Author Topic: ITS Booster Return - Final Landing and Mounting  (Read 14208 times)

Online sanman

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ITS Booster Return - Final Landing and Mounting
« on: 09/29/2016 10:14 AM »
As per Musk's presentation/animation, the returning ITS booster apparently lands on a mount, putting itself in position for quicker re-launch while also avoiding the mass penalty for onboard landing gear. Are there any other benefits to this idea?

While it's not clear whether this approach will withstand further design reviews, how robust/fault-tolerant is this approach, and how can it be made more robust/fault-tolerant (short of scrapping it altogether)?

What are the specific hazards or complicating factors that most contribute to risk of landing failure? How to avoid or prevent ground-coupled turbulence and backwash from causing problems? Would the standard flame trench/channel work?

Could air-bearings/maglev-bearings -- perhaps forming a cusp shape -- help to "funnel"/guide the rocket base onto the mount more smoothly?
You've still got some cryo-propellants in that landing booster -- could they be used to cool superconductive magnets in the rocket's aft/base to produce a suitable magnetic field for this purpose?
(Heh, sorry, still had some Hyperloop belches left in me)   ;)

Years ago, I wrote to a fellow in the UK who makes a toy called the Levitron, asking him if his idea could be adapted to making a "space-age" pen holder where the pen floats in an upright vertical orientation on your desk.
He replied to me that the idea was workable in principle, and that it would be dependent on rotation of the magnetic field for gyro-stabilization to offset any imperfections/asymmetries in the magnetic cusp. With high enough rotational speed of the field, enough gyrostabilization will be produced to keep a pen upright (and a rocket maybe?).



(Note: No actual Blue Origin tortoises were hurt in the making of that video)  ;)

Offline Kaputnik

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #1 on: 09/29/2016 09:18 PM »
One advantage of the plan is that the thrust of the booster even in landing mode is going to be substantial, and a flame trench with water deluge is going to be much more robust than a concrete apron.

Compared to F9, the booster will have a far wider range of thrust:weight options available, conceivably allowing it to hover or, depending on propellant, even have a wave-off and second attempt (perhaps a wave off and crash land on the beach is the best that actually realistic?)

Waiting for joy and raptor

Offline Lemurion

Re: ITS Booster Return - Final Landing and Mounting
« Reply #2 on: 09/29/2016 11:23 PM »
I see a number of trade-offs involved with the mount system vs. F9 landing legs. Without the mass limitations of flight hardware the mount system can be much more tolerant of hard landings, but less tolerant of off-center ones. Another advantage I see is that it eliminates the need to deal with taking the booster's weight off its legs and returning them to flight position. If nothing else, that can improve the launch cadence.

Online sanman

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #3 on: 09/30/2016 10:32 PM »
Can some clever geometry on the mount somehow cleverly channel the thrust of the booster to somehow force the booster to properly align itself onto the mount? Like some kind of Coanda effect?

Otherwise one bad misalignment could ruin your whole day.

Offline Bob Shaw

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #4 on: 09/30/2016 11:09 PM »
Imagine a sort of dance, where the returning first stage is the elephant and the launch platform is a mouse. The elephant does what it can do, but the launch platform can scurry around, fast and agile and smart.

The first stage has a job to do, which is to get within a low value of feet from the platform. It is limited by inertia, by wind, by sloshing fluids and by power and weight constraints. The platform is solidly attached to a planet, with as many Kw of energy as required. The answer, then, is to create a platform which can move, quickly and responsively and which will find itself in exactly the right place and at the right time to welcome the booster. The intelligence and manoeverability becomes distributed between both players, with as much of the heavy lifting as possible being left on the ground.

There are already examples of smart platforms: 3D printers. BAE Systems looked at a smart ship-borne Harrier recovery system some time ago (see also 1930s USAF airship parasite fighters and the 1950s Goblin parasitic escort jet fighter).
« Last Edit: 09/30/2016 11:10 PM by Bob Shaw »

Offline Saabstory88

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #5 on: 09/30/2016 11:10 PM »
One advantage of the plan is that the thrust of the booster even in landing mode is going to be substantial, and a flame trench with water deluge is going to be much more robust than a concrete apron.

Compared to F9, the booster will have a far wider range of thrust:weight options available, conceivably allowing it to hover or, depending on propellant, even have a wave-off and second attempt (perhaps a wave off and crash land on the beach is the best that actually realistic?)

A wave off and crash would be the least destructive as the booster could burn to prop depletion.

Offline Patchouli

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #6 on: 10/01/2016 05:16 AM »
Can some clever geometry on the mount somehow cleverly channel the thrust of the booster to somehow force the booster to properly align itself onto the mount? Like some kind of Coanda effect?

Otherwise one bad misalignment could ruin your whole day.

Maybe something like the hook and cable set up that was used for the X-13 Vertijet might be more tolerant of misalignment.
But still if something goes wrong you'll have a very bad day.
« Last Edit: 10/01/2016 05:18 AM by Patchouli »

Offline sevenperforce

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #7 on: 10/02/2016 07:23 PM »
Given that the fully-loaded and fully-fueled ITS only has a SL TWR of around 1.007 (given that the RVacs can't be used safely at SL), I'd anticipate the addition of a compact secondary LES inside the interstage. In an AMOS-6 style RUD, the LES would push the ITS clear of the fireball to give the SL raptors enough time to spin up, but on nominal launches, the LES would remain with the booster and return for reuse. That way you aren't lifting the LES all the way to orbit for no reason each time.

If that was the case, then it's conceivable that the LES could be configured to pull the booster free of the pad in a Very Bad Day situation. Moreso if it was a hypergolic LES rather than a SF one.

Online sanman

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #8 on: 10/02/2016 11:41 PM »
Given that the fully-loaded and fully-fueled ITS only has a SL TWR of around 1.007 (given that the RVacs can't be used safely at SL), I'd anticipate the addition of a compact secondary LES inside the interstage. In an AMOS-6 style RUD, the LES would push the ITS clear of the fireball to give the SL raptors enough time to spin up, but on nominal launches, the LES would remain with the booster and return for reuse. That way you aren't lifting the LES all the way to orbit for no reason each time.

If that was the case, then it's conceivable that the LES could be configured to pull the booster free of the pad in a Very Bad Day situation. Moreso if it was a hypergolic LES rather than a SF one.

Not that this has anything do with mount landings - but is it a given that there's no LES for Mars-side launches then?

Offline sevenperforce

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #9 on: 10/03/2016 12:16 AM »
Not that this has anything do with mount landings - but is it a given that there's no LES for Mars-side launches then?
Right. Elon said something to the effect that "if something goes wrong on the Mars launch you're screwed anyway."

