the earth, but absolute velocity around the center (I know that's not the right term, but I don't know how to say it better.) Geosynchronous orbits have no velocity relative to the surface of the earth, yet they don't consist of objects remaining motionless in space.

 

[Terry]

I disagree.

The tangenital (sounds dodgy!) velocity gain is negated because you are going at the same speed as the earth to begin with. Eg: The speed at which the horizon and therefore space approaches is solely equal to the speed you attain (relative to the earth of course)

If you go counter to the rotation, the horizon, and therefore space is coming towards you at the speed of the earths rotation + whatever speed you lauch at.

Sorry, but this is wrong. The only thing that matters for achieving orbit is the tangential (note spelling) velocity relative to the center of the earth. If you launch with the rotation, you get a "leg up". If you launch against it, you have a much bigger delta-v to achieve. This is why retrograde orbits are not common for artificial satellites. Consider that the earth can be replaced by an equivalent point mass without changing anything (ignoring frame-dragging GR effects which are miniscule for the mass of the earth). If you were to sudenly appear in a ship near a point mass, and had to achieve orbit, and you already had a tangential velocity of 500 m/s, would you fire your rockets with or against the existing velocity?

The one disadvantage of a horizontal launch of course is that you have to go through a lot more of the pesky atmosphere sh-t.
Perhaps a ski-jump type thingy with a few klicks of horizontal and then a vertical?

Yeah, that's why I said build it on a high plateau. And yes, the reason rockets start by going straight up, before curving their trajectories over to the horizontal is to get above that nasty sticky icky air stuff.


--Terry

 

[xouper]

Jon_in_london: I disagree. The tangenital ... velocity gain is negated because you are going at the same speed as the earth to begin with.

Michael Redman is correct. The orbital speed for a given altitude is independent of the direction of the Earth's rotation. Consider for example a satellite in polar orbit.

Launching due east from Cape Canaveral (28.5 degrees north latitude) means your initial speed is some 900 mph (as you observed), and thus it takes less energy to accelerate to the 17,500 mph required for a typical low earth orbit.

 

[Skeptoid]

A 747 would be crushed under the weight of a shuttle loaded with enough fuel to reach orbit (over a million and a half pounds).

 

[xouper]

Skeptoid: A 747 would be crushed under the weight of a shuttle loaded with enough fuel to reach orbit (over a million and a half pounds).

Good point. The load on a 747 when ferrying an empty shuttle is less than 200,000 lbs, near the payload limit for the 747. By comparison, the shuttle's external tank, fully loaded, is about 1.7 million pounds (mostly liquid oxygen). And that doesn't count the SRBs. which weigh about 1.3 million pounds each. Total weight of a fully loaded shuttle ready for takeoff is about 4.5 million pounds, more than five times the weight of a fully loaded 747.

 

[Ove]

Then we most use the TRUE jumbojet the Antonov225, according to this page: AN225 it can carry 250 tons to an altitude of 4 kilometers.

Now you say that a fully loaded shuttle weighs 4.5 mill pounds, if you skip the firework boosters and the fuel needed to reach 4Km then i think the calculation could look better.

Here's the TRUE jumbo:

 

[Zep]

FWIW, one of the main problems with ground-launched "delivery systems" is the requirement to travel through the resistance of the air in the atmosphere.

The velocity profile of a shuttle (or, indeed, any orbital rocket launch) involves a fairly steady and relatively slow acceleration through the low-level region of higher air-resistance. This is precisely what the high-powered "fireworks" boosters are required for - to carry the vehicle through the lower altitude air-resistance without expending the main booster fuel unnecessarily. They are then discarded when this job is done (i.e. very early in the flight profile). The actual velocity at that point is about 2,000 mph, far below the 17,000mph required for orbital velocity.

At an altitude where air-resistance tends to become negligible (somewhere about 100,000 to 150,000 feet - 20-30 miles), the flight path is becoming more horizontal w.r.t. the earth's surface, and the reduced-mass vehicle will then accelerate seriously up to orbital velocity with very little further air-resistance encountered.

And herein lies a way to a possible solution: We need to find a practical way of lifting the vehicle to a very high altitude from whence it can make that run up to orbital velocity. In fact, since the main booster in the current configuration also contributes to the initial liftoff power, it may be possible to reduce the size of this too.

OK, geniuses! Go to it!

