Since We Are Off Topic Somewhat....
Hi All,,
Since we are somewhat off topic for the moment with the conversation about the bird to come down shortly.. Ok, the question is, and i've asked it to several other places, and yet to even get a answer,
The question is,,,
Space shuttle launches,, starts off at sea level, and in less than ten minutes goes from zero to 17K MPh (or so) And gets to orbital altitude.
Time to come down,, the de-orbit burn happens to slow it down just a bit to cause the orbit to more or less decay.. It's at orbital altitude.. and moving at about 17K MPh.. 45 minutes or so later it's back on the ground and moving at zero MPh..
So in actuality it comes down from space even slower than going up. Yes? 45 min vs 10.
Ok, same goes with any satellite,,
How come, going up,, 0 to 17K MPh through the atmosphere, all is fine.. BUT
coming down,, 17K MPh to 0 unless it has protection it will burn up in the atmosphere from friction with the air.
why is it different?
Joe WB9SBD & NSS
The amount of time spent in the atmosphere at high velocity (I'd have to do some digging to give some real time data but basically it is as follows).
One the way up, the rocket goes through the 100 km of air during the slower part of the change of velocity and spends very little time in the atmosphere at the higher velocity.
On the way down, the object starts to encounter the atmosphere at maximum velocity and therefore maximum friction. It will be in the atmosphere for the a much longer period since it comes in a very shallow angle. The object will have that friction nearly the entire trip to the ground even though the drag from the atmosphere will slow the object.
Kenneth - N5VHO
________________________________
From: amsat-bb-bounces@amsat.org on behalf of Joe Sent: Thu 2/14/2008 5:55 PM To: 'AMSAT-BB' Subject: [amsat-bb] Since We Are Off Topic Somewhat....
Hi All,,
Since we are somewhat off topic for the moment with the conversation about the bird to come down shortly.. Ok, the question is, and i've asked it to several other places, and yet to even get a answer,
The question is,,,
Space shuttle launches,, starts off at sea level, and in less than ten minutes goes from zero to 17K MPh (or so) And gets to orbital altitude.
Time to come down,, the de-orbit burn happens to slow it down just a bit to cause the orbit to more or less decay.. It's at orbital altitude.. and moving at about 17K MPh.. 45 minutes or so later it's back on the ground and moving at zero MPh..
So in actuality it comes down from space even slower than going up. Yes? 45 min vs 10.
Ok, same goes with any satellite,,
How come, going up,, 0 to 17K MPh through the atmosphere, all is fine.. BUT
coming down,, 17K MPh to 0 unless it has protection it will burn up in the atmosphere from friction with the air.
why is it different?
Joe WB9SBD & NSS _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Does anyone have the actual speeds at each altitude going up vs coming down?
I tried to find such a graph, chart, table etc, to no avail,
Joe
Ransom, Kenneth G. (JSC-OC)[BAR] wrote:
The amount of time spent in the atmosphere at high velocity (I'd have to do some digging to give some real time data but basically it is as follows).
One the way up, the rocket goes through the 100 km of air during the slower part of the change of velocity and spends very little time in the atmosphere at the higher velocity.
On the way down, the object starts to encounter the atmosphere at maximum velocity and therefore maximum friction. It will be in the atmosphere for the a much longer period since it comes in a very shallow angle. The object will have that friction nearly the entire trip to the ground even though the drag from the atmosphere will slow the object.
Kenneth - N5VHO
From: amsat-bb-bounces@amsat.org on behalf of Joe Sent: Thu 2/14/2008 5:55 PM To: 'AMSAT-BB' Subject: [amsat-bb] Since We Are Off Topic Somewhat....
Hi All,,
Since we are somewhat off topic for the moment with the conversation about the bird to come down shortly.. Ok, the question is, and i've asked it to several other places, and yet to even get a answer,
The question is,,,
Space shuttle launches,, starts off at sea level, and in less than ten minutes goes from zero to 17K MPh (or so) And gets to orbital altitude.
