Syntin for the second stage of Falcon 9?

[LouScheffer]

Syntin is a synthetic hydrocarbon with slightly better properties than RP-1. It's a little denser and slightly higher ISP.  The main drawback seems to be that it has to be synthesized and is hence expensive.  But it seems like using it in the second stage could help Falcon 9 to GTO significantly.

Assuming current payload to GTO of 4.85t, empty second stage mass of 5t, and propellant load of 90t (200k lbs), and ISP of 340, then the delta-V provided by the second stage is:

340*9.8*ln( (4.85+5+90) / (4.85 + 5)) = 7717 m/sec

Syntin is about 5% denser.  Assuming you cool the LOX, you can get 8-9% denser on that, too. 

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050203875_2005204553.pdf

So assume you can cram  95t of propellant in the current stage.  The Russian engines got about 8 sec more ISP with syntin.   So now you can loft 6t to GTO...

348*9.8*ln( (6+5+95)/ (6+5)) = 7726 m/s

So how expensive is syntin in industrial quantities? 

EDIT:  Oops, I wrote 940/948 for the ISP where I meant 340/348.  But this was a copying error and the results are correct.

[Proponent]

This is vague, but Bruce Dunn suggested in the mid-1990s that it would cost more than $100/kg.

But the project seems like a lot of work for a slightly greater capacity.

[cartman]

Well if its $100/kg it is $9.5million for 95 tons plus the cost to test and qualify the fuel. Probably not worth it, at least in a launch that costs about $50million

[llanitedave]

Is there any indication that SpaceX has expressed interest in Syntin?

[Lars_J]

Why would it be worth it, if it only provides a slight benefit?

[LouScheffer]

Well if its $100/kg it is $9.5million for 95 tons plus the cost to test and qualify the fuel. Probably not worth it, at least in a launch that costs about $50million

Only half the propellant is Syntin, the rest is LOX, so it adds only 5 million or so.  And there are lots of commercial satellites in the 4.85t < M <6t mass range.  See this recent SeaLaunch example:

http://www.sea-launch.com/missions-q11373-Mission_Overview.aspx

The alternative (from the SpaceX view) would be to use a FH.  If you can compete for these same launches with an F9, it would save a lot of money, even if the fuel was a few million bucks more.

[Elmar Moelzer]

Hmm, pre chilling the RP1 might yield better results (might have other issues though).

[Danderman]

This would work, but:

Sintin is really not available.

and

the engine has to modified to burn Sintin.

As a result, the IRR on learning to burn methane is probably higher.

[cambrianera]

Only half the propellant is Syntin, the rest is LOX, so it adds only 5 million or so.

Actually less than one third; lowest O/F ratio for LOX and RP-1 is around 2.2 (most common around 2.5).

[john smith 19]

Well if its $100/kg it is $9.5million for 95 tons plus the cost to test and qualify the fuel. Probably not worth it, at least in a launch that costs about $50million

Only half the propellant is Syntin, the rest is LOX, so it adds only 5 million or so.  And there are lots of commercial satellites in the 4.85t < M <6t mass range.  See this recent SeaLaunch example:

http://www.sea-launch.com/missions-q11373-Mission_Overview.aspx

The alternative (from the SpaceX view) would be to use a FH.  If you can compete for these same launches with an F9, it would save a lot of money, even if the fuel was a few million bucks more.

Not really. IIRC Robobeat said Spacex are quoting NASA 16 tonnes to LEO and maybe half that to GTO for an expendable mission.

It sounds like Syntin is costing about the same as J10 (the synthetic fuel for cruise missiles) at about $100/lb.

RP1 is somewhere below $1/lb AFAIK. It's said that fuel costs are in the "noise" as far as launch costs are concerned but if that figure is right then Syntin is more expensive than any of the Amines.

The trouble with both  sub cooled propellants and advanced propellants is that they should be designed in before the LV is designed. That increased propellants weight means a) More thrust needed from the engines b)Slower acceleration,  so more stress on the vehicle, which means you either eat into your safety margins or strengthen the vehicle.

Similar issues with changing propellants. A 100x fold increase in propellant cost is pretty serious already but the logistics costs around it will cause even more cost and disruption.

The note on the LO2 densification article the OP mentions suggest that it's possible to build an HX with temperature difference across the exchanger of about 1 2/3K. That suggests that using standard boiling point LN2 you could cool any propellant to 79K (provided it's mp > 79k) without the trouble and expense of putting a large, high power vacuum pump on the exhaust to lower the BP of the LN2 (lowering the air pressure in the 2nd stage of the LN2 boiler by about 12 psi buys you about 10k).

Yes it's probably feasible. No it's probably not worthwhile 

[Jim]

Hmm, pre chilling the RP1 might yield better results (might have other issues though).

