RD-180 relplacement

Jeff Findley wrote:

In article ,
says...

Jeff Findley wrote:

In article ,
says...

I'm confused. The program to replace the RD-180 is focused on engines
with around 400,000 lb thrust at sea level. This focuses them on the
AR-1 (kerosene/LOC) and BE-4 (methane/LOX). Why are they not looking
at the RS-25 (LH2/LOX with similar thrust) or the Raptor engine
(methane/LOX)?


RS-25 is hella expensive and ULA already knows that LH2/LOX produces a
large, expensive, vehicle (e.g. Delta IV). So that's right out since
Delta IV is already flying (no development costs there). But do note
that ULA really wants to ax Delta IV in favor of Atlas V due to its high
cost.


So why aren't they using something other than RS-25 on SLS?


Because the cheaper RS-68, used on Delta IV, isn't regeneratively cooled
and can't handle the heating environment at the base of the core stage
caused by both the main engines and the SRBs. This was discovered early
on in Ares V development, which planned on using the much cheaper RS-68.

In general, Ares V/SLS is a giant cluster *&^# of a program. If it ever
does fly it will be the biggest, most expensive, lowest flight rate
launch vehicle in history.


I'm inclined to say that RS-25 'won' the studies because it got extra
points for being 'Shuttle-derived', which was a stupid requirement in
the first place.


Raptor (methane/LOX) isn't "fully baked" yet (BE-4 is ahead of it).


That sounds wrong to me. SpaceX test fired a full up Raptor engine
(albeit a lower thrust developmental engine) at their Texas facility
last year. The BE-4 has never been test fired and they didn't even
have a full engine put together until this year.


I should say it's my opinion that Raptor is behind BE-4. Since both
companies are private and somewhat secretive, good information is hard
to come by. But from what's been reported in the press, Blue Origin has
a full size complete BE-4 development engine built and is getting ready
to test fire it. SpaceX could be at that point too but all I've heard
so far is that they've fired a lower thrust development engine, which
indicates they're not quite ready for full scale testing. Blue Origin,
on the other hand, thinks BE-4 is ready for "full scale" testing.

But the proof will be on the test stand, will it not?


Blue Origin says BE-4 will be ready for delivery this year (or they
did; not sure if that's still their story now). Blue Origin has more
schedule pressure for this class engine than SpaceX does, since they
want it picked up by ULA for the engine for Vulcan (2020-2021 launch
dates) and the big thing they're touting is that it will be available
sooner than AR-1, which is the alternative engine. That being said,
BE-4 has apparently moved right at least some number of months, since
originally the full up engine tests were supposed to start last year
but they've only just got complete engines built. Meanwhile, SpaceX
has no real schedule driver for Raptor other than internal (ITS 2024
or so, which could easily move right) and their real priority
development right now is Falcon Heavy.


Seems like we're getting a lot of different engines when it might be
more efficient to settle on just a couple.


AR-1 is a "backup" engine at this point since it's so far behind BE-4 in
both schedule and (estimated) per unit price. But, AR-1 is about the
right size for two of them to be a "drop-in" replacement for RD-180 on
Atlas V. So, if ULA stumbles on Vulcan, an AR-1 engined Atlas V might
be a good stop-gap measure.


Aerojet Rocketdyne says they can start delivering AR1 engines in 2019,
so the finish line isn't all that far behind BE-4. Blue Origin says
the BE-4 will cost 60% of what an AR1 costs (at $12.5 million each);
so BE-4 engines are only around $7.5 million each? The government is
paying a lot of money to develop AR1, so I'd bet on it being pushed
for use somewhere. And AR1 does have the advantage of not needing a
bunch of new infrastructure to handle fueling and such.

ULA is more worried about the per flight cost down the road. If they
have to install liquid methane tanks and plumbing, they'll do it to
lower costs. SpaceX is already undercutting *everyone* on launch costs
and that's without taking reuse into account. ULA is desperate to stay
alive at this point with SpaceX eating into its DOD launches that it
used to have a monopoly on.


ULA is saying that base Raptor (with no solids) will cost around $100
million per launch. That gets you around 10 tonnes to LEO. Current
Falcon 9 has double the payload and is only 2/3 the cost, which makes
it about 1/3 the cost per pound. So ULA's new best effort at economy
still costs 3x what the competition costs.