Offline Lars-J

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #10 on: 10/03/2016 12:40 AM »
Not that this has anything do with mount landings - but is it a given that there's no LES for Mars-side launches then?
Right. Elon said something to the effect that "if something goes wrong on the Mars launch you're screwed anyway."

Exactly. But the ITS lander/ship has a lot of excess thrust capacity on Mars, so it could lose several engines and likely still make orbit.
« Last Edit: 10/03/2016 12:40 AM by Lars-J »

Offline rakaydos

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #11 on: 10/03/2016 12:53 AM »
Given that the fully-loaded and fully-fueled ITS only has a SL TWR of around 1.007 (given that the RVacs can't be used safely at SL), I'd anticipate the addition of a compact secondary LES inside the interstage. In an AMOS-6 style RUD, the LES would push the ITS clear of the fireball to give the SL raptors enough time to spin up, but on nominal launches, the LES would remain with the booster and return for reuse. That way you aren't lifting the LES all the way to orbit for no reason each time.

If that was the case, then it's conceivable that the LES could be configured to pull the booster free of the pad in a Very Bad Day situation. Moreso if it was a hypergolic LES rather than a SF one.

Not that this has anything do with mount landings - but is it a given that there's no LES for Mars-side launches then?
Where would you abort to?

Offline envy887

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #12 on: 10/03/2016 02:54 AM »
To survive an AMOS type anomaly the LAS has to separate the crew from the upper stage. There is no reason or feasible way to abort full 2000 tonne methalox tanks off a pad

Such a LAS would be of little use in returning the booster.

I heard that SpaceX is working on 10-tonne class pressure-fed gaseous methalox thrusters for the ITS orbiter RCS. A set of those might be useful for fine control of the returning booster. Similar to how N2 thrusters are used on F9, but 100s of times more powerful.

Offline Robotbeat

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #13 on: 10/03/2016 03:16 AM »
Given that the fully-loaded and fully-fueled ITS only has a SL TWR of around 1.007 (given that the RVacs can't be used safely at SL), I'd anticipate the addition of a compact secondary LES inside the interstage. In an AMOS-6 style RUD, the LES would push the ITS clear of the fireball to give the SL raptors enough time to spin up, but on nominal launches, the LES would remain with the booster and return for reuse. That way you aren't lifting the LES all the way to orbit for no reason each time.

If that was the case, then it's conceivable that the LES could be configured to pull the booster free of the pad in a Very Bad Day situation. Moreso if it was a hypergolic LES rather than a SF one.

Not that this has anything do with mount landings - but is it a given that there's no LES for Mars-side launches then?
Where would you abort to?
Surface or orbit. In either case, you'll have a budding which could send a rescue mission to you.

Remember, this isn't Apollo. There would be hundreds or thousands of people on Mars.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Lars-J

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #14 on: 10/03/2016 04:25 AM »
Given that the fully-loaded and fully-fueled ITS only has a SL TWR of around 1.007 (given that the RVacs can't be used safely at SL), I'd anticipate the addition of a compact secondary LES inside the interstage. In an AMOS-6 style RUD, the LES would push the ITS clear of the fireball to give the SL raptors enough time to spin up, but on nominal launches, the LES would remain with the booster and return for reuse. That way you aren't lifting the LES all the way to orbit for no reason each time.

If that was the case, then it's conceivable that the LES could be configured to pull the booster free of the pad in a Very Bad Day situation. Moreso if it was a hypergolic LES rather than a SF one.

Not that this has anything do with mount landings - but is it a given that there's no LES for Mars-side launches then?
Where would you abort to?
Surface or orbit. In either case, you'll have a budding which could send a rescue mission to you.

Remember, this isn't Apollo. There would be hundreds or thousands of people on Mars.

Yes, but the point is that the *whole* ship either aborts to orbit or lands downrange. There is nothing in the middle. Any detachable cabin essentially has to be a mini-ITS inside an ITS. Mars is not Earth, it is not practical.

Remember, this is an architecture to start colonization of Mars. Once a colony exists, there will be other (perhaps safer?) crew vehicles available, and they might have more abort options.

Offline RobLynn

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #15 on: 10/03/2016 09:20 AM »
Imagine a sort of dance, where the returning first stage is the elephant and the launch platform is a mouse. The elephant does what it can do, but the launch platform can scurry around, fast and agile and smart.

The first stage has a job to do, which is to get within a low value of feet from the platform. It is limited by inertia, by wind, by sloshing fluids and by power and weight constraints. The platform is solidly attached to a planet, with as many Kw of energy as required. The answer, then, is to create a platform which can move, quickly and responsively and which will find itself in exactly the right place and at the right time to welcome the booster. The intelligence and manoeverability becomes distributed between both players, with as much of the heavy lifting as possible being left on the ground.

There are already examples of smart platforms: 3D printers. BAE Systems looked at a smart ship-borne Harrier recovery system some time ago (see also 1930s USAF airship parasite fighters and the 1950s Goblin parasitic escort jet fighter).

I like this.  Could be done with a barge floating on a shallow pool with a few high-powered winches arrayed around it to rapidly position it.  Or perhaps a really big air-bearing supported cradle positioned by winches.

How about shooting high pressure jets of water up into the unused-at-landing outer ring of engine nozzles? very fast to steer the water nozzles, 'soft', and makes use of existing thrust structure to take peak landing deceleration loads.
I'm a "glass is twice as big as it needs to be" kinda guy

Offline Ludus

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #16 on: 10/04/2016 04:12 PM »
It would let a sea platform handle the entire workflow. ITS spaceport platforms could be built in shipyards like big oil platforms and towed into position. Tankers would land on the platform along with boosters for rapid reuse. Cargo or Passenger variants might be processed on shore and floated out to be lifted into place by the crane.

A spaceport might have several launch/landing platforms off the coast.

Offline jsgirald

Re: ITS Booster Return - Final Landing and Mounting
« Reply #17 on: 10/04/2016 06:17 PM »
Clearly this is the most insane part of the plan.
I mean, what's wrong with a reinforced landing pad, a large flatbed and a very big crane?
Clearly Musk has heard about risk reduction, and strongly disapproves ...  :)
"For every expert, there is an equal and opposite expert".

Offline Jim

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #18 on: 10/04/2016 06:19 PM »
Imagine a sort of dance, where the returning first stage is the elephant and the launch platform is a mouse. The elephant does what it can do, but the launch platform can scurry around, fast and agile and smart.

