Nasa's Shuttle

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  • #26
mgb_phys
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I didn't know you could use Hydrazine as a monopropellant - I suppose it doesn't need an oxiser if it isn't burning!
 
  • #27
Astronuc
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There's also diborane (B2H6), but that is really nasty stuff - much more flammable/explosive than H2. Also the most effective in terms of chemical energy would be H2 + F2 with an Isp ~ 450 sec, but then the HF in the atmosphere would be no-no.
 
  • #28
D H
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I thought the shuttle used liquid hydrogen and oxygen to achieve orbital speeds.
The main engines bring the Shuttle to just shy of orbital speed. The Shuttle separates from the external tanks that supply LH2/LOX shortly after MECO (main engine cutoff). Since the Shuttle is not quite yet at orbital speed, the external tanks fall back to Earth. They hit in the middle of the Indian Ocean. The OMS provides the delta-V needed for orbit insertion, to get to the Station (or wherever), and to de-orbit.
 
  • #29
rcgldr
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Saying something is efficient in terms of "mass" is the equivalent of an incomplete sentence.
I sit corrected, left out the part about specific impulse. LH2 and LOX do seem to be popular. DH's posts cleared things up.

I wonder which (unmanned) rocket achieved the highest speed of the payload before utlizing slingshot effect off planets or the sun, and the parameters, like initial fuel to weight ratio, number of stages, type of fuel, ...

The only other tidbid I remember about the Space Shuttles, is because of Apollo 13, there's an active plutonimum button / thermal couple power supply in what's left of the lunar module at the bottom of an ocean (don't remember which ocean).
 
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  • #30
rbj
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just wondering what would happen after it hit the speed of light
it doesn't hit the speed of light. even with all the fuel in the universe.

ok then
so i am guessing that is how you would time travel
we're all time-traveling. every second, we time-travel one second into the future.

you know, like the song Fly like an Eagle (Steve Miller Band): "Time keeps on slippin', slippin', slippin' Into the future ..."

Well, it only works in the forward direction. You can never go home again.
as is the case anyway... can't go back.
 
  • #31
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it doesn't hit the speed of light. even with all the fuel in the universe.
when i had said that i had meant when the shuttle gets to the speed of light then what would happen to it

I'm not sure what fuel is used to slow down the shuttle for reentry. The small maneuvering thrusters use a fuel that doesn't have the storage issues of hyrodgen and oxygen, but it's toxic.
To slow down i know they use the rudder and i am pretty sure they use the slats, flaps and spoiler. When planes are landing they use all of those except for the rudder

Shuttle rudder
 
  • #32
D H
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The Shuttle first has to enter the atmosphere. The aero surfaces don't do anything while the Shuttle is on-orbit. The Shuttle has to do a "de-orbit burn" directed against the orbital velocity vector. The burn changes the eccentricity of the Shuttle's orbit such that the perigee is below the top of the atmosphere. Half an orbit or so later, the Shuttle enters the atmosphere.

Once it does enter the atmosphere, it is the body of the Shuttle that slows the Shuttle down, not the aero control surfaces. That is why the bottom of the Shuttle is covered with tile. Those aero control surfaces exist to keep the Shuttle on the right angle of attack and in the right attitude.
 
  • #33
DaveC426913
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As D_H points out, the shuttle uses aerobraking, not aerodynamics to slow down - the very same aerobraking that all the Apollo capsules used - and they didn't have any wings or rudder.

At 25 times the speed of sound you don't want to be sticking anything out. The wings and rudder only come in to play once the shuttle slows below the speed of sound.
 
  • #34
rcgldr
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To slow down i know they use the rudder and i am pretty sure they use the slats, flaps and spoiler.
Shuttle rudder
The shuttle doesn't have flaps, but it does have speed brakes in the vertical stabilizer as seen in the picture. The speed brakes aren't used until the shuttle is well below sub-sonic speed. Wiki includes information about what occurs between re-entry and landing.

http://en.wikipedia.org/wiki/Space_Shuttle

Many (most) delta wing type aircraft don't have flaps, since delta wings can be flown at about double the angle of attack of a normal wing to allow for slower speed flight such as landing. The Concorde is a typical delta wing design, without flaps (the rear control surfaces are elevons).

http://www.concordesst.com/wing.html
 
  • #35
D H
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NASA has a "Landing 101" web page that describes shuttle landing from 4 hours prior to deorbit burn to wheelstop. http://www.nasa.gov/mission_pages/shuttle/launch/landing101.html

Note that (1) the aerosurfaces become active as soon as they have some air to work against, and (2) the Shuttle doesn't go subsonic until it is 25 miles shy of the landing site. Practically all of the descent is supersonic.

when i had said that i had meant when the shuttle gets to the speed of light then what would happen to it
The Shuttle goes Mach 25 or so (25 times the speed of sound). The speed of light is Mach 880991. Science fiction movies do not portray reality, and are particular guilty of veering from science to fiction when it comes to spacecraft. Spacecraft, unlike aircraft, do not need to bank to turn and cannot turn on a dime. Spacecraft are not at all like jet fighters. If you want a good analogy, think of a fully-loaded 18 wheeler on ice with a VW engine and no brakes.
 
  • #36
DaveC426913
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If you want a good analogy, think of a fully-loaded 18 wheeler on ice with a VW engine and no brakes.
I love it!
 
  • #37
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ok ok
i am young and i am into airplanes not shuttles
i guess i just drifted into a no fly zone.
and nice analogy
 
  • #38
rbj
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it doesn't hit the speed of light. even with all the fuel in the universe.
when i had said that i had meant when the shuttle gets to the speed of light then what would happen to it
the shuttle doesn't get to the speed of light. so how can your question be answered? there is no meaning to a question of "what are the consequences when something impossible happens?"
 
  • #39
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Spacecraft are not at all like jet fighters. If you want a good analogy, think of a fully-loaded 18 wheeler on ice with a VW engine and no brakes.
OMG I'm still laughing! The only caveat being that while controlling direction and velocity can be brutal, with thrusters and gyro's and no air there is a vast amount more freedom of attitude control.
 

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