At any rate, Aerojet Rocketdyne is being paid good money to develop AR-
1. Even if it meets the same fate as J-2X, they're getting money now
which helps keep the company alive.


How many billion dollars of taxpayer money are we going to spend
developing engines that never get used? Around $1.5 billion for AR1.
Around $1.2 billion for RS-25 (which only gets used if SLS keeps
flying). Another $1.2 billion for J-2X. Meanwhile Merlin engines
used on Falcon 9 cost around $1.2 million each with engines in the
Raptor/BE-4 class going for $7.5 million each? Meanwhile the entire
development budget for New Glenn is around $2.5 billion and what
little public data there is puts development costs for Raptor engines
in the hundreds of millions of dollars (vice billions) and I expect
BE-4 development is similar. What that says is that private companies
developing engines mostly on their own nickel is looking to be an
order of magnitude cheaper than traditional contracted engine
development programs...


Maybe the US Government should get out of the game of funding
development of engines and launch vehicles. SpaceX and Blue Origin have
both proven that private industry can do this themselves, with
sufficient funding.


USAF has (mostly) gone this direction. NASA hasn't. What NASA needs
to do is put together performance requirements specs for what they
want and then be flexible about trading away requirements for schedule
and dollars to commercial vendors. Along the lines of "You want X, Y,
and Z. We can give you X and Y in A years for B money, but Z will
double the cost and schedule. How badly do you need Z?"


AJR sat on its ass for how long after RD-180 was picked for Atlas?
They've known for *decades* that the US needed a high thrust
LOX/kerosene engine to remain competitive in the global launch market
and they literally sat on their hands waiting for a government handout
to start development. AJR deserves to go under at this point. It's
management is wholly dependent on old style cost-plus contracts. They
don't know how to innovate. They don't know how to compete on cost.


Yep. But they've been burned before on developing engines and not
being able to sell them after, so I can kind of understand why they
would risk a billion of their own money. Since they don't make
vehicles, engine development is riskier for them.


NASA and DOD need to switch their space support back to the same style
of support that NACA used to give to aircraft and (jet) engine
manufacturers in the US. NACA didn't design and build commercial
engines or aircraft. And NACA certainly didn't operate its own
airlines. It's well past time for the US Government to get the hell out
of the launch business and let good old fashioned capitalism and market
based competition sort out the cheapest way to orbit.


Yep, it's past time for this change. For what they're spending on
SLS/Orion development NASA could have pretty much funded the total
development of both ITS from SpaceX and New Glenn from Blue Origin and
had change left.


This is the kind of **** that the "crazy" people on the old sci.space
argued for back in the early 1990s when they were pushing CATS (cheap
access to space). It's now been over 30 years since then, and SpaceX
has proven them right. The government needs to get the *&%# out of the
way and support the commercial providers rather than building yet
another Government Luanch System which will be a drain on NASA's budget
for decades to come.


Yep, I remember that. Even back then people were saying 'performance
uber alles' was the wrong approach and proposing things like 'big dumb
boosters' and accepting the addition weight of using swaged steel
rather than aluminum because of the cost advantage. But it kind of
took Elon Musk to find the right path to cheaper launches.


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw

Jeff Findley wrote:

In article ,
says...

space x engines are built by robotics, the engine bells are made on 3d printers

No Bob, I do not believe the Merlin engine bells are made on 3D
printers. Do you have a cite for that?


As usual, Bob is confused. SpaceX uses additive manufacture for the
combustion chamber of the SuperDraco engines on Dragon V2 (which is
probably where he got "engine bells" from) and for the Main Oxidizer
Valve on Merlin engines. The 'printed' valve is more reliable than
the cast version that preceded it and cuts manufacturing time by 30x
(2 days vice 2 months for the cast article).

He's also wrong about them being "built by robotics". While there is
some amount of robotic assembly, rocket engines still involve a lot of
'touch labor' during assembly.