The first stage has a job to do, which is to get within a low value of feet from the platform. It is limited by inertia, by wind, by sloshing fluids and by power and weight constraints. The platform is solidly attached to a planet, with as many Kw of energy as required. The answer, then, is to create a platform which can move, quickly and responsively and which will find itself in exactly the right place and at the right time to welcome the booster. The intelligence and manoeverability becomes distributed between both players, with as much of the heavy lifting as possible being left on the ground.

There are already examples of smart platforms: 3D printers. BAE Systems looked at a smart ship-borne Harrier recovery system some time ago (see also 1930s USAF airship parasite fighters and the 1950s Goblin parasitic escort jet fighter).

I like this.  Could be done with a barge floating on a shallow pool with a few high-powered winches arrayed around it to rapidly position it.  Or perhaps a really big air-bearing supported cradle positioned by winches.

How about shooting high pressure jets of water up into the unused-at-landing outer ring of engine nozzles? very fast to steer the water nozzles, 'soft', and makes use of existing thrust structure to take peak landing deceleration loads.

None of that is viable in the real world

Offline Kansan52

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #19 on: 10/04/2016 06:34 PM »
Clearly this is the most insane part of the plan.
I mean, what's wrong with a reinforced landing pad, a large flatbed and a very big crane?
Clearly Musk has heard about risk reduction, and strongly disapproves ...  :)

Maybe the launch site is built to handle the landing and the tower crane does a final position after landing.

Offline jsgirald

Re: ITS Booster Return - Final Landing and Mounting
« Reply #20 on: 10/04/2016 06:38 PM »

I like this.  Could be done with a barge floating on a shallow pool with a few high-powered winches arrayed around it to rapidly position it.  Or perhaps a really big air-bearing supported cradle positioned by winches.

None of that is viable in the real world

Dunno about the rest, but the pool thing was floated (sorry  :-[) by Boeing's SPS SSTO back in 1978.
It lacked the barge, though, rockets landed directly on the water.
"For every expert, there is an equal and opposite expert".

Offline Ludus

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #21 on: 10/04/2016 07:21 PM »
It is the ultimate in rapid reusability and that makes it an appealing goal. The most efficient possible system of getting a reusable booster from landing to back on the launch pad is obviously to have it land on the launch pad.

This seems like the sort of thing they'd experiment with so maybe there will be legless grasshoppers in the near future and then structures on the LZ pads for real falcon boosters to lock into on landing.

They have plenty of recovered boosters to play with now so I suppose that's easier than purpose building them.
« Last Edit: 10/04/2016 07:25 PM by Ludus »

Online sanman

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #22 on: 10/04/2016 07:49 PM »
It is the ultimate in rapid reusability and that makes it an appealing goal. The most efficient possible system of getting a reusable booster from landing to back on the launch pad is obviously to have it land on the launch pad.

This seems like the sort of thing they'd experiment with so maybe there will be legless grasshoppers in the near future and then structures on the LZ pads for real falcon boosters to lock into on landing.

They have plenty of recovered boosters to play with now so I suppose that's easier than purpose building them.

When you put it that way, then perhaps this legless-landing-on-mount idea could be used to improve their regular terrestrial satellite launch operations - ie. SpaceX's "day job" - and thus be justifiable as a business investment.

And if they make it work successfully with Grasshopper and even for pads at the Cape, then could this tech even be used on the barges themselves? Or is that overkill? If it could be used to secure the landed F9 booster immediately on the barge, without having to send in a crew to quickly staple down those legs, then perhaps it could be justifiable there too.

Offline NotOnImpact

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #23 on: 10/04/2016 08:59 PM »
Can some clever geometry on the mount somehow cleverly channel the thrust of the booster to somehow force the booster to properly align itself onto the mount? Like some kind of Coanda effect?

Otherwise one bad misalignment could ruin your whole day.

I had to watch the video several times to catch this -- but Elon mentions that the purpose of the fins at the bottom of the rocket are to perfectly align the rocket on the pad on landing.   I would imagine that that would mean in the rotational orientation -- not so much laterally.

So imagine three slots that are wider at the top and narrow as they go down.  They wouldn't interfere on the launch of course.  And it would have the effect of guiding the rocket to an exact positions so that the hold-down clamps could engage appropriately.

Offline RanulfC

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #24 on: 10/04/2016 09:31 PM »
Can some clever geometry on the mount somehow cleverly channel the thrust of the booster to somehow force the booster to properly align itself onto the mount? Like some kind of Coanda effect?

Otherwise one bad misalignment could ruin your whole day.

I had to watch the video several times to catch this -- but Elon mentions that the purpose of the fins at the bottom of the rocket are to perfectly align the rocket on the pad on landing.   I would imagine that that would mean in the rotational orientation -- not so much laterally.

So imagine three slots that are wider at the top and narrow as they go down.  They wouldn't interfere on the launch of course.  And it would have the effect of guiding the rocket to an exact positions so that the hold-down clamps could engage appropriately.

It's a nice idea but I'm going to wait until they can show me a LOT more details on how they think this might work before I assume it's going to happen. That is some significantly detailed maneuvering of a rocket powered vehicle and pad playing VERY nice together which is tough enough even with something like a small drone. The fins would have to be armored and structural VERY robust to take even a glancing blow or scrape with the mass involved. (And even then how do you actually tell that no damage through the entire structure was taken during the event?)

You're talking very much a 'hover-settle' maneuver computer controlled or no.

Randy
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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 RanulfC

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #25 on: 10/04/2016 09:38 PM »

I like this.  Could be done with a barge floating on a shallow pool with a few high-powered winches arrayed around it to rapidly position it.  Or perhaps a really big air-bearing supported cradle positioned by winches.

None of that is viable in the real world

Dunno about the rest, but the pool thing was floated (sorry  :-[) by Boeing's SPS SSTO back in 1978.
It lacked the barge, though, rockets landed directly on the water.

As noted the Boing "Big Onion" booster was very different from the ITS being short, squat and immune from 'tip-over' events. The reason it landed IN the pool was because the settling motion of any platform for such a large vehicle is significant. (In other words the barge could 'ground' if the landing is significantly off-center)

Mostly though I suspect Jim means that using winches is not a viable option. You'd use azmi-pods like the SpaceX barge already has rather than mechanical devices as more practical BUT in general if you can get the booster close enough you don't need the pool and CAN use something like the 'positioning' table suggested earlier built into the pad. (I'm not sure it's actually going to work though as that's a lot of gear exposed to a lot of heat and vibration just to save some mass instead of landing gear. I don't think the scheme is going to work as well as they expect toward reducing their turn around time)

I have a suspicion we'd be looking at an off-shore pad set up rather than actually using the Cape for the majority of flights.

