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Protection of payloads in emergency

Posted by: Ekkehard Augustin - Tue Feb 14, 2006 11:53 am
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Protection of payloads in emergency 
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Post Protection of payloads in emergency   Posted on: Tue Feb 14, 2006 11:53 am
Which properties has a rocket stage to have to avoid the damage of its payload in case of termination of thrust and falling into the ocean?

I am asking this question because of my latest post in the SpaceX-thread in the Latest News section where I suppose to be possible perhaps that SpaceX and Elon Musk have designed and constructed their rocket so that the payload might be recovered and/or repaired which could bring down insurance costs in the longer run.

Which properties must the hull of the stages have for avoiding leaks and breaks? Leaks might cause desastrous ocean pollusion by cerosene leaking out of tanks into the ocean - breaks might cause corrosion of the payload.

Can the payload be installed so that the shock it might suffer at touch down into the sea is rduced partially?

Can it be ensured that the stage carrying the payload enters the sea downside first?

Are their other ways to protect the payload?



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Post    Posted on: Tue Feb 14, 2006 4:23 pm
Unless you are willing to pay a substantial mass penalty for a payload recovery system, said payload is pretty much doomed the moment you terminate thrust. Payloads are designed to be mechanically capable of surviving launch but outside of RTG's there's currently little justification for anything much beyond that.

I simply cannot see the payload of a wingless fuelled vehicle surviving an engines-off abort, it's bad in too many ways.


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Post    Posted on: Tue Feb 14, 2006 6:17 pm
The question was menat more concrete. For example - would there have to be more empty volume around the payloadd so that it can't crash into the interior walls of the stage? Would it be required that the equipment fixing the payload inside the stage is automatically unlocked at thrust termination to enable the payload to swing to the direction it has to swing to to keep the impact on it lower than it would be if it is kept fixed. I am speaking of "swing" - this means that their may be an elastic back up for the fixing which guides the motion and the swinghing of the payload.

What Elon Musk has said in the quote of the interview Peter posted in the Latest News section seems to mean that the termination of thrust prevents the rocket and its interior from broken down into lots of debris - in contrary to an explosive destruction of the rocket. So I think that it is logical that the rocket would be kept more intact compared to the explosive destruction. Logically even the payload would be kept more intact than in case of the explosion. This is of meaning.

May be there is a mass "penalty" - but what concretely is of that mass? The topic of this thread is a consequent extension of reusability.



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Post    Posted on: Tue Feb 14, 2006 7:34 pm
What form the mass of a recovery system would take depends to a large degree on what part of the flight you abort in, being able to survive everything is an overwhelmingly heavy option. Weight could be spent on e.g. an escape-tower, parachutes, ballutes, crushable structures, retro-rockets, heat shields, insulation, heat-sinks, ablatives, extensive ruggedization, inflatable structures...

I'm struggling to think of ways in which an abort won't involve a smashed vehicle, as violent an event as an explosive termination device would yield. (explosive termination can be expected to sometimes give less debris range than thrust termination but a greater footprint area.) If this is true, then unless the payload is very rugged the manner of mounting probably won't matter. If you want to reduce impact speed, of the vehicle itself getting rid of all the propellant as quickly as possible might be a good starting point.


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Post    Posted on: Tue Feb 14, 2006 8:34 pm
I cannot imagine any way other than separating the payload from the rocket and deploying a parachute. And the payload must be waterproof if it will land in the sea. That is how the Falcon 1 first stage (and shuttle SRB) is recovered; separately by parachute and it is waterproof.


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Post    Posted on: Tue Feb 14, 2006 11:56 pm
There is a long history of payload recovery systems for manned spaceflight. There is quite a mass penalty, but then the cargo is irreplaceable. Here are some interesting numbers about the Apollo system:

The Apollo Launch Escape System (tower, rocket and protective cover) had a mass of 4170 kg. The Apollo Command Module had a total mass of 5806 kg, which includes 245 kg of Recovery Equipment (presumably the parachutes, etc.)

So being able to recover 5561 kg of payload required an extra 4415 kg. Note that due to the purpose of the vehicle, it was already designed to withstand the stresses of reentry and recovery.

This info is from the following article:
http://en.wikipedia.org/wiki/Apollo_spa ... _.28LES.29

Also check out:
http://en.wikipedia.org/wiki/Apollo_abort_modes

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Post    Posted on: Thu Feb 16, 2006 3:43 am
Of course the Apollo escape tower was designed to lift the command module from a stationary position on the pad, to a safe parachute altitude & distance, in a very short time, in case of a first stage failure.

The Falcons are held down until all engines are confirmed to be operating normally, and can be shut down safely before that point. So any abort requiring payload recovery should only happen at reasonable altitude. The payload recovery system would require a lot less impulse and be much less massive in proportion.

