Author Topic: SpaceX Falcon Heavy Discussion (Thread 6)  (Read 533288 times)

Offline wannamoonbase

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #680 on: 05/30/2018 01:20 pm »
3) Crossfeed is MUCH better. it empties and ditches the side boosters sooner while having the most thrust available and a full core stage at staging. The only way to improve on crossfeed would be to stretch the upper stage.

Or, build a much larger fully reusable 2 stage vehicle. Much less complicated to fly.

I love crossfeed, I wish they were developing it, it'd be the coolest feature of any flying rocket.

But it's not needed, sadly.
Wildly optimistic prediction, Superheavy recovery on IFT-4 or IFT-5

Offline cscott

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #681 on: 05/30/2018 03:13 pm »
Apparently Europa Clipper direct to Jupiter is marginal currently on FH.  I wonder if crossfeed would improve those margins enough to make it worth the investment?

Of course that assumes that there is any way that SpaceX could get the contract to launch Europa Clipper, which seems impossible for political reasons.

Offline Lars-J

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #682 on: 05/30/2018 04:40 pm »
Something like the current profile but shutdown the center core part way up and then restart center after staging. Alternatively deep throttling could do much of this without stopping and restarting.

EDIT: we do know that the throttling of the first FH was VERY conservative. They only ran the engines at 90% thrust? How deep can a M1D throttle? 30% ?
Probably a LOT of room for improvement.
(1) Without some changes to the Octoweb, only three of the engines can be started (or restarted) during flight.
(2) It is not clear (to me, at least) whether the Merlins can be throttled down from 100% to 60% (40% down), or from 100% to 40% (60% down).

They can throttle down to 40% of the thrust. (So a 60% range)

Offline leetdan

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #683 on: 05/30/2018 06:10 pm »
The question came up in the LEGO FH thread, do we know if the Block 5 side booster nose cones are going to be TPS-black like the interstage?

To this layperson, the cones get the 9-engine center core plume at a closer range than the interstage gets the 1-engine stage 2 plume.  Other reentry stresses should be similar, so shouldn't the cones get the same TPS treatment as the interstage?

Offline speedevil

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #684 on: 05/30/2018 06:47 pm »
Apparently Europa Clipper direct to Jupiter is marginal currently on FH.  I wonder if crossfeed would improve those margins enough to make it worth the investment?

Of course that assumes that there is any way that SpaceX could get the contract to launch Europa Clipper, which seems impossible for political reasons.

It also assumes that developing crossfeed is not more expensive than stretching the second stage.
Elon: We’ve already stretched the upper stage once. Easiest part of the rocket to change.

The capacity of FH is reportedly marginal and unclear on the direct jupiter injection for EC.
Hardware mods are one way of fixing it - changing the spec and going from 'won't quite make it' to 'will just make it' are quite plausible.
As is a five ton kick stage.

Or you can go full Kerbal.
Quote
We could really dial it up to as much performance as anyone could ever want. If we wanted to we could actually add two more side boosters and make it Falcon Super Heavy

« Last Edit: 05/30/2018 07:36 pm by speedevil »

Offline docmordrid

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #685 on: 05/30/2018 07:35 pm »
Just adding the link..,

The Verge....(Feb 5, 2018)

>
Or you can go full Kerbal.
Quote
We could really dial it up to as much performance as anyone could ever want. If we wanted to we could actually add two more side boosters and make it Falcon Super Heavy
DM

Offline johnfwhitesell

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #686 on: 05/30/2018 08:12 pm »
Europa Clipper is too important to settle for 5 cores.  We need at least 9.  You'll know it's happening when they move JRTI to Taiwan.

Offline Prettz

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #687 on: 05/30/2018 08:42 pm »
I love crossfeed, I wish they were developing it, it'd be the coolest feature of any flying rocket.

But it's not needed, sadly.
On the other hand, think about it from the other direction. If it WAS needed, SpaceX would've needed to spend more precious time and money just to get FH flying.

Offline woods170

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #688 on: 05/31/2018 07:10 am »
Apparently Europa Clipper direct to Jupiter is marginal currently on FH.  I wonder if crossfeed would improve those margins enough to make it worth the investment?

Of course that assumes that there is any way that SpaceX could get the contract to launch Europa Clipper, which seems is impossible for political reasons.

Why did you even bother to bring the Off-Topic subject of Europa Clipper into this discussion? See your own last line (bolded).
« Last Edit: 05/31/2018 07:11 am by woods170 »

Offline hkultala

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #689 on: 05/31/2018 07:23 am »
Apparently Europa Clipper direct to Jupiter is marginal currently on FH.  I wonder if crossfeed would improve those margins enough to make it worth the investment?