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 RanulfC

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #26 on: 10/04/2016 09:41 PM »
Given that the fully-loaded and fully-fueled ITS only has a SL TWR of around 1.007 (given that the RVacs can't be used safely at SL), I'd anticipate the addition of a compact secondary LES inside the interstage. In an AMOS-6 style RUD, the LES would push the ITS clear of the fireball to give the SL raptors enough time to spin up, but on nominal launches, the LES would remain with the booster and return for reuse. That way you aren't lifting the LES all the way to orbit for no reason each time.

If that was the case, then it's conceivable that the LES could be configured to pull the booster free of the pad in a Very Bad Day situation. Moreso if it was a hypergolic LES rather than a SF one.

Not that this has anything do with mount landings - but is it a given that there's no LES for Mars-side launches then?
Where would you abort to?
Surface or orbit. In either case, you'll have a budding which could send a rescue mission to you.

Remember, this isn't Apollo. There would be hundreds or thousands of people on Mars.

You won't have more than dozens to maybe a couple of hundred for a while so any 'abort' is going to leave someone stranded on the surface with a wrecked ship and maybe the assistance of a 'buddy' flight to pick them up. Of course that might mean both crews end up on non-optimum return timetables so it will behoove early flights to fly short on crew just in case.

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 Martin.cz

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #27 on: 10/04/2016 10:40 PM »
I've been thinking about how to land the booster since seeing the video & slides for the first time and I think a combination off powerful RSC thrusters and an "active pad" can accomplish that in a rather efficient manner.

The 10-ton class gaseous oxygen/methane thrusters mentioned up-thread could be the ones used & should allow a much better & finer control authority than the basic nitrogen based RCS on the Falcon N9. Also - I guess they could basically run of the autogenous pressurization system as long as at least some raptors are running, so should have a plenty of fuel & oxidizer available during the final landing phase.

As for the "active pad" - the basic idea is that the launch mount elements would not be fixed in position but movable in multiple axes and with some limited reach - kinda like a giant cross-over between the Soyuz launch mount element and a robotic hand.

During the final stage of the landing the booster would maneuver as closely as possible to the correct landing orientation and attitude and then the movable launch mount elements would latch to their corresponding hold down points, correct any remaining deviations in booster rotation/position/angle and let it gently settle down as the landing raptors wind down.

I say settle-down as I don't thinks you want to hold a 275+ tons booster - it should be much easier to rate the launch mount element for high loading in the full-down position (they can be supported from below, etc.) than in the "agile" mode when they move in multiple axes.

And if you can make this work - you are ready to quickly fly again once the booster lands as it would be already connected to the launch mount kinda by definition in this case. No need to crane it/move it from a landing pad, etc. :) Just connect the umbilicals, load the consumable & place an ITS on top and you are ready to go. :)

Offline jsgirald

Re: ITS Booster Return - Final Landing and Mounting
« Reply #28 on: 10/05/2016 09:40 AM »
I can live with the idea of this ginormous Booster, what I really don't get is the logistics of the plan.
I mean, they'r basically saying that the booster becomes part of the launch pad. It makes no sense to have more than one booster per pad.

Let's look at it:
1) Booster launches ITS, it all goes to plan (meaning the SC reaches the intended orbit), only a couple Raptors fail, nothing too serious.
2) Booster goes back to launch pad ok. What happens now?
- a) We've got the power, ignore it and keep launching away.
- b) Repair/replace the failing engines ON THE PAD?
- c) Take the thing to a nearby workshop for repair and use your backup booster (there go your previous savings in ground handling equipment and crew).

If the answer is a) you assume some uncomfortable risk, if b) your whole system has to stop working for an unknown period and if c) then you are really not saving with this return to launch mount thingy. So what is the point anyway?

And this is the most benign hiccup I can think of right now (nothing went bang ...)
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Offline guckyfan

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #29 on: 10/05/2016 01:43 PM »

Let's look at it:
1) Booster launches ITS, it all goes to plan (meaning the SC reaches the intended orbit), only a couple Raptors fail, nothing too serious.
2) Booster goes back to launch pad ok. What happens now?
- a) We've got the power, ignore it and keep launching away.
- b) Repair/replace the failing engines ON THE PAD?
- c) Take the thing to a nearby workshop for repair and use your backup booster (there go your previous savings in ground handling equipment and crew).

Replacing engines on the pad is not that hard. They said once for Falcon 9 access to engines is easier vertical on the pad than horizontal.

They will need means of moving the booster anyway. So they can land on the launch mount and move it away. Or they can build another dedicated landing mount. Much easier and cheaper than the launch/landing mount. Having a second booster available would be very reassuring during a Mars launch campaign.

Offline rsdavis9

Re: ITS Booster Return - Final Landing and Mounting
« Reply #30 on: 10/05/2016 02:46 PM »
How quick can you translate horizontally with a 10 ton rcs thruster top and bottom?
How about with multiple 10 ton thrusters?
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Offline jsgirald

Re: ITS Booster Return - Final Landing and Mounting
« Reply #31 on: 10/05/2016 05:41 PM »
Replacing engines on the pad is not that hard. They said once for Falcon 9 access to engines is easier vertical on the pad than horizontal.

They will need means of moving the booster anyway. So they can land on the launch mount and move it away. Or they can build another dedicated landing mount. Much easier and cheaper than the launch/landing mount. Having a second booster available would be very reassuring during a Mars launch campaign.

That's more or less the point I was trying to get across, why bother with the launch/land mount? There's nothing to gain other than a pretty video, and a high risk of unplanned decommision of your launch pad if things go pear shaped.
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Offline guckyfan

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #32 on: 10/05/2016 06:45 PM »
That's more or less the point I was trying to get across, why bother with the launch/land mount? There's nothing to gain other than a pretty video, and a high risk of unplanned decommision of your launch pad if things go pear shaped.

There is everything to gain in simplicity, cost reduction and speed of operations. The risk to the pad is small as the returning vehicle contains very little fuel. Even worst case they can get the pad operational again quickly. See their turn around of the ASDS.

Offline jsgirald

Re: ITS Booster Return - Final Landing and Mounting
« Reply #33 on: 10/05/2016 07:33 PM »
That's more or less the point I was trying to get across, why bother with the launch/land mount? There's nothing to gain other than a pretty video, and a high risk of unplanned decommision of your launch pad if things go pear shaped.

There is everything to gain in simplicity, cost reduction and speed of operations. The risk to the pad is small as the returning vehicle contains very little fuel. Even worst case they can get the pad operational again quickly. See their turn around of the ASDS.

But if they need to be able to move the thing on the ground, and will probably have a spare landing area and a backup booster, where are the savings?

