Space Shuttle Theory

[Lynx7725]

Yes, if the Shuttle skip off the atmosphere, the odds are good that it would come back... eventually.

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See my last post. Eventually I believe is less then 90 minutes. They aren't going to starve or freeze in that time.

Carl

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That's the darnest thing about atmospheric/ space boundaries. Not everything is understood. The behaviour of a Shuttle skipping off the atmosphere is, to the best of my knowledge, not entirely predictable. And I doubt anyone is exactly eager to find out. Granted, it's an absolute worst-case scenario, but saying it will come back in around 90 mins.. I'm simply not sure.

A tamer but still bad version is probably this: Skipped off the atmosphere after a 2 week mission with a large crew, airfame damaged and injuries sustained to crewmembers. Trajectory altered by the skip into an unfavourable vector, and not enough reaction fuel to go up to the ISS (not that the Shuttle could do it normally, but this is an abnormal situation) OR to shoot for a decent reentry profile.

[wwwmwww]

That's the darnest thing about atmospheric/ space boundaries. Not everything is understood. The behaviour of a Shuttle skipping off the atmosphere is, to the best of my knowledge, not entirely predictable. And I doubt anyone is exactly eager to find out. Granted, it's an absolute worst-case scenario, but saying it will come back in around 90 mins.. I'm simply not sure.

316947[/snapback]

My thinking is this... and granted I'm not 100% sure its sound... The space shuttle is in a near circular orbit. It slows down for re-entry and now it's in a lower orbit that intersects the atmosphere. It hits the atmosphere and loses more energy and say it skips. Since it's lost energy it sould be in a still lower orbit and the one it was in before intersected the atmosphere so this new one should too. At orbital speed it takes about 90 minutes to complete the entire orbit. So that said I don't see a way to avoid a second re-entry attempt in that amout of time. If it lost alot of energy on the first skip that time would be even less. Once the shuttle's orbit intersects the atmosphere the shuttle is coming down one way or the other unless it fires it's rockets to add more energy into the system. I just don't see the atmosphere adding energy to the shuttle.

The exception I could see to the above is if the orbit the shuttle put itself on for the first attempt at re-entry were highly eliptical. Then maybe it could end up in a more circular orbit after a skip which had a lower total energy but was maybe still just above the atmosphere. I however think that's very unlikely as the shuttle's altitude is low enough that ANY orbit has to be nearly circular. A highly eliptical orbit with the energy the shuttle has would take it inside the planet.

Carl

Edited August 3, 2005 by wwwmwww

[Stamen0083]

I think the most likely scenario once the shuttle touches the atmosphere is that it slows down and converts its energy into heat, not bounce around. Skipping across the surface of the atmosphere will have to be a deliberate action, not unintentional. Afterall, skipping stones across the water isn't particularly easy. Skipping ships across the atmosphere can't be that easy either.

[JB0]

The Apollos were in orbit too. Just a larger orbit.

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You are correct of course. My bad. However was that orbit an orbit about Earth or an orbit about the Earth/Moon system?

Depends on where in the mission you are.

If I recall...

Saturn 5 lifts you to Earth orbit. From there, you turn the service module around and dock it with the lander module.

Then use the service module engine to boost out of orbit and towards the Moon.

Fire the service module engine again to insert into lunar orbit(in the case of Apollo 13, they never actually entered Lunar orbit, and used the Moon to slingshot back towards Earth).

And when you approach Earth again, you use the service module engine one last time to decelerate.

I think you enter orbit before dropping down(which would make TWO service module firings).

If you don't... you still pass through a velocity-altitude combo where you're TECHNICALLY in orbit for a moment or so.

Skipping off the atmosphere is sort of like jumping on a trampoline. You hit it, it bends a little, and then throws you back up.

316918[/snapback]

That's the first I've read anything about the atmosphere actually adding energy to the shuttle. I thought the friction with the atmosphere would result in kinetic energy being turned into heat and dissipated. Though most of that heat might just end up getting stored in the tiles at that altitude. Can you point me to an article on this trampline effect?