Perhaps this will also help 'Mayfly' understand why I keep pointing
out to him that 'exacting precision' and robotic assembly are at odds
with each other:

"There’s a lot to see: Rockets, like good suits, are bespoke objects,
hand-made to order; a SpaceX tour guide says much of the work is too
precise for robotic assembly."

https://qz.com/281619/what-it-took-f...space-company/

When you want to do robotic assembly and such, you make parts with
more 'meat' on them for the robots to use to attach the parts. Things
get heavier. For example, RS-25 engines are expected to gain several
hundred pounds as they inject newer automated manufacturing processes
and new materials into the design. I've also seen this first hand,
although I can't say where.


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw

On Friday, May 12, 2017 at 1:19:44 AM UTC+12, Fred J. McCall wrote:
William Mook wrote:


To know the kind of engine you need, you need to know the vehicle it will be used for.

To know the kind of vehicle you need, you need to know where it is going and what the vehicle is used for.

To know where you are going and what you are doing, you have to have a long-term plan.

Is anyone doing this?

NASA is not - not officially.

China is - officially.

* * *

Chinese Engines

YF-77 (165,000 lbf)
http://aviationweek.com/awin/chinese...xceed-saturn-v


So a smaller engine than RS-25, BE-4, AR-1, or Raptor. About the size
of the Merlin engines that SpaceX builds for use on Falcon.


Chinese Vehicles

Long-March 11 (140,000 lb LEO)
http://www.americaspace.com/2012/07/...g-new-rockets/


Uh, what does that citation have to do with Long March 11?

Meant long march 9 obviously.

It doesn't
even mention it

That's because I wrote Long March 11 incorrectly, when I meant to write long march 9.

and it's largely about paper rockets.

Only because of its date of publication. The YF-77 has flown already on the Long March 5.

Long March 11,
meanwhile, is about the size of Falcon Heavy.

Its largely solid, and is intended mostly for military missions that have long storage times and rapid response requirements. I meant Long March 9, not 11, I miswrote 11 and meant 9.

snip speculative MookSpew

The only spew is you idiotically focusing on 11 where I obviously meant 9. You got me! It was 9, not 11.

Fact is, the core stage of the Long March 9 upper stage can easily replace the solid rocket boosters in the configuration I described - and in tis way exceed SpaceX. Using a common building block to form a 140,000 lb and 400,000 lb launcher from 3 or 7 common components.

The Chinese appear to be building modular space habitat and mission module elements, which is what some at NASA wanted to do post-Apollo, but Nixon pulled the plug on that one forcing us down the path of the Space Shuttle.

* * *

The S-II, the second stage of the Saturn V, weighed 1,090,000 lbs and produced 1,000,000 lbs of thrust with its five J2 engines. Reducing its diameter from 33 ft to 29.2 ft and maintaining its 82 foot length reduces its mass to 781,250 pounds and maintains a 10% structure fraction using similar hardware to that used to recover the SpaceX stages and engines with a 420 sec Isp. Three of these, used as two stages or seven of these used as three stages, would be quite capable, and each one would cost about $60 million to build today.

https://history.msfc.nasa.gov/saturn...cond_Stage.pdf

This arrangement puts up as much as the system I described previously.

Praxair routinely handles vast quantities of liquid hydrogen without a problem. Hydrogen is not the problem NASA and others make it out to be.

Nuclear isn't the big bugaboo either. Its 1950s era technology for the USA..

http://www.popularmechanics.com/mili...lear-reactors/

Nuclear thermal and nuclear electric upper stages, that use hydrogen propellant, stored in zero boil off cryogenic tanks are the obvious way forward near term for space travel.

The USA had ROVER/NERVA in ground tests and S-II flying in the EARLY 1960s. Its very likely that by 2020s other nations will replicate this capability and build superior configurations with them and by the 2030s do what we should have done in the 1970s.

https://en.wikipedia.org/wiki/Saturn_C-5N

A reusable S-II stage made into a common core recoverable component and sported a nuclear thermal or nuclear electric deep space stage, would have given us mastery of the solar system in the 1970s and cost less than the Space Shuttle programme.

http://www.collectspace.com/ubb/Foru...ML/000880.html

http://www.up-ship.com/eAPR/images/v1n2ad5.gif

https://en.wikipedia.org/wiki/NERVA#...specifications




--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw

William Mook wrote:

On Friday, May 12, 2017 at 1:19:44 AM UTC+12, Fred J. McCall wrote:
William Mook wrote:


To know the kind of engine you need, you need to know the vehicle it will be used for.

