Author Topic: Falcon 9 alternate landing options.  (Read 31873 times)

Offline speedevil

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Falcon 9 alternate landing options.
« on: 09/13/2014 02:14 PM »
Apologies if this is a FAQ - I haven't found it on a quick search.

Neglecting the silly patent issue (though these options would sidestep it).

The falcon 9 weighs of the order of 20 tons and has an area of the order of 12 square meters base area.
This will fall at a speed of the order of 100m/s.
Sea level thrust of M1D is ~400kN at minimum thrust, and ~280 ISP.
Of the order of 5s burn to bring to a halt, and and a ton of fuel.

Two options spring to mind, one requiring rather more effort than the other.
Option A).
Delete the legs, replace with stubby latch mechanisms.
Take several (6?) jet engines, and make an open horseshoe type shape, with a peripheral airbag for initial centering, before the latch mechanism catches.

This ascends to ~10km or so, and then descends in more-or less freefall to intercept the F9 stage. The first stage aribag goes off when it's almost in position, and this centres the vehicle, and then it's firmly lartched, before throttling the engines up and bringing it into a contolled landing.
Option B) Find a nice barge with say a 40m clear deck, and place a rather large x-y stage on it.
Vehicle descends to deck, and comes more-or-less to rest.
Large (much of the stage height) semicylindrical catchers are brought up to meet the rocket, and as the engines go off, pyrotechnic airbags deploy and grip the stage firmly, but gently.
Soon (a minute or two later) the stage is properly secured to the deck with some form of rigid structure that allows the stage to be transitioned to horizontal once fuel is offloaded.

This is clearly a significant investment to do either of these.
But the payoff - in significantly increased flexibility due to being able to delete either the legs, or the legs and all fuel required to land would be moderately significant.

Offline eriblo

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Re: Falcon 9 alternate landing options.
« Reply #1 on: 09/14/2014 10:44 AM »
Welcome to the forum!

Yes, it has been frequently and possibly fully discussed in these threads already, but that is of course a lot of (mostly excellent) posts to read for a newcomer. Your Option B) has been suggested several times in multiple incarnations - nets, wires, inflatables, x-y translating catchers, cm-precision landing and so on. A jet-powered catching stage is a bit more innovative ;), but probably a complete non-starter.

Here is why: Why?

The landing legs and propellant is less than 1/5 of the mass of the returning stage, meaning that you could save 1/5 of the RTLS propellant and thereby reduce the payload hit from 30% to 24%* - i.e not much. Even the simplest ground side systems are likely to not be worth it due to costs of the system itself and its maintenance, its development, more complicated handling, replacement when something goes wrong and so on. This will be true until the launch rate becomes high enough, which might be 100s-1000s/year depending on system. Remember that the current system is likely to be a clean concrete pad and a transporter/erector or mobile crane+trailer/bogies - cheap and mostly COTS.

An autonomous jet-powered HTOL catching mitt with a payload at least 3x the V-22 Osprey would be spectacular  - but also a development program likely to cost much more than SpaceX has spent on all their rockets so far. Remember that it could only save a small amount of money for each catch (likely < 1 M$) and then add all the costs mentioned above...

Finally - remember that if you actually need that little extra bit of performance you have the FH-R to play with before even having to look at expending parts of the rocket.


* These are handwavy example numbers for first stage reuse only, the relationship between payload hit and RTLS propellant is likely not linear but it's a small change :)

Offline Jim

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Re: Falcon 9 alternate landing options.
« Reply #2 on: 09/14/2014 12:34 PM »
How is making a second flying vehicle better and/or cheaper than legs?

Offline S.Paulissen

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Re: Falcon 9 alternate landing options.
« Reply #3 on: 09/14/2014 03:27 PM »
Yeah, what Jim said...

  ?
 :o

...a whole new vehicle? EDIT: a whole new vehicle holding a moving stage or holding a 20 ton vehicle via friction with airbags. 
« Last Edit: 09/14/2014 03:30 PM by Exclavion »
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Offline Nindalf

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Re: Falcon 9 alternate landing options.
« Reply #4 on: 09/14/2014 04:19 PM »
I have been thinking of something along these lines, particularly in regards to the BFR and to the Blue Origin barge landing patent.