Time to come down,, the de-orbit burn happens to slow it down just a bit to cause the orbit to more or less decay.. It's at orbital altitude.. and moving at about 17K MPh.. 45 minutes or so later it's back on the ground and moving at zero MPh..
So in actuality it comes down from space even slower than going up. Yes? 45 min vs 10.
Ok, same goes with any satellite,,
How come, going up,, 0 to 17K MPh through the atmosphere, all is fine.. BUT
coming down,, 17K MPh to 0 unless it has protection it will burn up in the atmosphere from friction with the air.
why is it different?
Joe WB9SBD & NSS _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Found some generic info that might shed some insight as to how fast the shuttle gets into the thin air and at what speed.
The following is an excerpt from http://www.globalsecurity.org/space/library/report/1988/stsover-launch.h tml#stsover-flight
It reaches the point of maximum dynamic pressure (max Q) -- when dynamic pressures on the Shuttle are greatest -- about 1 minute after liftoff, at an altitude of 33,600 ft.
Little more than 2 minutes into the flight, the SRBs, their fuel expended, are jettisoned from the orbiter. The Shuttle is at an altitude of about 30 miles and traveling at a speed of 2,890 miles an hour.
At about 8 minutes into the flight, at an altitude of about 60 miles, main engine cut-off (MECO) occurs. The Shuttle is now traveling at a speed of 16,697 mph.
Kenneth - N5VHO
-----Original Message----- From: Joe [mailto:nss@mwt.net] Sent: Thursday, February 14, 2008 8:18 PM To: Ransom, Kenneth G. (JSC-OC)[BAR] Cc: AMSAT-BB Subject: Re: [amsat-bb] Re: Since We Are Off Topic Somewhat....
Does anyone have the actual speeds at each altitude going up vs coming down?
I tried to find such a graph, chart, table etc, to no avail,
Joe
Ransom, Kenneth G. (JSC-OC)[BAR] wrote:
The amount of time spent in the atmosphere at high velocity (I'd have
to do some digging to give some real time data but basically it is as follows).
One the way up, the rocket goes through the 100 km of air during the
slower part of the change of velocity and spends very little time in the atmosphere at the higher velocity.
On the way down, the object starts to encounter the atmosphere at
maximum velocity and therefore maximum friction. It will be in the atmosphere for the a much longer period since it comes in a very shallow angle. The object will have that friction nearly the entire trip to the ground even though the drag from the atmosphere will slow the object.
Kenneth - N5VHO
From: amsat-bb-bounces@amsat.org on behalf of Joe Sent: Thu 2/14/2008 5:55 PM To: 'AMSAT-BB' Subject: [amsat-bb] Since We Are Off Topic Somewhat....
Hi All,,
Since we are somewhat off topic for the moment with the conversation about the bird to come down shortly.. Ok, the question is, and i've asked it to several other places, and yet to even get a answer,
The question is,,,
Space shuttle launches,, starts off at sea level, and in less than
ten
minutes goes from zero to 17K MPh (or so) And gets to orbital
altitude.
Time to come down,, the de-orbit burn happens to slow it down just a
bit
to cause the orbit to more or less decay.. It's at orbital altitude.. and moving at about 17K MPh.. 45 minutes or so later it's back on the ground and moving at zero MPh..
So in actuality it comes down from space even slower than going up. Yes? 45 min vs 10.
Ok, same goes with any satellite,,
How come, going up,, 0 to 17K MPh through the atmosphere, all is fine.. BUT
coming down,, 17K MPh to 0 unless it has protection it will burn
up
in the atmosphere from friction with the air.
why is it different?
Joe WB9SBD & NSS _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the
author.
Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the
author.
Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
While discussing this topic of orbital decay, I wonder if someone would comment on the apparent anomoly whereby a sat in leo that encounters drag actually speeds up (since as it's altitude decreases, the orbital speed increases), and how this might be a factor in the comparison of the heating effects on an object that decays gradually from orbit vs an object like the shuttle that is taken out of orbit by actually reducing it's speed with thrust. I have my own intuitive theories on this but would like to hear more informed opinions.
