Author Topic: SpaceX Falcon Heavy Discussion Thread  (Read 410251 times)

Offline Funchucks

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SpaceX Falcon Heavy Discussion Thread
« on: 08/04/2013 08:49 PM »
Thread for Falcon Heavy discussion.
« Last Edit: 01/09/2014 12:06 AM by Chris Bergin »

Offline mmeijeri

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Re: SpaceX Falcon Heavy Discussion Thread
« Reply #1 on: 08/04/2013 09:13 PM »
To go up to 13200kg to Mars seems to require something more than just cross-feed, as does 21,200kg to GTO.

I was surprised by that too. The ~21mT had been bandied around before, but I thought it had been superseded. As for explanations for the increased performance, so far I've seen a tank stretch, higher chamber pressure, higher expansion ratio and cross-feed. It kind of worries me that they're changing so much all at once before we've had even a single F9 flight to GTO. What's driving all this? Previously I thought it was performance shortfalls to GTO, but if the 21mT is real, that can't be the case.
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Offline meekGee

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Re: SpaceX Falcon Heavy Discussion Thread
« Reply #2 on: 08/04/2013 09:38 PM »
.. maybe this thread and the FH Master Speculation Thread should be merged and renamed to drop the 5/22 reference...

My speculation:  Isn't it odd that a company in SpaceX's position (in the middle of active in-house stage development) will create a 3x powerful rocket, yet still use the same US for it?

I can see a company deciding to live with a sub-optimal US if it saves them expensive procurement at the present time - but SpaceX would be developing such a stage themselves.

Why not announce it, even if it is not yet ready?

My only thought is that perhaps the Methane stage is further along then we think, to the point where they won't put in the effort to make a 2-engine kerolox upper stage since they know they'll debut the methane engine on the US, say within 2 years, and the current US is good enough for the time being.
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Online pippin

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Re: SpaceX Falcon Heavy Discussion Thread
« Reply #3 on: 08/04/2013 09:47 PM »
Or (my take) the current upper stage is good enough for quite a while.
Most of what they are going to fly with FH in the next few years will probably be GEO comsats and since they didn't even announce a dual-launch capability, the current FH design is probably powerful enough for that. So why develop something new?
This is probably also why we won't see crossfeed in the forseeable future.

My take would be that FH is a transitional product for them until they can get the single-core F9 to a level where they can actually cover most of their comsat business with it.

It also all makes sense with an eye on reusability. If they really can pull that off, it will be first stage only, at least for quite a while. That could (_if_ it also works from a business POV) make using FH less of a cost driver and in that scenario it actually makes sense to have the expendable second stage as simple as possible. If, of course, they can really recover the FH center core, too, which I still don't see how and they seem to hint at that they don't really have a plan, either.

Offline SpacexULA

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Re: SpaceX Falcon Heavy Discussion Thread
« Reply #4 on: 08/04/2013 09:59 PM »
My only thought is that perhaps the Methane stage is further along then we think, to the point where they won't put in the effort to make a 2-engine kerolox upper stage since they know they'll debut the methane engine on the US, say within 2 years, and the current US is good enough for the time being.

SpaceX has always shopped out what they plan to have as much or more than what they do have.  All the flights of Falcon 1 where sold before it's first launch, all the flights on Falcon 9 1.0 where sold before it's first launch.

They are booked solid till at least 2016, it could just mean that have something in the works that will be ready by 2016.

Could be a Raptor based upper stage, or even something as "simple" as a Super Draco/Draco based 3rd stage.
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Offline SpacexULA

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Re: SpaceX Falcon Heavy Discussion Thread
« Reply #5 on: 08/04/2013 10:39 PM »
I just don't believe the 21 and 53 ton figures are based on anything that's not as described.

They must believe they can achieve that performance with the system as advertised, and at the advertised price.

The vast majority of the Falcon 9/heavy manifest where sold before Falcon 1.1 was even talked about.  They knew pretty quickly after the first launch that they where not going to be able to launch at the tempo needed with the Falcon 1.0 design, but they didn't let the cat out of the bag till just a few months ago.

Point being SpaceX is perfectly willing to sell flights on hardware not finished developing or announced yet.
« Last Edit: 08/04/2013 10:40 PM by SpacexULA »
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Offline SpacexULA

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Re: SpaceX Falcon Heavy Discussion Thread
« Reply #6 on: 08/05/2013 12:25 AM »
No I only stated they could not produce Falcon 1.0 fast enough profitably to meet their manifested launch rate, not that it could not lift the payloads.

Everything they have on their manifest to date I am 100% sure they have the hardware in the pipeline to complete the contract, no way they are that foolish.

There is nothing wrong with selling Falcon Heavy at a certain capacity as long as you know you can get it there before you ever launch the payload.
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Offline beancounter

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Re: SpaceX Falcon Heavy Discussion Thread
« Reply #7 on: 08/05/2013 05:57 AM »
To go up to 13200kg to Mars seems to require something more than just cross-feed, as does 21,200kg to GTO.