The BFR booster, if it is indeed powered by 9 Raptor engines, would have something like the thrust of a Falcon 9 taking off even while landing (unless there is some dramatic improvement in throttleability), and would therefore need something like a flame trench on the landing pad.  For the Falcon 9 as well, it is less than ideal to fire a powerful rocket engine directly into, and so near to, a solid landing pad.

And if the Blue Origin patent holds, if they want to land downrange, it can't be directly on a ship, under onboard propulsion.  Besides, there can be problems with the stability of the ship, particularly if the rocket can't land with exact precision in the center of the pad.

But rather than jet engines, I had in mind something like the Jetlev devices, which pump water up through a hose to a jet nozzle, for reasonably efficient hovering to limited altitude:


I think this is something close to minimum hardware for the task at hand.  I see no reason why this "catcher's mitt" or "jet crane" couldn't also transition the stage to a horizontal orientation, and either set it down directly on deck, or dock on a pair of cranes to the side of the ship.

The same system could be used in a landing pool for flyback landings.

Ideally, it wouldn't only be developed for this application, but it could also be used for launching and retrieving aircraft with a low stall speed from small ships or submarines, and for boarding operations.

Offline Adaptation

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Re: Falcon 9 alternate landing options.
« Reply #5 on: 09/15/2014 11:02 PM »
Your concept is functionally similar to a much simpler approach called mid air retrieval.  You snag a parachute a with an aircraft preferably a helicopter  and use that aircraft to gently land the rocket somewhere.  The largest helicopter in the world can barely handle an empty falcon 9 first stage, you would want to snag it while in a decent nearly matching the speed of the descending rocket.  Another caveat is that this it Russian made, no helicopter the us has could handle the mass required.

This is how satellite film was recovered in the early days.  It is also how the Genesis samples where supposed to be recovered but a manufacturing error caused the parachute to not deploy.   
« Last Edit: 09/16/2014 02:08 AM by Adaptation »

Offline RanulfC

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Re: Falcon 9 alternate landing options.
« Reply #6 on: 09/16/2014 09:48 PM »
Another more perhaps "pertinent" question might be; why are we so afraid of water? I mean really, the H1 of Saturn-1 fame was fired, dropped in a salt water pool, left for a day of so, pulled out, rinsed off with water, stored for a couple of weeks, pulled apart, checked, reassembled and fired with no issues what so ever. Granted it was "1950s" technology and robust as an elephant but really we can't do better today?
9/10ths of your "issues" are solved right there since its what SpaceX is practising at the moment.

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 CameronD

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Re: Falcon 9 alternate landing options.
« Reply #7 on: 09/16/2014 11:03 PM »
Another more perhaps "pertinent" question might be; why are we so afraid of water?

Because sea-water is corrosive to light metals and corrosion is an insidious beastie: (a) SpX are still in a testing phase and keen on future re-useability, so the last thing they need to worry about is failure due to undetected corrosion.  (b) Back in the 1950's things tended to be over-engineered a bit for other reasons, so corrosion wasn't necessarily on the critical path - but modern aerostructures are highly-engineered leaving little scope for off-nominal situations.. like a corroded bolt, etc.
With sufficient thrust, pigs fly just fine - however, this is not necessarily a good idea. It is hard to be sure where they are
going to land, and it could be dangerous sitting under them as they fly overhead.

Offline Kabloona

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Re: Falcon 9 alternate landing options.
« Reply #8 on: 09/19/2014 01:02 PM »
Also, water recovery is time-consuming and expensive. You have to send a ship, or ships, out a hundred or more miles to sea, then grapple and hoist whatever it is you're retrieiving, and if the weather is bad and seas or high, you have to wait until they calm down, which costs you another day or two. Then you waste another day steaming back to port, unloading, etc.

As a result of the somewhat troublesome Dragon recoveries in the Pacific, Elon said he didn't like "armadas."

Offline JasonAW3

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Re: Falcon 9 alternate landing options.
« Reply #9 on: 09/19/2014 08:32 PM »
Well, there's always the old Parachute and Airbags solution.

