Author Topic: Reusability as abort functionality  (Read 14687 times)

Offline bioelectromechanic

  • Member
  • Posts: 50
  • Liked: 4
  • Likes Given: 24
Reusability as abort functionality
« on: 11/01/2013 06:08 PM »
I was thinking a F9R could use it's ability to land to abort a failed launch.
E.g if an F9R suffers an early stage engine loss, or later double engine loss.
What would be needed to be done to allow it to land with a 2nd stage plus payload on top?

My first thought was it needs to vent a huge amount of propellant to avoid overloading the legs during landing.
Carpe diem et vadem ad astra

Offline Kabloona

  • Senior Member
  • *****
  • Posts: 4026
  • Velocitas Eradico
  • Fortress of Solitude
  • Liked: 2204
  • Likes Given: 446
Re: Reusability as abort functionality
« Reply #1 on: 11/01/2013 06:21 PM »
I was thinking a F9R could use it's ability to land to abort a failed launch.
E.g if an F9R suffers an early stage engine loss, or later double engine loss.
What would be needed to be done to allow it to land with a 2nd stage plus payload on top?

My first thought was it needs to vent a huge amount of propellant to avoid overloading the legs during landing.

Land where? On the ocean? Because it can't return to the launch site at that point. And anyway, an abort for a "failed launch" is going to result in flight termination. That's what the "red button" is for, and the addition of legs isn't going change range safety protocol.

Offline Jason1701

  • Senior Member
  • *****
  • Posts: 2238
  • Liked: 70
  • Likes Given: 39
Re: Reusability as abort functionality
« Reply #2 on: 11/01/2013 06:26 PM »
Jim will say that satellites are not designed to survive the loads that would be encountered during an abort.

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 31343
  • Cape Canaveral Spaceport
  • Liked: 9624
  • Likes Given: 299
Re: Reusability as abort functionality
« Reply #3 on: 11/01/2013 06:29 PM »
I was thinking a F9R could use it's ability to land to abort a failed launch.
E.g if an F9R suffers an early stage engine loss, or later double engine loss.
What would be needed to be done to allow it to land with a 2nd stage plus payload on top?

My first thought was it needs to vent a huge amount of propellant to avoid overloading the legs during landing.

It is a non starter. It would need stronger legs for the added weight of upperstage, payload and fairing.   Vent is a misnomer.  It has to get rid of the propellant fast and guess what?  It can't get rid of it faster than burning it through the engines.  That includes the upperstage propellant.  And then there is  the spacecraft.  Not to mention the that whole vehicle has to be able to take the new aeroloads from the pitch around maneuver.  That means strengthened interstage and fairing.  Also, there now is a live payload, with toxic and hazardous propellant onboard with no ability to command it if using current conops (typically, there is no electrical or rf interaction between spacecraft and LV except for breakwires, and maybe some occasion discreets )

This would require a whole redesign of the vehicle

Offline Lar

  • Fan boy at large
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 8654
  • Saw Gemini live on TV
  • A large LEGO storage facility ... in Michigan
  • Liked: 5394
  • Likes Given: 3565
Re: Reusability as abort functionality
« Reply #4 on: 11/01/2013 07:05 PM »
Maybe some large number of years from now aborts like this might actually be possible.

Right now payloads and launch costs are fairly similar... it's rare that one is an order of magnitude more than the other (JWST perhaps being one of those rarities) But consider what it would be like if launch costs are 100 USD/kg ... at that point, payloads are worth so much more than the launch that designing for abort becomes more economical....

Jim's response, just above, lists off a lot of the issues that would need to be dealt with.... what other issues would there be? Developing a list of such issues might be a good exercise.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline TrevorMonty

Re: Reusability as abort functionality
« Reply #5 on: 11/02/2013 10:56 AM »
The only option is for the 2nd stage to separate and try to land with the payload. I doubt it is viable, as the 2nd stage would need to burn most of its fuel before attempting a landing. Then it would be top heavy, making control difficult if not impossible.