To know the kind of vehicle you need, you need to know where it is going and what the vehicle is used for.

To know where you are going and what you are doing, you have to have a long-term plan.

Is anyone doing this?

NASA is not - not officially.

China is - officially.

* * *

Chinese Engines

YF-77 (165,000 lbf)
http://aviationweek.com/awin/chinese...xceed-saturn-v


So a smaller engine than RS-25, BE-4, AR-1, or Raptor. About the size
of the Merlin engines that SpaceX builds for use on Falcon.


Chinese Vehicles

Long-March 11 (140,000 lb LEO)
http://www.americaspace.com/2012/07/...g-new-rockets/


Uh, what does that citation have to do with Long March 11?

Meant long march 9 obviously.


Not obviously at all. The payload you cite is much to low for Long
March 9.

It doesn't
even mention it

That's because I wrote Long March 11 incorrectly, when I meant to write long march 9.


And where did you get the payload from?

and it's largely about paper rockets.

Only because of its date of publication. The YF-77 has flown already on the Long March 5.


Long March 9 is a paper rocket.

Long March 11,
meanwhile, is about the size of Falcon Heavy.

Its largely solid, and is intended mostly for military missions that have long storage times and rapid response requirements. I meant Long March 9, not 11, I miswrote 11 and meant 9.


And meant a different random payload number?

snip speculative MookSpew


snip MookSpew


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn

JF Mezei wrote:

On 2017-05-12 07:07, Jeff Findley wrote:

cost models had predicted. Yet we keep soldiering on with SLS/Orion
knowing it's costing us 10x what it should. SLS/Orion is pure pork.


One side of coin:

let industry deal with commoditized launches, while NASA focuses on
advancing the state of the art by pushing the limits. And that space of
the market is , by definition, not commodity and very expensive.


Yet SpaceX ITS has more payload and costs 10% of SLS.


(We can argue whether SLS does push the limits and enhances the R&D
efforts).

However, banning NASA from such "pushing of limits" would be wrong.


NASA doesn't do that anymore.


Other side of coin:

Outfits like SpaceX are doing more R&D and advanacement of spaceflight
than NASA, so NASA should get out of the way and just order stuff from
commercial.


Only side of the coin...


--
"Millions for defense, but not one cent for tribute."
-- Charles Pinckney

On 17-05-12 20:42 , JF Mezei wrote:
On 2017-05-12 07:15, Jeff Findley wrote:

The real problem is that SLS is expenable and always will be.
Expendable is a stupid thing for a launch vehicle to be in the 2020s.


Question:

A LH2/LOX rocket has a positive G force that always pushes the liquid to
the bottom of tank during launch. Right ?

Is it conceptually possible to fire the engines during free fall to
allow the first stage to land?

See https://en.wikipedia.org/wiki/Ullage#Rocketry and
https://en.wikipedia.org/wiki/Ullage_motor.

--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
. @ .

In article om,
says...

On 2017-05-12 07:07, Jeff Findley wrote:

cost models had predicted. Yet we keep soldiering on with SLS/Orion
knowing it's costing us 10x what it should. SLS/Orion is pure pork.


One side of coin:

let industry deal with commoditized launches, while NASA focuses on
advancing the state of the art by pushing the limits. And that space of
the market is , by definition, not commodity and very expensive.

(We can argue whether SLS does push the limits and enhances the R&D
efforts).

Oh yes we can argue about that since SLS is largely a technological
throwback to the 1970s with a few tweaks here and there to make it look
relevant to the 21st century.

However, banning NASA from such "pushing of limits" would be wrong.

NASA is pushing precious few "limits" with SLS/Orion. And the bits they
are pushing they could do as R&D demonstration projects and publish the
results for use by all US launch providers. An example of this would be
the advances they're making in stir friction welding for the core
(first) stage tanks. They're having problems, but I'm sure they'll work
through them.

Other side of coin:

Outfits like SpaceX are doing more R&D and advanacement of spaceflight
than NASA, so NASA should get out of the way and just order stuff from
commercial.

This. And when NASA has requirements, keep them simple. Commercial HLV
ought to be something like so many metric tons to a circular orbit so
many kilometers in altitude above the earth with an internal payload
fairing size so many meters in diameter and so many meters in length.