And a 200 t cylinder smashing into your pad is bound to cause some damage even if it's empty.
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Offline Jim

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #34 on: 10/05/2016 07:57 PM »
[
There is everything to gain in simplicity, cost reduction and speed of operations. The risk to the pad is small as the returning vehicle contains very little fuel. Even worst case they can get the pad operational again quickly. See their turn around of the ASDS.

Not a relevant analogy, AMOS-5 is closer

Offline guckyfan

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #35 on: 10/05/2016 07:59 PM »

There is everything to gain in simplicity, cost reduction and speed of operations. The risk to the pad is small as the returning vehicle contains very little fuel. Even worst case they can get the pad operational again quickly. See their turn around of the ASDS.

But if they need to be able to move the thing on the ground, and will probably have a spare landing area and a backup booster, where are the savings?

And a 200 t cylinder smashing into your pad is bound to cause some damage even if it's empty.

Some structure that is able to move the booster slowly is not in any way similar in cost and complexity to a system required for fast turn around. Same for a landing mount. It is vastly simpler and cheaper than a launch mount.

For a spare booster they may or may not decide they need one. IMO they will need one as long as they have only one launch pad. Maybe not, when they have two or more. I guess for the safety of the Mars settlement they will need more than one launch pad sooner rather than later. Initially they can have emergency spares on Mars so they can survive if supplies don't arrive for one synod.

Offline rsdavis9

Re: ITS Booster Return - Final Landing and Mounting
« Reply #36 on: 10/05/2016 08:24 PM »
If they can reliably get to 1 meter, like we have seen on the falcon 9. I see no reason with added hover time they can't get to cm's.
I was thinking about the rcs gaseous thrusters.
So
10 ton thruster.
100 ton vehicle
10/100 = accel
accel * t = v
t=1 sec
so 10/100*1=.1 m/s or 10 cm/s
So just translate horizontally while staying straight up and down.
So the key is to have an engine(s) which can exactly cancel weight allowing hover.
Small rcs's capable of shoving the vehicle around until we have mate.
 
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Offline jsgirald

Re: ITS Booster Return - Final Landing and Mounting
« Reply #37 on: 10/05/2016 08:32 PM »
Some structure that is able to move the booster slowly is not in any way similar in cost and complexity to a system required for fast turn around. Same for a landing mount. It is vastly simpler and cheaper than a launch mount.

Well, if it's kind of cheap and simple, why bother with the other option?
In other words, how fast do you want your turnaround?

Quote
For a spare booster they may or may not decide they need one. IMO they will need one as long as they have only one launch pad. Maybe not, when they have two or more. I guess for the safety of the Mars settlement they will need more than one launch pad sooner rather than later. Initially they can have emergency spares on Mars so they can survive if supplies don't arrive for one synod.

The sequence might look like this:

Booster1 + ITS crew launch Booster2 on landing pad (doubling as holding area)
Booster1 to landing pad Booster2 moving to launch pad
Booster1 refited Booster2 integrated with tanker and refueled
Booster1 ready at landing pad Booster2 with tanker launched

I doubt you can go any faster than that, and I don't think they'll need to, anyway.
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Offline RoboGoofers

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #38 on: 10/05/2016 08:38 PM »
Now that they know they can easily land back at the launch site, I suspect we will see the drone ships soon modified to support ITS Booster-like landing for F9 and FH core. They're the perfect experimental landing site, and will only be used for high energy launches, which will benefit from dropping the legs.


Offline rsdavis9

Re: ITS Booster Return - Final Landing and Mounting
« Reply #39 on: 10/05/2016 08:45 PM »
Now that they know they can easily land back at the launch site, I suspect we will see the drone ships soon modified to support ITS Booster-like landing for F9 and FH core. They're the perfect experimental landing site, and will only be used for high energy launches, which will benefit from dropping the legs.

Merlins can't throttle enough.
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Offline RoboGoofers

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #40 on: 10/05/2016 08:52 PM »
Merlins can't throttle enough.

Enough for what?

Offline starsilk

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #41 on: 10/05/2016 09:06 PM »
I can live with the idea of this ginormous Booster, what I really don't get is the logistics of the plan.
I mean, they'r basically saying that the booster becomes part of the launch pad. It makes no sense to have more than one booster per pad.

Let's look at it:
1) Booster launches ITS, it all goes to plan (meaning the SC reaches the intended orbit), only a couple Raptors fail, nothing too serious.
2) Booster goes back to launch pad ok. What happens now?
- a) We've got the power, ignore it and keep launching away.
- b) Repair/replace the failing engines ON THE PAD?
- c) Take the thing to a nearby workshop for repair and use your backup booster (there go your previous savings in ground handling equipment and crew).

If the answer is a) you assume some uncomfortable risk, if b) your whole system has to stop working for an unknown period and if c) then you are really not saving with this return to launch mount thingy. So what is the point anyway?

you make savings in the nominal case (which is hopefully the majority of launches). in the off-nominal case, you divert the returning booster to the 'service' landing pad and work on it there (or abort into the ocean if it can't be landed).

in the nominal case, you refuel, relaunch.

with 9/10 nominal launches, you've made huge savings of time, manpower, etc.

Offline rsdavis9

Re: ITS Booster Return - Final Landing and Mounting
« Reply #42 on: 10/05/2016 09:08 PM »
Merlins can't throttle enough.

Enough for what?

To hover for the tight fit to a landing/launch pad.
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Offline RoboGoofers

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #43 on: 10/05/2016 09:27 PM »
Merlins can't throttle enough.
Enough for what?
To hover for the tight fit to a landing/launch pad.

That's what I thought you meant. Elon never said hover. He only said lateral thrusters would likely be enough to provide the precision needed.
« Last Edit: 10/05/2016 09:28 PM by RoboGoofers »

Offline RanulfC

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #44 on: 10/05/2016 09:33 PM »
There is everything to gain in simplicity, cost reduction and speed of operations. The risk to the pad is small as the returning vehicle contains very little fuel. Even worst case they can get the pad operational again quickly. See their turn around of the ASDS.

The first part is an assumption that unfortunately isn't supported by any evidence available. Granted we have no transport analogy in Earth-bound transportation, (as I keep pointing out) but in general the ability to move the 'transport' out of the flight queue in case of issues is a well known and proven process. There is very little reason to make the assumption that this concept will change the parameters given, (simplicity, cost and speed) as suggested and every reason to think it won't.

Secondly the risk is higher than you seem to think as a loaded if not fueled ITS ship is sitting in the area of effect of a failed recovery scenario so the amount of propellant on the booster is immaterial. Secondly you then have to not only clean up, (and despite the idea that the ASDS is an applicable analogy as Jim points out it isn't since it has no launch support equipment onboard) and effect repairs you now have to move, mount, and load propellant on a NEW booster which arguably you could have done while landing the first booster somewhere else and prepping the next flight in line.


