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skrap1r0n
2005-Feb-07, 06:24 PM
Ok , I was looking into abort procedures about the shuttle to get some info for another thread and I was wondering why they orient the shuttle in an upside down position during their first roll manuver after the launch. I did google it (briefly) and the only things I found were speculation from others. These include:

1) So the pilot can see the horizon in the event they need to abort.

2) So Gravity will help seperate the shuttle from the main booster in the event of an emergency.

3) Because the shuttle orbits the earth in that position so they won't have to perform additional manuvers during Orbital insertion.

So I ask, whats the real reason it rolls into an upside down position during it's launch?

darkhunter
2005-Feb-07, 06:27 PM
IIRC its to reduce the shock of going supersonic on the stack. They also throttle back for a short time during the launch for the same reason.

edit: a misssspelled word can change you're whole meaning....

Romanus
2005-Feb-07, 06:30 PM
The Shuttle usually orbits "upside-down", so part of it is just getting it in its orbital configuration. Though I'm no expert, I think another part of it is getting its velocity vector as tangential as possible (practical?) to the Earth's rotation to get the maximum boost.

Hamlet
2005-Feb-07, 06:52 PM
From the Space Shuttle Reference Manual (http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_mes.html#mes_1st_stage)


The orbiter flies upside down during the ascent phase. This orientation, together with trajectory shaping, establishes a trim angle of attack that is favorable for aerodynamic loads during the region of high dynamic pressure, resulting in a net positive load factor, as well as providing the flight crew with use of the ground as a visual reference. By about 20 seconds after lift-off, the vehicle is at 180 degrees roll and 78 degrees pitch.


It would seem aerodynamic loading and visual reference are the main reasons.

EckJerome
2005-Feb-07, 06:59 PM
The roll is done for several reasons:
http://www.ksc.nasa.gov/facts/faq07.html

skrap1r0n
2005-Feb-07, 07:01 PM
From the Space Shuttle Reference Manual (http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_mes.html#mes_1st_stage)


The orbiter flies upside down during the ascent phase. This orientation, together with trajectory shaping, establishes a trim angle of attack that is favorable for aerodynamic loads during the region of high dynamic pressure, resulting in a net positive load factor, as well as providing the flight crew with use of the ground as a visual reference. By about 20 seconds after lift-off, the vehicle is at 180 degrees roll and 78 degrees pitch.


It would seem aerodynamic loading and visual reference are the main reasons.

CLICK! Angle of attack, that makes sense. Upside down, the aerodynamic load squeezes the Shuttle and boosters together, Right side up, the forces would try to pull them apart.

Thanks

joema
2005-Feb-07, 07:53 PM
...So I ask, whats the real reason it rolls into an upside down position during it's launch?
Two main reasons are usually given for this:

(1) It optimally orients the vehicle in case of an RTLS (Return To Launch Site) abort.

Oriented "heads down", a simple powered pitch around maneuver is needed to return. Oriented "heads up", a more complicated roll plus pitch maneuver would be required.

(2) It decreases structural loading on the wings vs a "heads up" orientation. Heads down, the vehicle pitch is oriented to a slight negative angle of attack (wind flow relative to wings). Wings generate lift -- the higher speed the more lift. A slight negative angle of attack nulls this out thus lowering wing stress.

There are also less important reasons: it helps with comm coverage (antennas are on top of the orbiter), it provides the crew with a better horizon view, etc.

The vehicle is physically capable of flying a "heads up" profile and in fact that helps payload slightly. However because of the RTLS abort and wing loading issues I doubt they'll ever do that.

Why not just build the launch pad pointed the right direction? To save money the shuttle uses the old Saturn V pad. That was oriented south to facilitate alignment of the older guidance platform. However the shuttle flies (or used to fly) different inclinations. ISS is 52 degrees, whereas Hubble is 28 degrees (angle from the equator). Each one would require a different amount of roll so even if the pad was pointed toward the most common ascent inclination, some roll would still be necessary.

tofu
2005-Feb-07, 08:06 PM
And, they used to fly heads down all the way to orbit, but the way they do it now is to actually roll back to heads up once in space, and they stay that way until main engine cut off. When flying the shuttle in orbitersim (and by flying, I mean watching the autopilot fly it) the heads down profile is much more aesthetically pleasing, but if you want realism, you have to let it make that roll and then just stare at the stars for a while.


Why not just build the launch pad pointed the right direction? To save money the shuttle uses the old Saturn V pad. That was oriented south to facilitate alignment of the older guidance platform. However the shuttle flies (or used to fly) different inclinations. ISS is 52 degrees, whereas Hubble is 28 degrees (angle from the equator). Each one would require a different amount of roll so even if the pad was pointed toward the most common ascent inclination, some roll would still be necessary.

Trivia time. Does anyone know why the pad (and KSC) are where they are? I mean, why not build the launch complex closer to the equator, maybe in puerto rico or something?

Doodler
2005-Feb-07, 08:17 PM
Trivia time. Does anyone know why the pad (and KSC) are where they are? I mean, why not build the launch complex closer to the equator, maybe in puerto rico or something?

Seems easy enough, the facility was built during the Cold War. Its the closest you can reasonably get to the equator in the continental US and not be near any major population centers. I imagine it was also selected for its proximity to water, which in the event of an emergency prior to orbit, you could abort and recover from the waters near the facility. This, of course, would have been the way you would want to recover a Mercury, Gemini or Apollo capsule, which is what flew when the Cape was first converted into a launch facility.

Added: kind of a reach, but I wonder if the location didn't also have to do with its purpose being to support moon launches, and the 'default' launch path would be favorable to the orbital alignments needed for TLI.

tofu
2005-Feb-07, 08:38 PM
Added: kind of a reach, but I wonder if the location didn't also have to do with its purpose being to support moon launches, and the 'default' launch path would be favorable to the orbital alignments needed for TLI.

That's the *only* reason :) If you launch from KSC and head due east, you're at the same inclination as the moon. At any other latitude (except the duplicate one in the southern hemisphere) a fuel expensive plane-change maneuver would be required for a trip to the moon. From KSC, you just wait for the moon to pass overhead, which it does once each day, and launch due east. Voila, you're in a parking orbit.

Other concerns, like proximity to water, are available pretty much anywhere on the east coast. They could have built KSC a little farther south and done the plane change maneuver at launch - that's cheaper than doing it in orbit. But the best option in terms of fuel use is to have the launch complex exactly where it is.

To get the ISS, the shuttle has to head a little farther north. I don't remember the exact inclination, but it's higher than the moon. Basically, the ISS's orbit is a compromise between what NASA and the Russian space agency can easily reach. If we had built the ISS ourselves, you can bet that it would have been in the exact same inclination as the moon.

Edit to correct this: you just wait for the moon to pass overhead, which it does once each day

What I mean is, the *orbit* of the moon passes overhead, or more accurately, the earth rotates putting KSC under the moon's orbit.

Doodler
2005-Feb-07, 08:45 PM
Added: kind of a reach, but I wonder if the location didn't also have to do with its purpose being to support moon launches, and the 'default' launch path would be favorable to the orbital alignments needed for TLI.

That's the *only* reason :) If you launch from KSC and head due east, you're at the same inclination as the moon. At any other latitude (except the duplicate one in the southern hemisphere) a fuel expensive plane-change maneuver would be required for a trip to the moon. From KSC, you just wait for the moon to pass overhead, which it does once each day, and launch due east. Voila, you're in a parking orbit.



Now that the dust is off the memory, didn't the moon only match that inclination a couple times a year? I do seem to recall there were certain launch windows that had to be observed.

ToSeek
2005-Feb-07, 08:52 PM
Added: kind of a reach, but I wonder if the location didn't also have to do with its purpose being to support moon launches, and the 'default' launch path would be favorable to the orbital alignments needed for TLI.

That's the *only* reason :) If you launch from KSC and head due east, you're at the same inclination as the moon. At any other latitude (except the duplicate one in the southern hemisphere) a fuel expensive plane-change maneuver would be required for a trip to the moon. From KSC, you just wait for the moon to pass overhead, which it does once each day, and launch due east. Voila, you're in a parking orbit.

Considering that Cape Canaveral was established as a rocket launch site in 1949, I don't think that the choice of site had anything to do with the Moon. Also, the Moon's inclination relative to Earth's equator varies over the course of a month from (roughly) 18 to 28 degrees. From what I recall of the Apollo launch windows, there were only a couple of days each month that were suitable.


To get the ISS, the shuttle has to head a little farther north. I don't remember the exact inclination, but it's higher than the moon. Basically, the ISS's orbit is a compromise between what NASA and the Russian space agency can easily reach.

Not so much a compromise but close to the only possible inclinations: flights from Baikonur have to have an inclination of at least 49 degrees (without a very expensive plane change), and KSC launches can only go up to 57 degrees (before going over land and compromising safety).

joema
2005-Feb-07, 09:16 PM
That's the *only* reason :) If you launch from KSC and head due east, you're at the same inclination as the moon....
In addition to avoiding plane change delta V, launching eastward from the Cape's latitude imparts major additional payload.

This is due to the earth's rotational velocity. It seems small -- just 1670 km/hr at the equator (1440 km/hr at the Cape), about 5-6% of orbital speed. However rocket payload is very sensitive to dry weight. The eastward rotation acts like an invisible booster, effectively lowering dry weight, giving a very non-linear payload improvement.

Even at the Cape's latitude that improvement DOUBLES the shuttle's payload, vs a polar inclination launch:

http://globalsecurity.org/space/systems/sts_brm.htm

The improvement is so significant the Sea Launch program built an entire towable sea platform, partially to launch further south at the equator:

http://www.sea-launch.com/

tofu
2005-Feb-07, 11:51 PM
aw man, the first time in my life that I'm wrong and wouldn't you know, toseek is there! :wink:

j/k. thanks for the correction. I'm going to do some googling and see what the complete history of the cape is. I'm not aware of any mechanism that would change the inclination of an orbit except for interation with another body, and tidal forces. When you say the moon's inclination changes, are you sure you're not thinking of libration?

ToSeek
2005-Feb-08, 12:40 AM
aw man, the first time in my life that I'm wrong and wouldn't you know, toseek is there! :wink:

j/k. thanks for the correction. I'm going to do some googling and see what the complete history of the cape is. I'm not aware of any mechanism that would change the inclination of an orbit except for interation with another body, and tidal forces. When you say the moon's inclination changes, are you sure you're not thinking of libration?

The Moon's inclination is relative to the ecliptic, not the equator. So as the orbit precesses around (which takes 18.6 years, not a month - I was wrong about that), it can add or subtract from the ecliptic's inclination depending on whether the Moon's inclination is the same as or opposite to the ecliptic's inclination. However, you are correct in that the inclination relative to the ecliptic doesn't change.

Gullible Jones
2005-Feb-08, 12:48 AM
Ehh? The shuttle's not upside down... The Earth is!

(Well, at least for the astronauts.)

Manchurian Taikonaut
2005-Feb-08, 02:48 AM
Just to make a somewhat un-related comment but I also understand it goes in reverse while in Space, there are other dangers aswell called space debris or space junk, space junk has serious destructive potential a few flicks of paint or garbage almost smashed in the front window on shuttle. So who will start cleaning this dangerous stuff up, the guys at NASA, the Russians should do it, the EU or UN should fund it ? Debris of all sizes can be dangerous, a paint fleck can gouge a shuttle window. Space collisions are frequent enough that NASA on average now replaces a window after each shuttle mission. In one shuttle two windows were replaced and scientists later found 51 pits in them. They contained meteoroids, paint chips, aluminum, stainless steel, silver, copper and plastic, now there is a plan to fly backwards to reduce the chances of exposing vulnerable parts of the craft to debris

tofu
2005-Feb-08, 04:27 AM
So who will start cleaning this dangerous stuff up,

It's impossible for us to clean it up. If you tried to chase down a single fleck of paint so that you could scoop it up into a waste basket, you would definitely end up shedding a few flecks of paint along the way. that's just the way machines are.

