Author Topic: Falcon Heavy center core - downrange barge landing or just expend it?  (Read 42491 times)

Offline meekGee

  • Senior Member
  • *****
  • Posts: 14158
  • N. California
  • Liked: 14046
  • Likes Given: 1392
EDIT: do you have a reference to Musk's comment? I remember something vaguely, but don't remember the context.

Quote from: elon twitter
Base is 300 ft by 100 ft, with wings that extend width to 170 ft. Will allow refuel & rocket flyback in future.
https://twitter.com/elonmusk/status/536263260056850432

Awesome, thanks.  Context is good, since it place the flyback idea with this current barge (no doubt with some improvements).

I always wondered whether they'll wheel a launch fixture underneath and launch from the same place it landed at, or will they somehow wheel the rocket (unfueled) to an outrigger platform so that it launches over the water, like that extension that supports the drill rig in the picture.
« Last Edit: 11/05/2015 04:50 pm by meekGee »
ABCD - Always Be Counting Down

Offline cmcqueen

  • Member
  • Posts: 18
  • Melbourne, Australia
  • Liked: 16
  • Likes Given: 41
I remember probably in the same presentation where he mentioned flyback he also said the Merlin engines have no meaningful limitation to their lifespan. After 40 cycles a few highly stressed components must be exchanged. He clearly was not worried about spending engine cycles.

A related question regarding engine cycles--for a flyback, how many of the 9 engines would be used? Maybe just one?

Offline meekGee

  • Senior Member
  • *****
  • Posts: 14158
  • N. California
  • Liked: 14046
  • Likes Given: 1392
I remember probably in the same presentation where he mentioned flyback he also said the Merlin engines have no meaningful limitation to their lifespan. After 40 cycles a few highly stressed components must be exchanged. He clearly was not worried about spending engine cycles.

A related question regarding engine cycles--for a flyback, how many of the 9 engines would be used? Maybe just one?

- The empty mass of the first stage (when landing back at the cape) is ~25 tons.
- The mass of the full second stage+payload+empty first stage, at staging time on the way up, is about 150 tons.
- The fuel load of the outbound first stage is about 400 tons.
(numbers from here

So IF the dV to and from the barge is the same, it's an 25/150 = 1/6 launch, so you need 1/6 the propellant.  But the 25 tons of empty first stage are the same, so takeoff weight will be 25+400/6 = 91 tons, compared with ~600 tons for the full rocket, and so 1/5. 

Give or take.   There are inaccuracies above, and aero losses are different, and the dV won't be the same since you can optimize for range instead of for height and altitude, etc...

So I'd say 2-3 engines.
« Last Edit: 11/05/2015 10:28 pm by meekGee »
ABCD - Always Be Counting Down

Offline douglas100

  • Senior Member
  • *****
  • Posts: 2177
  • Liked: 227
  • Likes Given: 105

....There are inaccuracies above, and aero losses are different, and the dV won't be the same since you can optimize for range instead of for height and altitude, etc...


(My bold)

A small point. As well as supplies of prop and other consumables for the returning vehicle, the barge will need to carry some nose fairings to be attached for the flight back. I'm not sure if the vehicle would get through max Q without one.

More importantly, as always, the driver for this is economics. There's no doubt technically that it could be done like you describe. But obviously it must be cheaper to recover and reuse the vehicle using this extra sea based infrastructure than expend it. In order for this to be worthwhile, the FH flight rate will have to be high. I think it's unrealistic to expect such rates in the near future.

Just because Musk mentioned the possibility of flyback, it doesn't mean they're going to do it. Once upon a time both F9 stages were going to be recovered, now that's on the back burner. The problem is that the three core design complicates recovery. And extra complications mean extra cost.

I'm strongly in favour of RTLS as being the cheapest solution to re-use because of its operational advantages. Recovering the side cores will be a good saving in itself.
Douglas Clark

Offline Stan-1967

  • Full Member
  • ****
  • Posts: 1128
  • Denver, Colorado
  • Liked: 1183
  • Likes Given: 614
Here's my gestating plan for re-use of the center core.   I'm making some assumptions I need to think through a bit more, but my thoughts are driven the following considerations:  T
1.  Enable advantages to minimize the payload penalty of the FH-R configuration,
2.  Reduce operation costs of maintaining a barge on station out in the ocean that has to do double duty as a a landing and launch platform.
3.  Re-examine smaller F1 class launchers with re-used components.