There is everything to gain in simplicity, cost reduction and speed of operations. The risk to the pad is small as the returning vehicle contains very little fuel. Even worst case they can get the pad operational again quickly. See their turn around of the ASDS.

But if they need to be able to move the thing on the ground, and will probably have a spare landing area and a backup booster, where are the savings?

And a 200 t cylinder smashing into your pad is bound to cause some damage even if it's empty.

Some structure that is able to move the booster slowly is not in any way similar in cost and complexity to a system required for fast turn around. Same for a landing mount. It is vastly simpler and cheaper than a launch mount.

Your argument ignores the fact they are the SAME structure. The landing mount IS the launching mount and it contains all the requisite systems which are in danger of damage or destruction from a failure either during launch OR landing. It effectively saves you 'nothing' overall except the idea that you somehow save by not having a means to move the booster which you HAVE to have in the first place to get the booster to the pad.

The funny thing is we've argued AGAINST this type of idea for 'saving' time/money/etc dozens of times in Advanced Concepts but now that Elon has suggested it somehow it is now a viable idea :) Sorry but Elon himself says he gets carried away sometimes and this is one of those items.

Quote
For a spare booster they may or may not decide they need one. IMO they will need one as long as they have only one launch pad. Maybe not, when they have two or more. I guess for the safety of the Mars settlement they will need more than one launch pad sooner rather than later. Initially they can have emergency spares on Mars so they can survive if supplies don't arrive for one synod.

Uhm that's backwards actually. They are going to require multiple boosters even if they only have one launch pad because the chances are very good that they will in fact need one at some point and the whole plan fails if they don't have one. The more launch sites the more boosters and they overall costs go down the more they fly and the more they fly the more they need primary and back up boosters so they won't ever have 'just one' outside of testing.

Randy
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Online matthewkantar

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #45 on: 10/05/2016 09:40 PM »
The pad support equipment can be hardened so that a failure is not as damaging. 42 engines means throttling can be arbitrarily low, so hover is no problem. The booster itself can start off with large margins until the requirements for landing are well understood.

This isn't the big deal everyone is making it out to be, I look forward to seeing this happen.

I also believe the booster will do all of the aiming and correcting, having the pad in motion as well is a no no, in my opinion.

Matthew

Offline mvpel

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #46 on: 10/05/2016 09:45 PM »
To hover for the tight fit to a landing/launch pad.

If you have enough control authority, you can guide a rocket through a kitchen window. Undoubtedly SpaceX's work on autonomous docking for Crew Dragon would come in handy. You could even paint a docking target pattern on the launch/landing pad, though I suppose designing a downward-facing camera for a terrain-matching guidance system would be a particularly thorny engineering challenge given the environment at the hot end of the rocket. They do grow diamond panes at the next center south of mine, so who knows.

And in addition, the landing mount doesn't necessarily have to be a tight fit - it can have its own sensors and cameras to adapt itself to the incoming booster.

(I wonder if 20% of one Raptor is less than the mass of a mostly-empty ITS booster?)
« Last Edit: 10/05/2016 09:47 PM by mvpel »
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Offline Robotbeat

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #47 on: 10/06/2016 01:15 AM »
Given that the fully-loaded and fully-fueled ITS only has a SL TWR of around 1.007 (given that the RVacs can't be used safely at SL), I'd anticipate the addition of a compact secondary LES inside the interstage. In an AMOS-6 style RUD, the LES would push the ITS clear of the fireball to give the SL raptors enough time to spin up, but on nominal launches, the LES would remain with the booster and return for reuse. That way you aren't lifting the LES all the way to orbit for no reason each time.

If that was the case, then it's conceivable that the LES could be configured to pull the booster free of the pad in a Very Bad Day situation. Moreso if it was a hypergolic LES rather than a SF one.

Not that this has anything do with mount landings - but is it a given that there's no LES for Mars-side launches then?
Where would you abort to?
Surface or orbit. In either case, you'll have a budding which could send a rescue mission to you.

Remember, this isn't Apollo. There would be hundreds or thousands of people on Mars.

Yes, but the point is that the *whole* ship either aborts to orbit or lands downrange. There is nothing in the middle. Any detachable cabin essentially has to be a mini-ITS inside an ITS. Mars is not Earth, it is not practical.
Soyuz-like landing thrusters, yeah, but doesn't have to be anything like ITS. I've thought a lot about this. I've done the calculations for just what kind of rocket you'd need to accomplish this sort of abort. It's possible, perhaps even practical, even though many like to assert it's not..
Quote
Quote
Remember, this is an architecture to start colonization of Mars. Once a colony exists, there will be other (perhaps safer?) crew vehicles available, and they might have more abort options.
No, this is the vehicle to get to $200k/person, which is well after the colony /exists/.
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Online darkenfast

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #48 on: 10/06/2016 08:30 AM »
A few observations:

1. A good deal of the "miss" on Falcon 9 first-stage recoveries appears to be drift at the last second as the engines start their shutdown.  That won't happen with the "capture" method and, of course, they will have a lot more experience by then.

2. Only the center engines will be firing and there will be a much lower lever of blast going through the pad opening and flame trench.  Because of the water suppression system and the fact that the pad hardware is above the trench, I think the loads of this rocket's return will be easier to handle at the pad than at a landing field such as they now use at the Cape.

3.  While there is only one launch complex, there may be multiple launch tables if they follow the same model as they have so far with Falcon 9.  The table is attached to the rocket in the hanger and then the whole thing is rolled out and erected.  If a launch table is damaged or needs maintenance there will be others available.  I would assume that a malfunctioning rocket would be directed away from the pad if possible.  A hit on the pad itself would only happen if there was a catastrophic failure at the last second.  By the time this thing flies, SpaceX should (hopefully) have a LOT of experience with landing boosters. 
« Last Edit: 10/06/2016 08:44 AM by darkenfast »

Offline jsgirald

Re: ITS Booster Return - Final Landing and Mounting
« Reply #49 on: 10/06/2016 08:54 AM »
you make savings in the nominal case (which is hopefully the majority of launches). in the off-nominal case, you divert the returning booster to the 'service' landing pad and work on it there (or abort into the ocean if it can't be landed).

in the nominal case, you refuel, relaunch.

with 9/10 nominal launches, you've made huge savings of time, manpower, etc.

No you don't. I'm afraid the ground crew would insist on being paid regardless of the landing being 'nominal' or not. Same applies to equipment.

