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Thread: Auto ejection for satellites

  1. #1
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    Auto ejection for satellites

    Well India had a very bad day on christmas eve with GSLV going into flames 63 seconds after lift off. Apprently it was failure of first stage itself. What I am curious to know is why does rockets does not have automatic bailout ejection system for satellites just like fighter pilot ejection seats?
    Space shuttle has this..but if regular rockets carrying satellites also have this then I think many satellites could have been saved..

  2. #2
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    Let's take that T+1 minute failure and look at it.

    We're very close to MaxQ - therefore the maximum aerodynamic loading on the rocket. Building an ejection system would involve wrapping the spacecraft in something as big and probably heavier as the nosecone of the rocket itself - but strong enough to withstand those forces from any direction.

    This adds mass, and reduces the available volume inside the real nosecone ( infact, most take this to the limit leaving only a few inches of wobble room ).

    Thereafter you will need parachutes - and a mortar to fire them - and moreover, no satellite is designed to survive a parachute landing in the ocean ( where most rockets launch over ) - so it would need either landing airbags or flotation bags. And a beacon so you know where to find it. And avionics to deploy the parachute. And batteries to run it all.

    And to survive failures later in launch - that aerocapsule would need thermal protection as you're nearly doing a reentry if you abort late.

    All of that adds a LOT of mass a LOT of complexity and a LOT of added risk and failure modes ( one need only imagine a spacecraft aborting before launch and punching out through the rocket itself )

    All that cost, risk and complexity is better spent making the rocket itself more reliable. Some commercial operators actually buy insurance against a launch failure. Moreover, the added mass and reduced volume an abort recovery system would involve making the launch itself more expensive, and the available volume less. Many missions have no such margin available.

  3. #3
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    Quote Originally Posted by manmeetvirdi View Post
    why does rockets does not have automatic bailout ejection system for satellites just like fighter pilot ejection seats?
    Did you take a close look at what exactly happened to the rocket in the video? Its payload fairing, satellite inside and upper stage got ripped off due to enormous aerodynamic forces. You propose ejecting the satellite into that airstream? You just saw what happens when an object can't handle structural loads such as that.

    Space shuttle has this
    No, it doesn't.

    ..but if regular rockets carrying satellites also have this then I think many satellites could have been saved..
    Satellites aren't built or qualified for over 12G loads at abort or impact loads during splashdown. If this was a good and worthwhile idea, people would already be doing it. The extra mass, complexity and cost aren't worth it. And it would still do nothing for a failure later in the flight which is where most failures typically occur anyways.

    Spacecraft operators will rather spend the performance margin of the rocket to shove more capability onto the satellite and just insure the launch than spend that mass on something that most likely won't be needed anyway.

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    It surely makes more sense to spend the money on improving the reliability of the launcher.

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    Its just a bunch of computers and radio components; simply not worth it.

    They're not launching gold bars or stuff that can't be put back together again.
    The cost is in BUILDING the stuff, not the parts themselves....

  6. #6
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    I had considered a satellite rescue as well.

    It does NOT add much annoying mass, because it's thrown away rather early. On a core-plus-sideboosters design, the rescue can be jettisoned after booster separation. As the launcher is still 300t then, 2t more is no issue; no comparison with 2t left at satellite separation. On a three-stage design, the rescue can be available just during the first stage burn and shortly after ignition of the second stage, for instance.

    Speed is still moderate then, like 2km/s, so atmospheric re-entry is easy.

    Forces on the payload wouldn't be big. During the atmospheric ascent, the acceleration of the rocket is under 2G usually, so ejection at 4G would suffice; this is less than the launcher's acceleration as it goes empty, and far less than the launcher's vibrations.

    The rescue rocket could be combined with the fairing, and separated at once at the same moment as the fairing is jettisoned now.

    Added electronics is negligible nowadays.

    Much more of a concern is the splashdown in the Ocean. You can't require satellites to resist salt water in addition to everything else. The only option I see is that the fairing is hermetic, including at its bottom, serving as a floating and protecting hull in the Ocean.

