I ask this conceptually, not whether it makes sense or not for SpaceX.

How difficult would it be to convert Falcon9 from kerosene/Merlin to Methane/Raptor engines?

is this a question of rebuilding first stage from scratch and only keep
the grid fins, landing gear and software?

Or just change engine mounts, and use the LOX tank design onto the
methane fuel tank ?

Since the Raptor engines are already designed/tested, they already have
the tooling to make engines, and the fuselage for Falcon9, the software,
grid fins, landing gear, and interafce to stage2, just curious whether
it would represent an order of magnitute similar to building new rocket
or whether it would be relatively minor % of developping from scratch.


And more generically from a market point of view: Will starship
obliterate the demand for smaller launchers such as Falcon9, or will
customers still want "their own" smaller launcher to get to their
desired obrit on their own timing without requiriong cooprdination with
many other customers who also want same orbit and are ready with their
payloads at same time?

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On Jun/18/2021 at 16:35, JF Mezei wrote :

I ask this conceptually, not whether it makes sense or not for SpaceX.

How difficult would it be to convert Falcon9 from kerosene/Merlin to Methane/Raptor engines?

is this a question of rebuilding first stage from scratch and only keep
the grid fins, landing gear and software?

More like the rebuilding from scratch. I don't think you could keep the software. Maybe the fins and the landing gear. SpaceX also could, if it
wanted, keep the Falcon 9 name, else than that not much.


Alain Fournier

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In article <es7zI.46245$k_.7859@fx43.iad>, jfmezei.spamnot@vaxination.ca says...

I ask this conceptually, not whether it makes sense or not for SpaceX.

How difficult would it be to convert Falcon9 from kerosene/Merlin to Methane/Raptor engines?

Difficult. Changing the fuel changes pretty much everything.

is this a question of rebuilding first stage from scratch and only keep
the grid fins, landing gear and software?

Rebuild from scratch. The lower density of liquid methane (430 kg/cubic meters) compared to kerosene (775-840 kg/cubic meters) would mean you'd
need to increase the diameter since Falcon is already pushing the
fineness ratio close to the limits. So, you wouldn't be able to reuse
any of the tooling and couldn't transport the stages with semi-trucks.

Or just change engine mounts, and use the LOX tank design onto the
methane fuel tank ?

See above.

Since the Raptor engines are already designed/tested, they already have
the tooling to make engines, and the fuselage for Falcon9, the software,
grid fins, landing gear, and interafce to stage2, just curious whether
it would represent an order of magnitute similar to building new rocket
or whether it would be relatively minor % of developping from scratch.

Pretty much redesign from scratch.

And more generically from a market point of view: Will starship
obliterate the demand for smaller launchers such as Falcon9, or will customers still want "their own" smaller launcher to get to their
desired obrit on their own timing without requiriong cooprdination with
many other customers who also want same orbit and are ready with their payloads at same time?

Time will tell.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

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Just this Sunday, Jeff Findley puzzled about:

In article <es7zI.46245$k_.7859@fx43.iad>, jfmezei.spamnot@vaxination.ca says...

I ask this conceptually, not whether it makes sense or not for SpaceX.

How difficult would it be to convert Falcon9 from kerosene/Merlin to
Methane/Raptor engines?

Difficult. Changing the fuel changes pretty much everything.

is this a question of rebuilding first stage from scratch and only keep
the grid fins, landing gear and software?

Rebuild from scratch. The lower density of liquid methane (430 kg/cubic meters) compared to kerosene (775-840 kg/cubic meters) would mean you'd
need to increase the diameter since Falcon is already pushing the
fineness ratio close to the limits. So, you wouldn't be able to reuse
any of the tooling and couldn't transport the stages with semi-trucks.

My back of envelope calculations are

-- you need 3.5 Raptors to match the thrust of 9 Merlins (depending on
which source you use for Raptor and Merlin thrust; WP for me)
-- my rough sketch suggests you can fit 5 Raptors in the skirt of an
F9, one of them in the center
-- for a density 438.9 g/l (which may be the super-chilled density at
-173 C), the existing RP-1 tankage could supply 5 Raptors for 91
seconds or 4 Raptors for 114 seconds.
-- F9 first stage time is typically 162 seconds.