----- Original Message ----- From: "Joe" nss@mwt.net To: "'AMSAT-BB'" amsat-bb@amsat.org Sent: Friday, February 15, 2008 12:55 AM Subject: [amsat-bb] Since We Are Off Topic Somewhat....
Hi All,,
Since we are somewhat off topic for the moment with the conversation about the bird to come down shortly.. Ok, the question is, and i've asked it to several other places, and yet to even get a answer,
The question is,,,
Space shuttle launches,, starts off at sea level, and in less than ten minutes goes from zero to 17K MPh (or so) And gets to orbital altitude.
Time to come down,, the de-orbit burn happens to slow it down just a bit to cause the orbit to more or less decay.. It's at orbital altitude.. and moving at about 17K MPh.. 45 minutes or so later it's back on the ground and moving at zero MPh..
So in actuality it comes down from space even slower than going up. Yes? 45 min vs 10.
Ok, same goes with any satellite,,
How come, going up,, 0 to 17K MPh through the atmosphere, all is fine.. BUT
coming down,, 17K MPh to 0 unless it has protection it will burn up in the atmosphere from friction with the air.
why is it different?
Joe WB9SBD & NSS
Hi Joe, WB9SBD & NSS
Going up the maximum speed to enter in orbit is reached when the Space Shuttle is well above the atmosphere in the vacuum and absence of the oxigen
Coming down the maximum speed is reached when the Space Shuttle is well into the atmosphere in friction with the oxigen.
73" de
i8CVS Domenico
At 10:55 AM 2/15/2008, Joe wrote:
How come, going up,, 0 to 17K MPh through the atmosphere, all is fine.. BUT
coming down,, 17K MPh to 0 unless it has protection it will burn up in the atmosphere from friction with the air.
I suspect if you look at the launch profile, you'll find that the passage up through the atmosphere is relatively slow, and that the bulk of the speed increase occurs above where the air density is sufficient to cause problems.
Also, maximum acceleration is towards the end of the main engine burn, due to simple physics. As the propellant is expended, the mass of the vehicle is less, but the thrust remains roughly constant, unless the engines are throttled back to reduce the G forces, as is done with the Shuttle to minimise stress on the crew. This implies that much of the speed increase occurs late in the burn, when you're high enough to avoid significant friction heating.
73 de VK3JED http://vkradio.com
Because on the way up, as its accelerating, the air is getting thinner. On the way down it only has the drag of the atmosphere to slow it, so it caries more of its velocity into the thicker air. Jim KQ6EA
--- Joe nss@mwt.net wrote:
Hi All,,
Since we are somewhat off topic for the moment with the conversation about the bird to come down shortly.. Ok, the question is, and i've asked it to several other places, and yet to even get a answer,
The question is,,,
Space shuttle launches,, starts off at sea level, and in less than ten minutes goes from zero to 17K MPh (or so) And gets to orbital altitude.
Time to come down,, the de-orbit burn happens to slow it down just a bit to cause the orbit to more or less decay.. It's at orbital altitude.. and moving at about 17K MPh.. 45 minutes or so later it's back on the ground and moving at zero MPh..
So in actuality it comes down from space even slower than going up. Yes? 45 min vs 10.
Ok, same goes with any satellite,,
How come, going up,, 0 to 17K MPh through the atmosphere, all is fine.. BUT
coming down,, 17K MPh to 0 unless it has protection it will burn up in the atmosphere from friction with the air.
why is it different?
Joe WB9SBD & NSS _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Also remember that during launch the space shuttle is facing directly into the direction of travel thus presenting the lowest drag (and least friction). During re-entry the space shuttle lifts its nose a bit to expose more area of the underside of the craft to produce more drag. This increases friction. As the shuttle descends, air density increases which increases friction. The shuttle slows due to this friction. The decent path is a smaller rate of decent (lower angle) than launch which is nearly vertical at first. This gives more time for slowing due to atmospheric friction. All this produces very high temperatures. Too steep a decent would increase temperatures beyond what the tiles on the skin of the shuttle can withstand and the shuttle would burn up just like a meteor. Hope this helps understanding.
