Recovery Chopper IX

Tipjet RecoveryOne of the objections to my Netting IX post was that there were very few or possibly no existing helicopters capable of carrying a recovered Falcon IV stage to a safe landing even if it were possible to catch the stage in the first place. There is a somewhat tested technique for building inexpensive special purpose helocopters capable of very large payload capacities.

The technique is the autogyro that generates lift off of the forward motion of the aerial vehicle without necessarily having any power directly applied through the shaft. Helicopters use a similar technique to autorotate in after losing power. Add the Roton type tip rockets and it is possible to build an arbitrarily large lift vehicle capable of lifting very large payloads, although at the expense of very high fuel consumption. An assembly consisting of a structural truss with several large helicopter blades with tipjets could carry payloads much larger than the Falcon IX to a safe landing.

The mission technique I see would be an airplane towing the recovery chopper to the projected recovery zone before the launch without using any of the chopper onboard propellant. As the reentering stage comes in, the airplane manuevers the towed vehicle as close as safely possible before casting loose to let the chopper catch the F IX stage while using the tip rockets. After the catch, the recovery chopper climbs to a safe altitude for a reconnect with the tow plane. The tow plane drags the autogyro mode chopper back to launch site and casts it loose again for the final landing of the stage in a safe cradle.

With good planning, it would seem possible that the recovery chopper would use ten minutes or less of full power and high fuel consumption during the operation with the tow plane supplying the vast majority of the propulsion needs.

Correction, the FIV on the cartoon was a mistake that should have been FIX. 

 

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johnhare

johnhare

I do construction for a living and aerospace as an occasional hobby. I am an inventor and a bit of an entrepreneur. I've been self employed since the 1980s and working in concrete since the 1970s. When I grow up, I want to work with rockets and spacecraft. I did a stupid rocket trick a few decades back and decided not to try another hot fire without adult supervision. Haven't located much of that as we are all big kids when working with our passions.
johnhare

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johnhare

About johnhare

I do construction for a living and aerospace as an occasional hobby. I am an inventor and a bit of an entrepreneur. I've been self employed since the 1980s and working in concrete since the 1970s. When I grow up, I want to work with rockets and spacecraft. I did a stupid rocket trick a few decades back and decided not to try another hot fire without adult supervision. Haven't located much of that as we are all big kids when working with our passions.
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19 Responses to Recovery Chopper IX

  1. ken anthony says:

    An autogyro being towed doesn’t reduce the total energy requirements. It just transfers them to the towing vehicle in the form of drag. Since the tow vehicle has to provide the energy anyway, why not let it do the capture? (Which involves matching velocities.) Especially since rotors would kind of get in the way for that kind of maneuver?

    If the purpose is to bring the spent rocket to a soft landing, again you don’t need rotors. The tow vehicle (although now not a tow vehicle) could carry uninflated balloons which it could inflate and release bringing the rocket to a soft landing.

  2. S says:

    Dirigibles, dude. Dirigibles can loiter on station forever.

  3. johnhare johnhare says:

    Fair enough. How much would it cost to develop one to do the job? Will the dirigible have the manueverability, speed and payload capacity to for the intended performance? How much for the ground handling gear and hangars compared to a chopper?

  4. S says:

    Not complicated at all compared to a helicopter. Do you know how hard it is to maintain a helicopter? Those things have really low availability rates.

    The best part about dirigibles is they can be neutrally buoyant at two altitudes when they pick up the extra mass of the stage. You can catch it at high altitude and then drift down to where it is neutrally buoyant at close to sea-level.

    If you use hydrogen as the lifting gas it would be a something like 3 million cubic feet for 60klbm of payload at sea-level. The Hindenburg was 7 million cubic feet, for reference.

  5. gbaikie says:

    “The best part about dirigibles is they can be neutrally buoyant at two altitudes when they pick up the extra mass of the stage. You can catch it at high altitude and then drift down to where it is neutrally buoyant at close to sea-level. ”

    So at 30,000 feet air density is about 1/4 at sea level. And at around
    45,000 feet it’s half of 30,000
    http://www.braeunig.us/space/atmos.htm
    So you catch [docking] at say 40,000 feet and with the added weight of rocket unable to support it from it’s buoyancy lift but descents until air density allows it to have enough lift.

    And it seems that if rocket power is used to brake at 40,000 ft, it should use less rocket fuel.

    With airship is at high elevation it will have less air resistance and can travel faster.
    Now say, uses a not very streamline shape such as donut shape.