Fortunately, LEO cleans itself. The atmosphere expands and contracts due to heating by the sun. That imparts just a tiny about of drag on everything in LEO. In the case of debre, it eventually causes it to reenter the rest of the way.

This is the reason that the ISS is at its current altitude. It's in the zone where the atmosphere is self-cleaning. Unfortunately, that means that left to itself, the ISS would eventually be pulled further into the atmosphere and burn up. To prevent this, the shuttle (and, I'm guessing, the progress supply ships) give the ISS a little boost every time they dock.

Basically, that's the best we can do. If we fly in space we are going to occasionally drop a nut or bolt or whatever. You either live with that reality or give up your intercontinental phone calls and news reports, live broadcasts of sporting events, advance warning of hurricanes, etc. etc.

Maddad
2005-Feb-08, 08:16 PM
Why does the shuttle roll upside down after launch?It's better than rolling upside down on landing.

skrap1r0n
2005-Feb-08, 09:00 PM
Ehh? The shuttle's not upside down... The Earth is!

(Well, at least for the astronauts.)

Are you an Aussie?

skrap1r0n
2005-Feb-08, 09:02 PM
Just to make a somewhat un-related comment but I also understand it goes in reverse while in Space, there are other dangers aswell called space debris or space junk, space junk has serious destructive potential a few flicks of paint or garbage almost smashed in the front window on shuttle. So who will start cleaning this dangerous stuff up, the guys at NASA, the Russians should do it, the EU or UN should fund it ? Debris of all sizes can be dangerous, a paint fleck can gouge a shuttle window. Space collisions are frequent enough that NASA on average now replaces a window after each shuttle mission. In one shuttle two windows were replaced and scientists later found 51 pits in them. They contained meteoroids, paint chips, aluminum, stainless steel, silver, copper and plastic, now there is a plan to fly backwards to reduce the chances of exposing vulnerable parts of the craft to debris

I'm not sure how we would go about cleaning up all that junk. any ideas?

um3k
2005-Feb-08, 09:07 PM
I'm not sure how we would go about cleaning up all that junk. any ideas?

We could send up big blocks of aerogel. :D

skrap1r0n
2005-Feb-08, 09:15 PM
solar powered elecrtomagnets?

Doodler
2005-Feb-08, 09:23 PM
solar powered elecrtomagnets?

Whats to keep the magent from flying to the satellite and not the other way around? Also, what about aluminum and other non-magnetics (paint, plastic and whatnot)?

skrap1r0n
2005-Feb-08, 09:48 PM
well just reducing the Ferrous material would be a start. and I have NO idea how we would do it in practicality.

joema
2005-Feb-08, 10:13 PM
My guess is there's not much ferrous material used in most space vehicles. Weight is so critical they're generally built from aluminum, magnesium, titanium, or even aluminium-lithium alloys, all of which are non-ferrous.

Lauch costs can be over $10,000 per pound (that's DOUBLE the price of pure gold), it pays to use exotic materials to reduce launcher and payload weight. Most of these are non-ferrous.

Evan
2005-Feb-08, 11:05 PM
There is a LOT of garbage in orbit. Apparently over 4 million pounds of trash bigger than one centimeter and an unknown but much larger quantity of smaller stuff. Estimates are over 330 million bits larger than one mm.

http://commons.wikimedia.org/upload/thumb/c/c5/600px-Debris-LEO1280.jpg

Note: Free use image from Wikimedia Commons.

The soviets were the worst offenders. Their nuclear powered radar satellites (RORSAT series) were a major contributor. At least sixteen of these leaked huge numbers of radioactive sodium-potassium droplets up to several centimeters in size from the reactor cooling systems. There are estimated to be over 115,000 of these frozen droplets alone at about the orbit of Hubble.

