Hypothetical new Falcon 1 type LV

[Dante80]

This is a hypothetical exercise for anyone interested (I think it could be fun), I do know that SpaceX is not looking into something like this.

From what we know, development of the Falcon 1 vehicle had a cost somewhat close to $100M. The vehicle itself was retired after 5 launches (the first three unsuccessful). Before cancellation, SpaceX was thinking about producing a slightly larger variant, 1e.

Assuming SpaceX wanted to make something like this again, with their current state of technology and knowledge, how would the end vehicle look like?

Assumptions for the exercise.

1. Using a M1-D FT engine.
2. A second stage using a new variant of the Kestrel engine (what?), or something of similar/close power/thrust.
3. Absolutely no re-usability equipment.
4. Same diameter (1.7m), with the 1e fairing shape.
5. Liberal use of commonalities with F9 FT and 3d printing methods.

What we are looking for.

a. How much would you think it would cost to develop and launch?
b. What could be its capability to LEO, SSO and polar orbits?
c. How would it look like (dimensions, weight)?
d. How would it fare in price against Vega, and the very small launchers under development (XCOR, Electron etc)?
e. Would it eat part of the Falcon 9 market?

[Dante80]

I'm trying to find some sketches for the old Falcon 1 LV for inspiration. Here are some, post others if you have them..C:

[Kansan52]

Wasn't some company already doing that? Designated as a cube launcher if memory serves.

[Dante80]

Wasn't some company already doing that? Designated as a cube launcher if memory serves.

There are a couple out there.

[Kansan52]

Thanks!

[Lars-J]

It would be an interesting exercise, but the first stage would likely need a substantial stretch. M1D FT has roughly twice the thrust that M1A had. 

The question of an upper stage is the toughest nut to crack. Kestrel is long out of production, and M1DVac has a nozzle that is waaaay too large. But I'm sure they could think of something.

And since the F1 tooling is no longer in use, I'm not sure the F1 diameter has to be a constraint. Perhaps a short and stubby F9?  (This would use the F9 FT upper stage as a first stage)

[Dante80]

A stretch would be warranted, yes. Falcon 1e was being designed to be four and a half meters longer than F1, as well as close to 40,000kg at take off.

If we extrapolate, a M1-D FT S1 could be even longer, bringing the total height of the rocket above 30 meters.

Regarding S2, a M1-D vac is overkill, especially since we are brainstorming about an expendable vehicle here  (S2 would have to do less work). That's why I talked about a Kestrel variant. I was thinking of something the size/power of Kestrel2/RD-58MF.

Here is the old upgrade path for Falcon 1. Kestrel 2 was being designed for 330s Isp at the same thrust level.

Regarding diameter, I think that it would be more fun to keep it constant for the exercise.
 

[CameronD]

An interesting idea...

Regarding S2, a M1-D vac is overkill, especially since we are brainstorming about an expendable vehicle here  (S2 would have to do less work). That's why I talked about a Kestrel variant. I was thinking of something the size/power of Kestrel2/RD-58MF.

Maybe something from XCOR with a vacuum-optimised nozzle?

[deltaV]

SpaceX presumably abandoned Falcon 1 because there wasn't enough demand for a launcher that size to justify the fixed costs. Now that Falcon 9 is on the verge of reusing its first stage the business case for an expendable Falcon 1 just got even worse. Why design a launch vehicle that's not worth building?

[Dante80]

SpaceX presumably abandoned Falcon 1 because there wasn't enough demand for a launcher that size to justify the fixed costs. Now that Falcon 9 is on the verge of reusing its first stage the business case for an expendable Falcon 1 just got even worse. Why design a launch vehicle that's not worth building?

Because this is a theoretical exercise and we know for a fact that SpaceX do not want to bring back the Falcon 1.

Maybe something from XCOR with a vacuum-optimised nozzle?

Thats an interesting thought (although I think that SX would use/develop an in-house engine).
Piston fed Kestrel2?

[S.Paulissen]

I don't think that they would constrain themselves to the given constraints that you provided. 

I suspect that they would have instead made a two stage rocket, with a single merlin 1d that amounts to being something near a shrunken F9 second stage and a triple sized falcon1 second stage.

Given that Merlin1D FT has about 756kN (77000 kg) of thrust at sea level, or enough to lift a vehicle with a 74000kg GLOM with a liftoff acceleration of about 0.05g, well in the range of other SpaceX launches (maybe even a little high).

The current F9-SII has a dry mass of about 4000kg and a propellant capacity of about 100000kg  naturally this cannot be lifted by a single merlin at take-off so it needs to be shrunk with each 1m of length subtracting about 220kg of dry mass and losing 20000kg of propellant.  Thus the stage could drop about 53000kg of propellant and 625kg of dry mass to have a first stage GLOW of ~44000kg leaving about 27500kg of mass for the second stage and payload.

I don't think there is a lot of performance to be wrung out of the kestrel engine design because it's pressure fed, thus any increase in performance would be at the cost of increased tank mass to contain additional tank pressure needed to get ISP.   I based it largely off of a stretched version of the falcon 1 second stage, including a diameter reduction after the second stage (yup, this would be an awkward looking bird, like some old-timey ICBM based stacks).  It would carry about 24250kg of propellant and have a dry mass of 1800 kg; because of this I used a triple sized Kestrel 2 engine that gets the same 317s ISP.  The relatively low mass fraction is required for the tanks to achieve the ~150PSI tank pressure needed to feed the 135PSI chamber pressure.  Tankage mass increases three fold for the same volume.  This is partially offset (compared to the merlin stage) by kestrel 2 only weighing 200kg (triple sized kestrel) compared to 490kg for merlin.

This stack can push 700kg to 28 degrees LEO (9.9km/s dV) and leaves a LOT of room for optimization and mass fraction gains.  Keep in mind this is a back of the envelope quality estimation of performance at best (as expected playing lego-rockets)

[Gliderflyer]

Maybe something from XCOR with a vacuum-optimised nozzle?

According to Wikipedia, the Kestrel had 6900 pounds of thrust, so a couple of 5K18s (Lynx engine) should be in the ballpark.

[Dante80]

I don't think that they would constrain themselves to the given constraints that you provided. 

I suspect that they would have instead made a two stage rocket, with a single merlin 1d that amounts to being something near a shrunken F9 second stage and a triple sized falcon1 second stage.

But what you wrote is inside the constraints I gave (save for the different diameter of the 2nd stage).

Very cool post btw, thanks for that. What would the total height of the rocket be in your example?