I was surprised by that too. The ~21mT had been bandied around before, but I thought it had been superseded. As for explanations for the increased performance, so far I've seen a tank stretch, higher chamber pressure, higher expansion ratio and cross-feed. It kind of worries me that they're changing so much all at once before we've had even a single F9 flight to GTO. What's driving all this? Previously I thought it was performance shortfalls to GTO, but if the 21mT is real, that can't be the case.

What's driving all this?  Well, root cause - Elon wants to get to Mars.  That's enough.  Everything else is a means to that end.
Ok call it wishful thinking but show me some other root cause for SpaceX.  It's not just about the money.
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Offline MikeAtkinson

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Re: SpaceX Falcon Heavy Discussion Thread
« Reply #8 on: 08/05/2013 08:24 AM »
To go up to 13200kg to Mars seems to require something more than just cross-feed, as does 21,200kg to GTO.

I was surprised by that too. The ~21mT had been bandied around before, but I thought it had been superseded. As for explanations for the increased performance, so far I've seen a tank stretch, higher chamber pressure, higher expansion ratio and cross-feed. It kind of worries me that they're changing so much all at once before we've had even a single F9 flight to GTO. What's driving all this? Previously I thought it was performance shortfalls to GTO, but if the 21mT is real, that can't be the case.

My reply went to the other thread, so I'm including it here as well.

"I don't understand what is driving this either. Getting 53 tonnes to LEO and 21.1 tonnes to GTO both seem on the edge of what is possible, doing both with the same upper stage is in my opinion impossible. The GTO/TMI stage would need about 30 tonnes extra propellant for GTO and 40 tonnes extra for TMI.

13.2 tonnes is too small for Dragon to Mars with crew, even inspiration Mars needs more than that. I think it is also more than Red Mars needs. Payload to L1/L2 will be about 15 tonnes (give or take depending on whether a slow trajectory is used), that should be more than adequate for crewed Dragon.

Perhaps they are just stating the optimised payloads to various orbits, but won't actually produce optimised hardware unless they get an (multiple launch?) order."

Offline Roy_H

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Re: SpaceX Falcon Heavy Discussion Thread
« Reply #9 on: 08/05/2013 02:51 PM »
It also all makes sense with an eye on reusability. If they really can pull that off, it will be first stage only, at least for quite a while. That could (_if_ it also works from a business POV) make using FH less of a cost driver and in that scenario it actually makes sense to have the expendable second stage as simple as possible. If, of course, they can really recover the FH center core, too, which I still don't see how and they seem to hint at that they don't really have a plan, either.

From KSC it would be difficult to recover the core booster stage, but from Brownsville I think they could pick a convenient island down range, Bahamas to Puerto Rico to land the FH core.
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Offline MikeAtkinson

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Re: SpaceX Falcon Heavy Discussion Thread
« Reply #10 on: 08/05/2013 03:34 PM »
"I don't understand what is driving this either. Getting 53 tonnes to LEO and 21.1 tonnes to GTO both seem on the edge of what is possible, doing both with the same upper stage is in my opinion impossible. The GTO/TMI stage would need about 30 tonnes extra propellant for GTO and 40 tonnes extra for TMI.
A tank stretch makes sense.  They already do the same bodies and tanks at three or four different lengths.  What's the problem with five or six?

Not much, but they would be similar 2nd stages, not the same.

Online pippin

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Re: SpaceX Falcon Heavy Discussion Thread
« Reply #11 on: 08/05/2013 04:25 PM »

From KSC it would be difficult to recover the core booster stage, but from Brownsville I think they could pick a convenient island down range, Bahamas to Puerto Rico to land the FH core.

Well, Musk has said on Twitter that it will be a challenge and they'd have to land on an Ocean platform. I trust him on that. And he sounded like they don't really have a solution for this. That was what I was referring to when I said "they don't seem to really have a plan".
« Last Edit: 08/05/2013 04:26 PM by pippin »

Offline Zed_Noir

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Re: SpaceX Falcon Heavy Discussion Thread
« Reply #12 on: 08/05/2013 08:19 PM »
It also all makes sense with an eye on reusability. If they really can pull that off, it will be first stage only, at least for quite a while. That could (_if_ it also works from a business POV) make using FH less of a cost driver and in that scenario it actually makes sense to have the expendable second stage as simple as possible. If, of course, they can really recover the FH center core, too, which I still don't see how and they seem to hint at that they don't really have a plan, either.

From KSC it would be difficult to recover the core booster stage, but from Brownsville I think they could pick a convenient island down range, Bahamas to Puerto Rico to land the FH core.

Why would anyone wants to have a flight path between Cuba and Florida. There are just too many populated areas along the flight path.

It would be better have a flight path between the Yucatan peninsula and Cuba mostly over water.

It will probably be an oceanic landing platform of some sort for core recovery. Think most if not all the governments on small Caribbean Islands really wants to explain why a ballistic vehicle heading their way is a good thing.

