Author Topic: SpaceX Eastern Range Landing Facilities  (Read 165153 times)

Offline hrissan

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Re: SpaceX Eastern Range Landing Facilities
« Reply #20 on: 01/08/2015 07:19 PM »
And just to be a pedant, the residual fuel is listed as being 15 gal LOX and up to 150 gal RP-1. 15 gal of LOX is not very much.

That really is a tiny amount.  At full thrust a single Merlin 1D uses something like 200 kg/s of propellant.

Perhaps they plan to vent the lox tank just before touchdown? idk, it doesn't make much sense to me.
The number of residual propellant is very small, which gives some ideas:

1. Why 10x less LOX than RP? IMHO they have long thin tube with LOX, but not with RP, so the precision of measuring remaining LOX may be much higher. Or there could be uncertainty in heat flux into LOX tank, so they load a bit more RP for the worst case LOX vaporization during flight, so there may be a bit of excess RP.

2. They know terminal velocity very well and so how much fuel is required, as the steering is by grid fins it does not ue propellant, so they will just extend the atmosperic entrance burn (the one before landing burn) to expend excess propellant leaving just required amount plus uncertainty.

Offline TrueBlueWitt

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Re: SpaceX Eastern Range Landing Facilities
« Reply #21 on: 01/08/2015 07:28 PM »
Does the potential ability to "boost" the first stage for BFR from construction site to the launch facility come into play at all?

Offline corrodedNut

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Re: SpaceX Eastern Range Landing Facilities
« Reply #22 on: 01/08/2015 07:29 PM »
Maybe the divert pads are for off-nominal landings or unexpected ground winds.

Offline rpapo

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Re: SpaceX Eastern Range Landing Facilities
« Reply #23 on: 01/08/2015 08:04 PM »
Does the potential ability to "boost" the first stage for BFR from construction site to the launch facility come into play at all?
Unless the entire flight path from factory to the landing pad near the launch site is uninhabited, to a good distance to either side, the FAA is not very likely to grant a license for that to happen.

At least that is how I see it.
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Offline sghill

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Re: SpaceX Eastern Range Landing Facilities
« Reply #24 on: 01/08/2015 08:46 PM »
I seem to recall you being vociferously in the "refurbishment-costs-may-make-reusability-unfeasible"  camp when we were discussing all this last summer and now you're in the "it'll-be-ok" camp?  The McGregor boosters never flew backwards at hypersonic speeds.  We don't know what the returning stage is going to look like beyond the grainy video of that charred booster landing in the ocean the airplane took during the last landing.

The point is that the booster may either need a complete tear down (and component replacements) requiring the abilities they have back at the CA factory- and I expect they will do this for the first few returns, or the booster may be good to go after an inspection, air in the tires, and fluid top-off, which allows them to use their existing HIF facilities, or get a new one (build or lease) for refurbishment in FL instead of CA.  The EA for LC-13 indicates that SpaceX believes the latter is true- which is what Dudely pointed out in his post.  I also pointed out that if the latter is indeed true, then we can also begin to put boundaries on questions about the economics of reusability because the refurbishment costs will likely be small.


My point is McGregor would be the likely site for any tear down vs Hawthorne.  They have replaced engines, attached engine structure to tanks before and fixed up stages from static fire.  Also, component replacements can be done at the launch site, since this happens prelaunch when failures are found.   If "teardown" doesn't include thrust structure or tank demates, any facility that can hold the stage on the access stands with roll rings can be used.

Fair enough statement, but we know now from the EA that SpaceX rejected KSC for landing sites in part because it was too far from a TBD refurbishment location.  Normal post-flight refurbishment won't be happening in TX even if tear-downs and major work does occur there.

It also gives some insight into Musk's "self-contained space center" comment recently....
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Offline deruch

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Re: SpaceX Eastern Range Landing Facilities
« Reply #25 on: 01/08/2015 11:23 PM »
I seem to recall you being vociferously in the "refurbishment-costs-may-make-reusability-unfeasible"  camp when we were discussing all this last summer and now you're in the "it'll-be-ok" camp?  The McGregor boosters never flew backwards at hypersonic speeds.  We don't know what the returning stage is going to look like beyond the grainy video of that charred booster landing in the ocean the airplane took during the last landing.