[Stan-1967]

I have wondered the same thing.  I posted this a few weeks back:
http://forum.nasaspaceflight.com/index.php?topic=38149.msg1463029#msg1463029

I was thinking of something in the class of a "Rutherford" electric pump fed engine with better ISP than a Kestrel.  I concluded that re-doing Kestrel would not be worth it.  I think the Rutherford engine is still pretty small, and I'm not sure of the mass estimates for the battery scaling issues if making a larger S2 engine.

I have been meaning to go back and see if I can make some WAGS on reasonable dimensions and mass for S1 and S2.   The exercise was academic, as no market emerged for this class of launcher, nor has it yet emerged.  It's just interesting because I think it makes an impressive rocket against the small launchers out there like VEGA or LauncherOne.   

1.  Use same S1 structure as F1-e, but stretch the tank to max fineness ratio
2.  Purchase used Merlin 1D FT engines from returned cores
3.  3-D print my upper stage engine if I can't buy it somewhere else.
4.  Build in-house only what is necessary.  Outsource the rest.   Too small a market to take on lots of fixed costs.

[Craftyatom]

Math time, boys.  Using specs on the F9 1.1 FT from SF101 (which are admittedly estimations):

fully-fueled first stage weighs about 431,700kg and is 94.9% propellant
First stage is 41.2m tall (without interstage) and 3.66m in diameter for a volume of 433 m^3 (this is not actual tank volume, but works fine for estimations)
Density of first stage is 997kg/m^3

A single Merlin 1D Full Thrust has a thrust of 756kN at sea level
A TWR of 1.1 should be completely sufficient
Which means that the engine can lift just over 70,000kg at liftoff

Based on earlier statistics and a diameter of 1.7m (as per Falcon 1), the F1SSTO, or "Fisto", is 31 meters tall, has no second stage, burns for 236 seconds (281kgprop/s), and assuming it reaches vacuum after the normal F9 burn time of 162 seconds, has a delta-v of... 8771m/s.  Not quite enough, given that the Falcon 9 uses 10304 to get its max payload to LEO using the same calculation scheme.

One day, Fisto...  One day.

[Nomadd]

 It did surprise me that a rocket with close to the same payload as the Pegasus at 1/5th the price didn't have much of a a market. But, customers like Orbcomm or Iridium can do a lot better with a reusable F9, so maybe SpaceX thought it was a dead end. It's not likely a single engine rocket could return to the launch site.

[sdsds]

If the premise is that SpaceX will not be doing this, it would be interesting to think about a startup that purchased M1D engines from SpaceX and licensed the technology required for the remainder of an F1e-like vehicle.

In particular I think SpaceX might license Kestrel2 technology. With M1D having maybe twice the thrust of M1A, perhaps the second stage could be powered by dual Kestrel2 engines? How badly would that "blow" the diameter of the vehicle?

[Dante80]

It's just interesting because I think it makes an impressive rocket against the small launchers out there like VEGA or LauncherOne.   

That was pretty much the same reason for me posting this thread. C:

If the premise is that SpaceX will not be doing this, it would be interesting to think about a startup that purchased M1D engines from SpaceX and licensed the technology required for the remainder of an F1e-like vehicle.

In particular I think SpaceX might license Kestrel2 technology. With M1D having maybe twice the thrust of M1A, perhaps the second stage could be powered by dual Kestrel2 engines? How badly would that "blow" the diameter of the vehicle?

Here is an old diagram about Falcon 5 using 2 uprated Kestrel engines for S2. The diameter was the same as Falcon 9.

Btw, keeping the same diameter as Falcon 1 would match the F9 FT thinness ratio at about 32 meters total height.

Assuming a 31kN Kestrel 2 with 330s Isp (as it was being designed), I think that you could keep S2 having a solitary engine and still be good for the job if the first stage with the new Merlin did more of the job (the rocket is expendable, so recovery operations are not a factor for S1-S2 SEP. Only maximum g-load is). Maybe a bigger niobium or carbon-carbon nozzle extension could do the job?

[Dante80]

A couple of F1-F1e sketches.

[S.Paulissen]

I don't think that they would constrain themselves to the given constraints that you provided. 

I suspect that they would have instead made a two stage rocket, with a single merlin 1d that amounts to being something near a shrunken F9 second stage and a triple sized falcon1 second stage.

But what you wrote is inside the constraints I gave (save for the different diameter of the 2nd stage).

Very cool post btw, thanks for that. What would the total height of the rocket be in your example?

My lift off height is estimated at about 25m.  4.5m are from fairing, 10.0m are from the first stage, and 7.5m are from the stretched second stage plus 3m of interstage.

I arrived at 10m for the first stage by losing 2m from the vacuum nozzle of the existing second stage as well as a 2.5m shrink of the tank to fit the proposed propellant 14.3m-2-2.5=~10m giving a little extra leeway for size.  I kept the interstage length constant (about three meters) as expansion ratio (and hence nozzle length) the same.  The upper stage tank is about 7.5m (3x Falcon 1) long plus the 3m of kestrel.  However the 3m of kestrel overlap with the already accounted for interstage length. 

[RoboGoofers]

I could see spacex "selling" end-of-life merlins to a subsidiary that would repackage them into expendable low cost launchers. customers would trade reliability for dirt-cheap orbital access. it would be a huge boon for universities and startups.

Such a subsidiary would also be a great "minor leagues" for spacex to train up talent.

[Hauerg]

OK, speeking of "free" or dirt cheap engines: What could a 3 core F1 Heavy (IIRC there WAS a plan for such a thing in the early days) achieve. Maybe with the core as "second" stage.
Plus: No need for new Kestrels.
Minus: Complex configuration
But: might this actually challenge the Vega?

[Hauerg]

Edit: Of course the core engine would be throttled soon after liftoff.

[Nomadd]

I could see spacex "selling" end-of-life merlins to a subsidiary that would repackage them into expendable low cost launchers. customers would trade reliability for dirt-cheap orbital access. it would be a huge boon for universities and startups.

Such a subsidiary would also be a great "minor leagues" for spacex to train up talent.

I couldn't. They expose themselves to a huge liability for little benefit. If the engine isn't OK for a Falcon, it's not OK for anything else except testing.

[ChrisWilson68]

I could see spacex "selling" end-of-life merlins to a subsidiary that would repackage them into expendable low cost launchers. customers would trade reliability for dirt-cheap orbital access. it would be a huge boon for universities and startups.

Such a subsidiary would also be a great "minor leagues" for spacex to train up talent.

There's no such thing as an "end-of-life" Merlin engine.

Musk has said that there is no limit to how many times a Merlin could be used.  After 30 or so firings a few components would have to be replaced, then it could continue to be used.

