Baling out at high altitude.
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OK, I guess Shock isn't a defined physical term anyway which is probably at the root of this issue.
Since drag is proportional to IAS I'd agree that the peak acceleration will not change with altitude.
However, the faster moving object (TAS) will take longer to slow down, so the deceleration profile will be 'stretched out', in regards to time, at higher altitude.
Given that injury is related to acceleration and duration, then altitude has to be a factor.
I know sweet FA about parachutes, but basic physics tells us that surviving a rapid deceleration is all about transferring Kinetic energy to some other form. If your TAS is higher, thats more Kinetic energy, and therfore it HAS to be more of a problem. Regardless of the actual mechanisms involved, and regardless of whether the Parachute or the person is the limiting factor.
mmmm... tasty. OK, I'll bite.
Well, with density zero, you are already below your terminal velocity. And your terminal velocity with a parachute is still fatal !
But lets say we fire a retro rocket to get us back into the upper fringes of the atmosphere, and preemptively spread our parachute out behind us ready to catch the first whisps of air. Why can't the parachute just deliver us safely back to terra firma?
Because power = force times velocity (yes, TAS again).
We might not have much drag, but if we are doing 8 Km.s-1 we are going to burn up. (i.e. too much collision energy to transfer to something else without getting all crispy). Our cloth parachute isn't up to the job, so we need a better one - an ablative heat shield will do quite nicely. That is just a more robust drag producer after all.
Since drag is proportional to IAS I'd agree that the peak acceleration will not change with altitude.
However, the faster moving object (TAS) will take longer to slow down, so the deceleration profile will be 'stretched out', in regards to time, at higher altitude.
Given that injury is related to acceleration and duration, then altitude has to be a factor.
I know sweet FA about parachutes, but basic physics tells us that surviving a rapid deceleration is all about transferring Kinetic energy to some other form. If your TAS is higher, thats more Kinetic energy, and therfore it HAS to be more of a problem. Regardless of the actual mechanisms involved, and regardless of whether the Parachute or the person is the limiting factor.
Using Reducto ad Absurbum what would happen if you bailed out in orbit?
Well, with density zero, you are already below your terminal velocity. And your terminal velocity with a parachute is still fatal !
But lets say we fire a retro rocket to get us back into the upper fringes of the atmosphere, and preemptively spread our parachute out behind us ready to catch the first whisps of air. Why can't the parachute just deliver us safely back to terra firma?
Because power = force times velocity (yes, TAS again).
We might not have much drag, but if we are doing 8 Km.s-1 we are going to burn up. (i.e. too much collision energy to transfer to something else without getting all crispy). Our cloth parachute isn't up to the job, so we need a better one - an ablative heat shield will do quite nicely. That is just a more robust drag producer after all.
Do a Hover - it avoids G
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Capt Pit Bull
If you want to talk about 'drag' then in that language one would have to say say that a parachute Cd 'effectively' varies with altitude due to porosity effects. But that is a bad way to think of things because drag is an aero concept and porosity is not - hence the use of the term porosity
The opening shock loads are merely the peak loads measured during the opening process and depend on how the canopy is designed, whether it uses taschengerts to control the incidence of the peripheral hem during opening and so on. Complex issues.
JF
If you want to talk about 'drag' then in that language one would have to say say that a parachute Cd 'effectively' varies with altitude due to porosity effects. But that is a bad way to think of things because drag is an aero concept and porosity is not - hence the use of the term porosity
The opening shock loads are merely the peak loads measured during the opening process and depend on how the canopy is designed, whether it uses taschengerts to control the incidence of the peripheral hem during opening and so on. Complex issues.
JF
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Isn't the question regarding the OPENING SHOCK of the canopy?
My logic says that the canopy always opens/deploys at a rate proportional to TAS - not IAS considering the canopy's lightness and hence low inertia.
Having opened with a bang and hopefully not ruptured the deployed canopy should then produce drag in relation to half rho v squared - ie related to IAS.
My logic says that the canopy always opens/deploys at a rate proportional to TAS - not IAS considering the canopy's lightness and hence low inertia.
Having opened with a bang and hopefully not ruptured the deployed canopy should then produce drag in relation to half rho v squared - ie related to IAS.
Cunning Artificer
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That changing the Barostatic Release Units business sounds like a good idea.