Eh-heh...

That was actually kind of a rushed post.

I should've clarfied that I THINK that's how it works. Or did, anyways.

I think I was being a dumbass earlier, now that I've looked at the problem in more detail.

Thinking about it, there's a lot of variables that should factor in.

Whether you're approaching with or against the Earth's rotation is going to be more relevant than any (hypothetical) trampoline effect. I think this is the most important variable.

If you're going against the Earth's rotation, the atmosphere should decelerate the ship if it just skims it.

If you're going WITH the rotation, it should accelerate the ship on a skim instead.

But even if it decelerates you, the bounce may convert too much forward motion to upward to get back down again. You aren't JUST gaining or losing speed. You're also having some of it changed from one type to another.

It's actually a fairly complex problem, now that I think about it, without a single clear answer.

You COULD skip off into space, or sit there bouncing across the atmosphere until you slow down enough to "fall in."

If it bounced up, it GAINED energy. You can't go up against gravity without actually accelerating. And you can't accelerate without gaining energy.

316918[/snapback]

This just doesn't sound quite right to me. Its possible to gain altitute without gaining any net energy.

Like I said above, that was rushed.

Got a more accurate version now, involving changed motion vectors.

You gain energy in one axis, but this may corespond to a loss in another axis.

It's not that it gained energy as much as the energy it DOES have is redirected(assuming that the ship comes down going "into the wind," so to speak).

Through a rock up into the air.  After it leaves your hand it has nothing left to give it energy yet it still continues to go up.

But when it STARTS going up, it's had energy imparted to it from the throw. That would be the instant of the atmospheric skip, when you release the rock. Using the analogy, anyways.

It's turning kinetic energy into potential energy while the net energy stays the same.  Actually its losing enegry due to friction the whole time.  I think the shuttle would be doing the same thing.  It would just be turning its forward kinetic energy into potential energy while it was gaining altitue.  I don't believe it's accelerating... I think its decelerating.

Assuming the shuttle's new vertical velocity is low enough that it doesn't break orbit before it starts falling again.

[Sundown]

You need the lateral speed to stay in orbit or as soon as you shut off your engines you fall back to the Earth.  That's just what SpaceShipOne did.  The speed required to get the altitude is actually a very small part of the puzzle.  You could probably get up there and back down again while never going over Mach 2.  However to stay in orbit you need a speed of something like Mach 25.  Burt Rutan is still an order of magniture away from being able to offer much more then a short joy ride at the moment.

I had the chance to hear Burt Rutan speak here in San Jose. Was very ambivalent about the SpaceShipOne project... rocket propelled plane thing, barely getting out of the atmosphere... whoopiee. But after hearing about it and his thoughts about privatized space travel, I came to appreciate the project a whole lot more. Rutan's well aware that there's still much to go and that SpaceShipOne was only breaking some of the initial ground... and that currently, it's only good for a short, scenic, 0-g ride in space.

I had a feeling that SS1's reentry methodolgy was probably limited in application, but it was a very neat idea, using the thin upper atmosphere to slow yourself down before you hit the hard stuff.

-Al

[Kin]

All this thinking makes me hungry... so, who's in for a keramik roasted re-entrysausage?

[JB0]

All this thinking makes  me hungry...  so, who's in for a keramik roasted re-entrysausage?

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Mmmm, sausage.

[wwwmwww]

If you're going against the Earth's rotation, the atmosphere should decelerate the ship if it just skims it.

If you're going WITH the rotation, it should accelerate the ship on a skim instead.

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If I recall correctly ALL Shuttle missions have gone WITH the rotation of the Earth. Its a "free" boost at list off and lets you get to orbit with less energy. However on re-entry the Shuttle is going so fast that you are going to be coming into a head wind regardless. I certainly don't believe there are any Mach 20+ winds in the upper atmosphere. I certainly can't imagine the Shuttle entering the atmosphere and having a tail wind push her back up into orbit.