Offline TrevorMonty

Re: Reusability as abort functionality
« Reply #6 on: 11/02/2013 11:02 AM »
Just had another thought on this, if payload was a Dragon and it landed separately then maybe it is possible. For all stages to survive the rocket would need to reduce its speed, before separate of the individual stages.

Offline eriblo

  • Full Member
  • **
  • Posts: 267
  • Sweden
  • Liked: 137
  • Likes Given: 104
Re: Reusability as abort functionality
« Reply #7 on: 11/02/2013 11:38 AM »
As previous posters have concluded: Asking a reusable multi-stage LV to perform an intact abort is to ask it to do something which is several times harder than a normal launch - after a failure has already made it impossible for it to do that...  ::)

Saving the payload is already done for crew and might be doable for more fragile satellites, but saving the entire LV is probably only possible/worth it for SSTO (especially space planes).
« Last Edit: 11/02/2013 11:39 AM by eriblo »

Offline Avron

  • Canadian Member
  • Senior Member
  • *****
  • Posts: 4915
  • Liked: 147
  • Likes Given: 150
Re: Reusability as abort functionality
« Reply #8 on: 11/02/2013 02:50 PM »
As previous posters have concluded: Asking a reusable multi-stage LV to perform an intact abort is to ask it to do something which is several times harder than a normal launch - after a failure has already made it impossible for it to do that...  ::)

Saving the payload is already done for crew and might be doable for more fragile satellites, but saving the entire LV is probably only possible/worth it for SSTO (especially space planes).

I think that the best way to use the existing technology is via  redundancy, If part of the re-usability provides redundancy then it can be used, however, when one has had multiple failures to a point where the redundant streams have failed, its time to press the red button and use the abort system built into say Dragon if applicable. If there is no built in abort system and one has had so many failures that the redundant systems have not been able to cope, one askes the question, does one really want that vehicle flying back on any half baked string..





Online Ben the Space Brit

  • Senior Member
  • *****
  • Posts: 6995
  • A spaceflight fan
  • London, UK
  • Liked: 553
  • Likes Given: 637
Re: Reusability as abort functionality
« Reply #9 on: 11/02/2013 03:31 PM »
When a civil airliner performs an ATLS (Abort to Launch Site) equivalent, the big problem is that it really weighs too much to land safely, so they have to jettison most of the fuel. Similarly, any attempt to modify the core return equipment to allow for a ATLS would require for the vehicle to dump most of its propellent. There are probably several serious safety issues, especially if it is done close to the pad. That amount of RP1/LCH4 and LOX being vented in the air around a hot launch pad and an even hotter exhaust flame? That spells "catastrophic burn-off".

Then there is the question of repositioning the vehicle over the landing pad and carrying out a controlled descent.  This would raise issues about stabilising the now top-heavy stack during translate and hover before descent.

Overall, it's far from impossible but would be a complex process to develop and prove. It certainly isn't a capability that I'd want available from the outset as it would lead to delays and unnecessary expenses.
"Oops! I left the silly thing in reverse!" - Duck Dodgers

~*~*~*~

The Space Shuttle Program - 1981-2011

The time for words has passed; The time has come to put up or shut up!
DON'T PROPAGANDISE, FLY!!!

Online douglas100

  • Senior Member
  • *****
  • Posts: 2152
  • Liked: 214
  • Likes Given: 95
Re: Reusability as abort functionality
« Reply #10 on: 11/02/2013 06:44 PM »

...Overall, it's far from impossible but would be a complex process to develop and prove. It certainly isn't a capability that I'd want available from the outset as it would lead to delays and unnecessary expenses.

If you're talking specifically about F9R as per the original poster, then I disagree. It is impossible for the current vehicle to recover  a standard payload (not Dragon of course) after launch commit.