    Not easy: to separate the rescue fairing, you have to cut or open a hermetic seal that resists the rescue separation and the splashdown, but this operation must remain perfectly clean and soft enough. Nice engineering challenge... Maybe a belt with gaskets.

    The movements of the fairing in the waves is not hard as compared with a launch, splashdown neither.

    -----

    People consider more and more orbital refuelling of existing satellites, satellite repair spacecraft, satellite and debris de-orbiting services... All things that looked odd few years ago.

    Maybe a payload rescue tower will seem natural some time in the future. But it has to be designed first.

    Marc Schaefer, aka Enthalpy

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    Quote Originally Posted by Enthalpy View Post
    It does NOT add much annoying mass,
    Yes it does. It makes a massive massive difference.

    , 2t more is no issue; no comparison with 2t left at satellite separation.
    are you proposign to DOUBLE the mass of the payload for part of the flight?

    Speed is still moderate then, like 2km/s, so atmospheric re-entry is easy.
    . It's not. It's damn hard - it will require a tough aeroshell.

    Forces on the payload wouldn't be big
    .

    They would infact, be massive.

    During the atmospheric ascent, the acceleration of the rocket is under 2G usually, so ejection at 4G would suffice; this is less than the launcher's acceleration as it goes empty, and far less than the launcher's vibrations.
    The spacecraft is sat in a nice safe nosecone. You're proposing to throw it overboard into 2km/sec winds. Lest we forget - it was winds far far slower than that that took a benign piece of insulating foam and turned it into a missile that smashed the leading edge of the space shuttle. You understimate the harshness of aerodynamics MASSIVELY.

    The rescue rocket could be combined with the fairing, and separated at once at the same moment as the fairing is jettisoned now.
    You want to add a full abort stage to the whole spacecraft and fairing with aeroshell, avionics, parachutes, a 'belt and gasket'.

    Added electronics is negligible nowadays.
    No, it's not.



    Much more of a concern is the splashdown in the Ocean.
    Ironically, you pick the 'easy' part and claim it's the concern.


    Sorry - you have no idea about the reality of the dynamics of launch vehicles and the environment in which they operate.

    As an idea it's totally untenable.

  8. #8
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    What is the failure rate for satellite launches anyway? If it was really high, like 50% or something, I could imagine trying to make it safer. But if the failure rate isn't that high anyway, then adding lots of mass to make recovery possible in the case of a launch failure would seem impractical.
    As above, so below

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    Lets take the last 5 years of popular LV's

    Ariane V - 34 / 34 successful launches
    Atlas V - 19 / 19 successful launches ( one delivered to a slightly lower orbit than intended - the DoD payload is presumed to have recovered to the intended orbit )
    Delta IV - 11 / 11 successful launches
    Delta II - 30 / 30 successful launches

    What we have here is a solution ( that is an engineering impossibility ) for a problem that doesn't really exist.

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    Enthalpy, djellison is 100% correct and you are wrong.

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    Quote Originally Posted by Enthalpy View Post
    Forces on the payload wouldn't be big.
    Take a look at the Challenger orbiter, on its last flight. Unless I misremember the accident report, it disintegrated due to atmospheric forces, not because of the explosion of the tank. It's designed aerodynamically to withstand the atmospheric drag in the correct attitude.
    Last edited by slang; 2011-Feb-04 at 04:47 PM. Reason: grammar
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  12. #12
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    Quote Originally Posted by djellison View Post
    Lets take the last 5 years of popular LV's

    Ariane V - 34 / 34 successful launches
    Atlas V - 19 / 19 successful launches ( one delivered to a slightly lower orbit than intended - the DoD payload is presumed to have recovered to the intended orbit )
    Delta IV - 11 / 11 successful launches
    Delta II - 30 / 30 successful launches

    What we have here is a solution ( that is an engineering impossibility ) for a problem that doesn't really exist.
    And before the single Delta II failure several years ago, they were up to something on the order of 250 successful launches of previous Delta I/II variants. I don't recall previous Atlas II/III variants having any failures for decades. I remember one Titan IV failure about a decade ago. Overall, the US cadre of launch vehicles has a success rate above 99%.

