SpaceX Falcon 1 Mass Budget

I'm trying to guesstimate the mass budget for a
Falcon 1. Public information seems to be limited
at the moment, especially since SpaceX has
removed its Falcon 1 payload users guide from its
web site. I'm wondering if anyone has the information
on-hand.

But I did download a copy of the guide last year.
From it, from information still on the SpaceX web
site, and from old news clippings, I have found the
following information.

Vehicle total mass: 27.2 tonnes
Stage 1 Sea Level Thrust: 34.92 tonnes
Stage 1 Vacuum Thrust: 41.72 tonnes
Stage 2 Vacuum Thrust: 3.175 tonnes
Acceleration at Stage 1 Burnout: 6.5 g
Acceleration at Stage 2 Ignition: 0.65 g
Acceleration at Stage 2 Burnout: 4.5 g
Payload to 200 km x 28.5 deg LEO: 0.57 tonnes
Claimed Stage 1 Mass Fraction Goal: 94%
Claimed Stage 2 Mass Fraction Goal: 91%

Payoad fairing separation occurs after Stage 2
ignition. The acceleration data was provided
without specifying the assumed payload mass,
and the payload fairing mass is unknown.

So I have a problem with too many unknowns
to provide absolute answers. If I guess
0.35 tonnes for both the payload fairing and the
modeled payload used to provide the acceleration
numbers, I get the following results.

Stage 1 Mass at Liftoff: 22.315 tonnes
Stage 1 Mass at Burnout: 1.533 tonnes
Stage 2 Mass at Ignition: 3.965 tonnes
Stage 2 Mass at Burnout: 0.357 tonnes
Payload Fairing Mass: 0.35 tonnes

This provides a 93% Stage 1 mass fraction and
a 91% Stage 2 mass fraction. The Stage 1
fraction seems believable because SpaceX
ended up with a heavier Merlin than originally
planned, according to updates on the SpaceX
web site.

But there is a great deal of uncertainty in these
numbers. A different payload mass assumption
would drive second stage mass above 4 tonnes,
for example. Does anyone have better numbers?

- Ed Kyle

In article .com,
Ed Kyle wrote:
...I get the following results.
Stage 1 Mass at Liftoff: 22.315 tonnes
Stage 1 Mass at Burnout: 1.533 tonnes
Stage 2 Mass at Ignition: 3.965 tonnes
Stage 2 Mass at Burnout: 0.357 tonnes
Payload Fairing Mass: 0.35 tonnes

Isakowitz4 says Stage 1 is 22388kg gross, 1296kg dry, propellant mass
fraction 0.94, and Stage 2 is 3745kg, 360kg, 0.91. Those are stages only,
no payload or fairing, and there is no number quoted for burnout mass
(which typically differs from dry mass because of propellant residuals and
such). It gives fairing dimensions but lists fairing mass as "?".
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

Henry Spencer wrote:
In article .com,
Ed Kyle wrote:
...I get the following results.
Stage 1 Mass at Liftoff: 22.315 tonnes
Stage 1 Mass at Burnout: 1.533 tonnes
Stage 2 Mass at Ignition: 3.965 tonnes
Stage 2 Mass at Burnout: 0.357 tonnes
Payload Fairing Mass: 0.35 tonnes

Isakowitz4 says Stage 1 is 22388kg gross, 1296kg dry, propellant mass
fraction 0.94, and Stage 2 is 3745kg, 360kg, 0.91. Those are stages only,
no payload or fairing, and there is no number quoted for burnout mass
(which typically differs from dry mass because of propellant residuals and
such). It gives fairing dimensions but lists fairing mass as "?".

The Isakowitz4 numbers seem to work with the acceleration
data provided in the Falcon user's guide if you assume a
"nominal" 350 kg payload mass and a payload fairing mass
of something like 440 kg. I don't have a good "feel" for fairing
masses, but 440 kg seems to be in the ballpark. The fairing
appears to be of aluminum with a cork ablator, a diameter of
1.5 meters, and an overall length of 3.5 meters.

- Ed Kyle

Ed Kyle wrote:
I'm trying to guesstimate the mass budget for a
Falcon 1. Public information seems to be limited
at the moment, especially since SpaceX has
removed its Falcon 1 payload users guide from its
web site. I'm wondering if anyone has the information
on-hand.

But I did download a copy of the guide last year.
From it, from information still on the SpaceX web
site, and from old news clippings, I have found the
following information.

Vehicle total mass: 27.2 tonnes
Stage 1 Sea Level Thrust: 34.92 tonnes
Stage 1 Vacuum Thrust: 41.72 tonnes
Stage 2 Vacuum Thrust: 3.175 tonnes
Acceleration at Stage 1 Burnout: 6.5 g
Acceleration at Stage 2 Ignition: 0.65 g
Acceleration at Stage 2 Burnout: 4.5 g
Payload to 200 km x 28.5 deg LEO: 0.57 tonnes
Claimed Stage 1 Mass Fraction Goal: 94%
Claimed Stage 2 Mass Fraction Goal: 91%

Payoad fairing separation occurs after Stage 2
ignition. The acceleration data was provided
without specifying the assumed payload mass,
and the payload fairing mass is unknown.

