Author Topic: SpaceX Falcon Heavy Discussion (Thread 6)  (Read 533375 times)

Offline sevenperforce

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #560 on: 02/20/2018 06:33 pm »
I can't seem to find that the full payload weight of the Tesla and mounting stand (for a better word) that the FH launched.  Basically I am wondering what the total weight.  SpaceX says FH can do 16,800 kg (37,000 lb) to trans-Mars injection.  A Tesla alone obviously doesn't eight 37,000 pounds.
A fully-recoverable FH can only do about 3.17 tonnes to TMI. That 16.8-tonne figure is with all three cores expended.

Offline envy887

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #561 on: 02/21/2018 03:04 am »
I can't seem to find that the full payload weight of the Tesla and mounting stand (for a better word) that the FH launched.  Basically I am wondering what the total weight.  SpaceX says FH can do 16,800 kg (37,000 lb) to trans-Mars injection.  A Tesla alone obviously doesn't eight 37,000 pounds.
A fully-recoverable FH can only do about 3.17 tonnes to TMI. That 16.8-tonne figure is with all three cores expended.

With 3-core RTLS and a massive center core boostback, maybe it can only do 3 tonnes to TMI. With all downrange landings it could do much more. Probably like 10 tonnes.

Offline hkultala

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #562 on: 02/21/2018 08:14 am »
I can't seem to find that the full payload weight of the Tesla and mounting stand (for a better word) that the FH launched.  Basically I am wondering what the total weight.  SpaceX says FH can do 16,800 kg (37,000 lb) to trans-Mars injection.  A Tesla alone obviously doesn't eight 37,000 pounds.
A fully-recoverable FH can only do about 3.17 tonnes to TMI. That 16.8-tonne figure is with all three cores expended.

Where is your 3.17 tonne number based on?
Calculations based on FH test flight staging point and delta-v of falcon second stage?

The test flight was using block 3 side boosters. Final FH will use block 5 side boosters which will have more thrust, giving both better T/W for both smaller gravity losses and possibly more fuel in center core at staging point if the center core average thrust is not increased as much.

Also the NASA launcher performance query seems to give much higher numbers.

« Last Edit: 02/21/2018 08:28 am by hkultala »

Offline niwax

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #563 on: 02/21/2018 12:34 pm »
I can't seem to find that the full payload weight of the Tesla and mounting stand (for a better word) that the FH launched.  Basically I am wondering what the total weight.  SpaceX says FH can do 16,800 kg (37,000 lb) to trans-Mars injection.  A Tesla alone obviously doesn't eight 37,000 pounds.
A fully-recoverable FH can only do about 3.17 tonnes to TMI. That 16.8-tonne figure is with all three cores expended.

It should be noted that their trajectory was nowhere near optimal. You wouldn't usually do a GTO-capability demonstration before launching to Mars and then fire above the company headquarters to show off. So you have Oberth effect losses and on top of that a happy mix of booster blocks that I'm sure will not perform as well as 3x Block V when they have figured out minimal fuel to land.
« Last Edit: 02/21/2018 04:03 pm by niwax »
Which booster has the most soot? SpaceX booster launch history! (discussion)

Offline cscott

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #564 on: 02/21/2018 02:37 pm »


I can't seem to find that the full payload weight of the Tesla and mounting stand (for a better word) that the FH launched.  Basically I am wondering what the total weight.  SpaceX says FH can do 16,800 kg (37,000 lb) to trans-Mars injection.  A Tesla alone obviously doesn't eight 37,000 pounds.
A fully-recoverable FH can only do about 3.17 tonnes to TMI. That 16.8-tonne figure is with all three cores expended.

It should be noted that their trajectory was nowhere near optimal. You wouldn't usually do a GTO-capability demonstration before launching to Mars and then fire above the company headquarters to show off. So you have Oberth effect losses and on top of that a happy mix of booster blocks that I'm sure will not perform as well a 3x Block V when they have figured out minimal fuel to land.