But even if it decelerates you, the bounce may convert too much forward motion to upward to get back down again. You aren't JUST gaining or losing speed. You're also having some of it changed from one type to another.

317035[/snapback]

Yes, but you need ALL that forward momentum to STAY in orbit. If all of it were converted to upward momentum you'd go strait up till all of it was converted to potential energy and after that you'd FALL straid back down again. And I'm quite sure that climb and fall would take less then 90 minutes.

It's not that it gained energy as much as the energy it DOES have is redirected(assuming that the ship comes down going "into the wind," so to speak).

317035[/snapback]

See above... the Shuttle would come down into a head wind regardless of the direction of its orbit. The re-entry problem would be no different if the Earth wasn't rotating at all.

Assuming the shuttle's new vertical velocity is low enough that it doesn't break orbit before it starts falling again.

317035[/snapback]

I'm quite sure the Shuttle doesn't have enough energy on board to break orbit and I'm also quite sure nothing in the upper atmosphere would be able to give it that much energy.

Carl

[wwwmwww]

I had the chance to hear Burt Rutan speak here in San Jose.  Was very ambivalent about the SpaceShipOne project... rocket propelled plane thing, barely getting out of the atmosphere... whoopiee.  But after hearing about it and his thoughts about privatized space travel, I came to appreciate the project a whole lot more.  Rutan's well aware that there's still much to go and that SpaceShipOne was only breaking some of the initial ground... and that currently, it's only good for a short, scenic, 0-g ride in space.

I had a feeling that SS1's reentry methodolgy was probably limited in application, but it was a very neat idea, using the thin upper atmosphere to slow yourself down before you hit the hard stuff.

-Al

317051[/snapback]

I certainly agree on all points. Its a big step and it's certainly a step in the right direction. However it's also just one step of many that will be needed. I can't wait to see Rutan's next step.

Carl

[Pat S]

Awesome article written before Columbia first flew, predicting it's demise, and explaining the history, and problems with the shuttles.

http://www.washingtonmonthly.com/features/...k-fulltext.html

[JB0]

Awesome article written before Columbia first flew, predicting it's demise, and explaining the history, and problems with the shuttles.

http://www.washingtonmonthly.com/features/...k-fulltext.html

317623[/snapback]

Doesn't really predict its demise, except possibly on the first flight.

You could argue it predicted the Challenger's death, as they mentioned exploding solid rocket boosters. But again, they were expecting them to fail on the test flight, not once they were in "routine" use.

And it doesn't do much explanation of the history at all, really. Just that the program was over budget, below spec, and behind schedule.

If you want history, read the CAIB report.

[Zentrandude]

"the most important event sine Creation"

I don't mind misspelling but not in quotes.

[Knight26]

Forwarded to me by a friend:

Eugene F. Kranz, author of "Failure Is Not an Option: Mission Control From Mercury to Apollo 13 and Beyond," is a former Apollo flight director.

By Eugene F. Kranz

TO read and listen to the coverage of the ongoing mission of Space Shuttle Discovery, you would think NASA's mission team have taken careless risks with the lives of the seven astronauts who went into space last Tuesday. During the launch, foam fell off the external tank. For the risk-averse, the only acceptable thing to do now is retire the shuttle program immediately and wait for the divine arrival of the next generation of spacecraft. I am disgusted at the lack of courage and common sense this attitude shows.

All progress involves risk. Risk is essential to fuel the economic engine of our nation. And risk is essential to renew American's fundamental spirit of discovery so we remain competitive with the rest of the world.

My take on the current mission is very straightforward. The shuttle is in orbit. To a great extent mission managers have given the spacecraft a clean bill of health. Let us remember that this is a test flight. I consider it a remarkably successful test so far.