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    I maintain each and every of my claims above.

    As my first post already addressed the subsequent objections, I don't feel a need to add answers.

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    Quote Originally Posted by djellison View Post
    Sorry - you have no idea about the reality of the dynamics of launch vehicles and the environment in which they operate.
    I was the project leader for a satellite.
    Were you?

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    Quote Originally Posted by Enthalpy View Post
    I was the project leader for a satellite
    That helps, but why would anyone involved in a satellite project have insight into drag and other atmospheric issues?

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    Lets say an ejection system were feasible wrt to mass, would it save you any money? The conditions the satellite would experience being popped off the rocket near max Q, then landing somewhere downrange, would likely require it be completely rebuilt anyway.

    A payload is designed to handle a certain envelope of mechanical stress, and that is hard enough to pull off itself. Designing it to handle being dumped from a moving rocket in the atmosphere and still be in any condition to be worth repairing for another flight sounds like it would entail massive over-engineering (and massive... mass)

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    Quote Originally Posted by Enthalpy View Post
    I was the project leader for a satellite.
    Were you?
    I don't want to be rude here - but I don't care what you say you were or were not.

    Your claim is still an engineering non-starter for a problem that's not even worth trying to solve.

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    Quote Originally Posted by Enthalpy View Post
    I was the project leader for a satellite.
    This seems quite a ridiculous claim, considering that you think that the only force to be reckoned with during ejection is acceleration, completely ignoring aerodynamic loads. On the other hand, it reinforces my experience that managers generally are (well, can be) good in managing, not engineering.
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    Quote Originally Posted by slang View Post
    ...Managers are good in managing, not engineering.
    We were 9 people on this micro-satellite, I engineered most of it, including the mechanical design.
    I claim to have a more comprehensive knowledge of satellite engineering than people who designed a sub-sub-part of a satellite, which means about everyone who took part to a big project.

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    Quote Originally Posted by NEOWatcher View Post
    ...would anyone involved in a satellite project have insight into drag and other atmospheric issues?
    Prior to the satellite, I designed and successfully flew half a dozen of small rockets. They flew at Mach 1.5 in the dense atmosphere, meaning that aerodynamic efforts were more difficult than at launchers.

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    Quote Originally Posted by Enthalpy View Post
    ...The rescue rocket could be combined with the fairing, and separated at once
    ...
    the fairing is hermetic, including at its bottom, serving as a floating and protecting hull in the Ocean
    ...
    The movements of the fairing in the waves is not hard...
    and some people still understood the satellite was to be thrown naked in the atmosphere?

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    Quote Originally Posted by djellison View Post
    ...a problem that's not even worth trying to solve.
    Have launchers become so reliable that satellites get an insurance policy for free? I'd have missed something then.

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    Quote Originally Posted by Enthalpy View Post
    and some people still understood the satellite was to be thrown naked in the atmosphere?
    Enthalpy you seem to be ignoring the fairly basic point that given the reliability of the available launchers and the costs of components that there is simply no requirement for such a system regardless of whether it is technically feasible or not. Frankly if you have the payload mass to spare for such a system it would be better spent on launching cubesats, or a second full scale satellite depending on how much mass we are actually talking about.

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    Quote Originally Posted by Enthalpy View Post
    We were 9 people on this micro-satellite, I engineered most of it, including the mechanical design.
    Fair enough, it does happen that an engineer has good enough people and leadership skills to advance into manager-type roles. In my experience that's though, so please excuse my wrong assumption.
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  25. #25
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    how big was this "micro satellite"? what did it do? what were the operating parameters?
    how big were the "small rockets" that you launched?

    what happens to the forces and technology required on the whole thing as everything gets scaled up to "big boy" territory?

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    Quote Originally Posted by Enthalpy View Post
    ....
    You claim an addition of 2 tons to a payload would make no difference to performance.

    You are wrong.

    You claim a 2km/sec re-entry isn't an engineering challenge of note.