Back on the 'V' Force, I spent some time encarcerated in Waddington's 'Gin Palace' working in the Instrument Calibration Laboratory. One of my incredibly boring tasks was testing the Barostatic Release Units for the ejection seats and the rear crew parachute packs. The parachute BRUs were all set the same - a 10,500' +/- 500' barostatic trigger initiated a three second timer. The device then fired a spring loaded plunger that pulled the ripcord. Ejection seats had a separate BRU that triggered separation from the seat at 12,500' +/- 500' The user could always override the devices by pulling either the seat release and/or the ripcord handle manually if he was conscious and so inclined.
BTW, in a high altitude abandonment, rear crew members would have had difficulty finding the holes in the snow made by their pilots, due to the difficulty of climbing out of their own great smoking hole in the ground. The chances of being able to get out at high altitude and ride silk were extremely remote.
After alighting on Mother Earth, any surviving pilots would of course have to face the Crew Chief and explain what happened to his beautiful piece of aeronautical machinery. Most would have preferred death to that...
Back on the 'V' Force, I spent some time encarcerated in Waddington's 'Gin Palace' working in the Instrument Calibration Laboratory. One of my incredibly boring tasks was testing the Barostatic Release Units for the ejection seats and the rear crew parachute packs. The parachute BRUs were all set the same - a 10,500' +/- 500' barostatic trigger initiated a three second timer. The device then fired a spring loaded plunger that pulled the ripcord. Ejection seats had a separate BRU that triggered separation from the seat at 12,500' +/- 500' The user could always override the devices by pulling either the seat release and/or the ripcord handle manually if he was conscious and so inclined.
BTW, in a high altitude abandonment, rear crew members would have had difficulty finding the holes in the snow made by their pilots, due to the difficulty of climbing out of their own great smoking hole in the ground. The chances of being able to get out at high altitude and ride silk were extremely remote.
After alighting on Mother Earth, any surviving pilots would of course have to face the Crew Chief and explain what happened to his beautiful piece of aeronautical machinery. Most would have preferred death to that...
Yanks hold the record for Hi Jumping
Colonel Joe Kittinger
1928 -
First To Fly Solo Across The Atlantic Ocean In A Helium Balloon, 1984
Inducted in 1998
Joe Kittinger, a native of Orlando, Florida, and eventually a Colonel in the Air Force, began flying aircraft in 1949. Kittinger qualified in practically all types of flying machines including hang gliders, hot air and gas balloons, propeller driven aircraft, and jet aircraft.
On August 16, 1960, he set three world records: the highest parachute jump (102,800 feet), the longest parachute free fall (4 minutes 36 seconds), and the first person to exceed the speed of sound without an aircraft or space vehicle (714 mph during free fall). In September 1984, Kittinger set a world record for the longest distance flown in a 3,000 cubic meter helium balloon. This first solo transatlantic balloon flight from Caribou, Maine, to Montenotte, Italy, covered 3,543 miles in 86 hours.
Colonel Kittinger received the Distinguished Flying Cross on five occasions, two for his balloon experiments and three for his combat tours in Southeast Asia. During his last combat tour as Commander of the 555th Fighter Squadron, his aircraft was shot down and he was imprisoned in a North Vietnamese POW camp.
1928 -
First To Fly Solo Across The Atlantic Ocean In A Helium Balloon, 1984
Inducted in 1998
Joe Kittinger, a native of Orlando, Florida, and eventually a Colonel in the Air Force, began flying aircraft in 1949. Kittinger qualified in practically all types of flying machines including hang gliders, hot air and gas balloons, propeller driven aircraft, and jet aircraft.
On August 16, 1960, he set three world records: the highest parachute jump (102,800 feet), the longest parachute free fall (4 minutes 36 seconds), and the first person to exceed the speed of sound without an aircraft or space vehicle (714 mph during free fall). In September 1984, Kittinger set a world record for the longest distance flown in a 3,000 cubic meter helium balloon. This first solo transatlantic balloon flight from Caribou, Maine, to Montenotte, Italy, covered 3,543 miles in 86 hours.
Colonel Kittinger received the Distinguished Flying Cross on five occasions, two for his balloon experiments and three for his combat tours in Southeast Asia. During his last combat tour as Commander of the 555th Fighter Squadron, his aircraft was shot down and he was imprisoned in a North Vietnamese POW camp.
I can't find the video after a quick search, but I have seen it and it is extraordinary...he just hops off and disappears tumbling because he is going so fast. Here's a picture though -
And although the intrepid Colonel did jump from a very great height, it wasn't orbital altitude, although it is likely that the same could be done from that level.