In fact, a nominal landing only saves time, which probably doesn't matters anyway because there's no real need for being that fast, it's not critical. Just think of how long it'll take to fill up a booster, we're talking of thounsands of tons of super chilled propellants.
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Online douglas100

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #50 on: 10/06/2016 09:57 AM »

...In fact, a nominal landing only saves time, which probably doesn't matters anyway because there's no real need for being that fast, it's not critical. Just think of how long it'll take to fill up a booster, we're talking of thounsands of tons of super chilled propellants.

Of course it saves time. That's the point. For current launch ops taking a day or two to move the booster from landing zone back to the pad doesn't matter. But if you have a number of ITS ships in LEO waiting to be refueled, then time is important, if not critical.

Why should it take any longer to load the rocket than current vehicles? It's a matter of the plumbing and power of the GSE. It's an engineering challenge (but so is almost every other aspect of ITS) but it should be straightforward in principle.
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Offline jsgirald

Re: ITS Booster Return - Final Landing and Mounting
« Reply #51 on: 10/06/2016 10:13 AM »

...In fact, a nominal landing only saves time, which probably doesn't matters anyway because there's no real need for being that fast, it's not critical. Just think of how long it'll take to fill up a booster, we're talking of thounsands of tons of super chilled propellants.

Of course it saves time. That's the point. For current launch ops taking a day or two to move the booster from landing zone back to the pad doesn't matter. But if you have a number of ITS ships in LEO waiting to be refueled, then time is important, if not critical.

Why should it take any longer to load the rocket than current vehicles? It's a matter of the plumbing and power of the GSE. It's an engineering challenge (but so is almost every other aspect of ITS) but it should be straightforward in principle.

When, and if, they get to the point of having a whole fleet of ITS ships waiting in LEO, don't you think they'll have more than one launch site? If only to prevent a hurricane stopping the whole campaign.

On the 'plumbing and power' challenge, I'm sure there's a logistical sweet spot between the complexity and cost of the ground systems (and I wouldn't be so sure that bigger is better) but that's a question to be addressed.
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Offline RanulfC

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #52 on: 10/09/2016 02:29 AM »
The pad support equipment can be hardened so that a failure is not as damaging. 42 engines means throttling can be arbitrarily low, so hover is no problem. The booster itself can start off with large margins until the requirements for landing are well understood.

This isn't the big deal everyone is making it out to be, I look forward to seeing this happen.

I also believe the booster will do all of the aiming and correcting, having the pad in motion as well is a no no, in my opinion.

7 not 42, only the inner 7 engines gimbal and are used for landing. Hardening the pad is probable but landing on the pad IN the launch mounts is a very, very difficult maneuver and frankly one that has never proven out in practice for any vertical landing vehicle. Hovering may not be a problem but that's not what the history of hovering landing has shown and the main reason you have landing gear is to dampen out all the vectors which thrust does not during hovering and landing. Being able to gimbal the engines isn't sufficient to do this either you need thrusters for that and grid finds don't work at low velocity.

I actually agree with not having the landing pad, (actually the launch/landing supports to be technically not the whole  pad) move is a good idea but the Booster will require much finer control than can be had from the engines to achieve the needed accuracy and since it doesn't appear the booster is being designed with those added thrusters and control the only way to achieve this is with a moving supports on the pad itself. And you can't harden those and still have them operate.

Randy
From The Amazing Catstronaut on the Black Arrow LV:
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Offline RanulfC

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #53 on: 10/09/2016 02:38 AM »
If you have enough control authority, you can guide a rocket through a kitchen window. Undoubtedly SpaceX's work on autonomous docking for Crew Dragon would come in handy. You could even paint a docking target pattern on the launch/landing pad, though I suppose designing a downward-facing camera for a terrain-matching guidance system would be a particularly thorny engineering challenge given the environment at the hot end of the rocket. They do grow diamond panes at the next center south of mine, so who knows.

Achieving that control authority is the issue as unlike Dragon there are a LOT of environmental effects that the Booster has to deal with the Dragon never sees. With much more benign and controllable propulsion than rockets landing with the kind of accuracy envisioned is really, really hard and landing something that big is going to be far more difficult than a little quad-copter drone.

Quote
And in addition, the landing mount doesn't necessarily have to be a tight fit - it can have its own sensors and cameras to adapt itself to the incoming booster.

It actually does even if the pad has to 'close' or attach to the descending rocket, and the equipment on the pad is going to vulnerable to the exhaust and damage from the booster. And it if moves it can break under the strain. Really, the idea of this being 'better' than landing gear boils down to having the rocket on the pad so you don't have to move it from the landing area and this seems less likely than landing on the pad with landing gear and then folding it back up for the next flight.

It would seem vastly simpler to jack up the empty booster and reposition it on the pad than to try and get this accurate with the actual landing.

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?

Online matthewkantar

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #54 on: 10/09/2016 03:06 AM »
7 not 42, only the inner 7 engines gimbal and are used for landing.

I am aware of the number of fixed and gimbaling engines in the SpaceX proposal. What I was referring to is that the minimum thrust achievable from the cluster of 42 engines on the bottom (20% of 1/42 of the takeoff thrust) is far below the vehicle's empty weight, so unlike the first stage of the Falcon 9, the ITS booster should be able to come in as slowly as it needs to. To achieve operational efficiency, it'll want to come in hot, but that can approached stepwise with mellower initial landing profiles.

Matthew

Offline jak Kennedy

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #55 on: 10/09/2016 03:44 AM »
I think I'm missing something. Why the rush to land back on the launch mount? Don't you have to wait for whatever you wish to rendezvous with to pass overhead?

Offline Patchouli

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #56 on: 10/09/2016 04:02 AM »

I like this.  Could be done with a barge floating on a shallow pool with a few high-powered winches arrayed around it to rapidly position it.  Or perhaps a really big air-bearing supported cradle positioned by winches.

None of that is viable in the real world

Dunno about the rest, but the pool thing was floated (sorry  :-[) by Boeing's SPS SSTO back in 1978.
It lacked the barge, though, rockets landed directly on the water.

I suspect as the ITS concept develops it's mission profile will change and may even explore aspects of similarly sized vehicles such as the SPS SSTO and Rombus.

Look at the evolutions past vehicles including Spacex's own went through.
« Last Edit: 10/09/2016 05:09 PM by Patchouli »

Offline guckyfan

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #57 on: 10/09/2016 06:31 AM »
I think I'm missing something. Why the rush to land back on the launch mount? Don't you have to wait for whatever you wish to rendezvous with to pass overhead?

As soon as there would be several ITS to service they can easily be spaced so they can be reached at different times of day. Though the time when they really need several launches per day is still a while off, they plan for it. It also makes pad operations a lot simpler and cheaper.

