Author Topic: Shuttle Columbia re-entry question:  (Read 7420 times)

Offline dandypanty

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Shuttle Columbia re-entry question:
« on: August 17, 2023, 12:45:23 PM »
     Years ago I was watching a program on the Space Shuttle Columbia disaster when it came up that some of the NASA heads had declined an offer to use a spy satellite to image the wing while still in orbit. I cannot recall what program/documentary this was so I might be fuzzy on the details but I remember that NASA turned down the offer because even IF they saw wing damage, there was nothing they could do about it.
     It reminded me of my Titanic Blu-ray special features that features multiple experts in a variety of different fields getting together to talk about the physical evidence of "how" the Titanic went down. (EXAMPLE: did it break apart at the surface? did the back end stand straight up and bobble? etc.) The last question the filmmaker - James Cameron asks goes something like this: "If you were the captain of the ship, knowing what you know now, what would you do differently to save as many people on board as possible?" This thought experiment starts at ONE second after the iceberg is hit and the answers included some very bold decisions but very interesting. One of these ideas was immediately throwing the ship in reverse and backing up toward the ship that they saw in the distance (I believe it was called the California). One was off-loading the passengers onto the iceberg, another being filling one of the water tight compartments with all the life jackets on board and throwing mattresses over the side to block/slow the water pouring into the ship.
     A bunch of you Apollo nerds are no doubt familiar with the re-entry of the command module. It would begin it's re-entry for a period of time but then skip out to cool off, then enter the steeper slope again. I have asked this question many times in the comments of various relevant YouTube videos hoping that maybe someone much smarter than me with the proper math formulas, simulations, knowledge could help me figure out what the re-entry would look like. For the record, not a single person I have received a response from believed there was such a possibility of entering without breaking up. The answers given are unconvincing. My first thought is: using 20 - 60 of these skip outs to very slowly over the course of several days, many revolutions, very gradually entering the atmosphere. But I would like to know more definitely if that could conceivably work. If not, what would it take? What are other ideas? Which tiles are less critical that they could remove and strap to the wing? What other materials did they have to work with in the shuttle that could be strapped or attached in a way that would protect the wing (long enough) to survive?
     I understand that this theoretical isn't just about having less heat but also aerodynamics causing the thrusters to ultimately run out of fuel leading to an out of control angle of attack that caused the breakup so maybe the solution would be to fly in a constant right turn keeping as much heat away from the hole. If nobody has any ideas using what was onboard at the time, what about a re-fueling rocket that could rendezvous with the Shuttle so that the main engine/s could be used to brake and bleed off as much speed as possible before going through the thickest part of the atmosphere?
    What would it take?
Thanks in advance for any clever Apollo 13 style ideas you guys might have.

Offline smartcooky

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Re: Shuttle Columbia re-entry question:
« Reply #1 on: August 17, 2023, 07:13:18 PM »
It might have been remotely possible to rescue the crew, but the Orbiter itself was doomed. The idea of flying a curved path was pure fantasy

There is a good article here from Nova that outlines a proposed plan for a rescue of the crew using the Orbiter Atlantis

https://www.pbs.org/wgbh/nova/columbia/rescue.html

This ARS Technica article goes some way to explaining just how hard it would have been to transfer the seven crew-members to Atlantis.

https://arstechnica.com/science/2023/02/the-audacious-rescue-plan-that-might-have-saved-space-shuttle-columbia-2/8/

There are couple of interesting constraints including the length of time required to make the crew trasnfers, and the number of crew who can transfer at one time.