The problem would come is if you actually were orbiting in which case you would re-enter at approx 15000 mph and then burn up. Coming straight down like Joe Kittinger did is not a problem up to a point; Apollo astronauts travelling to the moon left earth orbit at approx 25000 mph, but on their coast to the moon were continually being slowed down by the earth's gravity.
So much so, in fact, that by the time they crossed over the point where the moon's gravity was a greater influence than the earth's, they were "only" doing 1000 mph!
So if you jumped from that height I imagine the reverse would be true and you would accelerate towards the earth until you re-entered at approx 24000 mph.
So I suppose there is some upper limit to what height one can jump from, but I can't be @rsed to work it out.
And although the intrepid Colonel did jump from a very great height, it wasn't orbital altitude, although it is likely that the same could be done from that level.
The problem would come is if you actually were orbiting in which case you would re-enter at approx 15000 mph and then burn up. Coming straight down like Joe Kittinger did is not a problem up to a point; Apollo astronauts travelling to the moon left earth orbit at approx 25000 mph, but on their coast to the moon were continually being slowed down by the earth's gravity.
So much so, in fact, that by the time they crossed over the point where the moon's gravity was a greater influence than the earth's, they were "only" doing 1000 mph!
So if you jumped from that height I imagine the reverse would be true and you would accelerate towards the earth until you re-entered at approx 24000 mph.
So I suppose there is some upper limit to what height one can jump from, but I can't be @rsed to work it out.
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Thanks for replies. John Farley, especially. I flew Mustangs countless years ago and I recall we were warned about the shock of high altitude bale-outs and your reply John now bears that out. Where I am uncertain, however, is the TAS/IAS question.
If the shock of opening is dependant on the volume or pressure of air particles filling out the canopy, then at high altitude it would be the IAS that counts, wouldn't it? If not, I am at loss to understand where TAS comes into it at high altitude. If you jump at say 40,000 ft and open the chute at 230 IAS vertical speed (if you had a speedo on your body), then would not the opening shock be the same as opening the chute at 230 IAS at say 10,000 ft?
The porosity of the silk at high (cold?) altitudes is something I never thought about. And just to confirm part of my original question and that is assume that temperature and oxygen aspects are a different story -so ignore their effect on the pilot.
If the shock of opening is dependant on the volume or pressure of air particles filling out the canopy, then at high altitude it would be the IAS that counts, wouldn't it? If not, I am at loss to understand where TAS comes into it at high altitude. If you jump at say 40,000 ft and open the chute at 230 IAS vertical speed (if you had a speedo on your body), then would not the opening shock be the same as opening the chute at 230 IAS at say 10,000 ft?
The porosity of the silk at high (cold?) altitudes is something I never thought about. And just to confirm part of my original question and that is assume that temperature and oxygen aspects are a different story -so ignore their effect on the pilot.
Do a Hover - it avoids G
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HSWL
The way I think of it the amount of energy stored in your pink body as you go over the side is related to your TAS not IAS. That being so whatever force the chute applies to slow you down would have to be applied longer. Toss in the porosity and high altitude effects which make the chute snatch harder as it opens and you have a double whammy of a bigger initial load that also stays applied longer. So a hard time would be had by all.
JF
The way I think of it the amount of energy stored in your pink body as you go over the side is related to your TAS not IAS. That being so whatever force the chute applies to slow you down would have to be applied longer. Toss in the porosity and high altitude effects which make the chute snatch harder as it opens and you have a double whammy of a bigger initial load that also stays applied longer. So a hard time would be had by all.
JF
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Thanks for the whole porosity issue input JF. As you say, its a complex issue.
I was also pondering on the peak deceleration experienced by the body versus the 'chute. It occured to me that as the chute opens you carry on falling for a bit as the lines extend, and then as the snatch bites, you have an element of elasticity in the lines.
Which means the deceleration profile of the person is likely to look quite a bit different to the canopy. Its a bit like the old 'why don't we put a nice soft cushion on that Bang seat' question.
I do love to chew on this stuff
CPB
I was also pondering on the peak deceleration experienced by the body versus the 'chute. It occured to me that as the chute opens you carry on falling for a bit as the lines extend, and then as the snatch bites, you have an element of elasticity in the lines.
Which means the deceleration profile of the person is likely to look quite a bit different to the canopy. Its a bit like the old 'why don't we put a nice soft cushion on that Bang seat' question.