This is the same principle advanced by T/Space with their CXV proposal.
By air-launching , an abort just requires separation from the booster, and a parachute & floaties, (and TPS for high altitude/speed, if not already available).

We know from the sad fate of the Challeger crew, that close proximity to a booster explosion is survivable (for crew and/or payload). Rapid deceleration at sea-level is not. :(


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Post    Posted on: Fri Feb 17, 2006 10:05 am
Because of your numbers, Enthusiast, a short thought about the Falcon 1.

The Falcon 1 can lift a maximum payload of 500 kg. Since the relation between the numbers you listed is less than 1:1 a payload recovery system like you have in mind would need to weigh 500 kg only.

Is that right? If yes then this would mean that the mass penalty is neglectible - in particular if compared to the value of the payload and the insurance costs to be supposed I think.

I myself already have been thinking about seperation and parachutes in case of abort/thrust termination too. The separation would reduce the weight hanging from the parachutes - so it would be easier to decelerate while falling throught the atmosphere.

As far as I know the Falcon 1 is made of light weight materials, composites etc. - because of this it seems to me that the question merely is if the risk that such materials break is higher than the risk that aluminum breaks.

What about it?



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Post    Posted on: Fri Feb 17, 2006 3:43 pm
I don’t consider a 1:1 ratio to be a negligible mass penalty since it means giving up half the payload capacity of the rocket, or rather using up half the rocket’s payload capacity with the recovery system. This is an especially bad tradeoff if the rocket is truly reliable, where the recovery system is never (or very rarely) used.


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Post    Posted on: Sat Feb 18, 2006 1:44 pm
The aspect under which it is neglegible is that the technology might cause a reduction of the insurance costs for the payload, The additonal 500 or less kilograms mean an exponential increase of propellant but the costs of that propellant might be less than the drop of insurance costs - then the mass penalty would be neglegible.

What I said has to do with with the Synopsis technology thread. To add a payload recovery technology or a payload protection technology is an allocative step of the technology of a space vehicle. This allocation has costs and revenues and the revenues here might be a drop of insurance costs.

Since I don't wnat to do Economics here - the mass penalty simply provides an enhancemnet of reusability. Of course the safety of the payload or its recovery in emergency isn't reusability - but the payload wouldn't need to be produced quite from beginning but at least portions if it might be reused after recovery.

It is worth to develop and improve techniques and technologies for saftey and recovery of payloads.



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Post    Posted on: Sat Feb 18, 2006 6:33 pm
Ok, perhaps a fair point. If the bare launch prices go waaaay down, fitting recovery systems to high value payloads might become popular. But I don't think the economics of Falcon - whatever are at that point. Falcon 1 is not even reusable in the broad sense, the first stage is intended to be, but not the second - we're throwing that away no matter what. So fuel costs are still not significant, the cost of building stages however is.

Putting aside conditions where a 50% mass penalty could even be too optimistic, you're tacitly assuming the recovery system will actually work. That's what it's meant to do, but in reality there are risks. There's a chance the main vehicle will fail and the recovery system will not, but there's also the case in which the recovery system will also fail, or even that the main vehicle functions perfectly and the recovery system for some reason malfunctions. It isn't at all clear that having a separate recovery system is a good idea even in this case, without it the extra mass could be absorbed into the vehicle structure, presumably allowing some meaningful increase in reliability.

And even discounting the weight of the recovery system, it isn't free - you actually have to design and build it. You'll want to test it too, and to drive down insurance costs you may even have to demonstrate it. Even so recovery may be a misnomer since your payload might still end up in the belly of a whale or rusting away in some godforsaken jungle.

If launch becomes so inexpensive compared to insurance, why not build two at less than twice the price?


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Post    Posted on: Sat Feb 18, 2006 8:30 pm
WannabeSpaceCadet wrote:
Of course the Apollo escape tower was designed to lift the command module from a stationary position on the pad, to a safe parachute altitude & distance, in a very short time, in case of a first stage failure.

The Falcons are held down until all engines are confirmed to be operating normally, and can be shut down safely before that point. So any abort requiring payload recovery should only happen at reasonable altitude. The payload recovery system would require a lot less impulse and be much less massive in proportion.

This is the same principle advanced by T/Space with their CXV proposal.
By air-launching , an abort just requires separation from the booster, and a parachute & floaties, (and TPS for high altitude/speed, if not already available).


Good point about an air launch. I'm sure most of the mass of the Apollo LES was the solid rocket. However, for a ground launched vehicle any comprehensive abort strategy is going to include a low altitude abort capability, even with the hold down. Otherwise you're vulnerable from the time the vehicle lifts off until it gains at least a few hundred feet in altitude.

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Post    Posted on: Sun Feb 19, 2006 8:38 am
Hello, nihiladrem,

please keep in mind that the launch prices of the Falcons really are below what the world is familiar too.