So I have a problem with too many unknowns
to provide absolute answers. If I guess
0.35 tonnes for both the payload fairing and the
modeled payload used to provide the acceleration
numbers, I get the following results.

Stage 1 Mass at Liftoff: 22.315 tonnes
Stage 1 Mass at Burnout: 1.533 tonnes
Stage 2 Mass at Ignition: 3.965 tonnes
Stage 2 Mass at Burnout: 0.357 tonnes
Payload Fairing Mass: 0.35 tonnes

This provides a 93% Stage 1 mass fraction and
a 91% Stage 2 mass fraction. The Stage 1
fraction seems believable because SpaceX
ended up with a heavier Merlin than originally
planned, according to updates on the SpaceX
web site.

But there is a great deal of uncertainty in these
numbers. A different payload mass assumption
would drive second stage mass above 4 tonnes,
for example. Does anyone have better numbers?

- Ed Kyle

Do you think they removed the payload user's guide because of the most
recent engine testing results? Perhaps they had to increase chamber
wall thickness & weight of the engine?

Tom

Tom Cuddihy wrote:
Ed Kyle wrote:
I'm trying to guesstimate the mass budget for a
Falcon 1. Public information seems to be limited
at the moment, especially since SpaceX has
removed its Falcon 1 payload users guide from its
web site. I'm wondering if anyone has the information
on-hand.

But I did download a copy of the guide last year.
From it, from information still on the SpaceX web
site, and from old news clippings, I have found the
following information.

Vehicle total mass: 27.2 tonnes
Stage 1 Sea Level Thrust: 34.92 tonnes
Stage 1 Vacuum Thrust: 41.72 tonnes
Stage 2 Vacuum Thrust: 3.175 tonnes
Acceleration at Stage 1 Burnout: 6.5 g
Acceleration at Stage 2 Ignition: 0.65 g
Acceleration at Stage 2 Burnout: 4.5 g
Payload to 200 km x 28.5 deg LEO: 0.57 tonnes
Claimed Stage 1 Mass Fraction Goal: 94%
Claimed Stage 2 Mass Fraction Goal: 91%

Payoad fairing separation occurs after Stage 2
ignition. The acceleration data was provided
without specifying the assumed payload mass,
and the payload fairing mass is unknown.

So I have a problem with too many unknowns
to provide absolute answers. If I guess
0.35 tonnes for both the payload fairing and the
modeled payload used to provide the acceleration
numbers, I get the following results.

Stage 1 Mass at Liftoff: 22.315 tonnes
Stage 1 Mass at Burnout: 1.533 tonnes
Stage 2 Mass at Ignition: 3.965 tonnes
Stage 2 Mass at Burnout: 0.357 tonnes
Payload Fairing Mass: 0.35 tonnes

This provides a 93% Stage 1 mass fraction and
a 91% Stage 2 mass fraction. The Stage 1
fraction seems believable because SpaceX
ended up with a heavier Merlin than originally
planned, according to updates on the SpaceX
web site.

But there is a great deal of uncertainty in these
numbers. A different payload mass assumption
would drive second stage mass above 4 tonnes,
for example. Does anyone have better numbers?

- Ed Kyle

Do you think they removed the payload user's guide because of the most
recent engine testing results? Perhaps they had to increase chamber
wall thickness & weight of the engine?

Tom

I doubt that the recent engine test failure was the reason.
The failed engine was most likely a Merlin 1B, which is
being developed for Falcon 5 and Falcon 9. Instead, I
suspect that SpaceX needed to update the user's guide
to reflect how Falcon 1 turned out after going through
its development cycle. The old user's guide was posted
in 2004, but the final Falcon 1 qualification tests were
not completed until early 2005. Along the way, SpaceX
encountered problems with Merlin. The company had
to beef up manifolds that cracked, adding weight. The
engine didn't turn out to be as efficient as originally
planned, etc. The old guide said that Falcon 1 could
put 670 kg into a 200 km x 28.5 degree orbit from
Cape Canaveral. The current web site says only 570 kg,
etc.. SpaceX will now be able to provide more accurate
acceleration, vibration, and accoustic load data for
payloads, based on test results. Etc..

