Author Topic: Fairing reuse  (Read 590253 times)

Offline HMXHMX

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Re: Fairing reuse
« Reply #220 on: 03/24/2016 03:55 AM »
Has anyone considered going the other way with the Faring? By that I mean make it super cheap like the wrapping on a candy bar? I know there are aerodynamic loads and all that but just wondering if a dry nitrogen pressurized gas bag made out of some tough material could be used. After all NASA is investigating inflatables for potential reentry use, so maybe not so crazy? Just wondering.

It's not just aero loads.   The fairing shroud also provides an acoustic, thermal, chemical, & EMI environment that keeps the payload safe while waiting for launch as well as during ascent to orbit.  No cheap bag of gas is going to work for all those requirements.



Apropos of that:  http://www.parabolicarc.com/2016/03/21/paragon-wins-nasa-sbir-phase-ii-contract-improved-inspace-transportation/#more-57831

Online dorkmo

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Re: Fairing reuse
« Reply #221 on: 03/24/2016 04:23 AM »
Fairing halves will stay separate once separated.  As Stan-1967 said, rejoining would be of overwhelming complexity.

i think you could potentially be trading one complex problem for a slightly less complex problem.

in a hypothetical world where joining the halves makes rentry significantly more survivable, i think youd want to consider it.

edit: and to satisfy the calls for realism. the new thrusters could enable a rejoining operation. plus they make a lot of docking hardware/software for dragon already.
« Last Edit: 03/24/2016 04:31 AM by dorkmo »

Offline robert_d

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Re: Fairing reuse
« Reply #222 on: 03/24/2016 01:52 PM »
Has anyone considered going the other way with the Faring? By that I mean make it super cheap like the wrapping on a candy bar? I know there are aerodynamic loads and all that but just wondering if a dry nitrogen pressurized gas bag made out of some tough material could be used. After all NASA is investigating inflatables for potential reentry use, so maybe not so crazy? Just wondering.

there is a thread on this and reasons that it is not feasible.
OK. Sorry, didn't realize there was another thread. At least the downthread comment by HMXHMX shows people are trying different concepts. Even I know that most of what is proposed here would be unworkable due to weight and complexity.

I would think they would start simple to see what could be done with the current fairing. What could stabilize it in at least one dimension for some period of time? Maybe add a small reel of ribbon to each half near the base and unreel it after separation. Like a kite tail. See if it will stabilize in pitch and maybe a bit in yaw. See how long the ribbon survives. Then if that gets anywhere, add a few deployable tabs that would autonomously adjust for roll. If those don't help, it seems that a far larger (he he he - Falcon 2 core) first stage would be required to have a much more massive system in place. Too complex and expensive.


 

Offline sevenperforce

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Re: Fairing reuse
« Reply #223 on: 03/24/2016 02:35 PM »
I think you could potentially be trading one complex problem for a slightly less complex problem.

in a hypothetical world where joining the halves makes rentry significantly more survivable, i think youd want to consider it.

edit: and to satisfy the calls for realism. the new thrusters could enable a rejoining operation. plus they make a lot of docking hardware/software for dragon already.
All the active docking on Dragon V2 depends on the androgynous docking port. Not going to work in free-fall.

For second-stage reuse on lower-velocity missions with bulky payload requiring the fairing, the two fairing halves could be hinged, with struts connecting them to the landing legs. The fairing could be made more lightweight because the same opening mechanism is used for two different things. The landing legs would lock into place, maintaining the fairing halves firmly in a 30-degree open configuration. The two halves would thus feather like the hinged wings on SpaceShipOne, producing tremendous drag and distributing the heat flux very efficiently.

I attached a diagram to show how the overall sequence could work.

There are several major advantages. Rather than making the fairings sturdier to survive independent re-entry, the fairings can actually be made even lighter because they don't leave the vehicle. The heat redistribution is excellent and terminal velocity is much lower, placing less stress on the vehicle and requiring less dV. Recovery is in one piece and doesn't require retrieval of three different objects. Perhaps most importantly, this design means that the entire second stage can do a tiny burn at apogee and complete an entire orbit, then re-enter west of launch for a controlled RTLS landing. Finally, the greater weight of the fairing is a huge advantage with a suicide burn, as the T/W ratio is significantly lower.

