Are Those Nozzles "Thrust Augmented"?

In this article at AvLeak, there’s discussion of an Aerojet LOX/Kero booster engine project called HC Boost (emphasis mine) :

Dubbed HC Boost, the technology development program is aimed at providing an improved, home-grown alternative to the Russian RD-180, the only other viable current-production hydrocarbon rocket engine. Unlike the RD-180, however, the US engine would be designed to be re-usable for up to 100 missions, have up to 15% better performance and would operate for up to 50 missions between engine overhauls.

Now, the RD-180 is a very high performance engine. It’s combustion chamber pressures are actually quite a bit higher than the SSME. When you combine this with the statements in this paragraph (my emphasis again):

The last US-designed and produced hydrocarbon engine was the Rocketdyne RS-27, based on 1960s technology and now out of production. The HC Boost engine, on the other hand, is expected to have higher operability, faster turn time, a longer-life thrust chamber, turbopumps and a new design nozzle.

It really does seem to suggest that they might be talking about thrust augmented nozzles. By going with nozzle thrust augmentation, you could get that same high lift-off thrust, and good sea-level Isp without requiring anywhere near as high of a chamber pressure. Which would necessarily lead to less demand on the thrust chamber and pumps.

A similar engine concept I’ve talked about with a few friends in the propulsion business is if you took the Merlin-1C upgrade that’s been hinted at by SpaceX, and applied that extra pump power they’re looking at creating to providing higher flow, lower pressure propellants to a TAN section (say by diverting some of that extra high pressure flow into some sort of a jet pump), you’d be able to get away with a much larger expansion ratio nozzle (with good sea-level Isp), while also nearly doubling the thrust. I really like the idea of a Falcon 1f that can put say 5000lb of payload into LEO for little more than the cost of a Falcon 1e….It’s a powerful concept, though I would understand if for now a company like SpaceX is focusing on getting Falcon-1 and -9 flying reliably first. First get it working and working reliably, then add the afterburners…

Which reminds me, I need to go back and do a more detailed article on some of the additional concepts and technical information I’ve found about Thrust Augmented Nozzles at some point.

The following two tabs change content below.
Jonathan Goff

Jonathan Goff

President/CEO at Altius Space Machines
Jonathan Goff is a space technologist, inventor, and serial space entrepreneur who created the Selenian Boondocks blog. Jon was a co-founder of Masten Space Systems, and is the founder and CEO of Altius Space Machines, a space robotics startup in Broomfield, CO. His family includes his wife, Tiffany, and five boys: Jarom (deceased), Jonathan, James, Peter, and Andrew. Jon has a BS in Manufacturing Engineering (1999) and an MS in Mechanical Engineering (2007) from Brigham Young University, and served an LDS proselytizing mission in Olongapo, Philippines from 2000-2002.
This entry was posted in Space Transportation, Technology, Thrust Augmented Nozzles. Bookmark the permalink.

16 Responses to Are Those Nozzles "Thrust Augmented"?

  1. Anonymous says:

    TAN for SpaceX is a great idea, and I don’t see why they wouldn’t announce it as the Merlin 1-G for 2012. They seem to be skipping every other year and every other letter in announcing future improved versions of their engine. Their recent postings have rocket performance based on Merlin 1-E, the growth version of the Merlin 1-C they are installing in the Falcon 9. The Falcon 1 seems to still have the Merline 1-A.

  2. Anonymous says:

    PS Remember that the regenerative Merline 1-C already has high pressure fuel flowing around the nozzle as coolant (and through their hydraulic system).

  3. jcanal12 says:

    Isn’t Aerojet a partner in the integrated powerhead demonstrator? I wonder if they’re using that technology for HC Boost.

  4. Jon Goff says:

    I’m not sure if I see your point. What does the regen cooling of the nozzle have to do with TAN? Are you saying it would be an obstacle to implementing TAN in the nozzle? Or are you saying it would be a source for the fuel part of the TAN? Or something else entirely.


  5. Jon Goff says:

    I think they are involved with IPD, but wasn’t that a LOX/LH2 concept?


  6. Anonymous says:

    Your second concept, Jon: I was saying that having the pressurized fuel flowing around the regeneratively cooled nozzle would be a benefit. They have already implemented the plumbing to bring the fuel, now used as coolant, across the joint actuated by the guidance system.

    My first post was a facetious way of saying that they could, in principle, incorporate this very promising technology into their existing engine, but that they are overtaxed, and have not achieved design stability. They continue to jump from one “improvement” to another. Falcon V to 9, Merlin 1A to 1B and then 1C. Falcon 1 to 1e. And worst of all, from experimental retrieval of the first stage to a baseline plan for first and second stage reuse.

  7. Jon Goff says:

    Your second concept, Jon: I was saying that having the pressurized fuel flowing around the regeneratively cooled nozzle would be a benefit. They have already implemented the plumbing to bring the fuel, now used as coolant, across the joint actuated by the guidance system.