    So donut outside diameter of 100 meter with 80 meter diameter donut hole, give 20 meter diameter circular section. Giving about 88,000 cubic meter. Or more 88 tons lift at seal level and about 22 tons at 30,000 ft [subtracting mass of airship from this total- balloon material, hydrogen/helium, engines, ballast, etc.]
    So have engines allowing airship when it’s neutral buoyant to rise and lower fairly fast. And enough power which allows to to get to precise location, so that when the rocket is braking, drops on it [or rocket flies thru donut hole] and cables on donut rim can be pulled so go straight across the donut’s diameter. Allowing it grab top of rocket stage at time when it’s matching velocity of stage.
    And once attached, using engine to descent to level where airship has enough lift to support the rocket payload.

  6. gbaikie says:

    “100 meter with 80 meter diameter donut hole”
    Rats. That should be 60 meters rather than 80 meters
    And mistakely used 80 number for buoyancy number, so rather 88 ton
    it’s 78 tons [and 19 tons].

  7. S says:

    Congratulations, you figured out my idea. 🙂 I’m glad you like it.

  8. gbaikie says:

    “Congratulations, you figured out my idea. 🙂 I’m glad you like it.”

    Yes. It seems the hard part would be to catch it.
    And doing this in a short time period and near a 100% success
    rate.
    It’s sort of combination of helicopter and balloon. Or combination of balloon a Osprey- Bell Boeing V-22 Osprey:
    https://en.wikipedia.org/wiki/Bell_Boeing_V-22_Osprey
    A upside down Osprey. Or maybe something resembling a flying balloon hovercraft.

  9. PeterH says:

    An airship descending after catching a load isn’t going to pick up a lot of lift as it descends. The lift gas compresses alongside the surrounding air. As long as the lift gas is in thermal equilibrium with the surrounding air lift is independent of altitude. It’ll pick up some temporary lift as the lift gas heats on compression. But you really need to drop ballast to match the new load or add more lift (heat lift gas, use a storeable lift gas like ammonia)

  10. Paul451 says:

    I’m not really sure what the autogyro/rocket-copter/thing adds to the system, other than complexity and expense. Aircraft can hook a parachute. It’s a fairly standard technique. Recent failures (such as Stardust) were the ‘chute not deploying, not the catch craft missing.

    Any prop or jet-aircraft can also deal with greater error in position, covering ground quicker than any rotor-craft (especially a giant multi-rotor craft capable of catching a rocket first stage.)

    And if you’re going to the expense of building a custom multi-rotor rocket-tip autogyro, why not just make a custom plane that can house the stage, like the Stratolaunch. (Ie, Stratolaunch’s mirror universe version, Stratocatch.)

    But since the original topic was options for SpaceX for their test program, before they’ve added landing legs to the next version of Falcon (F9 v1.2? Or v2.0?) It seems overkill to design an entirely bespoke vehicle for a mere test recovery. (Now if this were a NASA program…)

  11. gbaikie says:

    “I’m not really sure what the autogyro/rocket-copter/thing adds to the system, other than complexity and expense. Aircraft can hook a parachute. It’s a fairly standard technique. Recent failures (such as Stardust) were the ‘chute not deploying, not the catch craft missing.”

    Stardust: “Stardust was a 300-kilogram robotic space probe launched by NASA on February 7, 1999. ”
    http://en.wikipedia.org/wiki/Stardust_%28spacecraft%29
    First stage of falcon 9 [and there is plans for falcon heavy]:
    “The first stage propellant load is given as 553,000 lbs, 250,000 kg, and the dry weight as 30,000 lbs, 13,600 kg.”
    http://exoscientist.blogspot.com/2012/08/the-coming-sstos-falcon-9-v11-first.html

    A heavier than air, aircraft, would need to be traveling faster than it’s stall speed.

    “And if you’re going to the expense of building a custom multi-rotor rocket-tip autogyro, why not just make a custom plane that can house the stage, like the Stratolaunch. (Ie, Stratolaunch’s mirror universe version, Stratocatch.)”