Offline Jim

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Re: Fairing reuse
« Reply #224 on: 03/24/2016 02:55 PM »
the fairings can actually be made even lighter because they don't leave the vehicle.

Can't say that.   Keeping them open and the landing loads would likely make them heavier than stand alone.

Offline sevenperforce

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Re: Fairing reuse
« Reply #225 on: 03/24/2016 03:26 PM »
the fairings can actually be made even lighter because they don't leave the vehicle.

Can't say that.   Keeping them open and the landing loads would likely make them heavier than stand alone.
They aren't support structures.

Easier (from a weight basis) than making them reusable independently.

Offline Jim

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Re: Fairing reuse
« Reply #226 on: 03/24/2016 03:48 PM »

They aren't support structures.

Easier (from a weight basis) than making them reusable independently.

Again, you have no data to support your claim.  All that might be needed to support independent reusability (as in standalone) is an attitude control system and parachute. 

Supporting the fairing on the stage partially open for entry and landing will require major reinforcement of the fairing.
« Last Edit: 03/24/2016 03:49 PM by Jim »

Offline sevenperforce

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Re: Fairing reuse
« Reply #227 on: 03/24/2016 04:11 PM »

They aren't support structures.

Easier (from a weight basis) than making them reusable independently.

Again, you have no data to support your claim.  All that might be needed to support independent reusability (as in standalone) is an attitude control system and parachute. 

Supporting the fairing on the stage partially open for entry and landing will require major reinforcement of the fairing.
Parachutes are heavy.

The reinforcement would primarily be needed for the landing legs, but they already need to be really strong.

Sure, I'm making educated guesses here, but it would be worth investigation.

Offline RanulfC

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Re: Fairing reuse
« Reply #228 on: 03/24/2016 04:12 PM »
You're assuming a very narrow, and highly limited criteria for the concept;
"For second-stage reuse on lower-velocity missions with bulky payload requiring the fairing"

And the fairing would require structural additions to stand the heating and aero-loading of being attached to the seconds stage in a high-drag configuration. "Easier" than being reusable independently will not automatically translate to saving in weight. Your heat loading is going to be greater on the deployed legs AND you will have added aerodynamic problems with that configuration. (There are very good reasons why no one suggests deploying landing legs prior to reentry)

I'd actually question the idea of fairing reuse on an operational and economic basis because it only makes sense in either case if doing so costs (operationally AND financially) as close as possible to nothing beyond current costs. Trying to make everything on the F9 system "reusable" is gong to end up being self-defeating as the LV system is only an interim vehicle anyway. The architecture can only go so far before it runs into engineered in issues that limit it. (You lose the payload/upper-stage, and probably the vehicle in any abort/incident once its off the pad. Dragon/Dragon-2 are the only exceptions because any attempt at a similar LES abort system for unmanned payload will significantly detract from the payload itself)

Once you move to making the entire second stage reusable (and all that implies which includes things like fully INTACT abort modes for payload recovery during ALL aspects of flight, which is tough even when you START with a 'reusable' design and not a expendable one) you move sharply away from an interim vehicle and have to make significant modifications (as we've seen in these discussions) costing time, effort and money that directly subtracts from other programs.

If Elon and SpaceX are as focused on Mars as they seem to be then there is a point very close to where we are now where "good enough" is as far as you want to go with the Falcon-9 family, and instead focus on the next generation vehicle design which will be reusable from the start.

Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline Jim

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Re: Fairing reuse
« Reply #229 on: 03/24/2016 04:21 PM »

Parachutes are heavy.

The reinforcement would primarily be needed for the landing legs, but they already need to be really strong.

More  (and heavy) reinforcements are needed for the fairing to handle to the additional loads that I list.

Offline sevenperforce

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Re: Fairing reuse
« Reply #230 on: 03/24/2016 06:00 PM »
If they can allow for an additional SECO event, then what about having the fairing hinged at the nose? They could SECO, unhinge the thing and push it away with RCS, then restart the engine. It could then close on its own (or not, if re-entry characteristics were better).