Heating works better.

[Elmar Moelzer]

Hmm, pre chilling the RP1 might yield better results (might have other issues though).

Heating works better.

I thought of pre chilling the RP1 for increasing the density. Wouldn't heating have the opposite effect?

[cambrianera]

Hmm, pre chilling the RP1 might yield better results (might have other issues though).

Heating works better.

I thought of pre chilling the RP1 for increasing the density. Wouldn't heating have the opposite effect?

We are talking about the second stage, what's important is the specific energy, not the mass density.
Heating increases total energy (and combustion efficiency).
http://forum.nasaspaceflight.com/index.php?topic=5118.msg81521#msg81521
http://forum.nasaspaceflight.com/index.php?topic=5118.msg81574#msg81574
http://forum.nasaspaceflight.com/index.php?topic=5118.msg81581#msg81581

[Dudely]

Man, rockets are hard.

[Elmar Moelzer]

I thought of pre chilling the RP1 for increasing the density. Wouldn't heating have the opposite effect?

We are talking about the second stage, what's important is the specific energy, not the mass density.
Heating increases total energy (and combustion efficiency).

Oh, that makes sense! Thanks!

[Robotbeat]

How much does heating really change the energy, though? Mass ratio is also really important.

[vigleik]

Let me point out a problem with the math in the original post: If you increase the mass of the second stage and the payload the delta v provided by the first stage goes down, and it looks to me like that wasn't taken into account. So the advantage is smaller than implied. (Exact numbers left as an exercise.)

[LouScheffer]

Let me point out a problem with the math in the original post: If you increase the mass of the second stage and the payload the delta v provided by the first stage goes down, and it looks to me like that wasn't taken into account. So the advantage is smaller than implied. (Exact numbers left as an exercise.)

This is certainly true, and it reduces the advantage by about 30%, to about +800kg.  But on the other hand, SpaceX has announced that the regular kerosene powered model can loft 5.3t to GTO, more than the 4.85t previously claimed.  So a Syntin-fueled second stage could still put 6.1t into GTO.  That covers an awful lot of the comsat market.

Of course the FH can do this job easily.  But even if the stages are recoverable, it's still expensive.  Say the engines are $1M each, and can be used 10 times.  Then each use costs $100k.  The 18 extra engines cost at least 1.8 million in wear and tear alone, not to mention recovery and re-stacking.

Furthermore, a 4t comsat could be launched on a recoverable F9.1 mission with Syntin, but would need an expendable or a FH with kerosene.

[Lars_J]

Syntin is not 'KISS'. It only provides a minimal performance boost. Therefore it won't happen.

[Robotbeat]

Syntin is not 'KISS'. It only provides a minimal performance boost. Therefore it won't happen.

Same with subcooling, which Musk suggests is likely?

I have no idea if syntin would be used, but something similar (and much cheaper) may be looked at by SpaceX if they need the performance. Which they probably do in order to reach all their performance goals. Subcooling sounds like a better idea, though, but I wouldn't put it past SpaceX to consider a reformulation of kerosene for the upper stage. A few seconds more Isp, a few percent better density, and you can now afford even upper stage recovery (or at least first stage recovery for an expanded customer list).

Propellant subcooling, carbon-carbon nozzle upper stage, possible other tricks like syntin for upper stage, maybe crossfeed for the Falcon Heavy... Pretty soon you've bought back much of the performance hit of reuse.

[sdsds]

As a 2009 point of reference, for 507,388 gallons of JP-10 (decane) and 11,350 gallons of PF-1 (priming fluid) the Defense Energy Support Center paid Dixie Chemical Company $10,355,053.
https://www.fbo.gov/index?id=411dccf10d9b778ec20da46b81c60c98

[Lars_J]

Syntin is not 'KISS'. It only provides a minimal performance boost. Therefore it won't happen.

Same with subcooling, which Musk suggests is likely?

One of these is not like the other.

[LouScheffer]

Seems like this might be worth considering again, now with new Falcon FT numbers.

Synthetic fuels 'syntin' or 'boctane' give about a 2% boost in ISP.  If used on something like the SES-9 mission (5.3t) and making normal assumptions  (111t fuel, 5t second stage mass), then upping the ISP from 348 to 355 gives about 170 m/s more.  Plus with higher density you might be able to cram more in (though I've seen nothing about sub-cooling it.)

This would be enough to make SES-9 a routine landing.  At cutoff, the booster is accelerating at about 4.2 Gs, or about 42 m/s.  So the extra ISP could let the booster burn for 4 seconds less.  Converting the 3 engine suicide slam (3 engines, 5 seconds) into a normal landing (33 sec of single engine) needs 18 seconds more engine time.  That's 2 seconds of the 9-engine booster firing.  Likewise the other 2 seconds could allow the re-entry burn (known to be marginal for SES-9) to be extended by 6 seconds.