Edit: initially replied to the wrong post
« Last Edit: 10/09/2016 06:36 AM by guckyfan »

Offline meekGee

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #58 on: 10/09/2016 07:12 AM »
7 not 42, only the inner 7 engines gimbal and are used for landing.

I am aware of the number of fixed and gimbaling engines in the SpaceX proposal. What I was referring to is that the minimum thrust achievable from the cluster of 42 engines on the bottom (20% of 1/42 of the takeoff thrust) is far below the vehicle's empty weight, so unlike the first stage of the Falcon 9, the ITS booster should be able to come in as slowly as it needs to. To achieve operational efficiency, it'll want to come in hot, but that can approached stepwise with mellower initial landing profiles.

Matthew

The slower you settle into the launch mount, the harder it is to nail the x-y component, since forces like wind have more time to act.

You want to land as fast as possible, not as slow as possible.

Since the launch mount doesn't have to fly, it can be made to damp out a larger vertical speed, making it easier to reduce X-Y error.

Even F-9, today, has never landed successfully more than a few feet from center-pad.

--

That said, landing the rocket in a cradle that's on a large transporter platform, so the landing occurs away from the launch infrastructure - that would reduce risk, and is probably cheaper than building a redundant launch complex.

(Though a redundant launch complex allows you to double the launch rate, whereas the transporter platform only slows you down)

They need to have multiple launch complexes, since there are people on Mars and the supply line must remain open.
ABCD - Always Be Counting Down

Offline Jim

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #59 on: 10/09/2016 01:08 PM »
Too complex of an idea to work.  The mount would have to take landing loads and launch loads before release.

Offline jak Kennedy

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #60 on: 10/09/2016 05:57 PM »
I think I'm missing something. Why the rush to land back on the launch mount? Don't you have to wait for whatever you wish to rendezvous with to pass overhead?

As soon as there would be several ITS to service they can easily be spaced so they can be reached at different times of day. Though the time when they really need several launches per day is still a while off, they plan for it. It also makes pad operations a lot simpler and cheaper.

Edit: initially replied to the wrong post

But I'm thinking they may also have more than one tanker too. Anyway I won't stress out over this.  ::)

Offline docmordrid

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #61 on: 10/09/2016 07:00 PM »
I'm thinking in time they'll add an orbiting propellant depot. Pre-fill it before the passengers are launched, then it's only one docking event for the spaceship before departure.
DM

Offline Kaputnik

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #62 on: 10/09/2016 07:00 PM »
How quick can you translate horizontally with a 10 ton rcs thruster top and bottom?
How about with multiple 10 ton thrusters?

A 10t thruster acting on the 275t dry mass of the ICT booster gives 0.04ms/s acceleration. To translate a metre, including coming to zero velocity again, would need ten seconds.
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Offline rakaydos

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #63 on: 10/09/2016 08:44 PM »
How quick can you translate horizontally with a 10 ton rcs thruster top and bottom?
How about with multiple 10 ton thrusters?

A 10t thruster acting on the 275t dry mass of the ICT booster gives 0.04ms/s acceleration. To translate a metre, including coming to zero velocity again, would need ten seconds.

But because it's an active cancelation system, it doesnt need to slow, because it's countering the crosswind that will do the slowing for you. The ide is that it never gets a full meter off course because it cancels problem as they develop.

Offline Kaputnik

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #64 on: 10/09/2016 09:10 PM »
How quick can you translate horizontally with a 10 ton rcs thruster top and bottom?
How about with multiple 10 ton thrusters?

A 10t thruster acting on the 275t dry mass of the ICT booster gives 0.04ms/s acceleration. To translate a metre, including coming to zero velocity again, would need ten seconds.

But because it's an active cancelation system, it doesnt need to slow, because it's countering the crosswind that will do the slowing for you. The ide is that it never gets a full meter off course because it cancels problem as they develop.

And if the wind is gusting by more than 0.04m/s?
Waiting for joy and raptor

Offline rakaydos

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #65 on: 10/10/2016 01:55 AM »
How quick can you translate horizontally with a 10 ton rcs thruster top and bottom?
How about with multiple 10 ton thrusters?

A 10t thruster acting on the 275t dry mass of the ICT booster gives 0.04ms/s acceleration. To translate a metre, including coming to zero velocity again, would need ten seconds.

But because it's an active cancelation system, it doesnt need to slow, because it's countering the crosswind that will do the slowing for you. The ide is that it never gets a full meter off course because it cancels problem as they develop.

And if the wind is gusting by more than 0.04m/s?

The rocket is 275 tons. Unless you're trying to land in a storm (which, since it's RTLS, means launching in a storm) mere air is going to have a hard time moving it.

12m diamiter and 77m height, that cross section catching air, minus 10 metric tones of retrothrust, is zero or less at anything less than 10 kilos of pressure per square meter.

Offline envy887

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #66 on: 10/10/2016 04:02 AM »
Too complex of an idea to work.  The mount would have to take landing loads and launch loads before release.

The landing mounts and launch holddowns could be separate mechanisms if part of prelaunch ops is disengaging one and engaging the other.

Offline Kaputnik

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #67 on: 10/10/2016 06:22 AM »
How quick can you translate horizontally with a 10 ton rcs thruster top and bottom?
How about with multiple 10 ton thrusters?

A 10t thruster acting on the 275t dry mass of the ICT booster gives 0.04ms/s acceleration. To translate a metre, including coming to zero velocity again, would need ten seconds.

But because it's an active cancelation system, it doesnt need to slow, because it's countering the crosswind that will do the slowing for you. The ide is that it never gets a full meter off course because it cancels problem as they develop.

And if the wind is gusting by more than 0.04m/s?

The rocket is 275 tons. Unless you're trying to land in a storm (which, since it's RTLS, means launching in a storm) mere air is going to have a hard time moving it.

12m diamiter and 77m height, that cross section catching air, minus 10 metric tones of retrothrust, is zero or less at anything less than 10 kilos of pressure per square meter.

I work it out that a 10t (or 100kN) thruster exerts the same force as a 31 mph wind, taking the cross section of the booster as a crude 12x75m area.
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Offline Impaler

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Re: ITS Booster Return - Final Landing and Mounting
« Reply #68 on: 10/10/2016 07:16 AM »
Regardless of what one thinks of the feasibility of the proposed landing directly into mountings, I think you want to do it onto a platform on top of a crawler a mile or so from the actual launch pad, then the crawler brings you back to the pad, this minimizes the destruction if their is a failure and is the obvious way to bring the booster into the VAB for maintenance when needed without causing a delay on the pad.  If anything it should actually allow for a higher launch throughput then the direct landing on the pad concept.

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