    Ok, so take Stratolaunch, give a hull section large enough to house
    the diameter of first stage rocket. Falcon 9: “Diameter 3.66 m (12.0 ft)”. Now, what is stall speed of Stratolaunch. Perhaps we instead should use it’s takeoff speed.
    “I don’t know what the takeoff speed is of Stratolaunch; say 90 m/s (747 territory)”. 200 mph. Let’s say 150 to 200 mph.
    So essentially you fly slow, catch it, then accelerate plane so mass of the first stage, does not slow your airplane down causing a stall.
    Question is what is load or gee force of accelerating the first stage
    to the speed of Stratocatch. And one could have a longer cable length which allows you to decrease this load. And we can start by assuming the cable is strong enough to dead lift: 13,600 kg.
    And may have to stronger than this depending the expected peak load.
    So, starting with:
    steel cable thickness of 9/16″ 0.59 lb per foot lifts 15.3 metric
    http://www.ingersollrandproducts.com/lifting/winches/wireropechart.htm
    Of course you would probably something lighter and strong than steel cable, but it’s some place to start.
    And once caught the fish, you need to get it into the plane.
    And sure how. I suppose best way- is scratch having it enclosed, pull it so beneath the Stratocatch, attach another cable to other end of rocket stage. And pull it up so it’s hanging under aircraft, and then aircraft can land on a runway.

  12. Neil Shipley says:

    All of the above seems to go against the SpaceX KISS principle. They tried parachutes as the simplest approach and it didn’t work. Next up, landing rockets and legs. If that doesn’t work then I honestly can’t see a ‘catch’ system being next on their list. Just seems like you need too many things going right at the same time.
    SpaceX wants something where everything goes right nearly all the time. The above suggestions, while ingenious, don’t lend themselves to that unfortunately IMHO.
    Cheers,

  13. S says:

    I agree the solution is more complex, but the key equation here is how the added inert mass of a landing gear, landing propellant, and the shortened life of an engine that restarts affects the overall profitability of a vehicle. If I can shift all that recovery system weight onto an external element and get extra payload, this can reap huge rewards on a reusable vehicle.

    Allow me to break this down:
    Those landing gear are not light and will never be light. Anything that has to take 20-50 ft/s terminal velocity and absorb the impact energy of a 30klbm vehicle is going to way 10-15% of the overall vehicle inert vehicle mass. For a second stage, since the landing gear must be taken to apogee and back, this is the worst possible impact on the amount of payload you can carry because every pound of landing gear and landing propellant is lost payload. For a first stage it is a lower hit but every pound of landing gear mass translates into probably about .2 lbm of lost payload. For a 30klbm payload, that means we are talking something like 10-15% decrease in payload revenue. Why not use another system to get that revenue back and be more competitive in the long run?

    The other added cost of a propulsive landing is the fact that engines are usually life-limited by the number of starts they undergo. When you have a restart in your mission profile, you are cutting your engine life in half in terms of number of flights. Since engine costs are by far the majority of the vehicle costs (especially when you talk about 9 engine first stages), this is a big hit to the fixed cost of the vehicle. Restart an engine, as well as recycling and conditioning propellant conditioning in mid-air at high mach number IS NOT SIMPLE. If I can double the life of a vehicle and turn it into a ballistic RV with some aero control surfaces and just catch it downrange, that is very nice.

  14. gbaikie says:

    Neil Shipley
    Probably, right.
    How about 3 logging helicopters:
    “This tandem rotor design also enables all power to transfer through the main rotors for maximum lift. This aircraft weighs 22,000 pounds empty; it can lift 10,000 pounds.”
    http://www.fs.fed.us/t-d/programs/im/sound_measure/helo_helicopters.shtml
    Each Helicopter having max of two hundred meters of cable, attached central point which capable of grabbing the parachute.
    Getting logs off a mountain and bringing them to landing zone for logs is fairly similar function.
    Mainly what doing is stopping the stage from submersion in sea water and perhaps speeding up operations.

  15. Neil Shipley says:

    S: Ok, good points however there’s a couple of things that you’ve missed.
    Firstly, landing leg weights are likely a lot less than you’re calculating since they are being constructed of carbon fibre and probably honeycomb structure providing significantly more strength than that of any other material. I don’t have experience with landing legs however a carbon fibre mast on my trailer sailor is approx. 30% the weight of my old aluminium one. That’s home-built and over-engineered. You could probably get to half that with proper engineering.
    Secondly engine restarts. SpaceX have consistently stated that their engines have been designed with multiple restarts in mind. Not just a single restart but multiples. Evidence their M1D Vac and the old 1C they’re using on their GrassHopper vehicle. Restarts don’t cut your engine life in half. Again, it’s only the one engine their using for reentry and landing, the other 8 aren’t being used for the first stage. Second stage will be interesting to see since it’s a vacuum-specific engine. Don’t know enough about that to comment at this point.

    gbalkie: Still very complex idea and can’t see SpaceX liking it much. Lift isn’t the issue, complexity is. In addition, you’re trying to catch a moving beast, not a log sitting on the ground. Also the intial test(s) are into seawater but if they go well, then it’s onto landing on dry land, no seawater involved.