IMO, it would have been extremely difficult to do. They are talking about 9 to 24 hours of EVA's to get the whole crew across. It would not take much to go wrong, and you could lose the rescue crew as well.
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Offline Allan F

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Re: Shuttle Columbia re-entry question:
« Reply #2 on: August 17, 2023, 10:21:23 PM »
The Apollo reentry were vastly different from the spacehuttle-reentries. The "skip-out" is not so much a change of course, but the path not slowing down fast enough to stay in the atmosphere. Like sticking a needle in the skin of an orange on a tangent.
The spaceshuttle didn't fall from the moon, remember? Once the deorbit-burn had happened, the ship was on a one-way trip. Not enough energy to go out again. Why don't you get Kerbal Space Programme, which is the most intuitive tool to learn about space-related stuff ever devised by man.
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Offline dandypanty

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Re: Shuttle Columbia re-entry question:
« Reply #3 on: August 18, 2023, 01:36:14 PM »
"The idea of flying a curved path was pure fantasy"
But the shuttle actually flew a "curved" path. It banked left and right doing S turns to help control the altitude. I do not know exactly how MUCH curve this was but that is the context of curve I am talking about.

I was trying to find more information about the trajectory of the shuttle during re-entry when I found some interesting information about the Orion capsule that is going to use a skip method. This paragraph interests me the most.
"The heat the spacecraft will experience upon reentry will be split over two events causing a lower heat rate at both occurrences and ultimately making it a safer ride for the astronauts."
I am simply wondering what kind of re-entry would be CONCEPTIALLY possible. For instance: one objection to re-entering over a longer period of time is that the shuttle heat tiles were not designed to sustain the heat for long periods of time. My suggested solution is to skip out multiple times to allow cooling. Objection: the shuttle would need fuel to re-enter the next skip and there isn't enough fuel left during this period of the flight. My suggested solution: send a refueling rocket to top off main engines and thrusters. The main rocket engines could be used to brake a great deal of the speed off so not only would the thrusters be fueled up but they would require much less fuel since the shuttle would only be traveling at perhaps half the original speed. Objection, to fly the skip out method requires MUCH more finesse that the autopilot wasn't programmed to fly. Solution: re-program the computer to fly the new entry program. etc etc. I'm not asking for realistic. I'm asking for conceivable/theoretically. Some of the crazy solutions to broken down space probes that I have read about. Using instruments to perform tasks they weren't designed to. It's hard for me to believe the shuttle could only enter 1 way and that way required a breakup.




Offline dandypanty

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Re: Shuttle Columbia re-entry question:
« Reply #4 on: August 18, 2023, 01:46:18 PM »
"Once the deorbit-burn had happened, the ship was on a one-way trip. Not enough energy to go out again."

Why did the deorbit burn have to be exactly what it was and not another way? Is there only one way the shuttle could re-enter? I understand that the skip couldn't be done on the shuttle because it didn't have the thruster fuel to begin to enter the atmosphere after the skip out however, if the fuel could have been topped off ahead of time, that would allow for a different entrance.

"Why don't you get Kerbal Space Programme, which is the most intuitive tool to learn about space-related stuff ever devised by man."
That's the kind of thing I often imagine I'm going to find some youtuber simulating this very thing but haven't seen it. I just want to know what it would take to make it happen. It survived a long time before breaking up and have a hard time imagining that had they REALLY wanted to get that shuttle back into the atmosphere without a breakup COULD have figured out some way of bringing it down less rapidly (like skipping out multiple times)

Offline smartcooky

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Re: Shuttle Columbia re-entry question:
« Reply #5 on: August 18, 2023, 07:28:13 PM »
It would have to have flown a constant curved path to the left in order to protect the leading edge of the left wing. Calling it a curved path is somewhat misleading. Most of the heat is generated when the Orbiter is traveling at its highest velocity during the period when its atmosphere is at its thinnest, but at that time, there would less aerodynamic  interaction, and control authority would be at its lowest level. The Orbiter would be more skidding sideways (called side-slipping) than actually turning and changing direction, and that would continually expose parts of the Orbiter, such as the tail and the sides of the fuselage, to much higher heating levels than usual. The thermal protective layers on the Orbiter are not all the same - those thermal blankets on the upper surfaces and the tail area were never designed to withstand the kind of temperatures they would be exposed to if the vehicle got too sideways.
If you're not a scientist but you think you've destroyed the foundation of a vast scientific edifice with 10 minutes of Googling, you might want to consider the possibility that you're wrong.

