Author Topic: Falcon 9 additional performance (12 tons)  (Read 48864 times)

Offline nomadd22

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Re: Falcon 9 additional performance (12 tons)
« Reply #100 on: 02/20/2009 11:22 PM »
Stage 2
Gross Mass:  ~46 tonnes
Propellant Mass:  ~43 tonnes
Thrust:  48.99 tonnes vacuum
ISP:  ~340 sec vacuum

I just read the F9 User manual that the 2nd stage burns for 345 seconds. With an ISP of 340 and a thrust of 49 tons, that means that the propellant *consumed* during the burn must be > 49 tons. Since your gross mass for the stage is 46 tons, something is off here.

Not to mention setting aside some 500 kg for residual prop.


49 tons of thrust when the tanks were nearing empty would be a hell of a ride. I suspect they'll throttle down a tad.

Offline mmeijeri

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Re: Falcon 9 additional performance (12 tons)
« Reply #101 on: 02/20/2009 11:27 PM »
49 tons of thrust when the tanks were nearing empty would be a hell of a ride. I suspect they'll throttle down a tad.

Side question: what is the limiting factor for maximum allowed acceleration on crewed flights: human endurance or the construction of the rocket?
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Offline HMXHMX

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Re: Falcon 9 additional performance (12 tons)
« Reply #102 on: 02/20/2009 11:29 PM »
Given that SeaLaunch's original capacity to GTO was 5 tons, launched on a Saturn class, 3 stage vehicle sitting on the Equator, its hard to imagine that a 2 stage vehicle with lower ISP, launched from Florida, would provide 4.5 tons to GTO. These numbers just don't make sense.


Its about the mass ratio of the vehicle.

PRECISELY!  Zenit might be considered a heavy NASCAR racer.  Falcon 9, by comparison, would be a lightweight Formula 1 race car. 

The Zenit first stage was originally designed to be a strap-on booster for Energia, so it likely had robust margin built into the design.  Both Zenit stages use separate tanks - and the second stage uses a torodial tank around the engine.  Zenit is built from aluminum, presumably aircraft grade aluminum.  The rocket has aluminum interstages and an aluminum thrust section, to the best of my knowledge.   

Falcon 9 is built from Aluminum-Lithium and carbon composites.  It has common bulkhead tanks.  While one RD-180 weighs 5.4 tonnes, nine Merlin 1C engines only weigh 4.22 tonnes all together - and produce more thrust.  When SpaceX lifted the Falcon 9 "run tank" onto the test stand in Texas, the company's web site said that the tanks and engine section (minus engines) weighed only 4.1 tonnes combined during the lift.  I'm still not sure I believe that number, but regardless it hints that the thing really is light. 

This is the revolutionary evolution that Falcon 9 seems to represent.  Using the latest materials and the lightest weight structural design methods, SpaceX is aiming to do things with a two-stage kerosene rocket that no one else has done since the Space Age began. 

If the company pulls it off, and it is an "if", it will be the equivalent of the emergence of lightweight aluminum monoplanes just before World War II.  They had engines and wings like their predecessors, but they weighed less while being stronger, and were faster than anything that had flown before.  Each piece of the puzzle was an evolutionary change, but when the puzzle was assembled, a revolution happened.

 - Ed Kyle

As I recall, the Long Tank Thor had a 0.95 propellant mass fraction, and that was nearly fifty years ago.

Offline Danderman

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Re: Falcon 9 additional performance (12 tons)
« Reply #103 on: 02/20/2009 11:29 PM »
I just read the F9 User manual that the 2nd stage burns for 345 seconds. With an ISP of 340 and a thrust of 49 tons, that means that the propellant *consumed* during the burn must be > 49 tons. Since your gross mass for the stage is 46 tons, something is off here.

Yes, your assumption that the engine runs at full throttle the whole time is off.

Yep, you are correct, SpaceX states in the User Manual that Stage has a throttle capability. What I don't know if this is simply a throttle down prior to shutoff, or a more useful, gradual throttle capability.