Replace "fire above company headquarters" with "keep the window open for four hours and fire just before losing telemetry downlink" and I'm with you.  You can keep the "to show off" part though. :)

Offline DeanG1967

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #565 on: 02/24/2018 11:26 am »
Great discussion but nobody answered the question I asked.

What was the ACTUAL payload weight of the FH demo?

google says a Tesla model S weights 4,469 to 4,941 lbs.  FH can lift more than that but besides the mounting hardware was there other ballast in the payload??

Offline Kabloona

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #566 on: 02/24/2018 01:08 pm »
Great discussion but nobody answered the question I asked.

What was the ACTUAL payload weight of the FH demo?

google says a Tesla model S weights 4,469 to 4,941 lbs.  FH can lift more than that but besides the mounting hardware was there other ballast in the payload??

I haven't seen any definitive numbers, but I can't think of any reason to add ballast. SpaceX was apparently planning all along to burn to depletion and thus get the highest aphelion possible, so why bother to add ballast.

Offline oiorionsbelt

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #567 on: 02/24/2018 09:33 pm »
Great discussion but nobody answered the question I asked.

What was the ACTUAL payload weight of the FH demo?

google says a Tesla model S weights 4,469 to 4,941 lbs.  FH can lift more than that but besides the mounting hardware was there other ballast in the payload??
The Tesla payload may have weighed less than a standard Tesla Roadster. The front disc brakes were removed, for example.

Offline speedevil

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #568 on: 02/24/2018 10:08 pm »
Great discussion but nobody answered the question I asked.

What was the ACTUAL payload weight of the FH demo?

google says a Tesla model S weights 4,469 to 4,941 lbs.  FH can lift more than that but besides the mounting hardware was there other ballast in the payload??
The Tesla payload may have weighed less than a standard Tesla Roadster. The front disc brakes were removed, for example.
Or more - payload fitting and attach structure, ...

Offline cscott

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #569 on: 02/25/2018 12:05 am »
By far the largest component of the weight of the stock roadster is the battery pack.

I'm sure any customers who need to know have the exact mass and performance.

Offline envy887

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #570 on: 02/25/2018 12:07 am »
Great discussion but nobody answered the question I asked.

What was the ACTUAL payload weight of the FH demo?

google says a Tesla model S weights 4,469 to 4,941 lbs.  FH can lift more than that but besides the mounting hardware was there other ballast in the payload??

The payload was a Roadster, not a Model S. I haven't seen any evidence of ballast beyond the mass of the extra hardware that was attached.

Offline deruch

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #571 on: 03/01/2018 01:52 am »
I can't seem to find that the full payload weight of the Tesla and mounting stand (for a better word) that the FH launched.  Basically I am wondering what the total weight.  SpaceX says FH can do 16,800 kg (37,000 lb) to trans-Mars injection.  A Tesla alone obviously doesn't eight 37,000 pounds.

No one outside those involved in the process can give you any hard numbers.  A 2008 Tesla Roadster's curb weight is ~1300kg (per Wikipedia), but it wouldn't surprise me to learn that Elon had upgraded the battery on his at some point after delivery.  That was one option offered to all early Roadster owners.  So, that mass is probably low for his actual car.  Then, we don't have any idea of how much hardware was taken out of the car prior to launch.  As orionsbelt mentioned, we know at least some brakes were removed.  Was the battery taken out?  Or, maybe ballast was added to achieve a specific payload mass (or center of gravity or some other property)?  Then, there's the payload adapter (the bit that connected the car to the Payload Attach Fitting and kept it at the desired angle) which is a total black box in terms of weight.  Plus the added booms for camera mounting and the mass of Starman, etc.  Basically, no outsider has any idea. 

[My guess] Total mass of everything forward of the PAF interface: 1500kg
[/guess]
Shouldn't reality posts be in "Advanced concepts"?  --Nomadd

Offline speedevil

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #572 on: 03/01/2018 01:58 am »
[My guess] Total mass of everything forward of the PAF interface: 1500kg

I can't find a source saying the burn was to depletion.
Is there one?