The insurance costs are determined by the payload mainly since the investment into the payload is subject to inssurance - and some payloads aren't insured.

To speak technologically the first Falcon launch will place into orbit a satellite developed and built by students. If the Falcon took of and the thrust is terminated during flight because of malfunctions or emergeny then the students as well as the technological purpose of the satellite and the technology of the satellite itself are better off if the satellite is protected agianst too much damage and can be recovered - even this only would provide first insights into what really will happen to such a payload in such a case.

This is worth the mass penalty - but this is my opinion. On the other hand opinions are allways involved in these questions and in principle it is required to turn to Economics to handle this properly since the Falcon is a private vehicle and the decision to launch the student's satellite by a Falcon was a free one (SpaceX can't force nobody to use their vehicles.)

The tests you are mentioning are an investment in case of a reusable vehicle - they will be depreciated - because theri results could be talken into account technologically also. They vould show up new ways and mnethods or even provide warnings.

This too is worth it in my opinion



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Post    Posted on: Sun Feb 19, 2006 9:29 pm
"please keep in mind that the launch prices of the Falcons really are below what the world is familiar too"
They're low enough that some changes can happen in payload design, what I disagree with is that recovery systems are the place to be doing that since they can never make the payloads themselves meaningfully cheaper. What you must also bear in mind is that Falcon is meant to mature into a system where launch failure occurs at a rate much less than 10%. We're hoping to reduce to a failure level which may be comparable to that of some of the payloads themselves, and there's good reason to think this might be possible because payloads are often complex.
This has implications for insurance costs, so the window where launch is cheap and reliable and insurance costs are high seems inherently small.

To benefit economically from the introduction of recovery systems in places where they previously didn't exist, the bare payloads already need to be many times more expensive than launch itself, otherwise you are just making things more expensive. But even this misses the point, the real way to save money when launch prices reduce - at least for many payloads is to do much more conservative engineering of the kind which has been almost entirely absent in space for fifty years. That is, to conduct sane-engineering-practices, not technology and analysis gone mad. Because excessive analysis and design stops you gaining the experience which in the long run would make things much easier. Conditions can exist where analysis and experience can be reversed in that argument, but that's not the situation where we are now.
Payload teams might not be involved in enough launchs to make a recovery system a worthwhile investment. The vehicle guys probably won't like the trouble and worry the more aggressive recovery systems would generate. If the vehicle guys don't see a big market for payload recovery, it makes things much more difficult to do since they will have firm requirements about what the vehicle-payload interface is allowed to do, the payload does nothing to increase the safety of their vehicle...
Needless to say, payloads which have traditionally had recovery systems will continue to do so for identical reasons, but I don't see much of a case for doing that with new things - this too being only a matter of opinion.


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Post    Posted on: Mon Feb 20, 2006 8:36 am
Hello, nihiladrem,

you are looking at it from a direction which is different than mine.

I didn't say that a payload recovery sytem will make the payload itself cheaper. What I said was that in asituation which requires the destruction of a rocket the payload will be destructed also - even if it would have worked very will. This really has been done in the past. This means that a malfunction of the rocket becomes the cause why insurance companies have to pay money to the insurance takers.

If now the payloads would have been protected or recovered iu those cases where the rocket as the carrier had to be destructed by explosion then the insurance companies wouldn't have had to pay or they would have to pay repairs only or those parts of the payload to be replaced.

The Falcon seems to be the first rocket not going to be destructed if there are malfunctions - regarding its first stage. This reduces the risk that a malfunction of the Falcon - its first stage precisely - destructs the payload.

So if the thrust of the first stage is terminated because of malfunction, emergency etc. during flight it should be made sure that the payload still is going to be destructed although the rocket as the carrier isn't - there is no explosion. May be that the payload needs to be repaired etc. but this may be cheaper than producing or building a complete new one.

The insurance company orients the charges on the value of the payload and on the probability of destruction or damage. Destruction is more expensive for that company than repair. So it doesn't matter that much for them how reliable the Falcon is and if it is going to be destructed or to get terminated thrust - what matters to the insurance company is if the payload is going to be destructed when the stage carrying the payload crashes into the ocean.

This is a sufficient reason to think abot ways to protect or to recover a payload newly - and please note: I am speaking about protection which may be something different than recovery.

I am speaking economically but want to speak technologically - the destruction of a technological payload like that of the students may delay a technological developmment, progress or even breakthrough. This can decide about the direction technology and techniques will go futurely. It can cancel chances of future missions, it might cancel the chances to find ways to achieve higher velocities etc.

To turn back to ciosts and price in short only - the recustion of launch costs shifts the structure so that the share of the insurance costs in percentage is increased - tzhey become more meaningful and a technology to make sure that the payload is kept intact may give reusability and especially the Falcon a boost - coming from the insurance companies.



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