NASA ought not to be picking types of engines, SRBs, contractors that
must be used, money that has to be spent in certain Congressional
districts, and etc.

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.

In article m,
says...

On 2017-05-12 07:15, Jeff Findley wrote:

The real problem is that SLS is expenable and always will be.
Expendable is a stupid thing for a launch vehicle to be in the 2020s.


Question:

A LH2/LOX rocket has a positive G force that always pushes the liquid to
the bottom of tank during launch. Right ?

Is it conceptually possible to fire the engines during free fall to
allow the first stage to land?

The "old tech" way of doing this is to use ullage rockets or simply
bleed a bit of LH2 (gas) out of the engine in order to "settle" the
propellants to the bottom of the fuel tanks. It really doesn't take
much thrust in order to do this. Newer tech ways use baffles and other
techniques to "wick" fuel into the "sump" area of the tanks so that the
engine is pumping liquid when it starts.

SpaceX may use a combination of ways of settling the tanks. The 1st
stage has a nitrogen "cold gas" thruster based reaction control system.
A couple of thrusters at the base of the stage is all you'd need to
settle the tanks.

Once back in atmosphere, is air resistance sufficient to get the
remaining fuel to remain at bottom of tanks to be sucked by engine when
needed?

Atmospheric drag is most certainly high enough to do this.

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.

In article ,
says...

This is the kind of **** that the "crazy" people on the old sci.space
argued for back in the early 1990s when they were pushing CATS (cheap
access to space). It's now been over 30 years since then, and SpaceX
has proven them right. The government needs to get the *&%# out of the
way and support the commercial providers rather than building yet
another Government Luanch System which will be a drain on NASA's budget
for decades to come.


Yep, I remember that. Even back then people were saying 'performance
uber alles' was the wrong approach and proposing things like 'big dumb
boosters' and accepting the addition weight of using swaged steel
rather than aluminum because of the cost advantage. But it kind of
took Elon Musk to find the right path to cheaper launches.


There was the "big dumb booster" crowd, but there was also the reusable
SSTO crowd and the reusable TSTO crowd. And there were also out of the
box ideas like POGO which would have been a reusable turbojet powered
first stage for a reusable near SSTO. There were even people who pushed
"modular" rockets like OTRAG since the modules could be mass produced
which would lower costs.

Lots and lots of ideas, but precious little funding in a world where
NASA had all the "experts" and many of the "experts" didn't think anyone
but NASA could innovate. It was also a time when DOD was funding two
EELVs and you'd have to compete with those as well. The bottom line was
that private investors were largely scared away because they didn't want
to compete with the US Government.

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.

JF Mezei wrote:

On 2017-05-12 14:55, Fred J. McCall wrote:

Yet SpaceX ITS has more payload and costs 10% of SLS.


In fairness, SpaceX ITS is vapourware. SLS is hardware (albeit not ready).


You obviously don't know the meaning of "vapourware". When you have
designs, a schedule (albeit aggressive), and are test firing engines,
you're way past 'vapourware'. Yes, SLS is further along. It's also
spent twice the entire budget for ITS and isn't done with their
initial phase article yet.




However, banning NASA from such "pushing of limits" would be wrong.
NASA doesn't do that anymore.


It should.


And? It is institutionally unable to do so.


Imagine for a second that they productized SSMEs into a TRULY reusable
rocket with enough engines to not need SRBs and which could land itself.
Despite higher production cost, wouldn't it becoem commercially viable
due to re-usability ?


Imagine for a second that they could breed lift demons and thrust
demons and not need wings or engines at all. What you're asking for
is not that much less preposterous.


The shuttle engines lasted far more than 10 flights which is what SpaceX
expects its engines to last.


If you do almost a total rebuild after every flight, things last a lot
longer. That 10 flights is the MINIMUM SpaceX expects their CURRENT
engines to last with only inspections required. And have Shuttle
engines "lasted far more than 10 flights"?

If you really want to go count them up, you can look here for which
engines flew on which missions. I started but got bored early.

https://science.ksc.nasa.gov/shuttle.../missions.html

I did find someone who was keeping track and these are their numbers.
Note that most engines are well under 10 flights, with a handful up
near 20 flights.

