Author Topic: F9 Block 5 Updates and Discussion  (Read 313437 times)

Offline ZachS09

Re: F9 Block 5 Updates and Discussion
« Reply #220 on: 03/31/2017 12:39 AM »
Part of the answer to ChrisGebhardt's question during the SES-10 post-launch conference included the fact that the Block 5 F9's liftoff thrust will be 10% more than the Full Thrust's current level, which is 7,607.4 kilonewtons.

Adding 10% more (760.74 kilonewtons) to the above-mentioned number will result in 8,368.14 kilonewtons, or about 1,881,233 pounds of thrust.
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Offline spacenut

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Re: F9 Block 5 Updates and Discussion
« Reply #221 on: 03/31/2017 02:07 AM »
So that means 10% more payload for FH to LEO?  Then would FH get 60 tons to LEO in reusable mode?  What about expendable mode? 70-75 tons?  That could mean lots of heavy units for NASA's proposed moon orbiting station, without using the SLS. 

Several years ago when they were trying to figure out what to do after Shuttle, a lot of guys on this thread said 50 ton units to orbit would be optimal and cheaper with expendable rockets.  They were advocating Atlas V heavy, or Atlas V phase II, and Delta IV heavy with solids and cross feed to get to 50 tons.  Now SpaceX will soon do it with reusable boosters instead of expendable. 

Offline envy887

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Re: F9 Block 5 Updates and Discussion
« Reply #222 on: 03/31/2017 02:09 AM »
I would assume the numbers on SpaceX's website (7607 kN, 54.4t for FH) are for Block 5.

Offline macpacheco

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Re: F9 Block 5 Updates and Discussion
« Reply #223 on: 03/31/2017 03:02 AM »
So that means 10% more payload for FH to LEO?  Then would FH get 60 tons to LEO in reusable mode?  What about expendable mode? 70-75 tons?  That could mean lots of heavy units for NASA's proposed moon orbiting station, without using the SLS. 

Several years ago when they were trying to figure out what to do after Shuttle, a lot of guys on this thread said 50 ton units to orbit would be optimal and cheaper with expendable rockets.  They were advocating Atlas V heavy, or Atlas V phase II, and Delta IV heavy with solids and cross feed to get to 50 tons.  Now SpaceX will soon do it with reusable boosters instead of expendable.
Nope that's not how it works. Extra thrust by itself only reduces gravity losses. For FH this helps a little more, cause the center booster can now throttle down sooner and save more fuel for after side booster separation. But that's not 10% more payload to LEO.
But the bottom line is only missions to the Moon/Mars and beyond actually need extra performance.
A risky enhancement would be to shutdown the 3 center booster engines equipped with restart capability, as the center booster could even shutdown all of its engine at some point if it had the ability to restart them right before side booster sep. Or equip even more center booster engine with restart capability and shut them down too. That would provide much of the cross feed benefits.
Perhaps, maybe, who knows, SX could do this for Red Dragon missions, as this would be solely SpaceX's risk.
Or after SX demonstrates thousands of M1D engines performing flawlessly.
In order to get more benefit from extra thrust, stages would have to be stretched, but the stages are already at the road transportability limit.
« Last Edit: 03/31/2017 03:06 AM by macpacheco »
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Offline Toast

Re: F9 Block 5 Updates and Discussion
« Reply #224 on: 03/31/2017 03:46 PM »
I would assume the numbers on SpaceX's website (7607 kN, 54.4t for FH) are for Block 5.

According to a tweet from Elon, they've been flying with that thrust since late 2016. I'm not a fan of taking his tweets as the gospel truth though, I'd love to get some info from some insiders on when that thrust upgrade went into effect and if it's the same thrust upgrade that's being discussed for Block 5, of if the Block 5 upgrade will be on top of that.

Offline Tuts36

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Re: F9 Block 5 Updates and Discussion
« Reply #225 on: 03/31/2017 04:29 PM »
Question, would the 10% thrust upgrade Elon mentioned in the presser include the vacuum version on the second stage?  If so wouldn't that be an immense improvement?  Would that possibly explain why we are suddenly talking about S2 recovery again (even if he said it'd be a 'Hail Mary')?

Offline Norm38

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Re: F9 Block 5 Updates and Discussion
« Reply #226 on: 03/31/2017 08:36 PM »
Steven Clarke: Do you have customers signed up for reused rocket flights? Where is FH?

Musk: Yes.  Excluded FH, there are three or four more this year signed up on contingency basis.  Think we'll see more customers in future.  FH sounded easy; actually no, crazy hard.  Required redesign of center core.  Done with testing.  Cores are in final prep.  Finished in 2-3 months.  Late summer launch.