The technical response to the Columbia accident led to a dramatic reduction in the amount of debris striking this shuttle during launch. Mission managers have said that the external tank shed 80 percent less foam this time than on previous launches. Only in the news media, apparently, is an 80 percent improvement considered a failure. Rather than quit, we must now try to reduce even more greatly the amount of foam that comes off the tank.

The instruments and video equipment developed to assess the launch performance and monitor debris falling from the tank worked superbly. For the first time, the mission team knows what is happening, when it is happening and the flight conditions under which it occurred. This was a major mission objective, and it is an impressive achievement.

Having spent more than three decades working in the space program, I know that all of the flights of the early days involved some levels of risk. Some of those risks, in hindsight, seem incomprehensible by today's timid standards. If we had quit when we had our first difficulties in Project Mercury, we would have never launched John Glenn on the Atlas rocket Friendship 7 in 1961. Two of the previous five Atlas rockets test-fired before Friendship 7 had exploded on liftoff.

On Gemini 9, 10 and 11, all in 1966, we had complications with planned spacewalks that placed the astronauts at risk. Rather than cancel the walks, we faced the risks and solved the problems. These set the stage for Gemini 12 later that year, during which Buzz Aldrin spent more than five hours outside the capsule and confirmed to NASA that spacewalks could be considered an operational capability.

Eventually, this capability enabled astronauts to retrieve satellites and repair and maintain the Hubble space telescope; and during the current mission, spacewalks were used to repair a gyroscope on the International Space Station and will allow the crew to fix some of the damage on that occurred during the launch. These are the rewards for the risks we took on those early Gemini flights.

I understand the tragedy inherent in risk-taking; I witnessed the fire aboard Apollo that killed its three crew members. It filled us with anger at ourselves and with the resolve to make it right. After the fire we didn't quit; we redesigned the Apollo command module. During the Apollo missions that followed, we were never perfect. But we were determined and competent and that made these missions successful.

I see the same combination of anger, resolve and determination in the Space Shuttle program today. These people are professionals who understand the business of risk, how to reduce risk and making that which remains acceptable. Most important, the current mission has demonstrated the maturity of the shuttle team that went through the tragedy of Columbia and had the guts to persevere. This is the most important aspect of the recovery from the Columbia accident, and is a credit to the great team NASA now has in place, headed by its administrator, Michael Griffin.

There are many nations in the world that wish to surpass us in space. Does the "quit now" crowd really believe that abandoning the shuttle and International Space Station is the way to keep America the pre-eminent space-faring nation? Do they really believe that a new spacecraft will come without an engineering challenge or a human toll? The path the naysayers suggest is so out of touch with the American character of perseverance, hard work and discovery that they don't even realize the danger in which they are putting future astronauts. Not to mention our nation. $

[wwwmwww]

Ok... after watching the news this morning I was struck with a second question.

It was stated they didn't want to land the shuttle at Edwards this morning partly because if there is a September launch Discovery would have been the Shuttle set aside for a rescue mission if one were needed. This implied that if the Shuttle were to land at Edwards there wouldn't be any chance of a September launch.

Why Discovery? We have more then two flyable shuttles don't we? Is there some reason I'm missing that Endeavour couldn't be set aside as the rescue shuttle for Atlantis?

I hate it when the obvious questions go unanswered.

Just curious,

Carl

[Goshawk]

WE have 3 flyable shuttles, Endeavour is in for extensive refit and upgrades, Alantis is the next shuttle to fly. Your right as they need anouther for a rescue mission. But with Endeavour having extensive refits right now its looking like setember there "may"not be a launch. They may not fly until the October firing window.

But right now they do have times for Tuesday and Wedsday landing already sched.

My wife still works at NASA, I used to before I tore my wrist up pertty bad at work one day.

Edited August 9, 2005 by Goshawk

[wwwmwww]

I watched the landing this morning and you guessed it. I've got another question. You guys have been very informative so far so I thought I'd try you again.