- Ed Kyle

Ed Kyle wrote:

Tom Cuddihy wrote:
Ed Kyle wrote:
Vehicle total mass: 27.2 tonnes
Stage 1 Sea Level Thrust: 34.92 tonnes
....
Claimed Stage 1 Mass Fraction Goal: 94%
Claimed Stage 2 Mass Fraction Goal: 91%

....
Stage 1 Mass at Liftoff: 22.315 tonnes
Stage 1 Mass at Burnout: 1.533 tonnes
Stage 2 Mass at Ignition: 3.965 tonnes
Stage 2 Mass at Burnout: 0.357 tonnes
Payload Fairing Mass: 0.35 tonnes
....
its development cycle. The old user's guide was posted
in 2004, but the final Falcon 1 qualification tests were
not completed until early 2005. Along the way, SpaceX
encountered problems with Merlin. The company had
to beef up manifolds that cracked, adding weight. The
engine didn't turn out to be as efficient as originally
planned, etc. The old guide said that Falcon 1 could
put 670 kg into a 200 km x 28.5 degree orbit from
Cape Canaveral. The current web site says only 570 kg,
etc.. SpaceX will now be able to provide more accurate
acceleration, vibration, and accoustic load data for
payloads, based on test results. Etc..

- Ed Kyle

Yeah, they have made some other changes during the
development too, like changed the thrust structure,
changed interstage to carbon fibre etc..
Some of these may not have been reflected in the
payload user's guide.

I wonder how much they'll tweak the Falcon I
rocket more. I understand they have a composite
fairing under work, and then they also have
the 10% higher-thrust non-gimballing Merlin 1B
engine, which could probably give parts to Merlin
1C with high thrust and gimballing.

Maybe it's not worth the trouble, if the main
aim of the rocket is minimum cost per launch.

meiza wrote:
Ed Kyle wrote:

Tom Cuddihy wrote:
Ed Kyle wrote:
Vehicle total mass: 27.2 tonnes
Stage 1 Sea Level Thrust: 34.92 tonnes
...
Claimed Stage 1 Mass Fraction Goal: 94%
Claimed Stage 2 Mass Fraction Goal: 91%

...
Stage 1 Mass at Liftoff: 22.315 tonnes
Stage 1 Mass at Burnout: 1.533 tonnes
Stage 2 Mass at Ignition: 3.965 tonnes
Stage 2 Mass at Burnout: 0.357 tonnes
Payload Fairing Mass: 0.35 tonnes
...
its development cycle. The old user's guide was posted
in 2004, but the final Falcon 1 qualification tests were
not completed until early 2005. Along the way, SpaceX
encountered problems with Merlin. The company had
to beef up manifolds that cracked, adding weight. The
engine didn't turn out to be as efficient as originally
planned, etc. The old guide said that Falcon 1 could
put 670 kg into a 200 km x 28.5 degree orbit from
Cape Canaveral. The current web site says only 570 kg,
etc.. SpaceX will now be able to provide more accurate
acceleration, vibration, and accoustic load data for
payloads, based on test results. Etc..

- Ed Kyle

Yeah, they have made some other changes during the
development too, like changed the thrust structure,
changed interstage to carbon fibre etc..
Some of these may not have been reflected in the
payload user's guide.

I wonder how much they'll tweak the Falcon I
rocket more. I understand they have a composite
fairing under work, and then they also have
the 10% higher-thrust non-gimballing Merlin 1B
engine, which could probably give parts to Merlin
1C with high thrust and gimballing.

The 1B has gimbaling, it just doesn't use turbine exhaust for roll
controll.

Maybe it's not worth the trouble, if the main
aim of the rocket is minimum cost per launch.

Unless they really do create a big bump in market demand, which will
probably take a few years.

tom

Ed Kyle wrote:

The Isakowitz4 numbers seem to work with the acceleration
data provided in the Falcon user's guide if you assume a
"nominal" 350 kg payload mass and a payload fairing mass
of something like 440 kg. I don't have a good "feel" for fairing
masses, but 440 kg seems to be in the ballpark.

Hmmm, I wonder if you could build a modern variant of the mercury
capsule to go on top of the Falcon and keep the gross mass under 790 kg?

In article .com, Michael
Smith says...

Ed Kyle wrote:

The Isakowitz4 numbers seem to work with the acceleration
data provided in the Falcon user's guide if you assume a
"nominal" 350 kg payload mass and a payload fairing mass
of something like 440 kg. I don't have a good "feel" for fairing
masses, but 440 kg seems to be in the ballpark.

Hmmm, I wonder if you could build a modern variant of the mercury
capsule to go on top of the Falcon and keep the gross mass under 790 kg?

Fairing mass is not orbital payload mass. The fairing is jettisoned
at about the same time as the first stage, and so has very little effect
on the vehicle's performance - the mass of the fairing is very small
compared to the mass of the fueled second stage, after all.

Dispensing with a 440 kg fairing *might* get you as much as a hundred
extra kilograms of propellant; I don't have the details on the Falcon
stack or my launcher performance estimation code handy, or I'd try it
and see. It won't give you enough of a boost to fit a Mercury capsule
on the bird.

And any capsule you could fit on a Falcon 1 would be a pure stunt ship.
Might be worth doing if it were the only way to keep interest in manned
spaceflight or in private-sector spaceflight alive, but probably better
to wait for one of the bigger Falcons at this point.


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