What really has some people worried is that we may be approaching a critical mass where collisions begin a chain reaction that could make LEO off limits for a long time.

skrap1r0n
2005-Feb-09, 01:55 AM
By chain reaction, I am assuming you mean one collides with another which collides with another etc?

If thats a concern then we could use that as an advantage. Well placed explosions, strategically places ABOVE this plane could knock areas out of orbit creating temporary windows.

Avatar28
2005-Feb-09, 05:29 PM
What really has some people worried is that we may be approaching a critical mass where collisions begin a chain reaction that could make LEO off limits for a long time.

How would that happen, exactly? I mean, sodium/potassium won't exactly fission, right?

Doodler
2005-Feb-09, 05:57 PM
Evan, might want to make that a link. The BA's bandwidth allotment is going to hurt from that pic.

Manchurian, the worry is that big lumps of space junk colliding makes lots and lots of little space junk, which is more deadly, because some of it can't be tracked by current technology, and there's suddenly a LOT more potential impactors on orbiting vehicles.

The chain reaction in question is more like a golf ball on a box of mousetraps. One event leads to several events, and it escalates geometrically.

skrap1r0n
2005-Feb-09, 06:42 PM
The chain reaction in question is more like a golf ball on a box of mousetraps. One event leads to several events, and it escalates geometrically.

Then we could potentially use that as our advantage. Notwithstanding working equipment orbiting in that region, it seems like a well calculated Nudge could cause a cascade effect that could deorbit a bunch of that junk.

Alternately, I'll bet that stuff would be worth a LOT if it could be sucessufully salvage iit. All we need are refineries in space and some garbage collectors. I mean recycling it seems like the best route to go, considering launch costs.

Doodler
2005-Feb-09, 06:48 PM
The chain reaction in question is more like a golf ball on a box of mousetraps. One event leads to several events, and it escalates geometrically.

Then we could potentially use that as our advantage. Notwithstanding working equipment orbiting in that region, it seems like a well calculated Nudge could cause a cascade effect that could deorbit a bunch of that junk.

I think you're underestimating the forces involved here. At the relative speeds we're talking about, these aren't 'nudges'. These are extremely fast, extremely destructive collisions which send debris off in chaotic and unpredictable paths. You're getting collisions between objects moving at tens of thousands of miles an hour. There's nothing controllable about them.

joema
2005-Feb-09, 06:58 PM
...Alternately, I'll bet that stuff would be worth a LOT if it could be sucessufully salvage iit....
At current launch costs (about $10,000 per pound for the Shuttle, maybe 1/2 that for Delta IV) if pure gold bricks were orbiting around the earth it wouldn't be worth it to retrieve them.

Evan
2005-Feb-09, 07:03 PM
Doodler, the pic isn't being served from the BBS server. It is just a link to the Wikimedia server and doesn't have any effect on the BBS server bandwidth. That's the same for any picture posted here.

The problem with the sodium-potassium droplets is the orbit they are in is high enough they won't decay very soon and so pose a hazard for a long time. When I used the term "critical mass" I wasn't referring to fission but simply to the quantity of junk.


The chain reaction problem is that if stuff starts to collide and break up it could all of a sudden result in an exponential increase of junk too small to track but plenty big enough to be hazardous.

skrap1r0n
2005-Feb-09, 08:08 PM
...Alternately, I'll bet that stuff would be worth a LOT if it could be sucessufully salvage iit....
At current launch costs (about $10,000 per pound for the Shuttle, maybe 1/2 that for Delta IV) if pure gold bricks were orbiting around the earth it wouldn't be worth it to retrieve them.

I don't mean retrieve them and bring them back, I mean retrieve them and recycle them in space. hell is nothing else, orbit a sorting facility with a few tugs that would go out and collect it, bring it back to the sorting facility and sort them, compact them into blocks or place them into containers then re-orbit the containers until need the materials?