This relates to the animation that was shown that shows the orbit of the shuttle at 57 degrees in relation to the equator and explained why there was a small window where the shuttle could actually land in Flordia. The Earth is rotating under the orbit and one must wait for Flordia to rotate under the orbit.

Actually this is two questions...

(1) Am I correct to assume this orbit was significantly different then the last shuttle orbit? From the animations that were shown it sure didn't look like the shuttle would have flown over Texas on the way into Flordia this time.

(2) All the landing windows that were shown were from the part of the orbit where the shuttle is gaining latitude (i.e. heading away from the equator). However Flordia would later rotate under the part of the orbit where the shuttle would be losing latitude. They cut the animation just short of this part put you could see it coming. So on Monday when they missed their opportunity why did they have to wait a full 24 hours? From the animation it looked to me as if Flordia would have been crossing the orbit again in something like 8 or 10 hours just that the orbiter would have been traveling south on that part of the orbit instead of north. Was there a reason they wanted to land in the dark or some reason they don't want to enter the atmosphere while traveling south in their orbit?

Just curious again,

Carl

Edited August 9, 2005 by wwwmwww

[Zentrandude]

might be more political to land in the dark this time. less ppl up to have vid cameras pointing up at it just in case.

so did they land in ca? i heard they said it was a storm over florida.

[wwwmwww]

so did they land in ca? i heard they said it was a storm over florida.

318768[/snapback]

Yes, they landed at Edwards.

Carl

[David Hingtgen]

Basically: if at all possible, they want to land in Florida. Ferrying the shuttle on the 747 back to KSC takes a lot of time, and a lot of money. Staying in space another 24 hours to hope the weather clears in Florida effectively costs nothing, and poses no danger. It was a 24-hour wait for weather, not to get the right orbital alignment.

But, since Florida weather wasn't getting any better, and they didn't want the shuttle up there for days and days and days waiting around for good weather in Florida, they decided to just go for the next possible landing---Edwards. If the weather had been bad at Edwards on that orbit, they might have waited one more orbit, and then see if Edwards was OK, or possibly Florida would have cleared by then. If neither was clear by then, they would have gone to White Sands on that orbit. They can wait a day or two for better weather with no problems, but anything more is going to be taxing on the crew. They were already one day "late" to perform more experiments since the rest of the fleet is now grounded, and they decided to wait yet another day for Florida weather to clear---any more delays would have been 3 days over the expected return.

Here's maps showing the tracks for all the possible landing tracks--various sites from various orbits. http://www.nasa.gov/returntoflight/crew/landing.html

Edited August 10, 2005 by David Hingtgen

[wwwmwww]

Basically:  if at all possible, they want to land in Florida.  Ferrying the shuttle on the 747 back to KSC takes a lot of time, and a lot of money.  Staying in space another 24 hours to hope the weather clears in Florida effectively costs nothing, and poses no danger.   It was a 24-hour wait for weather, not to get the right orbital alignment.

318798[/snapback]

I agree with and understand all of that but the last statement. The wait was because of weather, correct. The reason it was a 24-hour wait is because there is only a window of opportunity in the shuttles orbit where it can land at Flordia (or Edwards, or White Sands). If it missed that opportunity say due to bad weather it must wait for the Earth to make a complete revolution below it before that window returns and that revolution takes 24 hours. For example you couldn't land at Flordia if the orbit looked like this.

You have to wait till the next time it looks like this (or atleast closer to this).

Atleast that is the way it was presented on the news this morning. However my question came from the fact that the orbit passes over Flordia TWICE a day, not just once a day. Something like 9 or 10 hours after the first pass the second pass would look like this.

But to my knowledge they've never come in from that direction. Why? Is there a reason they have to come into the atmosphere flying north?

Still curious,

Carl

Edited August 10, 2005 by wwwmwww

[Zentrandude]

 

But to my knowledge they've never come in from that direction.  Why?  Is there a reason they have to come into the atmosphere flying north?