« Last Edit: 02/20/2009 11:30 PM by Danderman »

Online ugordan

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Re: Falcon 9 additional performance (12 tons)
« Reply #104 on: 02/20/2009 11:31 PM »
Side question: what is the limiting factor for maximum allowed acceleration on crewed flights: human endurance or the construction of the rocket?

Human endurance, or rather, human comfort level. Spacecraft typically can handle 5 Gs easily, while that'd be pretty uncomfortable for a person.

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Re: Falcon 9 additional performance (12 tons)
« Reply #105 on: 02/20/2009 11:33 PM »
What I don't know if this is simply a throttle down prior to shutoff, or a more useful, gradual throttle capability.

They'll have to throttle down some time prior to SECO if they want to keep structural loads low (note the T/W ratio of 2nd stage at ignition already and compare to say a Centaur). It also helps orbit insertion accuracy somewhat.
« Last Edit: 02/20/2009 11:34 PM by ugordan »

Offline Danderman

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Re: Falcon 9 additional performance (12 tons)
« Reply #106 on: 02/20/2009 11:43 PM »
FWIW, the Falcon 1 upper stage almost meets the mass fraction requirements needed to make the "magic" Falcon 9 numbers work.  And it uses a pressure-fed engine.  Not saying that a ~95% propellant fraction is easy, just saying it isn't impossible either. 

~Jon

Question: does the interstage section  mass count against the first stage or second stage mass fraction?

(Please do not embed images, as they are too wide for the page. Attach them. Thanks, Andy).
« Last Edit: 02/21/2009 12:01 AM by Andy USA »

Offline Lars_J

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Re: Falcon 9 additional performance (12 tons)
« Reply #107 on: 02/21/2009 01:43 AM »
The size of that interstage really makes me curious to see exactly how enormous the Merlin vacuum with attached expansion nozzle will be. :D

Offline kevin-rf

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Re: Falcon 9 additional performance (12 tons)
« Reply #108 on: 02/21/2009 02:28 AM »

Question: does the interstage section  mass count against the first stage or second stage mass fraction?

Why would it count against the second stage? It is left behind when the stages seperate.
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Offline edkyle99

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Re: Falcon 9 additional performance (12 tons)
« Reply #109 on: 02/21/2009 02:59 AM »
As I recall, the Long Tank Thor had a 0.95 propellant mass fraction, and that was nearly fifty years ago.

Yes, but that launch vehicle didn't have all of the "puzzle pieces" in place.  Thor, designed as an IRBM, was a smaller than ideal starting point for a GTO launcher.  It was topped by a hypergolic second stage, which was adapted from another launch vehicle (Vanguard), and so, even though an impressive engineering achievement, was a compromise.  Solid upper stages and solid strap-on boosters were required to provide sufficient performance.  It worked, and worked very well for many years, but it wasn't the revolution.

It is too early to say for sure if Falcon 9 will be a Brewster Buffalo or a Grumman Wildcat - a Boeing 247 or a Douglas DC-3 - whether it will be a near miss or a turning point in space history.

 - Ed Kyle
« Last Edit: 02/21/2009 03:01 AM by edkyle99 »

Offline edkyle99

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Re: Falcon 9 additional performance (12 tons)
« Reply #110 on: 02/21/2009 03:36 AM »
FWIW, I just noticed Falcon 9 User's Guide appeared on the SpaceX site.

Funny how, sometimes it seems, when we start talking about certain launch vehicle details, things like this suddenly appear on a company's or agency's web site!

Chock full of information, this.  Foremost is the revelation that the Block 2 LEO payload is now given as only 10,454 kg to 200 km x 28.5 deg!  The GTO x 28.5 deg payload is given as 4,536 kg. 

There is mention of a "delta-v mission kit" for use on some GTO missions.  This may or may not have something to do with the mention of an "RCS Apogee Kick" maneuver planned to be performed by the second stage, presumably to provide an inclination change.  When this maneuver is performed, the GTO mission duration is nearly 6 hours.

If Block 2 LEO payload is only 10,454 kg, Block 1 must be quite a bit less than currently believed.