[Stan-1967]

I could see spacex "selling" end-of-life merlins to a subsidiary that would repackage them into expendable low cost launchers. customers would trade reliability for dirt-cheap orbital access. it would be a huge boon for universities and startups.

Such a subsidiary would also be a great "minor leagues" for spacex to train up talent.

There's no such thing as an "end-of-life" Merlin engine.

Musk has said that there is no limit to how many times a Merlin could be used.  After 30 or so firings a few components would have to be replaced, then it could continue to be used.

Come on host!  Let's not let the good become the enemy of the perfect!  The elasticity of the market will take some time to create payloads for reusable hardware.  SpaceX's entire manifest is probably presumed to be deliverable with new components.  That means lots of Merlins are going to be laying around very soon!  There are 9 now, could be 18-27 in the next 60 days.  That years of launches in the smallsat space. 

There are paper rockets to be dreamed of Merlin 1D FT's that need to be lit!  I'm working on my paper rocket in my spare evening time.   Will have some ready to be unvieled later tonight.  ( after all that work and family stuff is done for the day )

[Lars-J]

I could see spacex "selling" end-of-life merlins to a subsidiary that would repackage them into expendable low cost launchers. customers would trade reliability for dirt-cheap orbital access. it would be a huge boon for universities and startups.

Such a subsidiary would also be a great "minor leagues" for spacex to train up talent.

I couldn't. They expose themselves to a huge liability for little benefit. If the engine isn't OK for a Falcon, it's not OK for anything else except testing.

Agreed. This has nothing but downsides for SpaceX. Selling new engines is one thing, but selling used engines is a surefire way to get blamed for every launch mishap.

[ChrisWilson68]

I could see spacex "selling" end-of-life merlins to a subsidiary that would repackage them into expendable low cost launchers. customers would trade reliability for dirt-cheap orbital access. it would be a huge boon for universities and startups.

Such a subsidiary would also be a great "minor leagues" for spacex to train up talent.

There's no such thing as an "end-of-life" Merlin engine.

Musk has said that there is no limit to how many times a Merlin could be used.  After 30 or so firings a few components would have to be replaced, then it could continue to be used.

Come on host!  Let's not let the good become the enemy of the perfect!  The elasticity of the market will take some time to create payloads for reusable hardware.  SpaceX's entire manifest is probably presumed to be deliverable with new components.  That means lots of Merlins are going to be laying around very soon!  There are 9 now, could be 18-27 in the next 60 days.  That years of launches in the smallsat space. 

And SpaceX has plans for those engines.  They're not just surplus.  Yes, they're going to have a bunch of them accumulating over the next couple of years.  But, after that they'll be using them to fly payloads.  By the time a new F1-class launcher could be ready, SpaceX will be flying all their engines.

[RoboGoofers]

And SpaceX has plans for those engines.  They're not just surplus.  Yes, they're going to have a bunch of them accumulating over the next couple of years.  But, after that they'll be using them to fly payloads.  By the time a new F1-class launcher could be ready, SpaceX will be flying all their engines.

This sounds like a paperwork nightmare, and defeats the idea of scaling up production to reduce per-unit manufacturing costs.

i think they'll just test and fly until they have a clear mean time to failure and then retire them.

but back to the topic, i only mentioned the used merlins because there might be a lot of them sitting around some day that could be used on a reborn F1.

[Stan-1967]

I could see spacex "selling" end-of-life merlins to a subsidiary that would repackage them into expendable low cost launchers. customers would trade reliability for dirt-cheap orbital access. it would be a huge boon for universities and startups.

Such a subsidiary would also be a great "minor leagues" for spacex to train up talent.

I couldn't. They expose themselves to a huge liability for little benefit. If the engine isn't OK for a Falcon, it's not OK for anything else except testing.

Agreed. This has nothing but downsides for SpaceX. Selling new engines is one thing, but selling used engines is a surefire way to get blamed for every launch mishap.

This is "Blood sucking lawyer 101" basics.   Buyer beware.   Assignment of risk can easily be transferred to the 3rd party.   SpaceX  could remove the engine, stick it on a test stand, and certify is still works to spec. and is free from damage per identifiable criteria.   Beyond that, the risk has transferred. 

[ChrisWilson68]

And SpaceX has plans for those engines.  They're not just surplus.  Yes, they're going to have a bunch of them accumulating over the next couple of years.  But, after that they'll be using them to fly payloads.  By the time a new F1-class launcher could be ready, SpaceX will be flying all their engines.

This sounds like a paperwork nightmare, and defeats the idea of scaling up production to reduce per-unit manufacturing costs.

Huh?  I really don't understand what you're saying here.  Are you saying you don't think SpaceX will refly their engines?  They've gone to an awful lot of trouble to recover and refly whole stages.

I'm not sure what paperwork nightmare you're worried about.  A 747 doesn't have a paperwork nightmare to fly its engines on each flight.  There's no reason in principle it has to be different for a rocket.  And no reason to think the paperwork for reusing an existing engine would be any worse than the paperwork for a newly-built engine.

i think they'll just test and fly until they have a clear mean time to failure and then retire them.

Knowing the mean time to failure doesn't necessarily mean it makes sense to set a retirement date for a piece of hardware.  For example, incandescent light bulbs don't last forever, but the chance of one failing in any given one-minute interval is nearly constant, not dependent on how long its been operating.  And an engine isn't a monolithic block.  Parts that wear out can be replaced.  With aircraft engines, after a given number of hours they need to be overhauled, and it's expensive, but the engines aren't just thrown away.

Finally, for some missions one or more core stages is expended for improved performance.  As long as that continues to be true, engines will be going away on the expended cores, so there's a limit to how many flights will ever go on any given engine even though no end-of-life engine is ever discarded in a way that makes it available for a cheap, high-risk launch vehicle.

but back to the topic, i only mentioned the used merlins because there might be a lot of them sitting around some day that could be used on a reborn F1.

But they'll only temporarily be sitting around, waiting to be reflown on future Falcon 9 and Falcon Heavy flights.

[ChrisWilson68]

I could see spacex "selling" end-of-life merlins to a subsidiary that would repackage them into expendable low cost launchers. customers would trade reliability for dirt-cheap orbital access. it would be a huge boon for universities and startups.

Such a subsidiary would also be a great "minor leagues" for spacex to train up talent.

I couldn't. They expose themselves to a huge liability for little benefit. If the engine isn't OK for a Falcon, it's not OK for anything else except testing.

Agreed. This has nothing but downsides for SpaceX. Selling new engines is one thing, but selling used engines is a surefire way to get blamed for every launch mishap.