I would propose that SpaceX emulate part of the ULA SMART re-use concept.   They can ditch the hypersonic inflatable re-entry and stick with supersonic retropropulsion since they have that part seemingly mastered.   The idea would be to ditch the tank structure right after the retropropulsion burn, pop out a drogue chute at the right altitude, then parafoil, and thereby preserve the engines/thrust structure + the avionics.   The landing barge needs to have a helo on duty to retrieve the decending thrust structure that will be under a parafoil.   The helo lands this onto the barge where it can be stored and possibly processed for later reuse.  The barge can also stay on station for multiple launches until it is full of retrieved parts, & if the barge staff can process the retrieved parts into smaller mass units, (i.e Merlin engine, avionics, thrust assemply ) it can ferry them to land as it is able.   Less fuel is needed for this sequence as you don't need any for the hover slam landing, hence some increase of payload to orbit.   This may be offset by added mass for chutes and other structure changes.

The part I like the best, but wage has the most uncertainty, is to either resurrect the F1 with a Merlin full thrust for giving another go for smallsat launches, or they could offer to sell very discounted Merlins into the smallsat market and let someone else manage that business.  SpaceX could beat upcoming small competitors by using re-used Merlins.   I also like that this solves some of the re-use issues about the economics of maintaining high volume on the main Merlin assembly line.   It is a way to plan in some obsolesense into the Merlin, and keep the production  line more stable.

I'm very curious what the payload capability of a F1 with full thrust Merlin would be?

Offline Burninate

  • Full Member
  • ****
  • Posts: 1145
  • Liked: 360
  • Likes Given: 74
I am pretty sure that once barge landing is routine, they will refuel on the barge and fly back.
So you get rapid reusability, plus no fly-back penalty.

Doubtful, I don't think that it will ever happen with F9, you would need a significantly redesigned launch vehicle. The legs cannot handle the propellant mass, and instead of a flat landing surface you need it also to be an operational launch pad. With all the LOX/RP1 and other consumables, and equipment to support it. And the man power. The people at the pads aren't just spending their work hours twiddling their thumbs.   ;)

Boating it back to shore will always be cheaper.

I must admit I was seriously shocked when Elon Musk mentioned flyback from the barge. I still can't believe it makes sense.

I must admit I was seriously shocked when Elon Musk mentioned flyback from the barge. I still can't believe it makes sense.

Neither can I.

Perhaps it is a proxy for some other capability that they are thinking about.

Color me skeptical as well.

On the other hand, there are certain things that could bring the center core back faster than a ship;  The center core is going to land quite a ways downrange, much farther than the Falcon 9 first stage.  A cargo airship could do it.  Lockheed Martin is in the process of bringing this capacity online, and Aeros is still around as a plausible competitor if they receive some funding.

Offline meekGee

  • Senior Member
  • *****
  • Posts: 14158
  • N. California
  • Liked: 14046
  • Likes Given: 1392

....There are inaccuracies above, and aero losses are different, and the dV won't be the same since you can optimize for range instead of for height and altitude, etc...


(My bold)

A small point. As well as supplies of prop and other consumables for the returning vehicle, the barge will need to carry some nose fairings to be attached for the flight back. I'm not sure if the vehicle would get through max Q without one.

More importantly, as always, the driver for this is economics. There's no doubt technically that it could be done like you describe. But obviously it must be cheaper to recover and reuse the vehicle using this extra sea based infrastructure than expend it. In order for this to be worthwhile, the FH flight rate will have to be high. I think it's unrealistic to expect such rates in the near future.

Just because Musk mentioned the possibility of flyback, it doesn't mean they're going to do it. Once upon a time both F9 stages were going to be recovered, now that's on the back burner. The problem is that the three core design complicates recovery. And extra complications mean extra cost.