 - Ed Kyle

Offline HMXHMX

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Re: Falcon 9 additional performance (12 tons)
« Reply #111 on: 02/21/2009 03:45 AM »
As I recall, the Long Tank Thor had a 0.95 propellant mass fraction, and that was nearly fifty years ago.

Yes, but that launch vehicle didn't have all of the "puzzle pieces" in place.  Thor, designed as an IRBM, was a smaller than ideal starting point for a GTO launcher.  It was topped by a hypergolic second stage, which was adapted from another launch vehicle (Vanguard), and so, even though an impressive engineering achievement, was a compromise.  Solid upper stages and solid strap-on boosters were required to provide sufficient performance.  It worked, and worked very well for many years, but it wasn't the revolution.

It is too early to say for sure if Falcon 9 will be a Brewster Buffalo or a Grumman Wildcat - a Boeing 247 or a Douglas DC-3 - whether it will be a near miss or a turning point in space history.

 - Ed Kyle

I wrote in haste.  I meant to say that the *first stage* prop mass fraction was 0.95.  That's not hard to achieve for a dense hydrocarbon pump-fed first stage.

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Re: Falcon 9 additional performance (12 tons)
« Reply #112 on: 02/21/2009 10:31 AM »
FWIW, I just noticed Falcon 9 User's Guide appeared on the SpaceX site.
Foremost is the revelation that the Block 2 LEO payload is now given as only 10,454 kg to 200 km x 28.5 deg!  The GTO x 28.5 deg payload is given as 4,536 kg. 

Ahh, so you noticed this as well   :)
Just when we almost came to the conclusion the LEO numbers were believable and GTO not so much, they lower the LEO numbers. That doesn't jibe well with this bit from the Fourth Asian Space Conference 2008 presentation, dated October:

"In the payload fairing configuration, the Falcon 9 is able to deliver approximately 22,000 lb (10,000 kg) to low Earth orbit (LEO) or 7,700 lb (3,500 kg) to a 28.5 degree inclined geostationary transfer orbit (GTO) from the SpaceX launch site at Cape Canaveral."

The figures above I assume apply to Block 1 as inferred from the context of the presentation.
Don't these numbers conflict each other? If block 2 LEO is that low, block 1 LEO payload would be just slightly higher than a Delta II heavy for a substantially heavier vehicle.

Given this LEO discrepancy and the 2 second staging delay stated at two different places, I wonder if this revision 1 document still has some errors. Certainly hope the staging delay is errouneous.

Offline Danderman

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Re: Falcon 9 additional performance (12 tons)
« Reply #113 on: 02/21/2009 02:56 PM »
Foremost is the revelation that the Block 2 LEO payload is now given as only 10,454 kg to 200 km x 28.5 deg!  The GTO x 28.5 deg payload is given as 4,536 kg. 

GTO payload is almost 50% of LEO payload? Huh?

 ??? ??? ???

Offline NUAETIUS

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Re: Falcon 9 additional performance (12 tons)
« Reply #114 on: 02/21/2009 03:37 PM »
FWIW, I just noticed Falcon 9 User's Guide appeared on the SpaceX site.


There where some good long term questions answered by this document.

-pg 10 - 1st stage of Falcon 9 will not be throttle capable, but the 2nd will be.  Pitch and roll are gimbal control on 1st stage, 2nd stage is gimbal and exhaust controlled.

-pg 10 - All 9 1st stage engines are gimbaled

-pg 28 - 5 seconds between Main engine cut off, and 2nd stage engine start

-pg 46 - Payload will be vertically integrated to the payload adapter, then rotated horizontal and encapsulated by fairing off site (does not say where, but I assume at a 3rd party clean room, because to my knowledge SpaceX will not have a full clean room any closer than California).  I will then be shipped to the launch site and integrated to Falcon 9's 2nd stage.