Of course that assumes that there is any way that SpaceX could get the contract to launch Europa Clipper, which seems impossible for political reasons.

It also assumes that developing crossfeed is not more expensive than stretching the second stage.
Elon: We’ve already stretched the upper stage once. Easiest part of the rocket to change.

The capacity of FH is reportedly marginal and unclear on the direct jupiter injection for EC.
Hardware mods are one way of fixing it - changing the spec and going from 'won't quite make it' to 'will just make it' are quite plausible.
As is a five ton kick stage.

Or you can go full Kerbal.
Quote
We could really dial it up to as much performance as anyone could ever want. If we wanted to we could actually add two more side boosters and make it Falcon Super Heavy

It's not only about development cost. It's also about needed facilities, building them , and their cost.

Cross-feed requires no changes to existing facilities, but requires considerable amount of development work and new technical solutions.

Stretching second stage is quite trivial to develop, but would require some changes to the launch infrastructure  and might make the pad infrastructure incompatible with F9. These changes should however be relatively cheap to make.

Going to kerbal mode and adding more side boosters would mean huge and very expensive changes to launch infrastructure.
« Last Edit: 05/31/2018 07:31 am by hkultala »

Offline Burninate

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #690 on: 05/31/2018 09:01 pm »
I'm curious about staging strategies but simply don't know enough to fully figure various options out. Irrespective of the economics, business strategy, or likelihood of implementation, what sort of impact on payload and reachable orbits would the following setups result in?

1) shortening the center core and elongating the 2nd stage by the same amount for more prop in the US.

2) launch using side cores, igniting center core at booster sep. Is this even possible? I presume this would make the core expendable also?

3) crossfeed vs the current throttling of the core. Does this result in the same performance as scenario 2?

Lastly, can anyone point me to a good resource that compares various parallel vs serial staging strategies? I would have thought this would be easy information to come across but maybe I'm just struggling with right search terms.

1) doesn't help much unless also combined with crossfeed

2) gravity losses probably cause this to be worse than the current launch profile with the center core throttling down early.

3) Crossfeed is MUCH better. it empties and ditches the side boosters sooner while having the most thrust available and a full core stage at staging. The only way to improve on crossfeed would be to stretch the upper stage.

After KSP taught me rocket science, crossfeed & asparagus staging seemed like a make-or-break thing - why would you ever operate a three-core rocket without it?  But it turns out, in reality the weight of the engines and tankage is proportionately much lower IRL than in KSP, and this provides a corresponding dramatic decrease in the dV benefits you get out of crossfeed and out of additional stages.

« Last Edit: 05/31/2018 09:16 pm by Burninate »

Offline Owlon

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #691 on: 05/31/2018 09:15 pm »
I'm curious about staging strategies but simply don't know enough to fully figure various options out. Irrespective of the economics, business strategy, or likelihood of implementation, what sort of impact on payload and reachable orbits would the following setups result in?

1) shortening the center core and elongating the 2nd stage by the same amount for more prop in the US.

2) launch using side cores, igniting center core at booster sep. Is this even possible? I presume this would make the core expendable also?

3) crossfeed vs the current throttling of the core. Does this result in the same performance as scenario 2?

Lastly, can anyone point me to a good resource that compares various parallel vs serial staging strategies? I would have thought this would be easy information to come across but maybe I'm just struggling with right search terms.

1) doesn't help much unless also combined with crossfeed

2) gravity losses probably cause this to be worse than the current launch profile with the center core throttling down early.

3) Crossfeed is MUCH better. it empties and ditches the side boosters sooner while having the most thrust available and a full core stage at staging. The only way to improve on crossfeed would be to stretch the upper stage.

After KSP taught me rocket science, crossfeed & asparagus staging seemed like a make-or-break thing - why would you ever operate a three-core rocket without it?  But it turns out, in reality the weight of the engines and tankage is proportionately much lower IRL than in KSP, and this provides a corresponding dramatic decrease in the benefits you get out of crossfeed and out of additional stages.

Yep, common misconception stemming from KSP! It really boosts LEO payload performance by something a bit over 10%, IIRC--from some old FH modeling I read here, at least.

...not to mention actually implementing crossfeed is hugely more complicated than slapping on your handy yellow external fuel ducts.

Offline Burninate

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #692 on: 05/31/2018 09:16 pm »
A reasonable KSP atmospheric stage may have a wet to dry mass ratio of 6:1, while a Falcon rocket might be 20:1.