The point is that the booster may either need a complete tear down (and component replacements) requiring the abilities they have back at the CA factory- and I expect they will do this for the first few returns, or the booster may be good to go after an inspection, air in the tires, and fluid top-off, which allows them to use their existing HIF facilities, or get a new one (build or lease) for refurbishment in FL instead of CA.  The EA for LC-13 indicates that SpaceX believes the latter is true- which is what Dudely pointed out in his post.  I also pointed out that if the latter is indeed true, then we can also begin to put boundaries on questions about the economics of reusability because the refurbishment costs will likely be small.


My point is McGregor would be the likely site for any tear down vs Hawthorne.  They have replaced engines, attached engine structure to tanks before and fixed up stages from static fire.  Also, component replacements can be done at the launch site, since this happens prelaunch when failures are found.   If "teardown" doesn't include thrust structure or tank demates, any facility that can hold the stage on the access stands with roll rings can be used.

Fair enough statement, but we know now from the EA that SpaceX rejected KSC for landing sites in part because it was too far from a TBD refurbishment location.  Normal post-flight refurbishment won't be happening in TX even if tear-downs and major work does occur there.

It also gives some insight into Musk's "self-contained space center" comment recently....

Be careful about assigning long term planning to the short term.  I think that's the major disconnect in the above back-and-forth.  Jim is talking about what will happen with the very first few recovered stages.  The quote from the EA is really only applicable to SpaceX's long term vision.  Eventually, they don't plan to be totally taking apart recovered stages.  They are planning for success.  i.e. Only "minor" work necessary to get a stage ready to fly again.  At that point, it makes way more sense to refurb them where they are going to be used. 

Quote from: LC-13 as landing pad EA
While difficult to calculate, there may be a slight positive impact on traffic since the re-landed vehicle would be transported to a local SpaceX facility, rather than transporting a new Falcon first stage vehicle from Texas to CCAFS.
(emphasis added)

The context of the report is SpaceX's long term plans, i.e. for when reuse means not having to bring another new stage from TX.
« Last Edit: 01/09/2015 12:34 AM by deruch »
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Offline Jdeshetler

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Re: SpaceX Eastern Range Landing Facilities
« Reply #26 on: 01/09/2015 04:15 AM »
http://www.patrick.af.mil/shared/media/document/AFD-141107-004.pdf

Major modifications:
- New 200 foot by 200 foot square concrete landing pad
- surrounded by an approximately 750 foot diameter compressed soil and gravel, flat pervious surface.
- four additional, 150 foot diameter concrete “contingency” pads 
- access roads between pads is to be made with compact gravels/riverbed rocks.
- at the location of the former blockhouse, a steel and concrete “stand” would be built to secure the Falcon stage during post-landing operations.
- clearing existing vegetation from the land between the LC-13 operations area to
the ditch to the east, and then up to the beach area but not dunes itself.

The X logo on the major pad is the same size as the barge's for scale.
« Last Edit: 01/09/2015 04:18 AM by Jdeshetler »

Offline Dudely

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Re: SpaceX Eastern Range Landing Facilities
« Reply #27 on: 01/09/2015 01:30 PM »
And just to be a pedant, the residual fuel is listed as being 15 gal LOX and up to 150 gal RP-1. 15 gal of LOX is not very much.

That really is a tiny amount.  At full thrust a single Merlin 1D uses something like 200 kg/s of propellant.

Perhaps they plan to vent the lox tank just before touchdown? idk, it doesn't make much sense to me.
The number of residual propellant is very small, which gives some ideas:

1. Why 10x less LOX than RP? IMHO they have long thin tube with LOX, but not with RP, so the precision of measuring remaining LOX may be much higher. Or there could be uncertainty in heat flux into LOX tank, so they load a bit more RP for the worst case LOX vaporization during flight, so there may be a bit of excess RP.

2. They know terminal velocity very well and so how much fuel is required, as the steering is by grid fins it does not ue propellant, so they will just extend the atmosperic entrance burn (the one before landing burn) to expend excess propellant leaving just required amount plus uncertainty.

I think 2 is probably right. It also explains why they have all those "contingency pads". . . because a big gust of wind might need too much fuel to overcome in order to hit the proper landing pad.

