upside down shuttle?

[beanbag]

i have a curious question. why does the space shuttle fly with it's bottom or flat side facing the sun? is the top side of the shuttle "sun-sensitive"? also, why does the shuttle fly around the earth in a wave-like pattern, and not just straight? thank you to anyone who gives me the answers! Jan

 

[MeteorWayne]

I'll handle the second question. It only looks wavy because you are looking at the orbit projected on a flat map.

If you plot the path on a globe in 3D, you will see it is really a circular path.

 

[hewes]

The orbiter is often flown with the bottom facing out to space and the aft engine compartment pointed in the direction of travel to protect the crew compartments from orbiting debris and (micro)meteorite strikes.

 

[Zipi]

I have understood that shuttle's cooling radiators are located at payload bay doors. Cooling works better if the sun is not shining to them directly.

Also astronauts can see earth if they are flying upside down because the windows are located so.

As well just popped to my mind that probably KU-band antenna needs the shuttle to fly upside down to make it work. But I'm not sure about KU-band...

 

[MeteorWayne]

IIRC, most time the KU band antenna is aiming at the TDRS Satellites; I'm not sure of their orbit, but I'm sure it's much higher than the shuttle, so payload bay up would work.

 

[hewes]

"Shuttle Flight Rule A2.1.3–32 states that the preferred attitude for orbiter operations is with the payload bay pointing down (toward the Earth) and the nose not pointing forward. Exposure time with the payload bay pointing forward and with the nose pointing forward while the payload bay points up or out of plane is kept to a minimum. If other attitudes are required by payload or orbiter requirements, they will be used. The flight rules are primarily designed to protect the orbiter windows and radiators (for which the hazard is 16 times greater when the payload bay points forward than when it points down) (Reeves, 1997). Although orientations that present the maximum risk of critical penetration are not prohibited, the shuttle program’s maximum allowable critical risk of 1/200 might force mission planners to minimize flight time in those attitudes."

Reference:
http://www.nap.edu/openbook.php?record_id=5958&page=42

 

[Testing]

Orbit of the TDRS network is just over 22K miles GEO

 

[MeteorWayne]

Aha, that answers that! I feel like a doofus fo not knowing that

 

[samkent]

Doesn't that mean they have to have several burns per orbit to maintain the Earth facing orientation?

 

[CalliArcale]

Doesn't that mean they have to have several burns per orbit to maintain the Earth facing orientation?

That's what the RCS is for. ;-) There's an autopilot that makes attitude corrections as needed, even while the crew sleep, if I recall correctly.

Regarding the Ku-band antenna, that's mounted on an arm that sticks out over the sill of the payload bay so it can "look" at the geosynchronous orbit, where the TDRS spacecraft live. It tracks an individual spacecraft for a while, then pivots to lock on to the next one as the first one goes out of the antenna's available field of view. The ISS has a similar system, mounted to the Z1 truss.

I seem to recall there was a mission when the Ku-band antenna was stubborn about retracting at the end of the mission, leading to concern that a spacewalk would be required to tuck it back in so the payload bay doors could close. Fortunately, if memory serves, it finally did retract and everything was fine. There have also been a few missions when it failed to deploy, and they had to rely on lower-bandwidth communications instead.

 

[newsartist]

Doesn't that mean they have to have several burns per orbit to maintain the Earth facing orientation?

If they can find the proper rotation rate, it will keep doing it as the orbit progresses, and need fewer and fewer fine corrections.

 

[ZenGalacticore]

Upsidedown relative to what? The Earth? When the shuttle is orbiting 'upsidedown', is the Earth above you, or below you? Our senses say to us that it is 'below' us, so the belly of the ship facing outward towards the Sun and space tells those same senses that the ship is 'upsidedown'. There is no 'up' or 'down' in zero g.

 

[hewes]

Upsidedown relative to what? The Earth? When the shuttle is orbiting 'upsidedown', is the Earth above you, or below you? Our senses say to us that it is 'below' us, so the belly of the ship facing outward towards the Sun and space tells those same senses that the ship is 'upsidedown'. There is no 'up' or 'down' in zero g.

If you're going to be pedantic, don't forget that it's *microgravity*, not "zero g."

 

[ZenGalacticore]

Upsidedown relative to what? The Earth? When the shuttle is orbiting 'upsidedown', is the Earth above you, or below you? Our senses say to us that it is 'below' us, so the belly of the ship facing outward towards the Sun and space tells those same senses that the ship is 'upsidedown'. There is no 'up' or 'down' in zero g.

If you're going to be pedantic, don't forget that it's *microgravity*, not "zero g."

Well I've got news for hewes: zero-g and microgravity are the same thing. Woops, didn't mean to be 'pedantic'. Can't help it. I guess I'm just an ostentatious academic!

The fact remains the same. There is no 'up' or 'down' in zero-g space. Is the Moon above you, or below you? It's all an illusion interpreted by our senses because those senses evolved in 1g. Is the North Pole 'up', the 'top' of the world? Or is the South Pole 'down', the 'bottom' of the world? Niether. It's our own bias.

While magnetic compasses point 'North', the magnetic poles reverse every few hundred thousand years. When Earth's magnetic field 'reverses' again-as they speculate is now happening with the South Atlantic Anomaly-then compasses will point to magnetic South.

I perceive that you meant 'pedantic' in a negative way. Funny that you would superficially try to instruct me that the proper term was 'microgravity' when in fact, 'zero g' and 'microgravity' are the same thing.

 

[trailrider]

Everybody knows that the air(space)craft doesn't change attitudes...it's the Earth or whatever body you are near that does. Go up in an airplane and do a barrel roll. The plane doesn't move! The ground and sky simply rotate around your longitudinal axis! :roll:

In addition, when you are doing experiments on the ISS or Shuttle, it's "microgravity" as the Earth and even the spacecraft do exert a very slight gravitational pull. But ask an astronaut how it feels, and they will tell you it's "zero-g"!

Ad LEO! Ad LUNA! (Ares and the stars will just have to wait!)

 

[ZenGalacticore]

Everybody knows that the air(space)craft doesn't change attitudes...it's the Earth or whatever body you are near that does. Go up in an airplane and do a barrel roll. The plane doesn't move! The ground and sky simply rotate around your longitudinal axis! :roll:

In addition, when you are doing experiments on the ISS or Shuttle, it's "microgravity" as the Earth and even the spacecraft do exert a very slight gravitational pull. But ask an astronaut how it feels, and they will tell you it's "zero-g"!

Ad LEO! Ad LUNA! (Ares and the stars will just have to wait!)

Look it up, in the spoken vernacular they are the SAME. Compared to 1g, if you are in outer space it may as well be 0g. Technically, yes, it's 'microgravity'. I don't know where in the universe that there'd be absolute zero gravity, even in intergalactic space. But I really don't care to have a debate on semantics. When you say 'zero g' or 'microgravity' people know they are interchangeable.

A plane flying over the Earth, fighting gravity, is a bad analogy. In space, it's completely different. There will never be 'dogfights' in 0g, oh, sorry, 'microgravity', like in Star Wars because THERE IS NO 'UP' OR 'DOWN'. Luke Wusswalker can't 'outmaneuver' or 'climb higher' than his opponent. And the converse is true as well. It would be very easy to zap a moving target in space.

TrailDestroyer- If the astronauts that have actually been into outer space say that it 'feels like zero-g', then maybe we should listen to the Pioneers themselves.