Alternatively, Falcon 9 could boost a 5.8t satellite with minimal margins like it had on SES-9.

Of course one of the main reasons against such a proposal is the expense of the synthetic fuel.  The Falcon-9 FT has about 32,000 kg of RP-1.  At $100/kg it would be $3.2M, perhaps worth it if it enables you to recover a stage.  At $1000/kg it's $32M, almost surely too much.  The exact cost cutoff is unclear.  However, Atlas was looking to use boctane for the first stage, so it can't be ridiculously expensive.  reference.

[Robotbeat]

Or just use a Raptor upper stage...

[gospacex]

Chemists talking about it:

http://www.chemicalforums.com/index.php?PHPSESSID=042724659af47dc60cb2ddb8ed62ce5e&topic=50579.15

[wannamoonbase]

Or just use a Raptor upper stage...

Exactly, Methane will be a much greater performance improvement than tinkering with RP1.

SpaceX has what they are going to use for a few year to come.  The current configuration is 'good enough'.

The Merlin US is the best they can do at the time and deliveries the payloads they have booked. 

SpaceX needs to ramp up flight rate, increase revenue, grow market share much more than they need to improve US performance.

[savuporo]

Nothing wrong with some theoretical rocket tuning. How about NOS injection paired with some Go Fast stickers?

[nicp]

I was about to post a question re Falcon 9 and syntin. But I was thinking the first stage.
Previous comments suggest syntin is too expensive, a non-starter.
Is it dead?

And given the density difference, does that affect turbopump design?
Which I think would kill it.

[go4mars]

Chemists talking about it:

http://www.chemicalforums.com/index.php?PHPSESSID=042724659af47dc60cb2ddb8ed62ce5e&topic=50579.15

Thank you!
The obvious question is 'why does it cost so much and can the price drop?'.
These chemists shed some light on that.

Perhaps the price can drop, but it doesn't seem straightforward yet to me. 
I my point in the journey I would lean toward trying methane or hydrosilicons.  Maybe hydrogen.

[russianhalo117]

Chemists talking about it:

http://www.chemicalforums.com/index.php?PHPSESSID=042724659af47dc60cb2ddb8ed62ce5e&topic=50579.15

Thank you!
The obvious question is 'why does it cost so much and can the price drop?'.
These chemists shed some light on that.

Perhaps the price can drop, but it doesn't seem straightforward yet to me. 
I my point in the journey I would lean toward trying methane or hydrosilicons.  Maybe hydrogen.

because its synthesized fuel which requires lots of energy to make. If everyone used it like synthetic oil. It would be much cheaper.

[TomH]

Going back to Jim's comment on heating the RP-1 on the S2, how hot would you heat it? How much would it expand? What % specific energy would you gain?

[Steven Pietrobon]

Here's an article on biosynthesis of Pinene. It has the same chemical composition as Syntin (C10H16), but is denser, 0.858 kg/L for Alpha-Pinene and 0.859 kg/L for Beta-Pinene compared with 0.851 kg/L for Syntin.

http://www.popsci.com.au/tech/aerospace/missiles-and-rockets-might-soon-smell-like-pine-trees,382230

[Proponent]

Chemists talking about it:

http://www.chemicalforums.com/index.php?PHPSESSID=042724659af47dc60cb2ddb8ed62ce5e&topic=50579.15

Unless I'm missing mention of syntin, that thread is about boctane (aka bicyclo[3.3.0]octane).

[spacenut]

Seems like SpaceX has about tweeked out the F9/FH without going to something like syntin or boctane,  Better yet like Robotbeat said, a Raptor based second stage, would greatly increase the capabilities of F9/FH.  This along with a stretch or a slightly larger fairing.  F9/FH first stage is small but very powerful.  Not much room for improvement there.  The synthetic fuels would add cost, but their costs would still be less than other's.  IF, they don't have to make too many modifications to Merlin. 

[karanfildavut]

As a Ph.D. organic chemist I usually don't get to contribute much, but since this is a topic that touches on my expertise I'll share my 0.02$

Syntin is definitely a non-starter for SpaceX. Currently RP-1 is highly processed petroleum for which substantial facilities (cracking, fractional distillation, desulfurization, dearomatization) exist. Thus, the production of RP-1 leverages the current infrastructure. Similarly, methane has a production and distribution network absent rocket use, that can then be leveraged for spacefaring systems.

In contrast syntin currently has no kiloton scale production capability worldwide. The cost and effort to set one up for exclusive SpaceX use would run, based on comparison for a simple ethylene plant, into the $1-3 billion of dollar range. SpaceX would also not be able to leverage any of the ancillary petroleum know-how in setting this up, making it even more costly.