I do love to chew on this stuff
CPB
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Sport canopies have used reefing systems for years. The faster you're going, the stronger the resistance to the canopy spreading, with the reefng force directly proportional, so the part-open canopy slows you until a speed when the spreading force overcomes the reefing. (If a modern, aerodynamic 'square' canopy opened without any reefing it would generate instant drag and lift, which would not be good for it or you.) I guess that a reefing system is impractical because of the need to cater for for a very low ejection, though.
Round canopys have been put into sleeve assemblys to slow the opening.....doesn't creat much delay but does soften the opening shock. Low Porosity canopies....feel very slick and solid next to other materials....definitely have a higher shock loading at time of deployment.
A sport jumper I knew at the Sunderland airport years ago...broke his back when his square canopy opened abruptly when someone had rigged the slider improperly. When I suggested that must have hurt....he smiled and said...."Not as bad as the landing did!" He went on to compete in the international championships that year after being told in hospital that he would probably not be able to walk. Quite a guy!
A sport jumper I knew at the Sunderland airport years ago...broke his back when his square canopy opened abruptly when someone had rigged the slider improperly. When I suggested that must have hurt....he smiled and said...."Not as bad as the landing did!" He went on to compete in the international championships that year after being told in hospital that he would probably not be able to walk. Quite a guy!
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Interesting Argument, Interesting Physics, Interesting Parachute Theory. But..... Out of what present a/c is anybody going to need a 'High Level' Ejection! Oh, I forgot, Typhoon when the Engines both Stop..... Silly Me!
MW
MW
I don't own this space under my name. I should have leased it while I still could
Blacksheep, fascinating. If what you say is true and as far as I remember my 10k/12.5k is also true, then someone was telling porkies.
I would not put is passed the system to have convinced the poor sods with only low level barastats that the other poor sod in the bang seat had them <g>.
Beags your shout.
I would not put is passed the system to have convinced the poor sods with only low level barastats that the other poor sod in the bang seat had them <g>.
Beags your shout.
Cunning Artificer
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I think you've read it wrong Pontius - the parachutes were all the same, but the seat separation units chucked an unconscious pilot out of his seat at 12,500 so he fell clear of the seat before the chute opened. He could always leave earlier if he was awake and felt like it.
One thing always bothered me. That three second delay - said to be to allow time to clear the aircraft. Did they teach aircrew not to wait for auto-deployment at lower levels? I mean, imagine a low level ejection. Three seconds for auto-deploy wouldn't have been much good to you below about a thousand feet, would it?
One thing always bothered me. That three second delay - said to be to allow time to clear the aircraft. Did they teach aircrew not to wait for auto-deployment at lower levels? I mean, imagine a low level ejection. Three seconds for auto-deploy wouldn't have been much good to you below about a thousand feet, would it?
I don't own this space under my name. I should have leased it while I still could
Blacksheep, no what I understood you to say was that the pilot barastat worked at 12.5 and the rear crew at 10k. That was the reverse of my understanding which was why the Akrotiri units bang seat barastats were the 5km version.
As far as the 3 second delay I think a pilot will need to answer that one.
As far as the 3 second delay I think a pilot will need to answer that one.
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Just a few points to add to the discussions here. I don't know whether the professional pilots among you know just how much work is continually on going in the development of military aircraft escape systems? Any advances that can be made to better ensure the safety of aircrew are looked at daily by a number of experts at a number of different companies.
All the different points mentioned here on ejection sequence timings, parachute opening shock at different altitudes etc are in constant development, and quite often with each new aircraft entering service comes a whole new range of systems - from a new seat, a new parachute, through to better designed clothing. Retrofits are also made, and a lot of work goes into ensuring the systems on current in service aircraft are enhanced where possible, the focus is not just on future aircraft.
With the latest ejections seats all the pilot needs to do is pull the handle, and some time later, depending on the conditions on ejection, he will land safely on the ground. Have a quick read here about the latest Mk16E seat being developed for use in JSF:
http://www.martin-baker.com/eject_mk16E.htm
The parachutes are constantly developed too by a company called IrvinGQ:
http://www.irvingq.co.uk/products/ees.asp
As well as the emergency escape system being there to save the life of the pilot, we in the research, development and testing world also want to make the whole sequence as safe as possible. If possible we want the aircrew to land following the ejection sequence in a fit state to go and fly again the next day. To aid this a lot of research is done in a number of areas including harness design, limb restraint, and even posture on ejection.
All systems go through a rigorous testing phase before they can be used in service - including live jumping of new parachute canopies, where there are a group of brave (crazy??) people who risk themselves to test these things.