-pg 47 - No access to Falcon 9 while vertical

-pg 53 - "Note that the integrated payload and launcher go vertical within 6 days of the lift off..."  Wonder what happened to bringing vehicle vertical 1 hour before launch (This is not even mentioned in the document)

-No mention of Umbilical Tower in the document, Umbilical to temporary handling unit are attached once vehicle is on the launch mount, terminate handling unit attached at the pad.  This leads me to believe that the erector is doubling as the Umbilical tower.

« Last Edit: 02/21/2009 03:38 PM by NUAETIUS »
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Offline Jim

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Re: Falcon 9 additional performance (12 tons)
« Reply #115 on: 02/21/2009 04:25 PM »

-pg 46 - Payload will be vertically integrated to the payload adapter, then rotated horizontal and encapsulated by fairing off site (does not say where, but I assume at a 3rd party clean room, because to my knowledge SpaceX will not have a full clean room any closer than California).  I will then be shipped to the launch site and integrated to Falcon 9's 2nd stage.


It says the Falcon 9 building will have a clean room.  I found other issues. 

1.  A fairing that can support the weight of the payload during ground ops would be "overbuilt" for flight loads.  This goes against the rest of the vehicle design for weight efficiency

2.  "Connectivity between the payload EGSE, located in the Instrumentation Bay below the launch pad, and the payload is provided by an electrical umbilical. This umbilical is routed up the
erector and mates to the payload‐dedicated electrical connector on the second stage umbilical plate."

So if the EGSE is at the pad, how can:

"Once inside the hangar at the launch complex, the encapsulated payload assembly is mechanically mated to the launch vehicle.
Electrical umbilicals between the second stage and the payload are mated and the payload is connected to electrical ground support equipment (if required)"
happen.

Figure 5‐14 says this happens at the pad

3.  It does have any time for spacecraft battery charging.


Offline Danderman

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Re: Falcon 9 additional performance (12 tons)
« Reply #116 on: 02/21/2009 05:20 PM »
2.  "Connectivity between the payload EGSE, located in the Instrumentation Bay below the launch pad, and the payload is provided by an electrical umbilical. This umbilical is routed up the
erector and mates to the payload‐dedicated electrical connector on the second stage umbilical plate."

So if the EGSE is at the pad, how can:

"Once inside the hangar at the launch complex, the encapsulated payload assembly is mechanically mated to the launch vehicle.
Electrical umbilicals between the second stage and the payload are mated and the payload is connected to electrical ground support equipment (if required)"
happen.

Figure 5‐14 says this happens at the pad

Nothing in the document says that this mating would occur anywhere but at the pad. "The hanger at the launch pad" must mean "launch pad".



Offline iamlucky13

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Re: Falcon 9 additional performance (12 tons)
« Reply #117 on: 02/21/2009 06:03 PM »
1.  A fairing that can support the weight of the payload during ground ops would be "overbuilt" for flight loads.  This goes against the rest of the vehicle design for weight efficiency

Is it that the fairing is supporting the weight of the payload, or that the payload adapter serves as the mounting for the fairing?

Offline HMXHMX

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Re: Falcon 9 additional performance (12 tons)
« Reply #118 on: 02/21/2009 06:18 PM »
1.  A fairing that can support the weight of the payload during ground ops would be "overbuilt" for flight loads.  This goes against the rest of the vehicle design for weight efficiency

Is it that the fairing is supporting the weight of the payload, or that the payload adapter serves as the mounting for the fairing?

It supports the second stage, and that in turn supports the payload adaptor, payload and fairing.  Pretty conventional layout; we all use the same approach.

Offline iamlucky13

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Re: Falcon 9 additional performance (12 tons)
« Reply #119 on: 02/21/2009 06:23 PM »
1.  A fairing that can support the weight of the payload during ground ops would be "overbuilt" for flight loads.  This goes against the rest of the vehicle design for weight efficiency

Is it that the fairing is supporting the weight of the payload, or that the payload adapter serves as the mounting for the fairing?

It supports the second stage, and that in turn supports the payload adaptor, payload and fairing.  Pretty conventional layout; we all use the same approach.

Can you clarify your "it?" I'm a little lost since you said "it" supports the 2nd stage, payload adaptor, payload, and fairing...what else am I missing?

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