Offline Peter B

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Re: Shuttle Columbia re-entry question:
« Reply #6 on: August 19, 2023, 06:51:36 PM »
I was trying to find more information about the trajectory of the shuttle during re-entry when I found some interesting information about the Orion capsule that is going to use a skip method. This paragraph interests me the most.
"The heat the spacecraft will experience upon reentry will be split over two events causing a lower heat rate at both occurrences and ultimately making it a safer ride for the astronauts."
I am simply wondering what kind of re-entry would be CONCEPTIALLY possible. For instance: one objection to re-entering over a longer period of time is that the shuttle heat tiles were not designed to sustain the heat for long periods of time. My suggested solution is to skip out multiple times to allow cooling.

With the greatest of respect, one thing you seem to be missing is that orbital speed (27,000 km/h / 17,000 mph) is very much a speed limit - it is simply impossible for a spacecraft to stay in orbit at a lower speed. Therefore, the main objection to the idea of dipping briefly into the atmosphere to lose some speed then climbing back out to cool down, and repeating this multiple times to lose most of the shuttle's speed, is that it's impossible because of the way orbital mechanics works.

Spacecraft orbit the Earth in sort of the same way that planes fly - if you're moving slower than a certain speed then you're going down in a very fundamental way.

Quote
Objection: the shuttle would need fuel to re-enter the next skip and there isn't enough fuel left during this period of the flight. My suggested solution: send a refueling rocket to top off main engines and thrusters. The main rocket engines could be used to brake a great deal of the speed off so not only would the thrusters be fueled up but they would require much less fuel since the shuttle would only be traveling at perhaps half the original speed.

There are at least four problems here. First, refueling rockets as you describe simply don't exist, even today. Second, there is no method to allow in-space refueling, even today. Third, the space shuttle main engines were designed to fire only once in each mission (during launch), meaning there was literally no way to relight them during a mission. Fourth, the only place to store the main engines' fuel was in the external tank, which had obviously already been jettisoned.

Quote
Objection, to fly the skip out method requires MUCH more finesse that the autopilot wasn't programmed to fly. Solution: re-program the computer to fly the new entry program. etc etc. I'm not asking for realistic. I'm asking for conceivable/theoretically.

I understand that changes to the shuttles' software was something that was tested rigorously back on Earth for months before being loaded. I'd doubt the software could even be edited during a flight.

Quote
Some of the crazy solutions to broken down space probes that I have read about. Using instruments to perform tasks they weren't designed to.

When you're talking about unmanned spacecraft, obviously there's a much smaller downside risk. Now sure, there were occasions during Apollo when manned missions were saved by reprogramming on the run (Apollo 14 and the loose solder in the LM comes to mind), but we're talking about (a) much simpler systems being easier to understand, and (b) the guys who wrote the code only a few years earlier being available to think up and test the reprogramming.

Quote
It's hard for me to believe the shuttle could only enter 1 way and that way required a breakup.

Unfortunately your incredulity isn't a strong defence. It's fine to ask questions, but then it's more reasonable to accept the answers, especially if explanations and evidence are provided, when the subject matter is outside your expertise. Some problems just don't have solutions, no matter how strong your McGyver Fu is.