What do people think about those center core changes?  Are those also part of Block 5?  Will every core have those changes, or will there be dedicated FH center cores that would never fly as a single stick?

Offline Okie_Steve

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Re: F9 Block 5 Updates and Discussion
« Reply #227 on: 03/31/2017 10:23 PM »
He also said FH was crazy hard, had to completely redesign the center core, and that the boosters were refurbs. That certainly seems to imply two core versions - F9/booster and FH/center, or vanilla and chocolate if you prefer.

Online Lars-J

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Re: F9 Block 5 Updates and Discussion
« Reply #228 on: 03/31/2017 10:53 PM »
He also said FH was crazy hard, had to completely redesign the center core, and that the boosters were refurbs. That certainly seems to imply two core versions - F9/booster and FH/center, or vanilla and chocolate if you prefer.
That's not new. It has been known for a while that the FH core is a different (and stronger) version than F9/booster cores.

Offline matthewkantar

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Re: F9 Block 5 Updates and Discussion
« Reply #229 on: 04/01/2017 01:40 AM »
Slight change of subject, if SpaceX is going to have 24 hour turnarounds for the F-9, something fairly drastic has to be done about the leg folding situation. Going to forged titanium grid fins is a seriously expensive, even extreme step. Now that we know the scale of the grid fin improvement, anyone have any ideas about  what an iteration on that scale would look like for the legs?

Matthew

Offline Space Ghost 1962

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Re: F9 Block 5 Updates and Discussion
« Reply #230 on: 04/01/2017 02:07 AM »
Get rid of the legs. Use a mobile, teleoperated vehicle not unlike the folding jackscrew one soon to be deployed, but instead capture the landing vehicle at the attach points with inverse legs / "tulip" fixtures.

Offline CharlieWildman

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Re: F9 Block 5 Updates and Discussion
« Reply #231 on: 04/01/2017 02:13 AM »
Slight change of subject, if SpaceX is going to have 24 hour turnarounds for the F-9, something fairly drastic has to be done about the leg folding situation. Going to forged titanium grid fins is a seriously expensive, even extreme step. Now that we know the scale of the grid fin improvement, anyone have any ideas about  what an iteration on that scale would look like for the legs?

Matthew

IMHO, landing back on the launch mount for RTLS is really the only way to achieve a true 24 hour turnaround.  No leg upgrade needed!  Ducking and running now...   :P
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Offline Stan-1967

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Re: F9 Block 5 Updates and Discussion
« Reply #232 on: 04/01/2017 02:32 AM »
Question, would the 10% thrust upgrade Elon mentioned in the presser include the vacuum version on the second stage?  If so wouldn't that be an immense improvement?  Would that possibly explain why we are suddenly talking about S2 recovery again (even if he said it'd be a 'Hail Mary')?

If I recall correctly, somewhere in the post SES-10 press conference, E. Musk re-iterated that future F9 upperstage would still have a 210,000 lb Thrust rating.  So no increase to the M1-D Vac engine. 

As to S2 recovery, whatever they think they are going to try may have more to do with progress in controlled landing of the fairings.    S2 will never have the margins for the type of propulsive return that S1 accomplishes.  At best I think you can kill a bit of re-entry speed, & what does that buy them?  More likely you take the mass penalty on a TPS, shed your velocity on a shallow entry profile  & see if you can deploy a parachute to make a soft landing.

The "hail mary" football analogy is apt, as most "hail mary's" end up sailing out of the endzone, off the recievers fingertips, or into the hands of the defenders.   It will be damn hard to do a precision landing of a S2 onto any platform, bouncy castle, or mid air capture zone.   

But it is theoretically possible....

Offline macpacheco

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Re: F9 Block 5 Updates and Discussion
« Reply #233 on: 04/01/2017 06:19 AM »
Question, would the 10% thrust upgrade Elon mentioned in the presser include the vacuum version on the second stage?  If so wouldn't that be an immense improvement?  Would that possibly explain why we are suddenly talking about S2 recovery again (even if he said it'd be a 'Hail Mary')?
The benefit of extra thrust on the 2nd stage is even less significant unless the stage were to be stretched, and this has been discussed ad nauseum, the stages are already as long as they can be due to road transport issues.
The faster the stage is going, the less its affected by gravity.
Gravity losses are the worst right at take off.
2nd stage recovery experiments can likely be done once Block V is flying, even if only on LEO missions. Worst case move booster recovery to ASDS and there will be plenty of performance left on the 2nd stage to re-enter.
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Offline MP99

Re: F9 Block 5 Updates and Discussion
« Reply #234 on: 04/01/2017 07:27 AM »


Musk: New design coming for Grid Fin.  Will be largest titanium forging in the world.  Current Grid Fin is aluminum and gets so hot it lights on fire... which isn't good for reuse.