Ed (just an old retired NASA engineer - not quite rocket scientist).
At 05:04 PM 2/14/2008, Jim Jerzycke wrote:
Because on the way up, as its accelerating, the air is getting thinner. On the way down it only has the drag of the atmosphere to slow it, so it caries more of its velocity into the thicker air. Jim KQ6EA
--- Joe nss@mwt.net wrote:
Hi All,,
Since we are somewhat off topic for the moment with the conversation about the bird to come down shortly.. Ok, the question is, and i've asked it to several other places, and yet to even get a answer,
The question is,,,
Space shuttle launches,, starts off at sea level, and in less than ten minutes goes from zero to 17K MPh (or so) And gets to orbital altitude.
Time to come down,, the de-orbit burn happens to slow it down just a bit to cause the orbit to more or less decay.. It's at orbital altitude.. and moving at about 17K MPh.. 45 minutes or so later it's back on the ground and moving at zero MPh..
So in actuality it comes down from space even slower than going up. Yes? 45 min vs 10.
Ok, same goes with any satellite,,
How come, going up,, 0 to 17K MPh through the atmosphere, all is fine.. BUT
coming down,, 17K MPh to 0 unless it has protection it will burn up in the atmosphere from friction with the air.
why is it different?
Joe WB9SBD & NSS _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
This might be excessively basic, but wouldn't the heat energy of the friction in re-entry be roughly equivalent to the energy from the engines which put the craft up there in the first place? This doesn't include the de-orbit burn, obviously, but since the shuttle has a lot of mass, there will be more time spent at high velocity dragging against the atmosphere, than a relatively small satellite which weighs much less mass, given the same descent path because of it's higher intertia(Kinetic Energy).
Also, since the shuttle enters at a sharp angle, the rate of deceleration would be higher since power=forceXdistance. If a satellite enters at a slow angle(typical), then the temperature of the heat generated from friction would be much lower, for much longer and pieces of the craft might have slightly better chances of not vaporizing.
I like the way that the first paragraph in this page: http://en.wikipedia.org/wiki/Kinetic_energy is worded, relative to this discussion!
Auke, VE6PWN
----- Original Message ----- From: "Edward Cole" kl7uw@acsalaska.net To: "Jim Jerzycke" kq6ea@pacbell.net; "Joe" nss@mwt.net; "'AMSAT-BB'" amsat-bb@amsat.org Sent: Friday, February 15, 2008 1:24 AM Subject: [amsat-bb] Re: Since We Are Off Topic Somewhat....
Also remember that during launch the space shuttle is facing directly into the direction of travel thus presenting the lowest drag (and least friction). During re-entry the space shuttle lifts its nose a bit to expose more area of the underside of the craft to produce more drag. This increases friction. As the shuttle descends, air density increases which increases friction. The shuttle slows due to this friction. The decent path is a smaller rate of decent (lower angle) than launch which is nearly vertical at first. This gives more time for slowing due to atmospheric friction. All this produces very high temperatures. Too steep a decent would increase temperatures beyond what the tiles on the skin of the shuttle can withstand and the shuttle would burn up just like a meteor. Hope this helps understanding.
Ed (just an old retired NASA engineer - not quite rocket scientist).
Yes, you are referring to the principle called conservation of energy. The space shuttle gains kinetic energy in gaining orbit and has to lose it upon return to earth. The kinetic energy is mostly converted to heat in re-entry. The heat is a function of velocity and mass. Temperature is a function of how fast kinetic energy is converted (how fast re-entry), but on difference is that the Shuttle is fitted with ceramic tiles to survive heat to reentry whereas a satellite has no protection. The usual reason anything survives reentry into earth's atmosphere is size or mass. Very large items (meteors, satellites or space shuttles) may have pieces that impact earth (this was seen with the Columbia).