Offline baldusi

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Re: SpaceX Falcon Heavy Discussion Thread
« Reply #13 on: 08/05/2013 09:26 PM »
The southerner flight path from Texas the higher the angle of the orbital plane inclination to the equator. What's the point of going to Texas if you end up in a 35deg orbital plane? They need about 15deg from the equator to get to the industry standard 1,500m/s delta-v deficit. Going lower means more delta-v, or way less payload. Plus, then they would overflight a lot of Brazil. I don't believe that's a good proposal. And they can't reach the ISS plane either.

Offline Lars_J

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Re: SpaceX Falcon Heavy Discussion Thread
« Reply #14 on: 08/05/2013 10:03 PM »
It also all makes sense with an eye on reusability. If they really can pull that off, it will be first stage only, at least for quite a while. That could (_if_ it also works from a business POV) make using FH less of a cost driver and in that scenario it actually makes sense to have the expendable second stage as simple as possible. If, of course, they can really recover the FH center core, too, which I still don't see how and they seem to hint at that they don't really have a plan, either.

From KSC it would be difficult to recover the core booster stage, but from Brownsville I think they could pick a convenient island down range, Bahamas to Puerto Rico to land the FH core.

Why would anyone wants to have a flight path between Cuba and Florida. There are just too many populated areas along the flight path.

It would be better have a flight path between the Yucatan peninsula and Cuba mostly over water.

It will probably be an oceanic landing platform of some sort for core recovery. Think most if not all the governments on small Caribbean Islands really wants to explain why a ballistic vehicle heading their way is a good thing.


This was discussed pretty in-depth in this thread: http://forum.nasaspaceflight.com/index.php?topic=31348.0

Offline Garrett

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Re: SpaceX Falcon Heavy Discussion Thread
« Reply #15 on: 09/13/2013 02:52 PM »
Wanted to read and post about Falcon Heavy, and since the locking and transfer of the old Master Updates thread to the archive section it looks like this is the main FH thread. Maybe an updates or a "discussion and updates" thread is required?

In the meantime, using Chris's opening post on the old Master Update thread, I thought it would be useful to create an updated list of links:

Links of reference:
Old Falcon Heavy Master Update Thread  (Read 198660 times)
http://forum.nasaspaceflight.com/index.php?topic=24711.0

Falcon Heavy Engineering Master Speculation Thread
http://forum.nasaspaceflight.com/index.php?topic=29214.0

Falcon Heavy announcement thread:
http://forum.nasaspaceflight.com/index.php?topic=24641.0

NSF news articles on the Falcon Heavy:
http://www.nasaspaceflight.com/tag/falcon-heavy/

NSF SpaceX Articles (Recent):
http://www.nasaspaceflight.com/tag/spacex/

NSF SpaceX Articles (Older - including lots of exclusive Elon interviews):
http://forum.nasaspaceflight.com/index.php?topic=21862.0

SpaceX Forum General Section:
http://forum.nasaspaceflight.com/index.php?board=45.0

SpaceX Forum Missions Section
http://forum.nasaspaceflight.com/index.php?board=55.0

L2's SpaceX content:
http://forum.nasaspaceflight.com/index.php?board=60.0
(including a locked FH thread: http://forum.nasaspaceflight.com/index.php?topic=24704.75)
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Offline Garrett

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Re: SpaceX Falcon Heavy Discussion Thread
« Reply #16 on: 09/13/2013 02:58 PM »
Following the recent F9 v1.1 rollout for a static fire, two forum users modified some photos to give us an idea of what the real FH will look like. I'm attaching their respective images to this post.
The first is by user NovaSilisko, the second by user TetraOmni.
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Offline M129K

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Re: SpaceX Falcon Heavy Discussion Thread
« Reply #17 on: 09/13/2013 03:06 PM »
Those concepts look awesome! Also, thanks for bumping this thread Garret, I didn't realize it even existed.

To get right onto the topic, has anyone been able to realistically model the 21.2 ton GTO payload? I have tried to do so but 18 tons seems kind of the limit. I've argued over the LEO payload before but GTO will actually be much more important for commercial applications.

Offline go4mars

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Re: SpaceX Falcon Heavy Discussion Thread
« Reply #18 on: 09/13/2013 04:18 PM »
I assume 53 tonnes to LEO implies within a 5.2 meter diameter fairing. 

As the fairing gets large in diameter, the 53 tonne number will shrink due to increased drag.   

If you wanted to get, say, 25 tonnes to orbit (including extra mass of plf), how large could the diameter be? 

Are there charts out there showing diameter vs. mass? 
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Offline Jim

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Re: SpaceX Falcon Heavy Discussion Thread
« Reply #19 on: 09/13/2013 04:21 PM »


As the fairing gets large in diameter, the 53 tonne number will shrink due to increased drag.   


no, it will be due to the larger mass of the fairing

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