This is "Blood sucking lawyer 101" basics.   Buyer beware.   Assignment of risk can easily be transferred to the 3rd party.   SpaceX  could remove the engine, stick it on a test stand, and certify is still works to spec. and is free from damage per identifiable criteria.   Beyond that, the risk has transferred.

That might be a logical way for the legal system to work, but it is not the way the legal system works in the United States.  The lawyers would still come after SpaceX no matter what agreement has been signed.

[Dante80]

Guys..we are theory-crafting about imaginary/alternate reality paper rockets in this thread. The M1-Ds can be brand new, taken from a scrapyard or exchanged for Vermulian Brandy.

Back to the topic if we can..<3

[Stan-1967]

Well I took the leap last night to give my best effort at making my own new "Phoenix" F1 class vehicle and testing it out on a simulator linked to by this site in the archives at Silverbird Astronautics.
http://www.silverbirdastronautics.com/LVperform.html

This was the first time I have ever done an exercise like this.  I have watched many other here do similar, some of you are very very good at it.  I do not profess to be good at all.

My designs started with the specifications for using the Merlin 1D FT engine w/ 756 kN thrust, and building the vehicle around that.  I also made an early decision to make the new vehicle with a 2m core, not the 1.7 I believe the old F1 had.  I think the Merlin 1D FT is too much rocket to stick on that small a diameter core without getting something too long and bendy.

I also wanted to make a better S2, so I selected to use a 100kN Methane upper stage.  ( Darma Technolgies CHASE 10 ) I had to guess what a vacuum engine could do for ISP, and guessed 350s.

G's at liftoff were set to be 1.18, so the mass of the complete vehicle would then be 65329 kg's.

After some iterations on the calculations, my mass distribution is a follows

Stage 1:
Dry mass = 3461 kg
Propellant = 55368 kg
Thrust = 756 kN
ISP avg = 304

Stage 2:
Dry mass = 619
Propellant = 5881
Trust = 100 kN
ISP = 350
Fairing 160 kg

I double checked that at 70% thrust on the Merlin just before MECO the vehicle was at 5.42 G's, so I think the ride up is OK.

Here is what the calculations returned:
Mission Performance:
Launch Vehicle:     User-Defined Launch Vehicle
Launch Site:     Cape Canaveral / KSC
Destination Orbit:     185 x 185 km, 45 deg
Estimated Payload:     1687 kg
95% Confidence Interval:     1294 - 2172 kg

That seems to square with increased performance that would be expected with a new FT Merlin over the old Merlin 1A and 1C.

This exercise also demonstrated that Merlin 1D FT is not a "smallsat" class engine.  I think it could compete against the VEGA launcher quite well.

Final note on the 2m core.  My intent with this was to made my next "Phoenix F1" into a LRB variant for the F9H vehicle.  I like the F9H, but I can't help note that the side boosters are using a crap ton of performance to carry its fuel for its full burn time of around  and then have to turn the rocket around for RTLS.  It's cool and everything, but very inefficient.  I wanted to see how much fuel I could pack into a 2 m core, and then see how quickly I can expend it with more engines.  The Merlin 1D FT's amazing T/W make that a no brainer early in the flight.   A 2m core would have room for 2 engines no problem, and possibly 3 if a skirt or aeroshells were added.

My next paper exercise is to make a 2m F1 class LRB that empties its tanks in around 90 seconds ( after Max Q ) and then jettisons.  Given how light the empty booster would be, a fly back booster might make sense, as it wont be too far down range. 

[Stan-1967]

Guys..we are theory-crafting about imaginary/alternate reality paper rockets in this thread. The M1-Ds can be brand new, taken from a scrapyard or exchanged for Vermulian Brandy.

Back to the topic if we can..<3

After that post, I went to design my paper rocket last night! ( see above!)  I then realized maybe a I had a post for the "You know you are a Space Geek when" thread.   I started humming the old Dire Straights song, "Money for Nothing"

But in my head I was also singing " I want my M1D,  I want my M1D"....

[mikelepage]

Well now, this is my kind of thread.

Well I took the leap last night to give my best effort at making my own new "Phoenix" F1 class vehicle and testing it out on a simulator linked to by this site in the archives at Silverbird Astronautics.
http://www.silverbirdastronautics.com/LVperform.html
[...]
Here is what the calculations returned:
Mission Performance:
Launch Vehicle:     User-Defined Launch Vehicle
Launch Site:     Cape Canaveral / KSC
Destination Orbit:     185 x 185 km, 45 deg
Estimated Payload:     1687 kg
95% Confidence Interval:     1294 - 2172 kg
[...]

So... assuming I was a billionaire, I had a couple of Mercury style capsules as payloads (m = 1400kg), and a death defying love of Koalas, I could have lunch in Cape Canaveral, get on a Phoenix at 3pm, have breakfast in Taronga zoo, Sydney (at 4pm/8am), get on another Phoenix at 5pm/9am and be back at KSC in time for dinner?

[fwskungen]

what about using 1 or 2 Super Draco engines for the upper stage? they are very lightweight and mostly need a upgrade for space flight via mounting a large bell on this

[Dante80]

what about using 1 or 2 Super Draco engines for the upper stage? they are very lightweight and mostly need a upgrade for space flight via mounting a large bell on this

One would do (for the amount of thrust needed), but the Isp would be much worse than what ye olde Kestrel had. Even with a bigger nozzle.

[RotoSequence]

what about using 1 or 2 Super Draco engines for the upper stage? they are very lightweight and mostly need a upgrade for space flight via mounting a large bell on this

One would do (for the amount of thrust needed), but the Isp would be much worse than what ye olde Kestrel had. Even with a bigger nozzle.

But would it be enough?

I remember someone ball-parking some dramatic payload improvements in the Falcon 9 in GEO missions by adding a third stage powered by a Super-Draco derivative. I wonder if there's any possibility of sane overlap in a Falcon 9 Super-Draco third stage and a Falcon 1e Super-Draco second stage?

[Dante80]

For a Falcon9/Falcon Heavy Payload Assist Module, the idea of using superdraco for the application might have some merit for deep space missions like interplanetary probes, or insertions to GEO. I think though that SpaceX have decided to maximize the Falcon architecture recoverable/re-usable fraction, so a development program like that might be viewed by them as counter-intuitive.

For an imaginary F1e, I think that the superdracos' low Isp would help less than a better Kestrel2.

[fwskungen]

yeh i suppose you will lose ISP the question tho is how much ISP one will lose i find the kestrel engine to have a ISP of 317   the only ISP i can find for the superdracos is 240 this is most likely sea level and with no bell. So anybody want to guess.