Seems like the fins will be a part of this upgrade.

And contribute to an improvement in payload to orbit, too.

I'm not sure what the mechanism is for improving payload? A smaller "boostback" / targeting burn?

Transcript of the post launch press conference by reddit user robbak:

Part 1

Part 2

Part 3

Part 4
Quote
treyrey
Elon: "The new grid fins will be, should be capable of taking a scorching and being fine. And they'll also have significantly more control authority so that should improve the re-usability of the rocket. But we will actually improve the payload to orbit by being able to fly at a higher angle of attack, and use the aerodynamic elements of the rocket to effectively glide like a big cylinder, it actually does have a L/D (lift / drag ratio) of roughly 1 if flown at the right angle of attack, but you need the control authority, particularly pitch control authority, that's higher than we currently have to achieve that." (Youtube video 31:30)

Edit: I believe he said "big cylinder" not fixed wing, based on hi-res video by Travis

Offline jpo234

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Re: F9 Block 5 Updates and Discussion
« Reply #235 on: 04/01/2017 09:35 AM »
Slight change of subject, if SpaceX is going to have 24 hour turnarounds for the F-9, something fairly drastic has to be done about the leg folding situation. Going to forged titanium grid fins is a seriously expensive, even extreme step. Now that we know the scale of the grid fin improvement, anyone have any ideas about  what an iteration on that scale would look like for the legs?

Matthew

IMHO, landing back on the launch mount for RTLS is really the only way to achieve a true 24 hour turnaround.  No leg upgrade needed!  Ducking and running now...   
The 24 hour reflight will supposedly come at the end of 2017. I don't see that they will make changes to the pads in just a few months.
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Offline cscott

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Re: F9 Block 5 Updates and Discussion
« Reply #236 on: 04/01/2017 11:34 AM »

I'm not sure what the mechanism is for improving payload? A smaller "boostback" / targeting burn?

Any chance the new grid fins will pop open on ascent?  Perhaps they can maintain AoA without thrust vectoring, allowing the engine thrust to be used more effectively.  For example, the "free" lift generated by the high AoA would be used to gain altitude allowing the engine thrust to more directly contribute to delta v?

Such a scheme would have to trade off against the extra drag generated by the deployed grid fins. I've no idea if it's worth it.  But something like this would match more directly with Elon's statements about increased payload, which don't seem to have the qualifications you'd expect if he were talking about only "increased payload for RTLS launches".

Online douglas100

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Re: F9 Block 5 Updates and Discussion
« Reply #237 on: 04/01/2017 12:30 PM »

Any chance the new grid fins will pop open on ascent? 

Doubt it. When Musk talks about extra control and higher angles of attack being flown due to the new grid fins, I think he's talking about descent only. Higher angle of attack would then create higher drag on entry and allow prop savings for both the entry and landing burns.
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Offline Herb Schaltegger

Re: F9 Block 5 Updates and Discussion
« Reply #238 on: 04/01/2017 12:59 PM »

Any chance the new grid fins will pop open on ascent? 

Doubt it. When Musk talks about extra control and higher angles of attack being flown due to the new grid fins, I think he's talking about descent only. Higher angle of attack would then create higher drag on entry and allow prop savings for both the entry and landing burns.

Indeed. Much higher ascent drag and really not the right place, geometrically, to get the best attitude control during ascent. You want to keep that CoL behind the CoM for stability reasons. Plus, you really don't need much if any engine gimbal for a whole lot of control authority, which only improves as the stage mass decreases.

Another consideration is that if the fins deployed on ascent, you'd have shock impingement heating further down on the side of the S1 tanks, which would not be a good thing at all.
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Offline The Amazing Catstronaut

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Re: F9 Block 5 Updates and Discussion
« Reply #239 on: 04/01/2017 01:16 PM »
Get rid of the legs. Use a mobile, teleoperated vehicle not unlike the folding jackscrew one soon to be deployed, but instead capture the landing vehicle at the attach points with inverse legs / "tulip" fixtures.

F9 looks somewhat naked without the legs. It's an important part of the aesthetic - and it brings tears to my eyes to note that good looks do not bring mass to orbit.

They've talked about reinforced, early-extendable legs to help with aerobreaking significantly before contact with the surface. Which is more useful, extra drag, or no leg mass and some practical BFR capture experience?

I'd go for the latter.
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