Next, the cost of starting materials will likely be prohibitive. Gasoline is cheaper than dirt cheap when it comes to chemicals. Most intermediate chemicals (such as the starting material of syntin) come at a cost in the range 10-100 cents per gram. Apply that to kiloton scale and suddenly fuel would become your primary cost driver. To add to this, the current route uses aluminum tri(t-butoxide) and hydrazine, both of which require special handling due to pyrophoricity of the former and extreme toxicity of the latter. There is absolutely no way syntin ever gets made on rocket fuel scale unless a) the government pays for it or b) some high-volume use outside of rocket fuel can be found.

Given SpaceX's future choice of fuel is abundant, here and in space, has rocket-independent infrastructure associated with cost reductions, and does not present a toxicity hazard in its production, I cannot imagine SpaceX using boctane or syntin or any other specific hydrocarbon fuel. They're all just too damn expensive on the scale necessary for rockets.

[BobHk]

Or just use a Raptor upper stage...

Esp if you want to send a capsule to the moon...

[Jim]

Or just use a Raptor upper stage...

Can we just stop with this.  There is no such thing.

[LouScheffer]

Next, the cost of starting materials will likely be prohibitive. [...] Most intermediate chemicals (such as the starting material of syntin) come at a cost in the range 10-100 cents per gram. Apply that to kiloton scale and suddenly fuel would become your primary cost driver.

 I cannot imagine SpaceX using boctane or syntin or any other specific hydrocarbon fuel. They're all just too damn expensive on the scale necessary for rockets.

I agree with your conclusions about infrastructure and safety, but the sad part is that 10 cents per gram ($100 per kilogram) is not a high cost by rocket standards.  The second stage has something like 30 tonnes of fuel (the rest is LOX), which would be about $3M at this price.  That's only 5% of even a low cost launch, and about half the cost of the fairing, which all current provider throw away without a second thought.  If syntin could give you a 5% performance boost, it would even be worth it in dollars per kg.

This type of cost structure, which pertains to the second stage and the payload, explains a lot about the space industry.  Of course SpaceX is working hard to get out of this regime, another reason for not following this path.

[Proponent]

The attached paper, entitled "Synthetic Hydrocarbon Rocket Fuels (Ways of lowering the cost of syntin)," may be of interest.  The catch is that it is in Russian, but the numerous chemical diagrams will be intelligible to any chemist, and there is a brief abstract in English at the very end.

[Kaputnik]

Next, the cost of starting materials will likely be prohibitive. [...] Most intermediate chemicals (such as the starting material of syntin) come at a cost in the range 10-100 cents per gram. Apply that to kiloton scale and suddenly fuel would become your primary cost driver.

 I cannot imagine SpaceX using boctane or syntin or any other specific hydrocarbon fuel. They're all just too damn expensive on the scale necessary for rockets.

I agree with your conclusions about infrastructure and safety, but the sad part is that 10 cents per gram ($100 per kilogram) is not a high cost by rocket standards.  The second stage has something like 30 tonnes of fuel (the rest is LOX), which would be about $3M at this price.  That's only 5% of even a low cost launch, and about half the cost of the fairing, which all current provider throw away without a second thought.  If syntin could give you a 5% performance boost, it would even be worth it in dollars per kg.

This type of cost structure, which pertains to the second stage and the payload, explains a lot about the space industry.  Of course SpaceX is working hard to get out of this regime, another reason for not following this path.

That makes $3m the lowest bound. According to karanfildavut's numbers, it could also be up to $30m, and that is just for the basic ingredients to start the production. You still have to process it, and pay for all of the facilities and handling and any additional materials, as well as disposal of any byproducts. Then you have to amortise the cost of setting up the infrastructure- unless you can persuade someone else to pay for that.

Seems pretty clear that CH4 is a far better long term bet.

[Proponent]

Syntin, by the way, is just three cyclopropane rings stuck together, with a methyl group thrown in.  Bruce Dunn found lox and cyclopropane itself to be an excellent propellant pair, offering an I_sp a couple of seconds better than lox/methane's and a bulk density of 969 kg/m³, which is closer to lox/RP-1's 1030 kg/m³ than to lox/methane's 828 kg/m³.  It's only slightly cryogenic (NBP is 240 K), and its viscosity at NBP is just 0.16 cP (see attachment), only a bit higher than methane's 0.12 cP and much lower than RP-1's  3.3 cP.

The thing is that cyclopropane is very expensive.  Even when it was used for anesthesia (showing that there is no serious toxicity problem), it was not cheap.  Could anyone find a cheap way to make cyclopropane?

[WmThomas]

It's time to end this discussion. The OPs idea has been soundly criticized. We're done.