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?

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Eagle Eye Observatory

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....

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441!!!! :)

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.

From the Space Shuttle Reference Manual
It would seem aerodynamic loading and visual reference are the main reasons.

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The roll is done for several reasons:
http://www.ksc.nasa.gov/facts/faq07.html

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

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Eagle Eye Observatory

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.

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.

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.

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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.

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.

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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.

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).

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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/

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.

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Ehh? The shuttle's not upside down... The Earth is!

(Well, at least for the astronauts.)

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

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.

It's better than rolling upside down on landing.

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