Offline x15_fan

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #573 on: 03/01/2018 02:00 am »
[My guess] Total mass of everything forward of the PAF interface: 1500kg

I can't find a source saying the burn was to depletion.
Is there one?

Watch Musk at the FH press conference on YT.

Offline BradyKenniston

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #574 on: 03/07/2018 06:46 pm »
Found this crop a few days ago in my Falcon Heavy remote photos, it's not uber sharp but feel free to use as a wallpaper!

Offline Nehkara

Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #575 on: 04/04/2018 09:19 pm »
Hey everyone.

I have a question!

In a fair number of discussions I've had lately there is talk of Falcon Heavy's weak upper stage.

I understand that the 2nd stage is not as efficient and has a lower ISP compared to other rockets (i.e. Ariane 5, Atlas V), however, there seems to be significant doubt that the Falcon Heavy can even do what SpaceX claims it can. (3500 kg to Pluto; hit all EELV reference orbits)

Are these concerns legitimate or are they just not really accounting for all of the factors?

---

I originally put this is in the wrong thread.  Thanks to envy887 for replying to me:

This should probably go in the Falcon Heavy thread, but there is no doubt that Falcon Heavy can lift the required mass to all the EELV reference orbits, and send 3500 kg to Pluto with a Jupiter assist.

The upper stage is undersized for booster reuse, but is fine if the boosters are expended (even just the center core). I_sp is only one third of the rocket equation... The other two thirds are initial mass and mass fraction, and the Falcon upper stage is by far the best at both of those.

---

Does anyone else have any thoughts on my question?

Offline hkultala

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #576 on: 04/04/2018 10:01 pm »
Hey everyone.

I have a question!

In a fair number of discussions I've had lately there is talk of Falcon Heavy's weak upper stage.

I understand that the 2nd stage is not as efficient and has a lower ISP compared to other rockets (i.e. Ariane 5, Atlas V), however, there seems to be significant doubt that the Falcon Heavy can even do what SpaceX claims it can. (3500 kg to Pluto; hit all EELV reference orbits)

Are these concerns legitimate or are they just not really accounting for all of the factors?


Compared to Delta IVH upper stage,  FH upper stage has ~4 times more propellant and ~8 times more thrust.

But empty weight of the stage is only ~2 times greater, meaning much better mass fraction.


So even though it has considerably lower isp, it still gives much higher impulse to the payload.
« Last Edit: 04/04/2018 10:17 pm by hkultala »

Online vaporcobra

Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #577 on: 04/23/2018 11:24 pm »
Hans' NEAF 2018 talk had some quasi-updated specs and details for Falcon Heavy, and they of course contradict what's on SpaceX's website :D

Quote
•   Falcon Heavy: 20t to GTO & 13t to TMI (website: 26.7t & 16.8t)
o   All center core Merlins were flight-proven
o   22,000kN @ SL
o   1410t @ liftoff: 370t RP-1, 910t LOX (all the above numbers were vaguely qualified)
o   Learned that it’s extremely hard to lift the T/E (“several million pounds of steel”) up the relatively steep hill between the HIF and launch mount
o   “When we do the three engine landing burns, there are certain attachments between the engines,” which is what caused the recovery failure
o   Roadster will orbit between the planets “until we go out and bring it back for a museum,” laughter
o   “[Crossfeed] may be introduced a bit later on”

Offline Kansan52

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #578 on: 04/23/2018 11:31 pm »
Will the Block 5 version come closer to the web site numbers?

Online vaporcobra

Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #579 on: 04/23/2018 11:41 pm »
Will the Block 5 version come closer to the web site numbers?

My assumption is that Hans' 20t and 13t figures are for missions that expend the center core, per Musk's recent tweets on the subject. It's a long shot from "~10%," but Musk issss known for his optimism... ;D

Quote
Side boosters landing on droneships & center expended is only ~10% performance penalty vs fully expended. Cost is only slightly higher than an expended F9, so around $95M.

« Last Edit: 04/23/2018 11:43 pm by vaporcobra »

 

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