Ed
At 12:36 AM 2/15/2008, Auke de Jong, VE6PWN wrote:
This might be excessively basic, but wouldn't the heat energy of the friction in re-entry be roughly equivalent to the energy from the engines which put the craft up there in the first place? This doesn't include the de-orbit burn, obviously, but since the shuttle has a lot of mass, there will be more time spent at high velocity dragging against the atmosphere, than a relatively small satellite which weighs much less mass, given the same descent path because of it's higher intertia(Kinetic Energy).
Also, since the shuttle enters at a sharp angle, the rate of deceleration would be higher since power=forceXdistance. If a satellite enters at a slow angle(typical), then the temperature of the heat generated from friction would be much lower, for much longer and pieces of the craft might have slightly better chances of not vaporizing.
I like the way that the first paragraph in this page: http://en.wikipedia.org/wiki/Kinetic_energy is worded, relative to this discussion!
Auke, VE6PWN
----- Original Message ----- From: "Edward Cole" kl7uw@acsalaska.net To: "Jim Jerzycke" kq6ea@pacbell.net; "Joe" nss@mwt.net; "'AMSAT-BB'" amsat-bb@amsat.org Sent: Friday, February 15, 2008 1:24 AM Subject: [amsat-bb] Re: Since We Are Off Topic Somewhat....
Also remember that during launch the space shuttle is facing directly into the direction of travel thus presenting the lowest drag (and least friction). During re-entry the space shuttle lifts its nose a bit to expose more area of the underside of the craft to produce more drag. This increases friction. As the shuttle descends, air density increases which increases friction. The shuttle slows due to this friction. The decent path is a smaller rate of decent (lower angle) than launch which is nearly vertical at first. This gives more time for slowing due to atmospheric friction. All this produces very high temperatures. Too steep a decent would increase temperatures beyond what the tiles on the skin of the shuttle can withstand and the shuttle would burn up just like a meteor. Hope this helps understanding.
Ed (just an old retired NASA engineer - not quite rocket scientist).
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
The *energy* is exactly the same, the sole exception being whatever little bits of delta-V were added or subtracted by OMS burns. I emphasize *energy* because the acceleration/deceleration is a change in energy that can be thought of as a form of power or work, both of which have a differential/integral relationship to energy. And it's that differential/integral relationship that supplies all the wiggle room in this problem, because you can't control how *much* kinetic energy you're getting rid of, but you can control how you spread out that energy dispersal over time, to some extent.
An extremely accurate analogy is driving your car down a back country road and seeing the railroad crossing ahead light up and the gates start to close -- your initial speed is the same no matter what you do, but you can choose to drive all the way up to the crossing and try to stop as hard as you can right there, which will send everything in the car flying and probably set your brakes on fire or raise a cloud of smoke from your tires, or you can choose to put a light pressure on the brake and gradually slow down until you finally stop at the crossing, and barely feel the deceleration and maybe only slightly warm up your brakes. Same initial kinetic energy, vastly different dispersal rates. :D
On Feb 15, 2008, at 3:36 AM, Auke de Jong, VE6PWN wrote:
This might be excessively basic, but wouldn't the heat energy of the friction in re-entry be roughly equivalent to the energy from the engines which put the craft up there in the first place? This doesn't include the de-orbit burn, obviously, but since the shuttle has a lot of mass, there will be more time spent at high velocity dragging against the atmosphere, than a relatively small satellite which weighs much less mass, given the same descent path because of it's higher intertia(Kinetic Energy).
"This is an amazing honor. I want you to know that I spend so much time in the world that is spinning all the time, that to be in the no- spin zone actually gives me vertigo." -- Stephen Colbert during an interview on FOX News, The O'Reilly Factor
participants (9)
-
Auke de Jong, VE6PWN -
Bill Jones -
Bruce Bostwick -
Edward Cole -
i8cvs -
Jim Jerzycke -
Joe -
Ransom, Kenneth G. (JSC-OC)[BAR] -
Tony Langdon