Still curious,

Carl

318807[/snapback]

my guess the air current that comes off the gulf of mexico to slow down the shuttle even more than wanted.

edit: or maybe would push the shuttle to the east too far.

or get even nerdier the gravity is stronger (super wild guess).

Edited August 10, 2005 by Zentrandude

[wwwmwww]

But, since Florida weather wasn't getting any better, and they didn't want the shuttle up there for days and days and days waiting around for good weather in Florida, they decided to just go for the next possible landing---Edwards.  If the weather had been bad at Edwards on that orbit, they might have waited one more orbit, and then see if Edwards was OK, or possibly Florida would have cleared by then.  If neither was clear by then, they would have gone to White Sands on that orbit.  They can wait a day or two for better weather with no problems, but anything more is going to be taxing on the crew.  They were already one day "late" to perform more experiments since the rest of the fleet is now grounded, and they decided to wait yet another day for Florida weather to clear---any more delays would have been 3 days over the expected return. 

Here's maps showing the tracks for all the possible landing tracks--various sites from various orbits.  http://www.nasa.gov/returntoflight/crew/landing.html

318798[/snapback]

That link is great. Thanks. However that really isn't the possible tracks from various orbits. Those are all tracks from STS-114's orbit (singular). It shows what I mean by the various windows.

On pass 217 or 218 they could have landed at KSC (Flordia).

On pass 218 or 219 they could have landed at NOR (White Sands).

On pass 219 or 220 they could have landed at EDW (CA).

This morning they gave the first two shots to Flordia. They landed on pass 219. Had the weather been bad at Edwards on that pass they COULDN'T have decided to try White Sands next as the ONLY site they could have landed at on pass 220 would have been Edwards. If they had missed pass 220 they would have had to wait another 24 hours. And on pass 233 they would have been able to try for Flordia again.

But again I'm back to my first question ALL those deorbit paths show the shuttle coming in from the south (flying north). I'd like to know why they can't land while the shuttle is flying south. If they could, they'd double the number of possible landing windows.

My question about orbits went back to flight STS-113 that fell aboart over TX. Both of these approaches...

show the shuttle flying south of TX. What put STS-113 as far north as it was? Was it's orbit much different from STS-114? I'm guessing it was but I don't know that.

Carl

Edited August 10, 2005 by wwwmwww

[Lynx7725]

A guess (and a guess only!) is that if they had came down North to South, it would be difficult to have a contingency airfield of sufficient size to accomodate the Shuttle. Flying southwards would mean a big turnaround at low (relatively - I'm thinking after reentry) altitudes should anything forces the airfield to be closed. The Shuttle may not have the luxury of making a big detour.

Flying South to North though, gives more options; First, less of a detour to another field. Second, overshooting US would be less of a concern, because the track would be more towards Canada and Europe -- countries traditionally friendly to US. Not to mention, more land under the orbital track.. otherwise, the Shuttle will be over water for quite a while.

EDIT: After reading David's post, I would like to clarify I'm thinking more of the flight between "after reentry" and "getting feet on the deck". Shuttle ain't powered, they can glide for a long way but there's essentially only that much they can do, so setting up a path that gives the most options makes sense to me.

Edited August 10, 2005 by Lynx7725

[David Hingtgen]

Think I understand what you're saying now.

And I certainly know the answer to the last sentence:

They re-routed the re-entry because of Columbia---if something went wrong, they didn't want it to shed parts all across the Southern US, or any populated land. Thus, it's over water for as much of re-entry as possible--both the Florida and California approaches are over water for 90+ percent of the time.

They especially want to avoid being over land during the most dangerous part--by the time it's over land it's done with the actual "firey descent" and is simply gliding around. I believe this is also why they waited for 24-hours etc between approaches---it's not simply needing a window, but a window where they can also avoid flying over populated areas, which is now more of a concern that before.

[Gaijin]

Sorta late but the Shuttle's launch is an High Def on demand thing for Time Warner Cable...pretty cool in high def.