[Lars-J]

For a Falcon9/Falcon Heavy Payload Assist Module, the idea of using superdraco for the application might have some merit for deep space missions like interplanetary probes, or insertions to GEO. I think though that SpaceX have decided to maximize the Falcon architecture recoverable/re-usable fraction, so a development program like that might be viewed by them as counter-intuitive.

For an imaginary F1e, I think that the superdracos' low Isp would help less than a better Kestrel2.

No, it has little merit for a deep space mission. Once you are out of the deep gravity well, Isp is king. Thrust does not matter. So a Draco (or cluster of them) would actually be superior to SuperDraco for the purpose of a final kick stage.

[abaddon]

No, it has little merit for a deep space mission. Once you are out of the deep gravity well, Isp is king. Thrust does not matter. So a Draco (or cluster of them) would actually be superior to SuperDraco for the purpose of a final kick stage.

Not that I disagree with you, but a Star 48 has an ISP of 292 (see http://forum.nasaspaceflight.com/index.php?topic=33084.msg1109220#msg1109220) which is also really poor.  SpaceX built the SuperDraco to essentially compete with an SRM: low ISP, high thrust, quick ignition, non-cryo propellant, with the notable difference being that it can throttle dynamically instead of being stuck with a fixed thrust profile.

But if you're going to do all of that, in space, a SRM has much better storability properties, probably weighs less (when you account for the plumbing), and is a known and available quantity already.  Just use a Star 48 or equivalent if that's what you want!

Really, SuperDracos were designed for a very specific purpose, and trying to use them elsewhere just doesn't make sense at all.

[Stan-1967]

Well now, this is my kind of thread.

Well I took the leap last night to give my best effort at making my own new "Phoenix" F1 class vehicle and testing it out on a simulator linked to by this site in the archives at Silverbird Astronautics.
http://www.silverbirdastronautics.com/LVperform.html
[...]
Here is what the calculations returned:
Mission Performance:
Launch Vehicle:     User-Defined Launch Vehicle
Launch Site:     Cape Canaveral / KSC
Destination Orbit:     185 x 185 km, 45 deg
Estimated Payload:     1687 kg
95% Confidence Interval:     1294 - 2172 kg
[...]

So... assuming I was a billionaire, I had a couple of Mercury style capsules as payloads (m = 1400kg), and a death defying love of Koalas, I could have lunch in Cape Canaveral, get on a Phoenix at 3pm, have breakfast in Taronga zoo, Sydney (at 4pm/8am), get on another Phoenix at 5pm/9am and be back at KSC in time for dinner?

That was my thoughts after posting the numbers as well!   "Hey...that enough mass for a Mercury capsule!"   However in addition for your love of Koalas, you must also be a billionaire who aspires to be a millionaire.
 

[Stan-1967]

No, it has little merit for a deep space mission. Once you are out of the deep gravity well, Isp is king. Thrust does not matter. So a Draco (or cluster of them) would actually be superior to SuperDraco for the purpose of a final kick stage.

But if you're going to do all of that, in space, a SRM has much better storability properties, probably weighs less (when you account for the plumbing), and is a known and available quantity already.  Just use a Star 48 or equivalent if that's what you want!

Really, SuperDracos were designed for a very specific purpose, and trying to use them elsewhere just doesn't make sense at all.

The Star 48 also has some excellent mass ratios that make it attractive in spite of the low ISP.

When I ran my sims for my Falcon 1 class vehicle, I did a lot of runs with various upper stage configurations, but my lessons agreed with what you would expect.

Every kg of propellant expended in a low ISP upper stage is a 1:1 mass penalty to payload.  ISP matters a lot!

Total thrust to weight also matters in getting S2 from MECO to LEO.   I modeled a 50kN, 100kN, and 150kN upper stage ( same ISP)  with the associated mass trades, and taking burning a smaller 50kN engine longer, with more gravity losses, dropped payload  several hundred kg's.   Alternately, using a heavier 150kN engine and having less available propellant also dropped the payload in comparison to the 100kN engine.

If I had to say how I'd prioritize my S2 engine, It would come down to the destination.  ( LEO or GEO etc. ) the higher the orbit, the ISP will rule.   Getting from S2 ignition to LEO was also sensitive to T/W and minimizing burn time without too heavy of an engine.

final edit:  This is exactly what you see play out with the F9 vehicle and the Merlin 1D-Vac upper stage.  A great T/W engine that quickly burns it's way to LEO.  Payload to LEO is fantastic, but drops off rapidly to higher orbits in comparison to other vehicles using high ISP upper stages.   Every kg of inneficient 340 ISP exhaust from the 1D-Vac eats into payload that gets to a higher orbit.

[MP99]

I suspect that the best way for SpaceX to tackle this market would be to put the development funds into making the F9 upper stage reusable instead.

This would be a big performance hit to F9, but should cover the market that F1 would otherwise cover.

Cheers, Martin

[CuddlyRocket]

Remembering that this is supposed to be a low-cost launcher and its design should therefore be optimised for cost, not performance, I'd suggest the following design parameters: Common propellant for both stages and using existing equipment where possible.

Given the above, how about the following proposal: A 2-stage rocket; both stages keralox with a single M1-D SL engine? The SL version is not as efficient as the Vac in space, but it should be sufficient (it has a vacuum isp of 308 versus 348). It's also lower thrust, which helps with problems of over-acceleration on the second stage (and it can throttle down to 70%).

Anyone care to run the numbers?

[S.Paulissen]

Remembering that this is supposed to be a low-cost launcher and its design should therefore be optimised for cost, not performance, I'd suggest the following design parameters: Common propellant for both stages and using existing equipment where possible.

Given the above, how about the following proposal: A 2-stage rocket; both stages keralox with a single M1-D SL engine? The SL version is not as efficient as the Vac in space, but it should be sufficient (it has a vacuum isp of 308 versus 348). It's also lower thrust, which helps with problems of over-acceleration on the second stage (and it can throttle down to 70%).

Anyone care to run the numbers?

Won't work, too much thrust for a merlin on second stage at minimum throttle the upper stage would hit 20gs at burn out.

[Lars-J]

Remembering that this is supposed to be a low-cost launcher and its design should therefore be optimised for cost, not performance, I'd suggest the following design parameters: Common propellant for both stages and using existing equipment where possible.

Given the above, how about the following proposal: A 2-stage rocket; both stages keralox with a single M1-D SL engine? The SL version is not as efficient as the Vac in space, but it should be sufficient (it has a vacuum isp of 308 versus 348). It's also lower thrust, which helps with problems of over-acceleration on the second stage (and it can throttle down to 70%).

Anyone care to run the numbers?

Won't work, too much thrust for a merlin on second stage at minimum throttle the upper stage would hit 20gs at burn out.