As whether it will be developed in a future vehicle, you rightly point out how difficult it would be for a multistage LV. If it were technically possible it would inevitably eat payload margin.

So the first question should be "who wants this capability?"
Douglas Clark

Offline Heinrich

  • Full Member
  • *
  • Posts: 115
  • Liked: 2
  • Likes Given: 84
Re: Reusability as abort functionality
« Reply #11 on: 11/02/2013 07:34 PM »
What about a TAL-style abort? Complete the S1 burn. Due to the engine failure the vehicle can't reach the desired orbit anymore. Do stage separation, and let the second stage do the breaking and landing burns towards a downrange location. (let's hpothetically assume this downrange location is available...)

One drawback I see is that the second stage would be able to land with its engine, but with the payload still on top it will be heavier...

Offline Lars_J

  • Senior Member
  • *****
  • Posts: 6161
  • California
  • Liked: 664
  • Likes Given: 195
Re: Reusability as abort functionality
« Reply #12 on: 11/02/2013 07:46 PM »
These kinds of intact aborts won't be possible until we have reusable SSTOs.

Offline LouScheffer

  • Full Member
  • ****
  • Posts: 1555
  • Liked: 1756
  • Likes Given: 199
Re: Reusability as abort functionality
« Reply #13 on: 11/02/2013 08:15 PM »
If you want intact recovery upon abort, rather than fiddle with the rocket, it might be better to replace the fairing with a giant capsule-ish construction.  If something goes wrong, it separates from the rocket, then descends with heat shields, parachutes, and maybe last-second retrorockets.  If all goes right it splits in half and releases the payload.

Sure it's big and heavy, but if cost to orbit is cheap and the payload is expensive it could easily be worth it.  Also it has no dependence on the rocket, which is already known to have problems if you are trying an abort

Depending on the loads the payload can endure, it might provide protection throughout the launch (as crew capsules do), or just a subset of possible failures.  It almost surely has a better chance at recovery than depending on the rocket, since any case where the rocket is still even partially functional would allow a low-stress separation.

Offline CuddlyRocket

Re: Reusability as abort functionality
« Reply #14 on: 11/03/2013 06:59 AM »
The answer is an obvious 'yes' despite the suggestions of the apparently more conservative members of the engineering fraternity. Any rocket that is, or some or all of its parts are, reusable is potentially recoverable (at least in part) in abort scenarios. What is needed is to analyse which scenarios are both achievable - taking into account safety considerations - and economically desirable.

We have to remember that current launch and range safety protocols have been developed under the assumption that once launch is commenced no part of the launcher is going to come back. Once you have LoM, it makes no difference precisely when the launcher or its parts are destroyed, whether deliberately or by catastrophic failure or impact. When the launcher of parts thereof is recoverable it certainly does make a difference; there's valuable equipment at stake! No one is going to be happy if a multi-million dollar piece of equipment is needlessly abandoned or destroyed (except the lawyers, perhaps).

Safety comes first. But some failures are perfectly safe! Lots of launchers have failed without engaging safety protocols (usually because the launcher is by then sufficiently high up and out to sea). Are there failure scenarios that don't require safety action (i.e. blowing up the launcher), or at least not immediate action? I think there are.

There are three main types of failure scenarios: Catastrophic, out of control (usually directional) and under control (usually loss of one or more engines in a multi-engine stage). Catastrophic tends to speak for itself; but even here there is potential for recovery. After all, a manned Dragon is designed to be recoverable under all scenarios, so a cargo Dragon is presumably potentially recoverable as well. And not just the capsule, there's also its cargo. Even if it has to be recovered from the ocean. Satellites are a different matter, as you'd have to design a kind of fairing that contains parachutes and will stay intact for an ocean landing etc; this involves weight penalties unless the launcher is drastically over-powered for the mission. And the satellite might not survive the loading, although it might be repairable (again, current protocols are based on the idea that if the satellite breaks there's no repair opportunity).