Offline meekGee

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Re: SpaceX Eastern Range Landing Facilities
« Reply #28 on: 01/09/2015 01:39 PM »
Maybe, but the cosine loss on even a 5 degree slew are minimal (0.5%)
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Offline cscott

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Re: SpaceX Eastern Range Landing Facilities
« Reply #29 on: 01/09/2015 03:14 PM »
I'm also having trouble imagining a wind gust that would divert the stage to that degree --- or a fuel issue that would cause an abort to a pad *further* from the coast.

Perhaps the real issue is political: in order to expedite the application, the first EIS is explicitly only for a single returning core, even though they manage to build 5 (!) pads by using the "contingency" fig leaf.  (And perhaps this is even technically the truth if they have ALHAT-style targetting of all five----even though no reasonable combination of conditions will actually cause a divert.)

And then once they have established single-core landing operations, and everyone is happy with their safety, environmental soundness, etc, they can apply for a new EIS expanding their operations to two or three pads.  This would mitigate risk, as they wouldn't be endangering their existing one-pad operations if this new application runs into trouble.

That is, when they write, "There are no plans to utilize the contingency pads in order to enable landing multiple stages at LC-13 during a single landing event," the reader is meant to insert "For the purposes of this initial EIS" at the beginning.

Alternatively, their pivot to barges and the relative risk assessments might mean they plan to perform at least the first F9H core recoveries at sea, and at the moment they think that's a reasonable plan for the five-year span of the initial license.  Again, reserving the right to pivot via a new EIS later if the ASDSes run into issues.
« Last Edit: 01/09/2015 03:21 PM by cscott »

Offline speedevil

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Re: SpaceX Eastern Range Landing Facilities
« Reply #30 on: 01/09/2015 03:58 PM »
In principle, if you have accurate meteorological data for the last 30s or so of flight when the engines are lit, and data from throughout the flight on engine performance, you can generate a really accurate figure for fuel required to get down vertically.

The engine burn - based on ORBCOMM starts about 30s up, and 1500m in altitude.

At ~1500m and 100m/s downwards, the grid fins, and the body lift generated by tilting the stage sideways has a really decent aerodynamic effect.

As you get closer to zero velocity, it's pretty much all got to come from the rocket.
Once you're at 500m or so, the freedom you have to manoever in the face of severe gusts goes way down.
The rocket weighs ~20 tons, and you have a thrust of ~27.

One degree of freedom that could be built in is to design the landing so that it does not go straight in - but spirals to a small degree - keeping an approximately constant gimbal angle, so as to allow really quite large horizontal deflections without any impact on final fuel use. Another is gravity losses - blipping the throttle early rather than late will change the landing duration and fuel use.

Falcon 9 is 150m^2 or so in side-area.
In order to generate 2 tons sideways, you need a windspeed of about 14m/s.

To counteract this with the engine needs you to cant it 15 degrees, reducing the vertical thrust by only half a percent.

This would seem to indicate that you need to do nothing special if your unplanned winds at the landing site vary by a fairly significant amount.

I would hazard a guess that - for a properly performing stage - the ancillary pads would only be used in the event of a really severe gust a few hundred meters up, after the amount of landing fuel has already been determined, and the trajectory flexibility built into that has run out.

The gust sensitivity depends strongly on how much 'extra' fuel you can land with.
For the ridiculously low amounts specified - it gets lots harder to fight gusts and hit the pad.

Offline meekGee

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Re: SpaceX Eastern Range Landing Facilities
« Reply #31 on: 01/09/2015 04:18 PM »
Hey maybe this doubles as a landing pad for a *really* large rocket with asymmetric leg placement.

Honestly, I'm stumped by the contingency pads. 

For LC40, do they also control the area between it and the coast line?  Or is it limited (as I suspect) to the perimeter of the pad area?

EDIT: actually never mind LC40.  Is it possible there's room within the LC39 area for a landing pad, nearer to shore?
« Last Edit: 01/09/2015 04:21 PM by meekGee »
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Offline Zed_Noir

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Re: SpaceX Eastern Range Landing Facilities
« Reply #32 on: 01/09/2015 05:33 PM »

...

Is it possible there's room within the LC39 area for a landing pad, nearer to shore?

If they couldn't find room for the HIB other than on the crawlway, there will also be no room for a landing pad.