Not if the 2nd stage is actually larger than the 1st stage.

[Dante80]

That would be somewhat counter-productive I think. A single m1-d can move..eh...lets say about 70,000kg off the pad for a low TWR. Lets say that S2 is bigger (40 tonnes, including payload). This means that the first stage should weigh about 30 tonnes.

M1-d does about 84,000kgf in vacuum (we are still talking about the SL version, not MVac). How much could you feasibly throttle it down before the payload liquefies?

[Patchouli]

No, it has little merit for a deep space mission. Once you are out of the deep gravity well, Isp is king. Thrust does not matter. So a Draco (or cluster of them) would actually be superior to SuperDraco for the purpose of a final kick stage.

Not that I disagree with you, but a Star 48 has an ISP of 292 (see http://forum.nasaspaceflight.com/index.php?topic=33084.msg1109220#msg1109220) which is also really poor.  SpaceX built the SuperDraco to essentially compete with an SRM: low ISP, high thrust, quick ignition, non-cryo propellant, with the notable difference being that it can throttle dynamically instead of being stuck with a fixed thrust profile.

But if you're going to do all of that, in space, a SRM has much better storability properties, probably weighs less (when you account for the plumbing), and is a known and available quantity already.  Just use a Star 48 or equivalent if that's what you want!

Really, SuperDracos were designed for a very specific purpose, and trying to use them elsewhere just doesn't make sense at all.

Another option use a hypergolic upper stage engine such as the AJ-10 or Aestus.

[Lars-J]

That would be somewhat counter-productive I think. A single m1-d can move..eh...lets say about 70,000kg off the pad for a low TWR. Lets say that S2 is bigger (40 tonnes, including payload). This means that the first stage should weigh about 30 tonnes.

M1-d does about 84,000kgf in vacuum (we are still talking about the SL version, not MVac). How much could you feasibly throttle it down before the payload liquefies?

My point is that is your upper stage is large enough, the situation is no different than what current small F9 payloads experience - such as CASSIOPE, DISCOVR, and now JASON-3 - and somehow those payloads don't seem to "liquefy". You are exaggerating the issue of g-loads at burnout.

[Dante80]

My pony is that is your upper stage is large enough, the situation is no different than what current small F9 payloads experience - such as CASSIOPE, DISCOVR, and now JASON-3 - and somehow those payloads don't seem to "liquefy". You are exaggerating the issue of g-loads at burnout.

I think that its not the same thing man. Running the numbers for a 110+ ton S2 lifted by 9 M-1ds to a 40 ton S2 lifted by one makes me think that the situation is different at S2 burnout with a small payload.

[hkultala]

Well I took the leap last night to give my best effort at making my own new "Phoenix" F1 class vehicle and testing it out on a simulator linked to by this site in the archives at Silverbird Astronautics.
http://www.silverbirdastronautics.com/LVperform.html

This was the first time I have ever done an exercise like this.  I have watched many other here do similar, some of you are very very good at it.  I do not profess to be good at all.

My designs started with the specifications for using the Merlin 1D FT engine w/ 756 kN thrust, and building the vehicle around that.  I also made an early decision to make the new vehicle with a 2m core, not the 1.7 I believe the old F1 had.  I think the Merlin 1D FT is too much rocket to stick on that small a diameter core without getting something too long and bendy.

I also wanted to make a better S2, so I selected to use a 100kN Methane upper stage.  ( Darma Technolgies CHASE 10 ) I had to guess what a vacuum engine could do for ISP, and guessed 350s.

G's at liftoff were set to be 1.18, so the mass of the complete vehicle would then be 65329 kg's.

After some iterations on the calculations, my mass distribution is a follows

Stage 1:
Dry mass = 3461 kg
Propellant = 55368 kg
Thrust = 756 kN
ISP avg = 304

Stage 2:
Dry mass = 619
Propellant = 5881
Trust = 100 kN
ISP = 350
Fairing 160 kg

Second stage having better T/W than first stage does not look like a very balanced design.

If your engine specs are fixed, consider moving some propellant from the first stage to the second stage.

[S.Paulissen]

That would be somewhat counter-productive I think. A single m1-d can move..eh...lets say about 70,000kg off the pad for a low TWR. Lets say that S2 is bigger (40 tonnes, including payload). This means that the first stage should weigh about 30 tonnes.

M1-d does about 84,000kgf in vacuum (we are still talking about the SL version, not MVac). How much could you feasibly throttle it down before the payload liquefies?

My pony is that is your upper stage is large enough, the situation is no different than what current small F9 payloads experience - such as CASSIOPE, DISCOVR, and now JASON-3 - and somehow those payloads don't seem to "liquefy". You are exaggerating the issue of g-loads at burnout.

This is a false equivalence for a couple of reasons.

A) The dry weight of the second stage in small payload cases like JASON-3 is that the second stage comes with its own ballast mass, excess propellant.  The second stage in a case like JASON-3 is at roughly target orbital speed with 13000kg of propellant still in the tanks leaving a small payload like this with only 3g acceleration at burn out.  This rockets full performance is required, burning all the way to empty, so there is no built in ballast, thus achieving very high gs.

B) Transferring that much propellant to the upper stage would cost considerable performance as it's mainly the loss of dry mass at staging that increases performance.  How much are you proposing to transfer in order to achieve normal launch g forces?

[Stan-1967]

Remembering that this is supposed to be a low-cost launcher and its design should therefore be optimised for cost, not performance, I'd suggest the following design parameters: Common propellant for both stages and using existing equipment where possible.

Given the above, how about the following proposal: A 2-stage rocket; both stages keralox with a single M1-D SL engine? The SL version is not as efficient as the Vac in space, but it should be sufficient (it has a vacuum isp of 308 versus 348). It's also lower thrust, which helps with problems of over-acceleration on the second stage (and it can throttle down to 70%).

Anyone care to run the numbers?

I just ran a sim on a S1 and S2 with equal mass ( 3300 kg dry weight, 31600kg propellant ).

Results were not impressive:( but that what 2 stages with crappy mass ratios will get you )
=====================
Mission Performance:
Launch Vehicle:     User-Defined Launch Vehicle
Launch Site:     Cape Canaveral / KSC
Destination Orbit:     185 x 185 km, 45 deg
Estimated Payload:     0 kg
95% Confidence Interval:     0 - 0 kg
======================

It is pushing 21 g's at burnout.