I'm strongly in favour of RTLS as being the cheapest solution to re-use because of its operational advantages. Recovering the side cores will be a good saving in itself.

That's a pretty high bar for speculation on an internet forum...

If I go on about this possibility, with some people saying it's technically absurd, and some saying it's a non-starter for economic reasons, and then Musk says "hey, in the future the barges will support refueling and fly-back", that's about as certain as I can get.

Nobody, including Musk, can see the future...   If it turns out that they changed plans and decided against it, so be it...

I can see the difficulties associated with this concept, but it's hard to quantify trades so far ahead of time.  All forward-looking discussions are mostly about what's in the "possible space", and then we wait and see.

Remember how unlikely the whole concept of even operating a landing ship was, what, two years ago? 
« Last Edit: 11/06/2015 01:31 am by meekGee »
ABCD - Always Be Counting Down

Offline douglas100

  • Senior Member
  • *****
  • Posts: 2177
  • Liked: 227
  • Likes Given: 105

...Just because Musk mentioned the possibility of flyback, it doesn't mean they're going to do it. ...

That's a pretty high bar for speculation on an internet forum...

Why? It's an obvious point. Musk has predicted a number of possibilities which haven't happened.

I agree with your other points about trades and predicting the future. It seems to me that all you gain from fly back is time. There is no payload gain. So the trade is heavily influenced by FH flight rate. That's why I'm skeptical at this time about fly back.
Douglas Clark

Offline spacenut

  • Senior Member
  • *****
  • Posts: 5181
  • East Alabama
  • Liked: 2587
  • Likes Given: 2895
To me it doesn't make any sense to launch off the barge to return to the Cape or Boca Chica.  The barge/ship is only about 200-300 miles off shore.  At 20-30 knots, they can be back at either launch site in less than a day.  While on the way back, a crew could inspect the engines and structure.  Then once back go to the hanger for refitting or replacement of any damaged components.  It would be less stress on the engines and structure of the rocket while allowing time for inspections.  It would have to be done anyway, so just do it while getting back.  Once back it would be that much less time for refueling, refitting, and relaunching.  Now launching from sea back to the launch site will require equipment for manufacturing lox and storage for the kerosene needed.  That would be extra expense. 

Offline Sam Ho

  • Full Member
  • ****
  • Posts: 817
  • Liked: 580
  • Likes Given: 71
To me it doesn't make any sense to launch off the barge to return to the Cape or Boca Chica.  The barge/ship is only about 200-300 miles off shore.  At 20-30 knots, they can be back at either launch site in less than a day.  While on the way back, a crew could inspect the engines and structure.  Then once back go to the hanger for refitting or replacement of any damaged components.  It would be less stress on the engines and structure of the rocket while allowing time for inspections.  It would have to be done anyway, so just do it while getting back.  Once back it would be that much less time for refueling, refitting, and relaunching.  Now launching from sea back to the launch site will require equipment for manufacturing lox and storage for the kerosene needed.  That would be extra expense.

Don't think I've ever seen a tug go 20-30 knots.  ASDS currently travels at about 5-6 knots under tow.

Offline cambrianera

  • Full Member
  • ****
  • Posts: 1438
  • Liked: 318
  • Likes Given: 261
EDIT: do you have a reference to Musk's comment? I remember something vaguely, but don't remember the context.

Quote from: elon twitter
Base is 300 ft by 100 ft, with wings that extend width to 170 ft. Will allow refuel & rocket flyback in future.
https://twitter.com/elonmusk/status/536263260056850432

Ah, what a shame, THAT barge will never see  a landing.
Much less a refuel and flyback :-(
Oh to be young again. . .

Offline spacenut

  • Senior Member
  • *****
  • Posts: 5181
  • East Alabama
  • Liked: 2587
  • Likes Given: 2895
Ok, I thought the ship/barge they landed on was self propelled.  Even at 5-6 knots.  It can travel 100 miles in a day.  How far offshore are they now?  I know the middle core on the FH would be further out, but still.  Checking and refitting 3 cores will take some time.  Ones that land back at launch site can be checked and readied while waiting on the 3rd core to get back.  I just don't see the need to launch back and take a chance at further stressing or damaging the core stage. 