Offline Zed_Noir

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Re: SpaceX Eastern Range Landing Facilities
« Reply #33 on: 01/09/2015 05:44 PM »
Had a thought about the contingency pads at LC13. If SpaceX upgrade LC40 to FH comparable then you can have dual FH launches with 4 strapped-on booster cores returning to CCAFS.

Or LC-39B could also hosted a FH launch.  Hmmm shades of that dual launch from that awful Armageddon movie. :)

Offline speedevil

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Re: SpaceX Eastern Range Landing Facilities
« Reply #34 on: 01/09/2015 05:53 PM »
If they couldn't find room for the HIB other than on the crawlway, there will also be no room for a landing pad.



That rather depends how tough the roof is.

Offline meekGee

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Re: SpaceX Eastern Range Landing Facilities
« Reply #35 on: 01/09/2015 05:55 PM »

...

Is it possible there's room within the LC39 area for a landing pad, nearer to shore?

If they couldn't find room for the HIB other than on the crawlway, there will also be no room for a landing pad.

??  The requirements for both structures are almost completely opposite.

(Though I agree it's not very likely, I'm just trying to find out where the second core will land)
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Offline Zed_Noir

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Re: SpaceX Eastern Range Landing Facilities
« Reply #36 on: 01/09/2015 06:12 PM »

...

Is it possible there's room within the LC39 area for a landing pad, nearer to shore?

If they couldn't find room for the HIB other than on the crawlway, there will also be no room for a landing pad.

??  The requirements for both structures are almost completely opposite.

(Though I agree it's not very likely, I'm just trying to find out where the second core will land)

The ground surface area require for both structures seems similar.

Offline meekGee

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Re: SpaceX Eastern Range Landing Facilities
« Reply #37 on: 01/09/2015 06:35 PM »

...

Is it possible there's room within the LC39 area for a landing pad, nearer to shore?

If they couldn't find room for the HIB other than on the crawlway, there will also be no room for a landing pad.

??  The requirements for both structures are almost completely opposite.

(Though I agree it's not very likely, I'm just trying to find out where the second core will land)

The ground surface area require for both structures seems similar.

And that's about all there is in common...

The landing pad will be between any other infrastructure and the shore (so there's no overflight during landing), whereas the HIF needs to support a lot of heavy traffic (stages, payloads, etc) and be on the "safe" side of the pad, since you don't want to put it at overflight risk during a launch.

The HIF is a complex building, whereas the pad is an almost bare-bones concrete pad.

The HIF is almost continuously occupied by a crew, the landing pad is pretty much unmanned.

The HIF needs a T/E path between itself and the pad (for a full-up FH), the pad only needs a road that carries a regular truck.

...

« Last Edit: 01/09/2015 08:27 PM by meekGee »
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Offline butters

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Re: SpaceX Eastern Range Landing Facilities
« Reply #38 on: 01/09/2015 07:59 PM »
The contingency pads could come in handy in case they make a crater out of the main pad...

Offline te_atl

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Re: SpaceX Eastern Range Landing Facilities
« Reply #39 on: 01/09/2015 08:56 PM »
Hey maybe this doubles as a landing pad for a *really* large rocket with asymmetric leg placement.

Honestly, I'm stumped by the contingency pads. 


This is the way I look at it.   Conceptually there are *6* contingency aborts.  4 concrete pads if the rocket is running wide or long on return, and two targets in the ocean about the same distance apart as the western concrete pads if its running short.  (the ocean "targets" are for illustration only.... in reality all of the ocean is just one big target)

If you add in the two ocean abort "targets" and then draw an ellipse on the contingency pads that extends into the ocean points and you get a good representation of a targeting ellipse like the ones used for the mars landers.  ie "We are pretty sure it will land somewhere in  here".   The contingencies are placed at nodes along the ellipse that divide it into pretty even abort zones.   The actual target ellipse is probably wider then the contingencies, but that's harder to visualize.

One thing to remember is documentation like this is many months in the writing and reviewing before it becomes public.  My guess is that the contingency aborts were originally planned as a hedge since they have yet to actually land on an exact target.   Likely started before the addition of the grid vanes.  Its possible they now have a higher confidence on targeting then they did when it was originally written.   

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