I appreciate the goal of using the same fuel for both stages to make this exercise about a low cost/simple rocket.  I did consider a cluster of "Rutherford" class electric pump fed engines.   Rocketlab hasn't published much regarding ISP for a vacuum Rutherford.  I recall seeing ISP of 327s speculated somewhere around here.  I  ran a sim with 4 Rutherford vac engines producing 100kN and aloted an additional 100 kg of battery  mass to the empty mass in the sim I did with the CHASE 10 Methalox.  ( no idea what real numbers would be for the battery) Here is how that played out:
=======================
Mission Performance:
Launch Vehicle:     User-Defined Launch Vehicle
Launch Site:     Cape Canaveral / KSC
Destination Orbit:     185 x 185 km, 45 deg
Estimated Payload:     1368 kg
95% Confidence Interval:     994 - 1830 kg
=======================

Not too bad performance, and if you can 3-D print your engine, low cost should be attainable.

[Lars-J]

My point is that is your upper stage is large enough, the situation is no different than what current small F9 payloads experience - such as CASSIOPE, DISCOVR, and now JASON-3 - and somehow those payloads don't seem to "liquefy". You are exaggerating the issue of g-loads at burnout.

I think that its not the same thing man. Running the numbers for a 110+ ton S2 lifted by 9 M-1ds to a 40 ton S2 lifted by one makes me think that the situation is different at S2 burnout with a small payload.

No, you are not getting what I'm saying. What I am proposing is that the upper stage basically be the F9 upper stage, but slimmed and stretched to F1 diameter, powered by a single M1D. This large upper stage would not have the burnout g-load issue that you are concerned with, since it would have a similar dry weight of the F9 upper stage. But since this stage would not be SSTO, I propose putting it on top of a smaller but same diameter 1st stage, with an M1D at full thrust.

This would be a real Frankenstein creation, but the the idea was to accomplish such a vehicle with existing SpaceX components.

Another option would be to have equal sized stages, but with the upper stage powered by an M1D at lowest thrust setting (~50%). The lower stage would run at full thrust.

[Dante80]

No, you are not getting what I'm saying. What I am proposing is that the upper stage basically be the F9 upper stage, but slimmed and stretched to F1 diameter, powered by a single M1D. This large upper stage would not have the burnout g-load issue that you are concerned with, since it would have a similar dry weight of the F9 upper stage. But since this stage would not be SSTO, I propose putting it on top of a smaller but same diameter 1st stage, with an M1D at full thrust.

But I understood what you said. That's why S2 is a little bigger than S1 (as you said), and it's less than half the weight of the F9 S2. The diameter is 1.7m.

edit: Oh, a second stage as big as the F9 S2 but taller and slimmer? If the second stage (same weight as F9 S2, less diameter) is put on top of a S1 with 1 M-1d, the M-1d cannot lift it I think.

[Lars-J]

But I understood what you said. That's why S2 is a little bigger than S1 (as you said), and it's less than half the weight of the F9 S2. The diameter is 1.7m.

No, you are still not getting what I mean. The diameter would be 1.7m, but it would contain almost the same amount of propellant as the F9 upper stage. It would be MUCH longer. And due to this non-optimal size, the dry mass of the stage would be the same or likely higher. Therefore no burnout g-load issue.

[Dante80]

The first stage would not lift it. It can't..the F9 S2 needs 9 M-1ds to lift it man. You are talking about a stage with about the same weight here...

The stage TWR of the MVac engine when starting in F9 is less than one (the engine can do 94,000kgf and the stage is 110,000kg+ at SEP). Now imagine replacing the MVac with a standard M-1d, add below it  another tank, and an engine with less thrust trying to lift it from the pad.

But since this stage would not be SSTO, I propose putting it on top of a smaller but same diameter 1st stage, with an M1D at full thrust.

I might have gotten this wrong, I don't understand (english is not my native language).   

[Stan-1967]

But I understood what you said. That's why S2 is a little bigger than S1 (as you said), and it's less than half the weight of the F9 S2. The diameter is 1.7m.

No, you are still not getting what I mean. The diameter would be 1.7m, but it would contain almost the same amount of propellant as the F9 upper stage. It would be MUCH longer. And due to this non-optimal size, the dry mass of the stage would be the same or likely higher. Therefore no burnout g-load issue.

It will take at least 30 meters of 1.7 meter core to hold around 78,500 kg of fuel, which is what the latest F9 S2 reportedly contains.   The burn time for a Merlin to go through this fuel will be around 295s.  The Merlin 1D at 756 kN cant lift that load of fuel.  Merlin Vac manages because it produces 934 kN.

[Lars-J]

But I understood what you said. That's why S2 is a little bigger than S1 (as you said), and it's less than half the weight of the F9 S2. The diameter is 1.7m.

No, you are still not getting what I mean. The diameter would be 1.7m, but it would contain almost the same amount of propellant as the F9 upper stage. It would be MUCH longer. And due to this non-optimal size, the dry mass of the stage would be the same or likely higher. Therefore no burnout g-load issue.

It will take at least 30 meters of 1.7 meter core to hold around 78,500 kg of fuel, which is what the latest F9 S2 reportedly contains.   The burn time for a Merlin to go through this fuel will be around 295s.  The Merlin 1D at 756 kN cant lift that load of fuel.  Merlin Vac manages because it produces 934 kN.

Yes, so reduce it in size a bit then so it matches the M1D thrust. But I never claimed it was a great design.

[S.Paulissen]

It's not, because it can't make it to orbit, even with no payload.... And still will pull over 10g acceleration at cutoff with 65% throttle with no payload assuming it's mass is nearly a falcon 9 second stage mass.  As mentioned above, falcon 9 fixes this by having excess margin propellant as ballast.  Jim says this all the time, excess performance is transferred to the upper stage and this is largely (but not entirely) why. 

Long story made short, no, acceleration g force concerns were not overblown.

[CuddlyRocket]

Remembering that this is supposed to be a low-cost launcher and its design should therefore be optimised for cost, not performance, I'd suggest the following design parameters: Common propellant for both stages and using existing equipment where possible.

Given the above, how about the following proposal: A 2-stage rocket; both stages keralox with a single M1-D SL engine? The SL version is not as efficient as the Vac in space, but it should be sufficient (it has a vacuum isp of 308 versus 348). It's also lower thrust, which helps with problems of over-acceleration on the second stage (and it can throttle down to 70%).

Anyone care to run the numbers?

Won't work, too much thrust for a merlin on second stage at minimum throttle the upper stage would hit 20gs at burn out.

Shame! By the way, what is the maximum g at burn out one should aim for?

So, either we reduce the thrust of the M1-D SL, which would mean a redesign, or we find a smaller keralox engine. The trouble is, there's not that many about, especially non-Russian ones! Presumably SpaceX still has the plans for its Kestrel engine. I don't know if they could still manufacture it if they were paid to do so, but they might sell the design to someone else so to do. Or someone could bite the bullet and develop a new small keralox engine!