 

[AmateurScientist]

According to the book (one of my favourites) "Apollo, the race to the moon" By Charles Murray and Catherine Cox there are actually TWO complete Saturn 5 rockets making them probably the worlds most expensive museum pieces (in Houston and at the Cape). Apparently when congress cancelled the two last Apollo missions the rockets was already buildt. There are also one complete dummy(test vehicle) in Huntsville i think.

Yes, Ove, I live in Huntsville and we do have a complete Saturn V at the U.S. Space and Rocket Center Museum. We also have a full scale replica which stands upright, but which was only built in the last 10 years or so.

I don't know if "dummy" is accurate for the real rocket engines (in three stages), because they were used in rocket engine tests here. They are in fact real rocket engines. The entire Saturn I and V projects were developed and managed here. Dr. Werner von Braun made Huntsville his home and that of his German rocket team after they briefly lived in New Mexico. Huntsville has been known as "Rocket City" ever since.

NASA's Marshall Space Flight Center in Huntsville still manages the propulsion system for the shuttle, and manages payload projects as well.

AS

 

[SquishyDave]

And herein lies a way to a possible solution: We need to find a practical way of lifting the vehicle to a very high altitude from whence it can make that run up to orbital velocity. In fact, since the main booster in the current configuration also contributes to the initial liftoff power, it may be possible to reduce the size of this too.

OK, geniuses! Go to it!

I already told you, Space Eelevator, if you don't believe it's possible see here and here. These guys make it seem physically possible, and not with huge amount of impossible materials either, and I think if it's possible, some of us humans somewhere, sometime will do it. So we should stop all this bent knees running around and put all our time and effort into this, the sooner it's up, the better for everyone.

edited to add an "e"

 

[Ove]

The entire Saturn I and V projects were developed and managed here. Dr. Werner von Braun made Huntsville his home and that of his German rocket team after they briefly lived in New Mexico. Huntsville has been known as "Rocket City" ever since.

One of my favourite anecdote in the book comes from Huntsville. One of Von Braun's people,dr. Rudolph i think, moved into an apartment in a large block where there also lived "african americans". One of the locals later asked him how he felt living next door to negroes (they called a spade a spade back then). He answered: "Ohh i got no problem but i wonder how he feels living next door to an ex Nazi"

 

[Ove]

I don't know if "dummy" is accurate for the real rocket engines (in three stages), because they were used in rocket engine tests here. They are in fact real rocket engines.

Yes, i believe the correct term is "Test Vehicle". It was used for testing all the facilities at the Cape, the VAB, the Crawler, the launch tower etc. This Page :The Cape tells the fascinating story about buinlding the facilities at the Cape.

 

[AmateurScientist]

One of my favourite anecdote in the book comes from Huntsville. One of Von Braun's people,dr. Rudolph i think, moved into an apartment in a large block where there also lived "african americans". One of the locals later asked him how he felt living next door to negroes (they called a spade a spade back then). He answered: "Ohh i got no problem but i wonder how he feels living next door to an ex Nazi"

Yes, unfortunately, the U.S. Department of Justice decided in 1983 to investigate the possibility of prosecuting Dr. Arthur Rudolph for war crimes he allegedly committed in WWII. By then, he and his wife had left Huntsville to live near their daughter in California. In order to avoid prosecution, he renounced his U.S. citizenship and returned to Germany in 1984. I think he died in the 1990s.

Many of his friends and former colleagues in Huntsville were very sad and even outraged that the DOJ chose to force their friend out of the country. They wrote Congress and the President and asked for intervention on his behalf.

Although I never met Dr. Rudolph, I had the pleasure of going to school with many of the children of von Braun's Peenemünde rocket team. One of them, the son of one of the most famous ones, was even a teacher at my high school.

My city owes its current prosperity and status as a metropolitan area to the German rocket team and their decision to locate here. Before they arrived, Huntsville had only 16,000 residents and was mostly a cotton mill town.

Today, its metro area is about 350,000 and has a robust, high tech economy with the highest standard of living of any city in the southern U.S., including Atlanta.

AS

 

[Ove]

Yes, unfortunately, the U.S. Department of Justice decided in 1983 to investigate the possibility of prosecuting Dr. Arthur Rudolph for war crimes he allegedly committed in WWII. By then, he and his wife had left Huntsville to live near their daughter in California. In order to avoid prosecution, he renounced his U.S. citizenship and returned to Germany in 1984. I think he died in the 1990s.

Yes i heard that story too. It is an utter disgrace and the responsible people really ought to be ashame of themselves. Unfortunately they are probably made of the same selfrighteous stuff that made Sen. McCarthy and so will be convinced that they "did the right thing"