Offline Sam Ho

  • Full Member
  • ****
  • Posts: 817
  • Liked: 580
  • Likes Given: 71
Ok, I thought the ship/barge they landed on was self propelled.

The ASDS does have 4 thrusters, but they are used only for stationkeeping.  In any case, using them for travel would be even slower than a tug, and might also cause some legal issues regarding the distinction between a ship and a barge.

There is a huge thread about the ASDS (over 1 million views):
http://forum.nasaspaceflight.com/index.php?topic=36326.0

Offline meekGee

  • Senior Member
  • *****
  • Posts: 14158
  • N. California
  • Liked: 14046
  • Likes Given: 1392
Of course he has...

All I'm saying is that as far as predictions go, best I can aim for is to align with SpaceX's intent at the time.

At least as far as judging whether it's technically possible (which was debated) or economically feasible (same).

If I hit their intent, I know that at least I've got a reasonable argument.

Reality will eventually win though, by definition... 




...Just because Musk mentioned the possibility of flyback, it doesn't mean they're going to do it. ...

That's a pretty high bar for speculation on an internet forum...

Why? It's an obvious point. Musk has predicted a number of possibilities which haven't happened.

I agree with your other points about trades and predicting the future. It seems to me that all you gain from fly back is time. There is no payload gain. So the trade is heavily influenced by FH flight rate. That's why I'm skeptical at this time about fly back.
ABCD - Always Be Counting Down

Offline meekGee

  • Senior Member
  • *****
  • Posts: 14158
  • N. California
  • Liked: 14046
  • Likes Given: 1392
Ok, I thought the ship/barge they landed on was self propelled.  Even at 5-6 knots.  It can travel 100 miles in a day.  How far offshore are they now?  I know the middle core on the FH would be further out, but still.  Checking and refitting 3 cores will take some time.  Ones that land back at launch site can be checked and readied while waiting on the 3rd core to get back.  I just don't see the need to launch back and take a chance at further stressing or damaging the core stage.

Let's say 5 days in, 5 days out.

Rapid reusability means one day turn-around at most, all included.

So there's a disparity there.

The only way to avoid the fly-back penalty and retain rapid reusability is fly-back.  That's all.

Maybe  they won't (fly back) and then they have to give up either performance (if they fly the core back to shore), or turn around time and launch frequency (if they haul it back by sailing). Or operate some 10 barges following your suggestion.
ABCD - Always Be Counting Down

Offline Lars-J

  • Senior Member
  • *****
  • Posts: 6809
  • California
  • Liked: 8485
  • Likes Given: 5384
Ok, I thought the ship/barge they landed on was self propelled.  Even at 5-6 knots.  It can travel 100 miles in a day.  How far offshore are they now?  I know the middle core on the FH would be further out, but still.  Checking and refitting 3 cores will take some time.  Ones that land back at launch site can be checked and readied while waiting on the 3rd core to get back.  I just don't see the need to launch back and take a chance at further stressing or damaging the core stage.

Let's say 5 days in, 5 days out.

Rapid reusability means one day turn-around at most, all included.

So there's a disparity there.

The only way to avoid the fly-back penalty and retain rapid reusability is fly-back.  That's all.

Maybe  they won't (fly back) and then they have to give up either performance (if they fly the core back to shore), or turn around time and launch frequency (if they haul it back by sailing). Or operate some 10 barges following your suggestion.

F9 will never have rapid reusability like that (a one day turnaround), which renders your point moot. A follow-on vehicle might, but is another discussion. So it will never be economical to fly back FH/F9 cores.

Offline meekGee

  • Senior Member
  • *****
  • Posts: 14158
  • N. California
  • Liked: 14046
  • Likes Given: 1392
Ok, I thought the ship/barge they landed on was self propelled.  Even at 5-6 knots.  It can travel 100 miles in a day.  How far offshore are they now?  I know the middle core on the FH would be further out, but still.  Checking and refitting 3 cores will take some time.  Ones that land back at launch site can be checked and readied while waiting on the 3rd core to get back.  I just don't see the need to launch back and take a chance at further stressing or damaging the core stage.