[Modal]

Remembering that this is supposed to be a low-cost launcher and its design should therefore be optimised for cost, not performance, I'd suggest the following design parameters: Common propellant for both stages and using existing equipment where possible.

Given the above, how about the following proposal: A 2-stage rocket; both stages keralox with a single M1-D SL engine? The SL version is not as efficient as the Vac in space, but it should be sufficient (it has a vacuum isp of 308 versus 348). It's also lower thrust, which helps with problems of over-acceleration on the second stage (and it can throttle down to 70%).

Anyone care to run the numbers?

Won't work, too much thrust for a merlin on second stage at minimum throttle the upper stage would hit 20gs at burn out.

Shame! By the way, what is the maximum g at burn out one should aim for?

IIRC, 7g's at a maximum for satellites.

[bstrong]

Or someone could bite the bullet and develop a new small keralox engine!

Like the FRE-1? (thrust: 6,200 lbf, isp: 325 sec)

http://www.fireflyspace.com/vehicles/firefly-a
http://www.fireflyspace.com/news/ournews/first-rocket-engine-test-a-success-for-firefly-space-systems

Edit: actually, those two links disagree on the thrust. the second says 7,000 lbf

[S.Paulissen]

So, it's a kestrel clone, in performance and mode of operation if not design.  The problem with these size of engines (technically just a glorified valve in front of a combustion chamber, not the literal definition of an engine) is that they're too small to lift the size of upper stage needed to best utilize the lift off a Merlin 1d FT.

[JamesH]

So, it's a kestrel clone, in performance and mode of operation if not design.  The problem with these size of engines (technically just a glorified valve in front of a combustion chamber, not the literal definition of an engine) is that they're too small to lift the size of upper stage needed to best utilize the lift off a Merlin 1d FT.

So is the Lamborghini a Ferrari clone?  Same performance, same mode of operation. Not really a clone I would say.

[CuddlyRocket]

Or someone could bite the bullet and develop a new small keralox engine!

Like the FRE-1? (thrust: 6,200 lbf, isp: 325 sec)

http://www.fireflyspace.com/vehicles/firefly-a
http://www.fireflyspace.com/news/ournews/first-rocket-engine-test-a-success-for-firefly-space-systems

Edit: actually, those two links disagree on the thrust. the second says 7,000 lbf

So, it's a kestrel clone, in performance and mode of operation if not design.  The problem with these size of engines (technically just a glorified valve in front of a combustion chamber, not the literal definition of an engine) is that they're too small to lift the size of upper stage needed to best utilize the lift off a Merlin 1d FT.

By the look of it, these engines are designed to be clustered (not necessarily in an aerospike) so it depends on how many will fit under the 2nd stage. At least there should be no problems with excessive acceleration!

[swervin]

In light of all experience gained at SpX for recovery, and the proposed S2 recovery for F9 via the ‘party baloon’ concept, any thoughts on utilizing a similar system to make any part of this theoretical LV recoverable? Yes, margins are beyond thin or non-existent for mass/space, and SpX isn’t furthering the dev of this rocket, but hey, this is a theoretical topic anyway!

Also, non-theoretical: did SpX ever make a 6th F1 core? What happened to all the tooling and already built Kestrel engines?

Hope y’all don’t get mad at an old topic resurfacing... 😳

Cheers,
Splinter

[IanThePineapple]

Yes, there is a sixth F1 core and an F1 fuel tank sitting in SpaceX's junkyard in Hawthorne

[swervin]

Thx, Ian! I didn’t realize they had a ‘junkyard’ at Hawthorne. Anyone have a sat pic of it! I don’t see it on google maps...

[IanThePineapple]

There was a post on /r/SpaceX about it a few months back, just search "junkyard" on the subreddit

[Elthiryel]

Yep, it can be found on reddit.

https://www.reddit.com/r/spacex/comments/61pizd/looking_through_the_spacex_junkyard_on_google/
https://imgur.com/a/QZ7Wi

/u/randomstonerfromaus:

For those that are not aware, this is at the SpaceX Wilkie facility which is an annex of Hawthorne which IIRC is tasked with R&D. Here it is on maps. The legs are located on the East side of the building, about half way up. The junkyard is above the North East corner of the building.

[Giovanni DS]

Wouldn't make more sense to base this hypothetical new small launcher on Raptor? They would need an engine for the 2nd stage but It would be in a very different performance class compared to Falcon1 while still having a similar level of complexity.

[speedevil]

Wouldn't make more sense to base this hypothetical new small launcher on Raptor? They would need an engine for the 2nd stage but It would be in a very different performance class compared to Falcon1 while still having a similar level of complexity.

A launcher with a 170 ton engine is not most peoples idea of a small launcher.

[rakaydos]

Wouldn't make more sense to base this hypothetical new small launcher on Raptor? They would need an engine for the 2nd stage but It would be in a very different performance class compared to Falcon1 while still having a similar level of complexity.

Upper stage would be a cluster of the Gas Methalox RCS they are developing for BFB landing control- the number I remember is 10 tons of thrust each, and it's effectively the same propellant on both stages and as their larger launcher.

A single raptor booster might be small enough for parachute recovery, too.

[Lars-J]

Wouldn't make more sense to base this hypothetical new small launcher on Raptor? They would need an engine for the 2nd stage but It would be in a very different performance class compared to Falcon1 while still having a similar level of complexity.

A launcher with a 170 ton engine is not most peoples idea of a small launcher.

Falcon 1 doesn't fit that criteria for some people either.    Is your goal to just create a hypothetical smallest launcher, or is it to create a hypothetical small launcher that would actually be more compatible with SpaceX efforts going forward? If the latter you base it on Raptor, and it is would still be a very "small" launcher in SpaceX's lineup.

[speedevil]

Falcon 1 doesn't fit that criteria for some people either.    Is your goal to just create a hypothetical smallest launcher, or is it to create a hypothetical small launcher that would actually be more compatible with SpaceX efforts going forward? If the latter you base it on Raptor, and it is would still be a very "small" launcher in SpaceX's lineup.

Hmm.

If we're going 'going forward',, I propose a F9S2 methalox sized S1, with a smaller metholox stage on top.

Perhaps 9 tons to LEO, or if you stick it in BFR, as a third stage, you get about 45 tons to mars orbit. Add aerobraking hardware, which is conveniently already available, extend the duration a lot, and for one launch, not seven, you get 30 tons in low mars orbit, or perhaps making some assumptions, 20 tons to the moon. (with a second stage/lander).