This reduces the benefit you get out of additional stage drops drastically.
« Last Edit: 05/31/2018 09:19 pm by Burninate »

Offline cscott

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #693 on: 06/02/2018 02:34 am »


Why did you even bother to bring the Off-Topic subject of Europa Clipper into this discussion? See your own last line (bolded).

Just casting about for other eventualities that might trigger another look at crossfeed. As I said, Europa Clipper looks like an extreme long-shot, but I thought that mentioning the possibility might shake out some other large NASA missions that *just might* (as a long shot) manage to get funded and create a forcing function for further FH development.

It would have to be something with an existing design or hardware, though---otherwise you'd just design your mission 10% lighter.

Offline docmordrid

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #694 on: 06/22/2018 02:10 am »
https://twitter.com/jeff_foust/status/1009912347362844672?s=19

@jeff_foust
SpaceX has won a $130M contract from the US Air Force to launch the AFSPC-52 mission on a Falcon Heavy: https://t.co/UC6wV436GW

Quote
AIR FORCE

Space Exploration Technologies Corp. (SpaceX), Hawthorne, California, has been awarded a $130,000,000 firm-fixed-price contract, for launch services to deliver the Air Force Space Command-52 satellite to its intended orbit.  This launch service contract will include launch vehicle production and mission, as well as integration, launch operations and spaceflight worthiness activities.  Work will be performed in Hawthorne, California; Kennedy Space Center, Florida; and McGregor, Texas, and is expected to be completed by September 2020.  This award is the result of a competitive acquisition, and two proposals were received.  Fiscal 2018 space procurement funds in the amount of $130,000,000 will be obligated at the time of award.  The Contracting Division, Launch Systems Enterprise Directorate, Space and Missile Systems Center, Los Angeles Air Force Base, California, is the contracting activity (FA8811-18-C-0003). (Awarded June 20, 2018)
« Last Edit: 06/22/2018 02:14 am by docmordrid »
DM

Online gongora

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #695 on: 06/22/2018 03:04 am »
https://twitter.com/jeff_foust/status/1009912347362844672?s=19

@jeff_foust
SpaceX has won a $130M contract from the US Air Force to launch the AFSPC-52 mission on a Falcon Heavy: https://t.co/UC6wV436GW

Quote
AIR FORCE

Space Exploration Technologies Corp. (SpaceX), Hawthorne, California, has been awarded a $130,000,000 firm-fixed-price contract, for launch services to deliver the Air Force Space Command-52 satellite to its intended orbit.  This launch service contract will include launch vehicle production and mission, as well as integration, launch operations and spaceflight worthiness activities.  Work will be performed in Hawthorne, California; Kennedy Space Center, Florida; and McGregor, Texas, and is expected to be completed by September 2020.  This award is the result of a competitive acquisition, and two proposals were received.  Fiscal 2018 space procurement funds in the amount of $130,000,000 will be obligated at the time of award.  The Contracting Division, Launch Systems Enterprise Directorate, Space and Missile Systems Center, Los Angeles Air Force Base, California, is the contracting activity (FA8811-18-C-0003). (Awarded June 20, 2018)

Well that didn't take long, the FH isn't even certified yet.  I bet the $130M price was very competitive.  I wonder if the mission requirements required ULA to bid a DIVH or a Atlas-V with multiple SRB's?

There is a thread for this:
https://forum.nasaspaceflight.com/index.php?topic=45886.0

Offline wannamoonbase

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #696 on: 07/21/2018 04:28 pm »
Have to admit to some surprise that the Telstar 19 going up tonight is 7000 kg and larger than FH’s Arabsat 6. 

The FH seems to have less and less market, currently.  Which is a shame. 
Wildly optimistic prediction, Superheavy recovery on IFT-4 or IFT-5

Offline Hauerg

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #697 on: 07/21/2018 04:44 pm »
Only for us launcherjunkies.

Offline envy887

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #698 on: 07/21/2018 04:46 pm »
Have to admit to some surprise that the Telstar 19 going up tonight is 7000 kg and larger than FH’s Arabsat 6. 

The FH seems to have less and less market, currently.  Which is a shame.

FH could give it a much better orbit for a not much higher price.

Offline Nomadd

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #699 on: 07/21/2018 05:19 pm »
Have to admit to some surprise that the Telstar 19 going up tonight is 7000 kg and larger than FH’s Arabsat 6. 

The FH seems to have less and less market, currently.  Which is a shame.

FH could give it a much better orbit for a not much higher price.
I've seen a few six hour 2nd stage coasts and firings now. Is the Falcon considered able to do direct GSO?
Those who danced were thought to be quite insane by those who couldn't hear the music.

 

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