If the first stage catastrophically fails, it might be possible to fire the second stage early, thereby potentially recovering it. The question would be when to detach the payload, immediately or after a delay. (For a manned payload, this would almost certainly be immediately.) This might depend on whether the second stage has T/W>1 or not.

An out-of-control failure is basically a catastrophic failure with more time. One consideration is whether the loss of control means the launcher is heading in a dangerous direction or not. If not (for instance it's heading out to sea), the range officer won't need to blow it up!

An in-control failure (for instance loss of four engines on an F9 first stage), gives much more opportunity for recovery. The main problem is burn off of propellant, because it's unlikely that any landing system for a launcher or component will be robust enough to handle much more than the empty weight. If you have control, you can just fly around of course - maybe simply pogoing up and down - though you may be limited for how long you can do this by supplies of attitude control thruster propellant.

I think planning for some of these scenarios is going to happen sooner than some might think. Basically, as soon as it becomes clear that the F9 first stage is recoverable. If there was a launch where four engines failed, SpaceX is going to want to try and recover the first stage (assuming the centre engine isn't one of them!). You'd simply keep the engines firing to burn off the propellant; launch the second stage and then try to land!
« Last Edit: 11/03/2013 07:03 AM by CuddlyRocket »

Offline KelvinZero

  • Senior Member
  • *****
  • Posts: 3566
  • Liked: 482
  • Likes Given: 124
Re: Reusability as abort functionality
« Reply #15 on: 11/03/2013 10:05 AM »
So recovery looks pretty difficult if it is not dragon and already designed to land with payload.

This is a bit of a flakey idea, but could the second stage drop the payload say 10 meters over a body of water and then return to shore?

Offline Lee Jay

  • Elite Veteran
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 6644
  • Liked: 914
  • Likes Given: 137
Re: Reusability as abort functionality
« Reply #16 on: 11/03/2013 01:18 PM »
Isn't this exactly what a Shuttle RTLS was?

Online douglas100

  • Senior Member
  • *****
  • Posts: 2152
  • Liked: 214
  • Likes Given: 95
Re: Reusability as abort functionality
« Reply #17 on: 11/03/2013 03:57 PM »
The Shuttle didn't dump the payload for RTLS.
Douglas Clark

Online douglas100

  • Senior Member
  • *****
  • Posts: 2152
  • Liked: 214
  • Likes Given: 95
Re: Reusability as abort functionality
« Reply #18 on: 11/03/2013 04:27 PM »

...I think planning for some of these scenarios is going to happen sooner than some might think. Basically, as soon as it becomes clear that the F9 first stage is recoverable. If there was a launch where four engines failed, SpaceX is going to want to try and recover the first stage (assuming the centre engine isn't one of them!). You'd simply keep the engines firing to burn off the propellant; launch the second stage and then try to land!

I don't think planning for the kind of failure you cite is worth it. Losing four engines is very unlikely. Instead the effort should go into improving the reliability of the vehicle so aborts become less likely in the first place.

The correct way to go in the event of first stage engine failure is to abort the first stage recovery sequence to recover the margin needed to allow the second stage and payload to achieve orbit.
Douglas Clark

Offline Lar

  • Fan boy at large
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 8654
  • Saw Gemini live on TV
  • A large LEGO storage facility ... in Michigan
  • Liked: 5394
  • Likes Given: 3565
Re: Reusability as abort functionality
« Reply #19 on: 11/03/2013 04:44 PM »
The correct way to go in the event of first stage engine failure is to abort the first stage recovery sequence to recover the margin needed to allow the second stage and payload to achieve orbit.

Today. And in the near future too. But if Musk's vision materializes, economics would change. I think it interesting to explore what happens if they do change.   

By analogy we don't typically sacrifice cargo aircraft in order to deliver the cargo, they abort to somewhere and get fixed and try again.  Right now rockets are NOTHING like that. But what if they were? What changes would need to happen?
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Tags: