The 747 Shuttle Transporter is alive and well. Actually there are two of them. I was up at NASA Dryden a couple of weeks ago and there is one out there at Edwards. For reasons already stated, the Shuttle can’t be launched from it (in spite of what you may have seen on Moonraker. (Come to think of it, didn’t the 747 get destroyed in that one?)
For information on, and photos of, Pegasus, go here: http://www.dfrc.nasa.gov/gallery/photo/Pegasus/
The Shuttle was launched from the 747, but not powered. Before the first orbital flight, there was a series of (three?) drop tests to check the gliding and landing performance. Star Trek fans campaigned to have that first Shuttle named Enterprise, but it was built just for the drop tests and never went into space.
There was a follow-up to the X-15 already in the works when the U.S. decided to shift all their manned spaceflight efforts to capsules. It was the X-20, nicknamed the DynaSoar. The fuselage looked similar to the Shuttle (but I’m pretty sure it was much smaller, possibly a two-man crew?) and it had vertical fins at the wingtips instead of a single stabilizer. It was to be launched on top of a rocket (probably an Atlas, but I’m doing this from memory), orbit, and then glide to a landing at Edwards.
There is an advantage to launching rockets eastward from close to the equator, but having the launch complex in Florida is also partly a coincidence. The U.S. was trying to develop a long-range missile test site, and I don’t know if people were really looking forward enough to think about putting people and things in orbit. They needed a place to launch over water (obvious safety considerations), but with enough land to build tracking stations downrange. They also considered launching westward from western Washington, with tracking stations on the Aleutian Islands (ruled out because of the frequently overcast weather), and launching southward from southern California, with tracking stations down the Baja Peninsula (don’t know why that was ruled out, might have been difficulty negotiating with Mexico).
bibliophage: Yes, Hawaii certainly has advantages over Florida, especially latitude – but getting the Shuttle, the fuel, the payloads, and the personnel to Hawaii would increase costs dramatically. Not to mention that Cape Canaveral was set up during the Cold War, when the Pacific was at a higher risk of Soviet invasion than Florida.
And wolfman, don’t underestimate the amount of fuel it takes to change the orientation of one’s orbit. Most of the maneuvering the Shuttle does in space is vertical, boosting into a higher orbit to release a satellite or whatnot, not orientational, which would require a lot more fuel (since it involves much larger distances).
The two Shuttle Transporters are still alive and kicking, but NASA now considers them somewhat risky, due to their age, and “highly encourages” the Astronauts to get that Shuttle back on the tarmac at Kennedy. In the past, the Shuttle has landed both at Edwards AFB in CA and White Sands, NM.
These days, NASA is much more willing to make the orbiting shuttle wait out bad weather in FLA rather than ditch at one of the other sites, as the cost of transport is high, the transport vehicles are aged, and there hasn’t been any money allocated to replace the transports in something like fifteen years.
In the past I have ranted about the narrowness of the Kennedy landing strip, the crosswinds at Kennedy, the lack of a flyaround system in case of an overshoot, and that bastard William Proxmire. I don’t need to do it again.
Here’s a little more info on the water part…http://www.straightdope.com/classics/a940617a.html
[Edited by TubaDiva on 08-30-2000 at 08:22 AM]
wolfman said:
What do you mean, “back into geocentric orbit”? The shuttle doesn’t go anywhere near geocentric orbit. The Shuttle flies in low Earth orbit, about 150 to 250 nautical miles high. Geocentric orbit is something like 20,000 miles high (that’s a big swag on my part). And while it would take far less fuel to get to geocentric orbit from LEO than it took to get to LEO, it would take more fuel than the orbiter carries. Although the Shuttle does launch satellites that go to geosynch. They have additional boosters on them.
What I think you meant was launching into one orbit, then changing orbital tracks. While this is possible, and again less fuel than getting to orbit the first place, it takes a lot of fuel in itself. And realize that those big engines on the back of the Shuttle are NOT used on orbit. They are only used during lauch, burning the hydrogen and oxygen in the external tank. The SRB’s are the white boosters, they burn their own self-containes fuel - it’s a solid, thus the name.
It is far easier to launch into the orbit you want to be in than to launch to a wrong orbit then change.
VarlosZ said:
A little clarification is in order here. There are several fuel systems on the Shuttle. As I mentioned before, there is the SRBs, and the ET fueling the main engines (3 of those). Those are the two systems used for launch, only launch, and they do use up all the fuel, none left.
Once on orbit, they have two other reaction systems for maneuvering: the Orbital Maneuvering System (OMS), and the Reaction Control System (RCS).
OMS is the primary on-orbit thrusters. It provides gross movement for altitude adjustments. It takes over after the ET separation for stabilizing and achieving orbit. It also provides the thrust to deorbit.
The RCS is the fine control system - attitude adjustment (pointing in different directions) and stabilizing motion, small movements, etc. There are RCS thrusters on the front and back (forward and aft).
The Shuttle does not necessarily burn all it’s OMS or RCS fuel before return. It may burn off some of the foreward propellant to help with center of gravity issues on entry, but can land with fuel in the tanks.
The fuel for both these systems is the same: two helium tanks supply gaseous helium pressure to the oxidizer and fuel tanks. The oxidizer and fuel are then supplied under gaseous helium pressure to the RCS engines. Nitrogen tetroxide is the oxidizer, and monomethyl hydrazine is the fuel. The propellants are Earth-storable and hypergolic (they ignite upon contact with each other). The propellants are supplied to the engines, where they atomize, ignite and produce a hot gas and thrust.
See
http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-oms.html#sts-oms
However, even if they have some of this fuel left, it is unusable on reentry. Once they reenter the atmosphere, they become a big glider. Well, a glider that falls like a rock. There is no powered flight for landing. They lose speed as they return, flying big curving paths to drag and slow down until altitude and speed are right as they hit the landing area. They only get one shot at landing - no powered flight.
They used to land at Edwards or White Sands because of needing the runway, but now they have a supplemental drag system, a parachute, that helps slow them, so they can land at Kennedy. That makes it easier and cheaper to land and KSC, and as mentioned, there are incentives to do so.
bibliophage said:
[quote]
The best place to launch an orbiter from is [ul]
[li]a place near the equator (to take advantage of the boost from the earth’s rotation.)[/li][li]a place at a high altitude (to avoid as much air resistance as possible.)[/li][li]a place with no population toward the east (to avoid civilian casualties from debris or from a crash)[/li][li]a place with good climate (i.e., dry)[/ul] [/li][/quote]
While true, there is some modification to point 1. Yes you get the most boost from the Earth’s spin at the equator, but it also depends on what orbit you wish to achieve. From KSC, the easiest to reach orbit is at an inclination of KSC’s latitude. However, the shuttle can launch with a variety of inclinations. But to do so takes extra fuel. FYI the ISS is in a 53 deg inclination because of the Russians - they can’t get to the 23 deg inclination of the shuttle. So if you wish to fly an orbit that tracks directly over the equator, then launching from the equator is best. But if you wish to establish some high inclination, then launching from a higher latitude helps.
Johnny L.A., there are a couple different X-projects in work. The X-33 is the single stage to orbit vehicle you mention. It is, however, more parabolic shaped than lifting-body shaped. The lifting body shape you mention is the X-38. The X-38 is the prototype for the crew return vehicle for ISS. There is also conceptual work for a lifting body design for launch, but I think that’s just sketches right now.
Wolfman, back to the OP.
The location provides advantage because it’s closer to the equator for the continental U.S., and it is coastal so things drop into the ocean. However, politics probably did play a role. It certainly played a role in JSC being located in Houston.
You’re thinking “geosynchronous”, which is 22,300 miles (good SWAG). The shuttle was originally supposed to be able to reach geosynchronous orbit, but budget cuts scotched that plan.
All orbits around the earth are geocentric.
Sorry to confuse the issue with that, when I said geocentric orbit, I just meant safe orbit, rather than falling on the south pole.
Because flying all the launch apparatus up to 30,000 feet is expensive. [Rimshot]
Seriously, though, the advantage of launching near the equator is significant, and hasn’t been discussed much yet. The Earth is an oblate spheroid, not a sphere. It bulges out in the middle. That means when you’re near the equator, you’re farther from the center of the earth, so gravity is less. Obviously, the difference is very slight, but when you’re dealing with spacecraft, every pound counts. That’s why you see various European agencies launching from Guiana, in northern South America. That’s an even better spot than Florida, because the Earth bulges the most just south of the equator.
Obviously, all the other points mentioned so far are also valid. I just wanted to make this a little clearer.
The photos I’ve seen of the X-33 show a wingless vehicle which, by definition, is a lifting body. The X-33 and X-38 are both lifting-body-shaped.
Smeghead, I was under the impression that launching from the equator was more a matter of speed than height.
Just remember that you're standing on a planet that's evolving,
and revolving at 900 miles an hour...