The lessons I'd humbly suggest to be learned here are: 1. there were fundamental flaws with the Shuttles' underlying design which could only be managed and not eliminated, and 2. there were problems with NASA management over the years of the program which meant these flaws weren't managed as well as they could have been. In the case of Columbia, by the time it launched, it was already too late to manage the flaw which doomed it.
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Offline dandypanty

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Re: Shuttle Columbia re-entry question:
« Reply #7 on: August 21, 2023, 11:51:45 AM »
It would have to have flown a constant curved path to the left in order to protect the leading edge of the left wing. Calling it a curved path is somewhat misleading. Most of the heat is generated when the Orbiter is traveling at its highest velocity during the period when its atmosphere is at its thinnest, but at that time, there would less aerodynamic  interaction, and control authority would be at its lowest level. The Orbiter would be more skidding sideways (called side-slipping) than actually turning and changing direction, and that would continually expose parts of the Orbiter, such as the tail and the sides of the fuselage, to much higher heating levels than usual. The thermal protective layers on the Orbiter are not all the same - those thermal blankets on the upper surfaces and the tail area were never designed to withstand the kind of temperatures they would be exposed to if the vehicle got too sideways.
Yes! I like this and I have some follow up because I don't really know very much about the shuttle or development but I would imagine they were planning to get more than 1 flight out of the tiles even though they replaced a lot of them between flights, I also heard that when the museum got the shuttle, it still had a large number of the original tiles that it came with. My question is, was there a path or angle of attack that could have conceivably kept the wing cooler but torched a great number or even ALL of the other tiles to where some of them would have burned through but only after the shuttle was, say halfway through reentry? I know the first shuttle launch had a ton of missing tiles after they reached orbit right? Burning through wasn't necessarily a death sentence depending on which tiles right? I'm sure it's much better to lose certain tiles over others but what I'm asking is, even if the shuttle would have had to fly completely sideways at some very obscure angle, assuming the computer auto pilot could have been programmed to fly the shuttle this way, and if they could have at least refilled the thruster fuel to be topped off, is it conceivable?

Offline dandypanty

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Re: Shuttle Columbia re-entry question:
« Reply #8 on: August 21, 2023, 01:48:31 PM »
“…it is simply impossible for a spacecraft to stay in orbit at a lower speed.”

I understand that. I’m not talking about staying in orbit. I’m talking about skipping again and again repeatedly until the speed is bled off. The reason there is a “reentry corridor” or tolerance: too steep = burn up, too shallow = skip out. So enter shallow purposely to skip out intentionally. The same thing the Orion is going to do but instead of once or twice, as many skips as possible.
 
“…it's impossible because of the way orbital mechanics works. Spacecraft orbit the Earth in sort of the same way that planes fly - if you're moving slower than a certain speed then you're going down in a very fundamental way.”

I believe I understand that correctly. If you have no power to the control surfaces, you have no attitude control but if you’re in something like a glider (shuttle) yes it is going down in a fundamental way but still under control of it’s attitude.

“…refueling rockets as you describe simply don't exist, even today. Second, there is no method to allow in-space refueling, even today.”

That is true however, there are containers of this fuel on Earth and a connector/hose/method of getting this fuel into the shuttle at the pad so it is conceivable that some jerry rigged system using already produced/used parts could have been hobbled together in a week or two and fitted inside another rocket capable of making a rendezvous with the shuttle. I’ve heard of some crazy rescue stories using equipment never intended or designed for purposes ultimately used to save people in short amount of times. 
 
“Third, the space shuttle main engines were designed to fire only once in each mission (during launch), meaning there was literally no way to relight them during a mission. Fourth, the only place to store the main engines' fuel was in the external tank, which had obviously already been jettisoned.”

Oh I didn’t know that. I know why I thought that; I mistakenly thought I had seen the main engines still lit after tank separation but I was seeing SRB separation. Okay scratch using the mains. I guess unless they could get some loaded SRB’s attached in orbit, there isn’t going to be any braking in this scenario.

“I'd doubt the software could even be edited during a flight.”

Well it kind of seems like it’s possible according to this page:
https://www.globalsecurity.org/space/library/report/1988/sts-oms.html#google_vignette

It says here: “The two OMS engines are used to deorbit. Target data for the deorbit maneuver is computed by the ground and loaded in the onboard GPCs via uplink. This data is also voiced to the flight crew for verification of loaded values. After verification of the deorbit data, the flight crew initiates an OMS gimbal test on the CRT keyboard unit.’

“When you're talking about unmanned spacecraft, obviously there's a much smaller downside risk.”

Yes and despite far less on the line, they have come up with dozens of amazing solutions for failed components on these probes so I doubt saving 7 human lives would result in anything LESS amazing and inventive.

“Unfortunately your incredulity isn't a strong defence.”

It’s no defense because I am not presenting my incredulity as an argument. Just hearing for years very non-specific reasons that the shuttle could not have entered in any other way than it did. Reasons like, “the shuttle reentry is already optimized”. Yes, optimized for what though? Probably not optimized for a giant hole in the wing.

 “It's fine to ask questions, but then it's more reasonable to accept the answers, especially if explanations and evidence are provided, when the subject matter is outside your expertise.”

Well I haven’t really heard any yet. We only just started talking a few comments ago. 
 
“Some problems just don't have solutions, no matter how strong your McGyver Fu is.”

Hahaha no not my McGyver Fu. But a world full of geniuses hell bent on saving the crew? I’m just not convinced the way the shuttle entered the atmosphere was the ONLY way the shuttle could have reentered, especially if we could grant certain conceivable arrangements like topping off the fuel for the two OMS engines and RCS thrusters or reprogramming the autopilot.

I think the question I’m asking should be: IF we could reprogram the autopilot to fly a different path, are there any such hypothetical paths that would allow the shuttle to break up 5 minutes later than it did? If so, what change did we make to help it last another few minutes? If the answer is something like, “decrease the angle of attack by 5°, what would happen if we changed it to 10°? 15° and so on.
What is the actual reason that skipping is not possible? What is the longest possible time you could stretch the reentry to? Is it possible to extend it to several minutes? Hours? Can it be extended for several days?

Thanks for the schooling guys! I’m determined to understand this.

Offline smartcooky

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Re: Shuttle Columbia re-entry question:
« Reply #9 on: August 21, 2023, 04:35:28 PM »
I understand that. I’m not talking about staying in orbit. I’m talking about skipping again and again repeatedly until the speed is bled off. The reason there is a “reentry corridor” or tolerance: too steep = burn up, too shallow = skip out. So enter shallow purposely to skip out intentionally. The same thing the Orion is going to do but instead of once or twice, as many skips as possible.

You are missing a fundamental part of orbital mechanics.

In orbit, the Shuttle Orbiter is traveling at orbital velocity (about 28,000 kph) - it is traveling at the exact speed it needs to stay in its orbit; any slower and its falling back to earth - any faster and its going to raise to a higher orbit; high enough and it reaches escape velocity. In order to re-enter the earth's atmosphere, the Orbiter translates (turns around) using its Reaction Control System (RCS) to face away from its direction of travel and then fires the Orbital Maneuvering System (OMS) engines for about 20 minutes. This slows the Orbiter down by about 300 kph, and at this point, its a done deal - the Orbiter is going down and there is no way to stop it - and when it reaches somewhere near the Karman line, it will begin to be affected by the atmosphere. For the Orbiter to now start "skipping" as you suggest, will require an increase in velocity. Every second the Orbiter is falling through the atmosphere, it is losing velocity due to friction. The only engines with enough thrust to increase its velocity quickly enough to overcome the rate at which it is losing velocity are the three RS-25 main engines, and they don't have any fuel. The OMS engines are not powerful enough to increase the Orbiter's velocity. Now you might be thinking that because the Orbiter is now in atmosphere that it is aerodynamic so pulling up on the control stick will make it climb, but no, that won't work - you can think of it as the Orbiter being effectively in a deep, very high speed aerodynamic stall - pulling the stick up will not make it climb but it will dramatically increase the friction, the heating and the velocity, and therefore the g-forces on the crew - it only takes a tiny change of re-entry angle to make a dramatic change to the G-Forces on the crew - changes so great they will be fatal. Worse than that, if you pull up on the stick while in a stall, and while you are turning hard left to protect that damaged left wing, you will probably flip the bloody thing right over - and as Bugs Bunny would say... that all folks!
   
So you might now ask how the Orion spacecraft is able to skip to help with its re-entry. The answer is, that it is returning from the Moon... its approaching the earth at a much higher velocity, and hits the atmosphere at about 39,500 kph, over 11,000 kph faster than Orbiter on re-entry. It has a crap-load of energy to get rid of, and if it doesn't, it is toast - literally!
« Last Edit: August 21, 2023, 04:41:57 PM by smartcooky »
If you're not a scientist but you think you've destroyed the foundation of a vast scientific edifice with 10 minutes of Googling, you might want to consider the possibility that you're wrong.

Offline dandypanty

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Re: Shuttle Columbia re-entry question:
« Reply #10 on: August 29, 2023, 08:58:20 AM »
Okay correct me if I have this wrong. You're saying the reentry characteristics are based on whatever velocity/orbit the object is in so to change the profile of reentry (to any meaningful level) would require higher speeds than the shuttle was capable of given the motors/amount of fuel etc.

You're saying there was no way of changing the reentry profile of the shuttle without inputting more speed or more braking than the shuttle was conceivably capable of?

Let me ask you this. How much speed do you think the shuttle would have had to shed before safely reentering? Does that make sense? Or this. Given what we know about the damage to the wing, what do you think the minimum speed the shuttle would have had to be going to safely deorbit if the shuttle had both SRBs and 3 main engines plus the thrusters; launch configuration. As soon as you begin to braking, you're  getting lower and lower into dangerously thick atmosphere. Could the shuttle have slowed down quickly enough with all engines/boosters firing, could the shuttle have slowed down enough by the time it got into the thicker dangerous atmosphere to survive the friction?

Thanks again for the lesson!

Offline Allan F

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Re: Shuttle Columbia re-entry question:
« Reply #11 on: August 29, 2023, 11:02:29 AM »
Yep. As the capabilities of the shuttle were fixed, and the amount of orbital maneuvering fuel present was limited, there was no other way to reenter. Higher speeds would only mean more heating - more time in a high-temperature plasma torch. Going "back out" not really an option.

Again: Get KSP and play around with it for some hours.
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Offline smartcooky

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Re: Shuttle Columbia re-entry question:
« Reply #12 on: August 29, 2023, 03:06:47 PM »
Okay correct me if I have this wrong. You're saying the reentry characteristics are based on whatever velocity/orbit the object is in so to change the profile of reentry (to any meaningful level) would require higher speeds than the shuttle was capable of given the motors/amount of fuel etc.

You're saying there was no way of changing the reentry profile of the shuttle without inputting more speed or more braking than the shuttle was conceivably capable of?

Let me ask you this. How much speed do you think the shuttle would have had to shed before safely reentering? Does that make sense? Or this. Given what we know about the damage to the wing, what do you think the minimum speed the shuttle would have had to be going to safely deorbit if the shuttle had both SRBs and 3 main engines plus the thrusters; launch configuration. As soon as you begin to braking, you're  getting lower and lower into dangerously thick atmosphere. Could the shuttle have slowed down quickly enough with all engines/boosters firing, could the shuttle have slowed down enough by the time it got into the thicker dangerous atmosphere to survive the friction?

Thanks again for the lesson!

Here is an even better lesson - watch the following video. It is one of the best, easiest to understand descriptions that I have seen on the web, of how the Shuttle Orbiter re-entry worked ... very little math, just simple graphics and good descriptions. Its less that 20 minutes long. You won't get very far into the video before it should dawn on you the reasons why your suggestion simply cannot work.

If you're not a scientist but you think you've destroyed the foundation of a vast scientific edifice with 10 minutes of Googling, you might want to consider the possibility that you're wrong.