    You are wrong.

    You claim the aerodynamics are not a problem.

    You are wrong.

    These are not opinion based issues - who you you are and what you claim to have worked on has nothing to do with this.

    You are simply very very wrong on several key issues. Sorry.

  27. #27
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    Quote Originally Posted by Enthalpy View Post
    Have launchers become so reliable that satellites get an insurance policy for free? I'd have missed something then.
    Airliners are extremely reliable, but they don't get an insurance policy for free either. In fact, I can't think of anything that gets a free insurance policy. How would the insurer possibly make a profit from such an arrangement?
    As above, so below

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    Quote Originally Posted by Enthalpy View Post
    ...It does NOT add much annoying mass, because it's thrown away rather early....
    The now-cancelled Ares I Launch Abort System was about 16,000 pounds to handle a 19,250 pound capsule -- 83% of vehicle weight!!

    Te Apollo Launch Escape System was about 8,000 lbs, vs the CM roughly 13,000 lbs -- 62% of vehicle weight.

    The Apollo LES was jettisoned early in 2nd stage, I think Ares was planned similarly.

    As is obvious with such large mass relative to functional payload, he performance hit was large.

    With Ares it was so bad they seriously were considering firing the abort rockets while still attached to the booster stack, rather than just jettisoning them. At least that way they'd recover some of the delta-V lost from carrying that mass uphill.

    A satellite ejection system need not be man-rated, so you'd lose some mass there. However it's not *designed* for ejection, unlike a man-rated booster where this is structurally part of the design from day one.

    It's always harder (from a mass and reliability standpoint) to take an existing design and add ejection capability. Structural analysis always find things you didn't think of.

    E.g, thrust termination ability for the shuttle SRBs was initially planned. They'd just blow off the nose caps to neutralize thrust then jettison the SRBs. It seems easy, right? Not even real ejection, just ditch the SRBs. Well, a structural analysis found it required 20,000 lbs of structural upgrades to the orbiter and stack.

    Likewise with satellite ejection, you can't just calculate the delta-V and propellant mass needed for the ejection system itself. The entire structure must be analyzed, and the satellite must be kept within survivable G limits AND shock limits, else there's no reason to eject it. Likewise any needed recovery systems (e.g, parachutes, inflatable raft, beacons, etc) are part of the mass penalty and must be included.

    Then there's aerodynamic analysis. The payload is potentially ejected into a supersonic windstream, so must be aerodynamically: (a) protected, and (b) stabilized. Without this an otherwise-successful separation would still result in the payload being ripped apart by the windstream (like happened to Challenger, STS-51-L), or spun to pieces. The protection and stabilization hardware adds to the mass penalty.

  29. #29
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    Quote Originally Posted by Jens View Post
    Airliners are extremely reliable, but they don't get an insurance policy for free either. In fact, I can't think of anything that gets a free insurance policy. How would the insurer possibly make a profit from such an arrangement?
    And despite that I haven't seen anyone advocating ejector seats for passenger airliners. There is such a thing as cost-benefit analysis, and both passenger ejector seats and satellite ejections systems would I imagine fare pretty badly.

  30. #30
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    Quote Originally Posted by djellison View Post
    You claim an addition of 2 tons to a payload would make no difference to performance.

    You are wrong.

    You claim a 2km/sec re-entry isn't an engineering challenge of note.

    You are wrong.

    You claim the aerodynamics are not a problem.

    You are wrong.

    These are not opinion based issues - who you you are and what you claim to have worked on has nothing to do with this.

    You are simply very very wrong on several key issues. Sorry.
    He fails to understand that fairing is only designed for aeroloads in a nominal ascent, not those encountered during a max-q abort, which will include significant side loads, also the fairing and spacecraft are not designed for parachute shock load. And most importantly landing loads on land (not just water). It is ludicrous to think a fairing can be made seaworthy and maintain a stable attitude.

    The thought of this concept severely discredits the poster and calls into question the validity of his claim to have worked on a spacecraft, at least one of some expense or import and not a student project.

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