    Ah, ok. Gotcha. Actually, I’m not sure if that would be the best approach, here’s why. For a pump, the required power scales roughly linearly with pump volume flow, pressure. At least some of the fluid in the nozzle is going into the main combustion chamber, and therefore has to be at fairly high pressure to overcome the pressure drop of the cooling channels and the pressure drop at the injectors. So, it’s probably somewhere on the order of 1200-1500psi at the inlet to the nozzle. For thrust augmentation however, you only really need about 150-300psi injector pressure. Which means that you’d be wasting lots of pump power to get the thrust augmentation.

    A much better approach would be to tap off a little of the high pressure flow, and either use it to run a lower pressure hydraulic turbine, or run some sort of jet pump. That way you can get a lot more TAN flow for much less pump power. As it is, the pumps are on the engine side of the gimbal setup, so you’d still get the same benefit.

    As it is though, I doubt they’ll be doing a TAN upgrade anytime soon, because as you point out, they have way too much on their place already. It makes a lot of performance sense, but just getting something working well enough to start succesfully putting payloads into orbit probably is (and should be) a higher priority.

    And worst of all, from experimental retrieval of the first stage to a baseline plan for first and second stage reuse.

    Careful, we *don’t* yet know that for sure–that’s only extrapolation based on one line in a new payload users guide. For all we know, his pricing could still be based on not actually reusing either stage, but he may want to do an extra surcharge because they won’t be able to get the stage back for inspection or something like that.

    IOW, I’d be careful about drawing too many conclusions quite yet.


  8. Anonymous says:

    “And worst of all, from experimental retrieval of the first stage to a baseline plan for first and second stage reuse.”

    “Careful, we *don’t* yet know that for sure–that’s only extrapolation based on one line in a new payload users guide.”

    Not so, although I can be less careful than you. In the new “Falcon Launch Vehicle Lunar Capabilities Guide” issued earlier this month, there is this line on page 10 under Price: “Missions to Trans Lunar Injection will have an additional charge of $10M
    since the second stage is nonÔÇÉrecoverable.”

    It doesn’t get much clearer than that. Plus it fits with the user’s guide pricing for the Falcon 9 on their web page. They plan to charge an extra $10.5M for the last 500kg of performance to GTO and $10.0M for TLI over LEO missions. That was not explicit, but the new quote is.

  9. Jon Goff says:

    I actually read the same users guide you were referring to (I saw the link there on The phrasing actually is still ambiguous. While it says that non-recoverability is the excuse for the $10M surcharge, it doesn’t specifically say why. It could be they expect the second stage to cost $10M, so for expending it you have to buy it. Or it could also have to do with them wanting to recover the stage just for post-flight inspection purposes. Or it could even just be that they wanted to provide a valid sounding excuse to cover some of their other additional expenses that a lunar mission would occur.

    I almost had an opportunity last night to get more info on this, but until I’ve had some clarification from them, I’m at least not going to assume that’s what they mean.


  10. Anonymous says:

    Precisely, No, and Perhaps but I doubt it, in that order.

    It really looks like an “excuse” to raise prices.
    It is hard to believe that they would charge $10M for losing a diagnostic recovery.
    They have been very explicit about the items for which they are charging. A dry nitrogen purge is listed among the “extras” that cost more. They have not appeared to hide or “cover” any charges.

    It is a strain to read this as ambiguous.

    Good luck getting more information from them. My contact is not responding. Until then, it looks a lot like tens of millions of dollars are embedded until they work out reusability, which is a groundbreaking technology.

  11. Will Doohan says:

    After reading this post and the comments, I still don’t see an explanation of thrust augmentation. And if they want an engine with more power than the RD-180, couldn’t they re-build the F-1 engine from the Saturn V ? (I’ve been reading a lot of stuff about the Apollo program lately and am semi-obsessed with it ­čśŤ . I know it’s not gonna happen, but it would be cool to see them re-build those rockets.)

  12. Jon Goff says:

    Did you see the previous article I wrote on the topic, that included a link to the Aerojet paper?

    As for bringing back the F-1, unfortunately at this point it would be little easier than developing a clean-sheet engine, and would have nowhere near as good of performance or even necessarily reliability. It’s an old design with at least some deprecated technology and materials, and with no remaining manufacturing experience.


  13. Anonymous says:

    I can no longer find the post, but Antonioe recently posted on a forum a critique of TAN, with some very good points. He considers it a bandaid when one can’t stage to change from a low expansion engine to a high expansion one. This is well outside of my realm, but his points made as much sense as yours.

  14. Jon Goff says:

    Thanks for the heads up. I found Antonio’s comment here:

    and posted a reply here:

    I have a *lot* of respect for Antonio and his team, but even experts in the field can sometimes jump to conclusions about other peoples’ technologies. Some of his concerns are valid, but others not as much.


  15. Hey, how’d I miss this discussion? Was I hybernating? I am a huge fan of TAN. Of course, we don’t actually know if this HC Boost is TAN, but it sure sounds like it.

    Jon, Did you ever see the PDF file by Aerojet on TAN? I can send you a copy if you like.

  16. Jon:

    I ead your exchange at the links to the other blog. According to the Aerojet PDF file, they dealt with the fuel injection issue by going back to their research on scramjet fuel injection. I think that takes care of the issue “Antonio” brought up that he thought was a barrier.

Leave a Reply

Your email address will not be published. Required fields are marked *