     As the stage comes back, after slowing to sub sonic speeds, pop a ballute from the top of the stage followed by a set of large drouge parachutes to slow the stage further. These will then pull out the mains, wghich will "unzip a sectionalong the side of the stageallowing a set of cables, (5) that are attached to the top and bottom of the stage and equadistant along the length of the stage.  This turns the stage on its side and 2 rows of airbags, (two sets per row) to each side of the now underside of the stage pop out.  As the stage landsthe lower set of airbags blow out, further cushioning the stage landing while the upper set of airbags support the mass of the stage until retreval.  In this scenerio, only the ballute and drougs are typically unrecoverable, although with a small GPS unit and determined presonnel, they could be retrieved.

The main issue here is that it would add several tons of mass, estimated at 2 tones each row of airbags and 3 tons for parachutes and rigging.  However, as this would dramatically reduce the amount of fuel required to return the stage to the ground, this should be well within the mass margin.

The parachutes can be repacked cabling reseated in their trench along the side of the stage the airbags replaced with tested and repacked airbags and stored in their slot along the side of the stagethe covering for each of the slots along the sides of the stage would likely be the quivelent of a biodegradable version of Gaffers tape.

If need be a single large parafoil could be used to steer the stage to a desired location and allow it to land fairly flatly as the foil would be steered to land with the wind rather than against it.  Also, a motorized attachment can be sadded between the parafoil and the cables attached to the stage, allowing the system to automatically reel in cable from one end when it is too low to level the stage for landing.  (And yes it would let out the slack if it started tilting the other way).

I could be off on the mass due to the size of the stage and exact location of the parachute/parafoil fulcrum point for the cables is likely to be closer to the engines. (Center of prone center of gravity).

At this point, offloading of any remaining fuels would be done before transit to reburbishment.  While this would slow turnaround operations, requiring replacement of the cables, parachutes and airbags, but the use of prepacked Parachutes, attachement cables (in a cellophane wrap) and prepacked airbags, (likely packed like the parachute system) should speed the replacement speed to similar levels as to what SpaceX wishes to have.

Likely the parachute package would have to have some sort of insulation covering, similar to the current parachute panel on the Dragon Capsule, to protect the parachutes fron the cold of space and the likely flames of the upper stage.

Note; this is assuming the stages were to land on either a very mobile ship, or on dry land.

As the rockets are currently prepped while lying on their side, this system would simply start from that point on.

The upper stages could be landed in a similar fashion using a combination of parachutes, landing gear and final landing thrust, (similar to the Russian Soyuz capsule, but with the main engine) for it's landings.  As the majority of the extra fuel that the upper stage would normally be used during the landing would now be available, a full hypersonic deceleration burn could be done reducing the stage speed during reentry, eliminating the need for a heavy duty TPS shield system.  Parachute swap out could be accomplished during turn around inspectionusing a prepacked parachute package.

True airline like turn around times will not likely be accomplished until a true SSTO type craft is developed, likely a VTOL craft similar to the DC-X design, or some form of lifting body that would use either a VTOHL or a true HTOL design.  At present only about 5% of a SSTO craft's total wet mass would be actual payload, as current technologies have pretty much reached the maximum capibilities of chemically fueled rockets.  near future developments may change this equation, but that is a discussion for another thread.
« Last Edit: 09/19/2014 08:33 PM by JasonAW3 »
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Offline douglas100

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Re: Falcon 9 alternate landing options.
« Reply #10 on: 09/19/2014 09:07 PM »

Well, there's always the old Parachute and Airbags solution...

Which is what Kistler planned to do. They even planned to do boost back and had what looked like a viable design for a re-usable second stage. As someone said on another thread, over the last 60 years of spaceflight, just about everything that's proposed for current projects has been thought of before. Almost.
Douglas Clark

Online ChrisWilson68

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Re: Falcon 9 alternate landing options.
« Reply #11 on: 09/19/2014 09:27 PM »
Why are you guys wanting to replace a great system (lightweight legs and a little extra propellant to fire the engines that are already there anyway -- easy, cheap, simple, and reliable) with much more complex and expensive systems?