Let's say 5 days in, 5 days out.

Rapid reusability means one day turn-around at most, all included.

So there's a disparity there.

The only way to avoid the fly-back penalty and retain rapid reusability is fly-back.  That's all.

Maybe  they won't (fly back) and then they have to give up either performance (if they fly the core back to shore), or turn around time and launch frequency (if they haul it back by sailing). Or operate some 10 barges following your suggestion.

F9 will never have rapid reusability like that (a one day turnaround), which renders your point moot. A follow-on vehicle might, but is another discussion. So it will never be economical to fly back FH/F9 cores.

A) How do you know? 
B) If the follow-on vehicle is of the same class, then it's the same barge size, and so the discussion is equally valid
C) Musk had something in mind when he said what he said about fly-back.  So irrespective if it pans out - which rocket do you think he was talking about?
ABCD - Always Be Counting Down

Offline meekGee

  • Senior Member
  • *****
  • Posts: 14158
  • N. California
  • Liked: 14046
  • Likes Given: 1392
At some point, you have to accept that the guy who's designing all of this said that this barge "will allow refuel & rocket flyback in future".

Of course it might not work out, but with the above having been stated so explicitly, you can take off the table any talk of it being absurd/irrelevant/moot/etc.  It clearly is (or has been) in the plan.

I will also suggest that if flyback is/was in the plan, then barge use is not envisioned as some temporary hack, but a permanent conop, which matches the fact that they've built one for each coast.
« Last Edit: 11/06/2015 08:21 pm by meekGee »
ABCD - Always Be Counting Down

Offline Lars-J

  • Senior Member
  • *****
  • Posts: 6809
  • California
  • Liked: 8485
  • Likes Given: 5384
F9 will never have rapid reusability like that (a one day turnaround), which renders your point moot. A follow-on vehicle might, but is another discussion. So it will never be economical to fly back FH/F9 cores.

A) How do you know? 
B) If the follow-on vehicle is of the same class, then it's the same barge size, and so the discussion is equally valid
C) Musk had something in mind when he said what he said about fly-back.  So irrespective if it pans out - which rocket do you think he was talking about?

A) I'm a realist. You disagree? We'll just have to revisit this a decade from now, but I'm confident in my statement.
B) Why? Why would it the same barge size? The original has already been decommissioned.
C) Not F9. To achieve rapid re=usability you'll they will have to take everything they learn from F9 and apply it to a clean sheet vehicle. Whatever follows. Something larger, in all likelihood.

Musk was clearly more general in his statement than you seem to want to admit. You apparently keep reading things in his statement that aren't there. No mention of F9. Or FH. Read it again, more carefully this time. Evidence #1. That specific barge has already been retired and replaced. Whichever platform/barge ultimately allows fly-back (if done at all) will be VERY different.

I will also suggest that if flyback is/was in the plan, then barge use is not envisioned as some temporary hack, but a permanent conop, which matches the fact that they've built one for each coast.

They couldn't possibly need two because they plan on *landing* on them? In what world do you now manage to twist the mere existence of a west coast barge into proof that it must be used to launch from?
« Last Edit: 11/06/2015 10:48 pm by Lars-J »

Offline spacenut

  • Senior Member
  • *****
  • Posts: 5181
  • East Alabama
  • Liked: 2587
  • Likes Given: 2895
I foresee the barge will, in the future, only be used for Falcon Heavy center core.  The outside cores will flyback to the launch site.  In the meantime, the two outer cores can be refitted and flown as Falcon 9's while the center core is brought back to the launch site to be mated with two more cores for another FH.  Realistically only I only see one launch every 10 days from the same launch site.  By the time they check out the rocket, replace parts, refuel, and launch.  10 days is also what ULA said about Atlas V....IF they had that big a launch rate.  That would be about 40 cores a year, which is the maximum production of both Atlas and Falcon 9 factories.  Now, reuse will allow for more launches.  How many is anyone's guess.  With three launch sites and 4 launch pads, They will be extremely busy if it ever gets to that. 

All it is going to take is one successful completely reusable BFR, and I think Falcon will go away, especially if the price of BFR is cheap. 

Tags:
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
1