If you’ve got access to land near the equator (and Guiana looks to be about 5 degrees north, actually), you don’t lose very much for being off by just a few hundred miles. But since orbit requires speed and altitude, I think that 900 mph head start is probably more signifigant than the oblate spheroidicity of the Earth.
And of course if you’re trying to put something in geostationary orbit (a very popular place for satellites), launching from the equator saves the fuel you’d need to correct the orbital inclination.
Boeing (along with several partners) has just started testing a new rocket which launches from a ship. I don’t know exactly what latitude they choose to launch from, but I’ll see if I can track it down.
Okay I’m confused
How does flying East (against the earth’s rotation) give you a boost? I can’t see how one can gain more “boost” upward by flying East.
I do see how the relative speed of the shuttle is faster to a person on earth if it is going East as opposed to West, but that’s about all.
Since the Earth spins eastward, you will be adding some velocity to the shuttle’s orbital speed. That is, the shuttle’s course is mostly eastward, and you are flying in the same direction the Earth is spinning. It doesn’t give you a boost upwards, but that is a pretty small fraction of the distance the shuttle travels. Gaining altitude is where most of the fuel is spent, of course, but with such extreme fuel limitations, the shuttle needs all the help it can get.
Think of it this way: the shuttle needs to be travelling XX velocity parallel to the Earth’s surface to be in safe orbit around the Earth (not to add to the confusion … safe orbit is obviously not the same as geosynchronous orbit, but can safe orbit also be called “parking orbit”?). It is easier to get to XX velocity when you can add YY velocity from the Earth’s rotation, so you usually launch eastwards.
Or, think of it this way (and forgive my juvenile terms): if you are on a merry-go-round going clockwise, and you are facing away from the merry-go-round, you can throw a ball further to your right than to your left.
Okay, maybe launching eastwards will give you a boost upwards, since travelling along a straight tangent through your launch point will take you off the ground, and eastward launches will have more velocity along that tangent. This is analogous to the point that, if you fire a bullet fast enough parallel to the earth’s surface, it will still reach orbit.
Johnny LA, on the lifting bodies thing, I don’t think any wingless vehicle is a lifting body. I thought just the flat-topped, curved-bottom ones were lifting bodies; wingless vehicles like bombs or whatever wouldn’t count.
Well, check this one out:
http://www.dfrc.nasa.gov/gallery/photo/X-24/Small/EC75-4643.jpg
That’s the X-24B and it has a curved top and a flat bottom; just the opposite of what you said. Here is a note from http://quest.arc.nasa.gov/aero/question/aerotheory/Help_in_designing_a_lifting_body_with_fuselage.txt :
Space capsules (such as Gemini and Apollo) were able to aerodynamically alter their course on re-entry (or entry, if you prefer), but they didn’t generate any measurable lift and can’t be considered a lifting body. They’re more like the bombs you mention. But a wingless vehicle that develops usable lift, such as the X-33, is by definition a lifting body.
If you go here: http://www.dfrc.nasa.gov/gallery/photo/NIX/liftingbody-aircraft.html you will see different lifting bodies. While most of them are curved on the bottom, the X-24B (and to a lesser degree, the X-24A, from which it was re-built) are flat on the bottom. The M2 series lifting bodies were definitely flat on top, but later models such as the X-24 and the record-setting HL-10 were curved on top.
Okay, it looks like lifting bodies come in more shapes than I had previously thought. Thanks for the links.
I have a soft spot in my head… er, heart for the bloody thing. 
Well Boris, I chewed on your explanation and I appreciate it but somehow it still does not make sense to me that you would get that boost going East.
Since I’m being such an intellectual gimper today I’ll think about your juvenile explanation more (it’s easier to understand).
Merry go round spinning clockwise…got it!
Sitting facing away from merry go round. All this is analgous to the space center on earth…Got that too!
Throw a ball to the right…it goes further than throwing to the left…Ok, I’m in my chair at my computer now spinning clockwise…I can see that throwing right would put the ball further because I’m including the momentum from spinning into the ball…
WAIT A SECOND!!! Isn’t throwing with the spin of the merry go round the same as going WEST from the spsce center???
AWWW CRRAAAP! Now I’m back to being confused. I’m beginning to think that one doesn’t get a boost from the earth if one flys East. (And I still somehow suspect one doesn’t get a boost at all, even flying West.)
Thanks for the help but I think I need more.
Yes. If the Earth were spinning clockwise like your merry-go-round. But the Earth is spinning anti-clockwise, so the boost is too the east.