Online TrevorMonty

Re: Falcon 9 alternate landing options.
« Reply #12 on: 09/19/2014 09:44 PM »
Your concept is functionally similar to a much simpler approach called mid air retrieval.  You snag a parachute a with an aircraft preferably a helicopter  and use that aircraft to gently land the rocket somewhere.  The largest helicopter in the world can barely handle an empty falcon 9 first stage, you would want to snag it while in a decent nearly matching the speed of the descending rocket.  Another caveat is that this it Russian made, no helicopter the us has could handle the mass required.

This is how satellite film was recovered in the early days.  It is also how the Genesis samples where supposed to be recovered but a manufacturing error caused the parachute to not deploy.
Does anybody know if Russians actually retrieved a booster using this method. The new Angara boosters (URM-1) at 10 mt would be ideal tests for this retrieval method. Russian has heavy lift helicopters that will lift >20mt.

Offline billh

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Re: Falcon 9 alternate landing options.
« Reply #13 on: 09/19/2014 11:06 PM »

Well, there's always the old Parachute and Airbags solution...

Which is what Kistler planned to do. They even planned to do boost back and had what looked like a viable design for a re-usable second stage. As someone said on another thread, over the last 60 years of spaceflight, just about everything that's proposed for current projects has been thought of before. Almost.

Isn't that how the CST-100 will land,  also?

Offline Patchouli

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Re: Falcon 9 alternate landing options.
« Reply #14 on: 09/20/2014 01:03 AM »
Another option which might be usable esp if Spacex went to a single engine on F9 would be to make a winged version like the recoverable Saturn SC-I concept.

This would be easier then making some custom vehicle to catch it and far safer then trying to capture it with a helicopter.

Though it would probably be a better solution for BFR then for F9.
« Last Edit: 09/20/2014 01:06 AM by Patchouli »

Offline llanitedave

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Re: Falcon 9 alternate landing options.
« Reply #15 on: 09/20/2014 01:11 AM »
Why are you guys wanting to replace a great system (lightweight legs and a little extra propellant to fire the engines that are already there anyway -- easy, cheap, simple, and reliable) with much more complex and expensive systems?

That's what armchair engineers do!  They don't have a choice in the matter.
"I've just abducted an alien -- now what?"

Offline Lars-J

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Falcon 9 alternate landing options.
« Reply #16 on: 09/20/2014 01:12 AM »

Another option which might be usable esp if Spacex went to a single engine on F9 would be to make a winged version like the recoverable Saturn SC-I concept.

This would be easier then making some custom vehicle to catch it and far safer then trying to capture it with a helicopter.

Though it would probably be a better solution for BFR then for F9.

Really? ::)
« Last Edit: 09/20/2014 01:12 AM by Lars-J »

Offline zodiacchris

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Re: Falcon 9 alternate landing options.
« Reply #17 on: 09/20/2014 01:30 AM »
How about the first stage lands on the ocean surface, floods it's tanks with sea water and comes back as a submarine? That way the tanks are nicely washed out ready for reuse, and the stage would be safe from bad weather and high waves when cruising back 200 feet below the surface. Of course there is always the risk of collision with whales, but a harpoon or torpedoes should cover that... 8)

Offline bilbo

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Re: Falcon 9 alternate landing options.
« Reply #18 on: 09/20/2014 11:08 PM »
Well, there's always Lithobraking!

Offline Damon Hill

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Re: Falcon 9 alternate landing options.
« Reply #19 on: 09/20/2014 11:31 PM »
There was a proposal to recover Saturn V first stages by blowing the forward LOX tank dome and have blowout ports near the bottom of the LOX tanks.  The stage would impact the ocean surface beneath a big(!) array of parachutes, the compressing air in the LOX tank serving as a kind of dashpot.  The stage would then float with the engines up in the air until the recovery ship arrived.  I don't know if a reentry burn was proposed; I assume a direct ballistic entry with guidance via the big aerodynamic fins.

I'm not sure the long and skinny Falcon 9 is robust enough for this, nor does it eliminate the logistics of recovery and transport.

Nah, direct return to the launch site and landing legs, is much more elegant, and doable.  And it's such a spectacle with powered liftoff _and_ landing.  Two or even three landings, if F9H is involved.  That way, if one of the returning stages prangs, we can all say "Good try!" so long as the payload makes it to orbit.

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