Offline robert_d

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Re: Fairing reuse
« Reply #231 on: 03/25/2016 02:03 AM »
Does anyone think it would be worth the cost of a bottom up test program as in dropping fairings with parachutes from airplanes to see if that end of things can be made to work? Seems to again lead to a lot of cost for questionable gains.

Offline cscott

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Re: Fairing reuse
« Reply #232 on: 03/25/2016 02:53 PM »
SpaceX is already doing a test program, and its lift to altitude is free.  They get a test opportunity about once a month.  How can you beat that?

Offline sevenperforce

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Re: Fairing reuse
« Reply #233 on: 03/25/2016 03:19 PM »
You know, if it would be possible to hinge the damn thing, why not simply hinge it along one long edge? Then it could open along that edge and tumble away still connected.

Offline JasonAW3

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Re: Fairing reuse
« Reply #234 on: 03/25/2016 03:48 PM »
You know, if it would be possible to hinge the damn thing, why not simply hinge it along one long edge? Then it could open along that edge and tumble away still connected.

Aerodynamics, while minimal at the altitudes that fairings are generally dropped from, would likely either bounce the fairing pairs back into the rocket, or simply tear them apart at the hinge.
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Offline JasonAW3

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Re: Fairing reuse
« Reply #235 on: 03/25/2016 03:53 PM »

Parachutes are heavy.

The reinforcement would primarily be needed for the landing legs, but they already need to be really strong.

More  (and heavy) reinforcements are needed for the fairing to handle to the additional loads that I list.

What about an RCS system with a Ram-air Ballute?  Less issues with rigging and can be made fairly low mass.

     I'm not certain, but I think it might even be able to be made with a lower overall mass than a conventional parachute.
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Offline sevenperforce

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Re: Fairing reuse
« Reply #236 on: 03/25/2016 04:56 PM »
You know, if it would be possible to hinge the damn thing, why not simply hinge it along one long edge? Then it could open along that edge and tumble away still connected.

Aerodynamics, while minimal at the altitudes that fairings are generally dropped from, would likely either bounce the fairing pairs back into the rocket, or simply tear them apart at the hinge.
I thought the fairing was only jettisoned once it was far enough into space that there was no risk of harm to the payload from any aerodynamic effects.

Offline cambrianera

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Re: Fairing reuse
« Reply #237 on: 03/25/2016 05:42 PM »
You know, if it would be possible to hinge the damn thing, why not simply hinge it along one long edge? Then it could open along that edge and tumble away still connected.
If you push a long edge hinged fairing over the other long edge, you get an inward movement of the hinge.
You can add a reaction beam to keep the hinge clear from the payload, but this would increase the mass of the fairing.
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Offline sevenperforce

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Re: Fairing reuse
« Reply #238 on: 03/25/2016 11:41 PM »
You know, if it would be possible to hinge the damn thing, why not simply hinge it along one long edge? Then it could open along that edge and tumble away still connected.
If you push a long edge hinged fairing over the other long edge, you get an inward movement of the hinge.
You can add a reaction beam to keep the hinge clear from the payload, but this would increase the mass of the fairing.
This is probably crazy, but what about manufacturing the fairing in three pieces rather than two: one the current size, then two 90-degree ones. Have the larger section hinge to both the other smaller sections so they open up like double doors.

Offline NWade

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Re: Fairing reuse
« Reply #239 on: 03/26/2016 07:16 AM »
C'mon folks, this is all a bit ridiculous.  ??? You're forgetting a major issue: MASS
 
If you keep the fairing attached to the second stage you are having to accelerate a lot more mass up to your final velocity - plus carry it around for any maneuvering and de-orbit burns. And on top of that, having it hinged open or cantilevered out means your center of thrust may no longer be going through your center of mass - have fun with that! All of these things are tremendously wasteful and makes all of your operations harder. The best thing to do is keep the fairings as light as possible and jettison them as early as possible. The slower the rocket is going when you ditch them, the lower your re-entry energy is going to be (coming in from slower or a lower altitude, or both).
 
The K.I.S.S. principle applies, always.
 
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