Although these manufacturers do a lot of there own equipment testing, of course there is also independent testing and verification, as well as seperate research work done by other companies, such as QinetiQ (formerly DERA, DRA, RAE...):
http://www.qinetiq.com/
Hopefully some of that information is new / interesting to some people.
All the different points mentioned here on ejection sequence timings, parachute opening shock at different altitudes etc are in constant development, and quite often with each new aircraft entering service comes a whole new range of systems - from a new seat, a new parachute, through to better designed clothing. Retrofits are also made, and a lot of work goes into ensuring the systems on current in service aircraft are enhanced where possible, the focus is not just on future aircraft.
With the latest ejections seats all the pilot needs to do is pull the handle, and some time later, depending on the conditions on ejection, he will land safely on the ground. Have a quick read here about the latest Mk16E seat being developed for use in JSF:
http://www.martin-baker.com/eject_mk16E.htm
The parachutes are constantly developed too by a company called IrvinGQ:
http://www.irvingq.co.uk/products/ees.asp
As well as the emergency escape system being there to save the life of the pilot, we in the research, development and testing world also want to make the whole sequence as safe as possible. If possible we want the aircrew to land following the ejection sequence in a fit state to go and fly again the next day. To aid this a lot of research is done in a number of areas including harness design, limb restraint, and even posture on ejection.
All systems go through a rigorous testing phase before they can be used in service - including live jumping of new parachute canopies, where there are a group of brave (crazy??) people who risk themselves to test these things.
Although these manufacturers do a lot of there own equipment testing, of course there is also independent testing and verification, as well as seperate research work done by other companies, such as QinetiQ (formerly DERA, DRA, RAE...):
http://www.qinetiq.com/
Hopefully some of that information is new / interesting to some people.
Read that page mate - cheers for that; one quote to catch the eye:-
'..that is based on the NASA T-38N design to ensure accommodation of the larger aircrew'
Snigger.
'..that is based on the NASA T-38N design to ensure accommodation of the larger aircrew'
Snigger.
beating the seat
Blacksheep
The USAF, I believe, used to teach beating the seat on it's non-Martin Baker types ( seem to remember seeing a USAF film on the subject in around 1980), and certainly when Neil Armstrong ejected from the Lunar Landing Training Vehicle in late 68/early 69 he is on record as trying to beat the seat :
"I always thought I might be able to match the automatic system, but I found out that when I was reaching for the D ring the automatic system had already fired"
As a user of one of Martin Bakers older models IMHO on those it was a non-starter - on ejection you are, in sequence, kicked very hard in the backside, have your head rammed between your knees as umpteen g are applied by the rocket pack and in all probability thrust into a roaring gale....and also generally smacked around a lot. It would be the rare individual who could sit there immediately after burn out and go straight into the manual separation drill. Added to which on the older MB seats the first action in the drill (pulling the manual separation handle) neatly disconnects you from the drogue chute (which is attached to the top of the seat) which you need to extract the main chute PDQ if at low level. So in a nutshell, on the older RAF seats you were not taught to beat the seat, with good reason.
The USAF, I believe, used to teach beating the seat on it's non-Martin Baker types ( seem to remember seeing a USAF film on the subject in around 1980), and certainly when Neil Armstrong ejected from the Lunar Landing Training Vehicle in late 68/early 69 he is on record as trying to beat the seat :
"I always thought I might be able to match the automatic system, but I found out that when I was reaching for the D ring the automatic system had already fired"
As a user of one of Martin Bakers older models IMHO on those it was a non-starter - on ejection you are, in sequence, kicked very hard in the backside, have your head rammed between your knees as umpteen g are applied by the rocket pack and in all probability thrust into a roaring gale....and also generally smacked around a lot. It would be the rare individual who could sit there immediately after burn out and go straight into the manual separation drill. Added to which on the older MB seats the first action in the drill (pulling the manual separation handle) neatly disconnects you from the drogue chute (which is attached to the top of the seat) which you need to extract the main chute PDQ if at low level. So in a nutshell, on the older RAF seats you were not taught to beat the seat, with good reason.
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Its a pity that all the so called R&D companies (especially Qinetic - Sp?) never actually take into account 'Normal' and 'Operational' military flying activities when they come up with new gear. I have found as time goes by, all the latest stuff is more uncomfortable, more restrictive, hotter, more expensive and more delicate - Often to the point that most aircrew either wear it wrongly (in order to get more comfortable for that 8 hour trip over Baghdad) or dont wear it at all!