I've made no corrections for differing oxygen consumption rates. I
don't think we'd have to worry about tank walls, as the F9 LOX tank is
already the same material (an Al alloy), AIUI, and probably can skip
adding insulation to the tank given the just-in-time tanking policy.

Or just change engine mounts, and use the LOX tank design onto the
methane fuel tank ?

See above.

Since the Raptor engines are already designed/tested, they already have
the tooling to make engines, and the fuselage for Falcon9, the software,
grid fins, landing gear, and interafce to stage2, just curious whether
it would represent an order of magnitute similar to building new rocket
or whether it would be relatively minor % of developping from scratch.

Pretty much redesign from scratch.

And more generically from a market point of view: Will starship
obliterate the demand for smaller launchers such as Falcon9, or will
customers still want "their own" smaller launcher to get to their
desired obrit on their own timing without requiriong cooprdination with
many other customers who also want same orbit and are ready with their
payloads at same time?

Time will tell.

The expectation is that certain payloads will keep F9 around for a
while; the two Dragon variants are among those payloads, and
speculation is that some NROL payloads will also mandate F9 for a
while. This is a frequent talking point on NSF livestreams, but a 6
hour tanking test allows for a lot of talking points.

The other issue is that F9 has a well-understood deployment design,
while Starship satellite deployment isn't really known outside of
SpaceX, although the "alligator" renders are one possibility. We will
know more when the first Starship Starlink launch occurs.

/dps

--
You could try being nicer and politer

instead, and see how that works out.

-- Katy Jennison

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On 2021-06-20 21:31, Snidely wrote:

-- you need 3.5 Raptors to match the thrust of 9 Merlins (depending on
which source you use for Raptor and Merlin thrust; WP for me)
-- my rough sketch suggests you can fit 5 Raptors in the skirt of an
F9, one of them in the center
-- for a density 438.9 g/l (which may be the super-chilled density at
-173 C), the existing RP-1 tankage could supply 5 Raptors for 91
seconds or 4 Raptors for 114 seconds.
-- F9 first stage time is typically 162 seconds.

But would they be able to keep fuselage width of Falcon to get enough
delta V to match kerosene fuelse Falcon9 ? Just crusoiu on whether this
is close, or not even in the same ballpark.

Can they stretch Falcon 1 like they do commercial aircraft to lenghten
the methane tank that replaces the kerosene one? (I realise that
changes centre of gravity so software needs adjustments).

If demand for Falcon 9 is to be long term, just curious if there comes a
point where it make sense to have engine commonality betwene it and Starship/Super Heavy since those engines will be mass produced.

Would it be fair to state that if you keep Falcon 9's mission the same,
(same payload to LEO), and you're just replacing 9 Merlins with enough
Raptors to offer same thrust, much of the bahavoiur remains the same in
terms of thrust at take off, structural loads (mroe or less, sicne fuel
is different) ?

Obviously, accountants will have to chime in. It all depends on how many
F9 launches they expect after Starship has stolen some of the luanch
busines from it, and how often engines are re-used (aka: how many
Merlins you need to produce each year to replace older ones).

So it is an issue of the cost of keeping Merlin production going at low
rate vs using mass produced Raptors and shutting down Merlin production.

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JF Mezei explained :

On 2021-06-20 21:31, Snidely wrote:

-- you need 3.5 Raptors to match the thrust of 9 Merlins (depending on
which source you use for Raptor and Merlin thrust; WP for me)
-- my rough sketch suggests you can fit 5 Raptors in the skirt of an
F9, one of them in the center
-- for a density 438.9 g/l (which may be the super-chilled density at
-173 C), the existing RP-1 tankage could supply 5 Raptors for 91
seconds or 4 Raptors for 114 seconds.
-- F9 first stage time is typically 162 seconds.

But would they be able to keep fuselage width of Falcon to get enough
delta V to match kerosene fuelse Falcon9 ? Just crusoiu on whether this
is close, or not even in the same ballpark.

From the difference in burn time, I don't expect enough delta V

Can they stretch Falcon 1 like they do commercial aircraft to lenghten
the methane tank that replaces the kerosene one? (I realise that
changes centre of gravity so software needs adjustments).

Jeff already answered this: No. The Falcon 9 is as tall as its width supports (see fineness).

/dps

--
Maybe C282Y is simply one of the hangers-on, a groupie following a
future guitar god of the human genome: an allele with undiscovered
virtuosity, currently soloing in obscurity in Mom's garage.
Bradley Wertheim, theAtlantic.com, Jan 10 2013

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On 2021-06-21 03:24, Snidely wrote:

Jeff already answered this: No. The Falcon 9 is as tall as its width supports (see fineness).

I hadn't understood the part about inability to stretch it. So if it
can't be stretched and current tanks sizes not enough, then I guess it
can't happen.


Different question: is methane competitive for commerial launch business
or does kerosene have a big advantage (simpler, smaller rockets) ?

aka: if it weren't for a desire to refuel on Mars, would SpaceX have
selected Methane for a large commercial launcher?

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JF Mezei presented the following explanation :

On 2021-06-21 03:24, Snidely wrote:

Jeff already answered this: No. The Falcon 9 is as tall as its width
supports (see fineness).

I hadn't understood the part about inability to stretch it. So if it
can't be stretched and current tanks sizes not enough, then I guess it
can't happen.

Different question: is methane competitive for commerial launch business
or does kerosene have a big advantage (simpler, smaller rockets) ?

aka: if it weren't for a desire to refuel on Mars, would SpaceX have
selected Methane for a large commercial launcher?

You might ask Jeff Bezos.

/dps

--
There's nothing inherently wrong with Big Data. What matters, as it
does for Arnold Lund in California or Richard Rothman in Baltimore, are
the questions -- old and new, good and bad -- this newest tool lets us
ask. (R. Lerhman, CSMonitor.com)

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After serious thinking Jeff Findley wrote :

In article <es7zI.46245$k_.7859@fx43.iad>, jfmezei.spamnot@vaxination.ca says...

I ask this conceptually, not whether it makes sense or not for SpaceX.

How difficult would it be to convert Falcon9 from kerosene/Merlin to
Methane/Raptor engines?

Difficult. Changing the fuel changes pretty much everything.

is this a question of rebuilding first stage from scratch and only keep
the grid fins, landing gear and software?

Rebuild from scratch. The lower density of liquid methane (430 kg/cubic meters) compared to kerosene (775-840 kg/cubic meters) would mean you'd
need to increase the diameter since Falcon is already pushing the
fineness ratio close to the limits. So, you wouldn't be able to reuse
any of the tooling and couldn't transport the stages with semi-trucks.

Hence Starship and SuperHeavy.

/dps

--
As a colleague once told me about an incoming manager,
"He does very well in a suck-up, kick-down culture."
Bill in Vancouver

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In article <mn.b30b7e5656bc3204.127094@snitoo>, snidely.too@gmail.com
says...

After serious thinking Jeff Findley wrote :

In article <es7zI.46245$k_.7859@fx43.iad>, jfmezei.spamnot@vaxination.ca says...

I ask this conceptually, not whether it makes sense or not for SpaceX.

How difficult would it be to convert Falcon9 from kerosene/Merlin to
Methane/Raptor engines?

Difficult. Changing the fuel changes pretty much everything.

is this a question of rebuilding first stage from scratch and only keep
the grid fins, landing gear and software?

Rebuild from scratch. The lower density of liquid methane (430 kg/cubic meters) compared to kerosene (775-840 kg/cubic meters) would mean you'd need to increase the diameter since Falcon is already pushing the
fineness ratio close to the limits. So, you wouldn't be able to reuse
any of the tooling and couldn't transport the stages with semi-trucks.

Hence Starship and SuperHeavy.

Exactly! Things that are different, just aren't the same.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

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