    Look, I’m not trying to be negative here. These are interesting discussions but most of the solutions presented have serious difficulties in getting to what would probably be SpaceX levels of reliability and simplicity. I’m not at all sure what would be next if SpaceX fail at their current approach but I also don’t think they’d give it up.
    Elon has mentioned that if he fails on reuse, he’ll consider his company a failure. That’s pretty strong coming from someone who, IMO has developed a competitive and sustainable commercial organisation which looks like significantly lowering launch costs such that basically no one in the existing launch business, government or private, can compete.
    Cheers

  16. Neil Shipley says:

    Hi S: gotta an estimated weight figure for the legs on F9R expected to be less than 2 tonne. Bit more than I expected. Don’t know how that fits with your calculations however given that the Merlin 1D considerably more powerful than the old 1C, that should help close the performance gap.
    Cheers.

  17. Paul451 says:

    gbaikie,
    “How about 3 logging helicopters”

    You can’t tie helicopters together with cables. The force vectors are ugly. (Hollywood has a lot to answer for.) You’d need to mount the engines/rotors/etc on something like John’s frame to deal with compressive horizontal loads.

    “so take Stratolaunch, give a hull section large enough to house
    the diameter of first stage rocket.”

    Stratolaunch carries its rocket-stages externally. That’s why I picked it.

    Re: Capture shock.
    The Stratolaunch is already being designed to go from carrying a fully fuelled two stage Falcon-5-class rocket, to instant zero mass on release. The Stratocapture reverses that, but has the advantage of being able to lessen the shock via descent trajectory, cable feed braking, and other shock-absorption methods that spread the shock out. I suspect the capture of an empty stage is within Stratolaunch’s structural capability.

    “A heavier than air, aircraft, would need to be traveling faster than it’s stall speed.”

    However, there’s no reason why it needs to be in a straight line. There are capture manoeuvres that involve a descending spiral, where the tip of the capture-cable is virtually stationary (it’s massively counter-intuitive. You expect the cable to swing wide due to centripetal force, but inertia actually pulls it to the centre.)

    Re: Transition from vertical to horizontal.

    Aerodynamics solves most of your problem here. The stage won’t be hanging vertically after capture. It will be dragged behind the aircraft, transitioning itself to horizontal. A couple of small tail-fins on the stage should be enough to stabilise that horizontal flight. Winch it in until the nose of the stage reaches the back of the cradle, lock the nose, then pull the stage through the cradle until it’s balanced properly for landing.

    Disclaimer: I consider all these proposals to be vastly worse than SpaceX’s proposal. Hideously complex, and vastly more expensive to develop and test. But in the spirit of John’s post, I’m just trying to suggest the most likely possibility.

  18. Dan S. says:

    How about this thought… the catch aircraft (1 to 3) would loiter near where the stage will cross some arbitrary altitude (say 15K’) under drogue, at which point the stage would fire up one engine (since it has very little fuel left) and hover at that altitude, plus possibly matching the horizontal velocity of he aircraft in the same direction of the aircraft. Said aircraft would catch this moving platform from above with the appropriate hook, stage will power down, and aircraft will carry it to landing site, drop it at say 3K’, and the single engine would restart again and land vertically as SpaceX currently envisions. Multiple catch aircraft only needed for multiple tries. Shock loads on catch aircraft greatly diminished due to near matching of horizontal velocities. ‘Engine restarts being bad for engine life’ argument mitigated since only one engine would be used.

  19. Paul451 says:

    S,
    “When you have a restart in your mission profile, you are cutting your engine life in half in terms of number of flights. Since engine costs are by far the majority of the vehicle costs (especially when you talk about 9 engine first stages), this is a big hit to the fixed cost of the vehicle.”

    It’s also worth point out that SpaceX won’t be restarting all 9 engines. Just the centre engine. Ie, if engines typically last 20 launches, and the restart does indeed halve the lifespan, you’ll need to replace the centre engine once. So the cost over the life of the stage increases from 9 engines-worth to 10, or 11% increase.

    If SpaceX drops their launch costs by an order of magnitude for reuse, say $1m per launch, then any capture scenario must not only eliminate engine restart but cost less than $110,000 per capture in order to complete.

    (However, I recall that an engine restart is part of their new pre-reentry slow-down procedure, so already unavoidable.)

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