Evan
2005-Feb-09, 08:17 PM
It just isn't possible. The garbage is in every conceivable orbit. Prograde, retrograde, polar and everywhere in between at all sorts of altitudes and eccentricities. No conceivable "space tug" can be built with the delta vee to go get it. Catching the stuff at up to twice orbital velocity is like catching a bullet in your teeth except much worse.

About the only thing that I can think might work is an orbiting high power laser system that could vaporize objects to plasma. This would then deorbit in short order. There would of course be some stiff opposition to this as it would constitute a space weapons system.

Brezelfish
2005-Feb-09, 08:30 PM
How long does it take for a mobilephone sized garbage item in standart Shuttle orbit to come back down to earth and glow in the athmosphere??

skrap1r0n
2005-Feb-09, 09:04 PM
It just isn't possible. The garbage is in every conceivable orbit. Prograde, retrograde, polar and everywhere in between at all sorts of altitudes and eccentricities. No conceivable "space tug" can be built with the delta vee to go get it. Catching the stuff at up to twice orbital velocity is like catching a bullet in your teeth except much worse.

About the only thing that I can think might work is an orbiting high power laser system that could vaporize objects to plasma. This would then deorbit in short order. There would of course be some stiff opposition to this as it would constitute a space weapons system.

Well how long do the estimate it will be before our launch capabilities are severely hindered?

Evan
2005-Feb-09, 11:07 PM
I have no idea when or even if a "chain reaction" will occur and neither does anyone else. It is just a possibility that seems plausible. All it might take is some catastrophic event such as the breakup of the ISS from an impact or some other event such as a booster explosion.

As for orbital decay it seems that the shuttle itself at 350km would deorbit in about a year. For other objects it greatly depends on the surface area/density ratio. The greater the mass ratio the longer it will stay in orbit. Anything above about 1000km will last >100 years. The ISS is decaying about 1 to 2 km per week at 345 km.

This is greatly dependent on solar activity which can expand the atmosphere when active.

Hamlet
2005-Feb-10, 01:24 AM
The ISS is decaying about 1 to 2 km per week at 345 km.

This is greatly dependent on solar activity which can expand the atmosphere when active.

A nice little graph of the ISS orbital decay can be seen here (http://www.heavens-above.com/issheight.asp).

man on the moon
2005-Feb-15, 09:39 PM
Air and Space this month has yet another explanation. They do discuss the antenna issue, however, there is a reason the antennas aren't just lined up with the ground to begin with...

according to the blip in the magazine, it has to do with the way the shuttle is attached to the booster on the assembly building. when it is attached, it is apparently facing the wrong way. since the moving thing (launchpad...what's it called, dang) can't exactly turn around easily once it clears the building, the task is done shortly after launch when it's a (relatively) simple matter of control surfaces and not a whole rocket+pad+tower+whatever other problems may be encountered on the ground.

joema
2005-Feb-15, 11:58 PM
...according to the blip in the magazine, it has to do with the way the shuttle is attached to the booster on the assembly building. when it is attached, it is apparently facing the wrong way...
I've heard that reasoning before, but not sure it's the whole story.

Pad 39A/B were built for the Saturn V, oriented due south. That means the road, the ramp, the flame trenches, etc. were all designed for a vehicle approaching from the south. See below images.

Of course NASA could have just built a new pad and ramp but considering the pad base contains 52000 cubic meters of concrete that would be pretty expensive.

Maybe they could have mounted the shuttle sideways on the crawler/transporter, and designed the stacking hardware in the Vehicle Assembly Building for that orientation.

However due to different launch trajectories (28 degrees for Hubble, 52 degrees for ISS) a roll maneuver would still be required.

Their reasoning probably was why spend all the money since it would only reduce (not eliminate) the roll maneuver.

http://www.enviropacific.com/images/clip_image013.jpg
http://www.crista.uni-wuppertal.de/deutsch/pad39a.jpg
https://www.patrick.af.mil/heritage/Cape/Cape2/Images/cape090f.jpg