Space Shuttle Main Engine Use

SN-2005 5
STS-1, STS-2, STS-3, STS-4, STS-5

SN-2006 5
STS-1, STS-2, STS-3, STS-4, STS-5

SN-2007 5
STS-1, STS-2, STS-3, STS-4, STS-5

SN-2011 7
STS-9, STS-51J, STS-61B, STS-33, STS-31, STS-41, STS-50

SN-2012 22
STS-6, STS-7, STS-8, STS-41B, STS-41C, STS-51A, STS-51C, STS-51D,
STS-51G, STS-51I, STS-35, STS-43, STS-45, STS-53 STS-60, STS-67,
STS-74, STS-79, STS-83, STS-86, STS-90 STS-93

SN-2015 9
STS-6, STS-7, STS-8, STS-41B, STS-61C, STS-40, STS-44, STS-49, STS-52

SN-2017 14
STS-6, STS-7, STS-8, STS-51J, STS-61B, STS-27, STS-49, STS-53, STS-57,
STS-61, STS-65, STS-66, STS-70, STS-

SN-2018 12
STS-9, STS-41D, STS-51A, STS-51C, STS-51D, STS-51G, STS-51I, STS-61C,
STS-54, STS-56, STS-58, STS-59

SN-2019 19
STS-9, STS-51J, STS-61B, STS-26, STS-28, STS-36, STS-38, STS-37,
STS-48, STS-50, STS-54, STS-57, STS-61, STS-65 STS-70, STS-76, STS-83,
STS-86, STS-93

SN-2020 6
STS-41C, STS-41G, STS-51B, STS-51F, STS-61A, STS-51L

SN-2021 6
STS-41D, STS-41G, STS-51B, STS-51F, STS-61A, STS-51L

SN-2022 8
STS-26, STS-29, STS-28, STS-32, STS-38, STS-40, STS-42, STS-47

SN-2023 5
STS-41G, STS-51B, STS-51F, STS-61A, STS-51L

SN-2024 7
STS-32, STS-35, STS-43, STS-45, STS-53, STS-56, STS-58

SN-2026 6
STS-39, STS-42, STS-47, STS-68, STS-74, STS-80

SN-2027 7
STS-30, STS-34, STS-36, STS-38, STS-40, STS-42, STS-46

SN-2028 11
STS-26, STS-29, STS-28, STS-32, STS-35, STS-43, STS-45, STS-59,
STS-68, STS-71, STS-72

SN-2029 15
STS-27, STS-30, STS-34, STS-39, STS-44, STS-47, STS-55, STS-51,
STS-62, STS-64, STS-63, STS-69, STS-75, STS-80, STS-84

SN-2030 10
STS-27, STS-30, STS-34, STS-36, STS-39, STS-44, STS-49, STS-52,
STS-65, STS-66

SN-2031 17
STS-29, STS-33, STS-31, STS-41, STS-37, STS-48, STS-50, STS-55,
STS-51, STS-62, STS-64, STS-67, STS-73, STS-79, STS-84, STS-87, STS-93

SN-2032 7
STS-46, STS-60, STS-71, STS-74, STS-80, STS-84, STS-90

SN-2033 9
STS-46, STS-54, STS-56, STS-61, STS-59, STS-68, STS-67, STS-79, STS-94

SN-2034 9
STS-52, STS-57, STS-51, STS-60, STS-66, STS-71, STS-75, STS-81, STS-94

SN-2035 3
STS-63, STS-69, STS-76

SN-2036 3
STS-70, STS-72, STS-78

SN-2037 5
STS-73, STS-77, STS-82, STS-94, STS-87

SN-2038 3
STS-73, STS-77, STS-82

SN-2039 4
STS-72, STS-78, STS-85, STS-87

SN-2040 4
STS-77, STS-82, STS-86, STS-91

SN-2041 5
STS-78, STS-81, STS-85, STS-90, STS-88

SN-2042 3
STS-81, STS-85, STS-91

SN-2043 7
STS-89, STS-95, STS-103, STS-101, STS-97, STS-100, STS-108

SN-2044 7
STS-89, STS-88, STS-99, STS-106, STS-98, STS-105, STS-111

SN-2045 8
STS-89, STS-95, STS-92, STS-102, STS-105, STS-110, STS-113, STS-121

SN-2047 6
STS-91, STS-96, STS-106, STS-98, STS-104, STS-109

SN-2048 4
STS-95, STS-92, STS-110, STS-112

SN-2049 7
STS-96, STS-103, STS-101, STS-97, STS-100, STS-108, STS-107

SN-2050 5
STS-88, STS-99, STS-108, STS-111, STS-113

SN-2051 4
STS-96, STS-104, STS-110, STS-112

SN-2052 5
STS-99, STS-106, STS-98, STS-105, STS-121

SN-2053 5
STS-103, STS-92, STS-102, STS-109, STS-107

SN-2054 6
STS-101, STS-97, STS-100, STS-111, STS-114, STS-121

SN-2055 1
STS-112

SN-2056 6
STS-102, STS-104, STS-109, STS-113, STS-107, STS-114

SN-2057 1
STS-114

SN-2107 5
STS-33, STS-31, STS-41, STS-37, STS-48

SN-2109 17
STS-41B, STS-41C, STS-41D, STS-51A, STS-51C, STS-51D, STS-51G,
STS-51I, STS-61C, STS-55, STS-58, STS-62, STS-64, STS-63, STS-69,
STS-76, STS-83


Look at aviation: the 777 won over the 747 because it has 2 expensive
engines instead of 4 medium price engines. Maintenance becomes a huge
issue for cost savings when you have half the number of engines to
inspect/maintain in your fleet.


No, that's not why it 'won'. It 'won' because it costs less to
OPERATE, not because it costs less to BUY.


Imagine if SSMEs were truly re-usable and you could launch to space with
half the number of engines needed by SpaceX,


Imagine Dragons. Imagine unicorns ****ting magic pixie dust.

Now look at the actual numbers. For reusability to matter you have to
have a way to get the engines back. For SSME that way was attaching
them to a Space Shuttle. SLS has no way to return engines. If you
put that in, you're adding weight and reducing performance. But let's
pretend you aren't. If you're not going to use solids, you need to
get another 7.2 million pounds of thrust from somewhere. That means
you're going from 4 SSMEs to 22 of them for a total thrust of just
under 9.2 million pounds of thrust (vice 8.87 million pounds of thrust
for the current vehicle). That's for Phase 1 SLS with a payload of
around 70 tonnes to LEO and we're not counting the engine in the upper
stage.

Now look at Falcon Heavy. With 27 engines in the first stage vice 24
of the much more expensive RS-25 engines, you get a payload about 90%
that of SLS Block 1B. SSMEs are much more expensive engines. An
RS-25 engined vehicle is never going to be able to compete
economically, no matter what magic you assume happens. Assume each
vehicle will lose around 15% of the performance I've described if
flown 'recoverable'.


At the end of the day, the "heavy lift" will be used to LEO to assemble
and fuel what goes to Mars. Politicially uninteresting to fund a
replacement for the shuttle that is limited to LEO. But that is a
necessary building block for the Mars expedition ship.


If you're talking about Mars, ITS uses about twice as many Raptor
engines on its first stage as your magic reusable SLS (42 vice 22) but
also has almost eight times the payload. And ITS is already designed
for full reusability.


It all comes down to economics. If Rocketdyne were told it would compete
against SpaceX for lifting cargo to LEO, how much more cost efficient
would production of SSME/RS25 become ?


It wouldn't. AJR doesn't design boosters. They build engines.


As long as SSMEs remain in PORK territory, Rocketdyne has no incentive
to compete. It just gets money to deliver 6 engines at some fat price
and doesn't care about a commercial market for those engines.


And if SSMEs don't remain in PORK territory, AJR has no incentive to
build engines because they cannot compete.


With proper incentives, perha]s Rocketdyne can do something with SSMEs,
or perhaps the economics are TRULY not good and the SpaceX "many small
engines" economics are better.

But unless Rocketdyne is given incentive to compete, we'll never really
know if the RS25 could be manufacturerd at much lower price that makes
it competitive (or same ballpark at least).


There is no market for the RS-25 other than SLS. There is no market
for R-1 unless BE-4 is a magnificent failure (unlikely) and AJR
wouldn't be developing it without government funding. You see, AJR
doesn't have a billionaire funding it, so they have to make all their
money as they go and can't sink billions into developing engines with
no market for them.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn