Is that what the Merlin is? A little early to say, I’d say, but I think one could come up with some creative new vehicles using it in the lower stages and the R-10 up above. If I were in control of NASA R&T budgets, something I’d have done a long time ago was to pay Pratt to test them to destruction to determine how many restarts they could do and how many hours they could fire without refurbishment. If I were SpaceX, I’d be doing the same with Merlin. Perhaps they already are.
Speaking of rocket design, I see that the rocket scientists on the Hill have been sharpening their pencils. I guess that Bill Nelson not only flew into space once, but he must have stayed at a Holiday Inn Express, too.
IMHO, the most important R&D line item would be to fly a fuel depot / prop transfer demonstration as described here:
http://www.nasaspaceflight.com/2010/08/nasa-commercial-combine-outline-ftd-propellant-depot-plan/
Jon Goff has suggested elsewhere that a ~$500 million budget could fly this mission by 2015.
Adding this project as a line item to the current Senate Authorization Bill would seem the most direct way forward for depot advocates.
The point of this article is so obvious and true it hardly seems worth mentioning. But if everybody is trying to reinvent the wheel perhaps they do need a slap in the head.
I do think that it makes sense to marry an RL-10 to the Falcon 9. From what I remember Elon wanted to do this but balked at the price that Pratt Whitney wanted to charge for the engine. A very rough calculation shows that the single engine RL-10 would boost the delivered mass to orbit of the Falcon 9 by over 35%.
The trade off would seem to be becoming dependent on the RL-10 supplier at it’s higher price and delivery or the development cost of the Merlin 2.
I think trust weighs heavily in the decision. Elon has reason to trust his own people more. Look how the launch abort system affected them. This industry needs a lot more maturity and competition.
Interesting choice of names for Elon’s engines. The Kestrel was a predecessor of the famous Rolls Royce Merlin engine as fitted to the Spitfire, P51 and many other WW2 aircraft.
Musk has made the point that outsourcing in aerospace can actually increase costs, vs. vertical integration. Legacy costs structures can be prohibitively expensive.
IMHO, the most important R&D line item would be to fly a fuel depot / prop transfer demonstration… Jon Goff has suggested elsewhere that a ~$500 million budget could fly this mission by 2015.
That sounds about right. In the 1990’s, JSC studied a “Human Lunar Return” architecture that could have sent astronauts to the Moon for around $2.5 billion. It included a propellent depot as one of its elements.
http://www.nss.org/settlement/moon/HLR.html
Unfortunately, any interest the Moonies had in such low-cost approaches vanished when the Bush Administration invoked images of Apollo and big budgets.
What about the SpaceX ‘Raptor’ engine? I don’t know what SpaceX’s plans are for this but the could produce a Lox/LH2 engine by tweeking the Merlin 1. That would give them an in house alternative to the RL-10 with a higher thrust.
>>test them to destruction to determine how many restarts they could do and how many hours they could fire without refurbishment.
Ooooh … i see you are taking this “fuel costs becoming significant fraction of operations costs” mantra seriously ! 😉
Dean,
One of the things I noticed in the SpaceX presentations that were talked about a lot a week ago, was that they showed the Raptor engine as a staged combustion engine with over 1500psi chamber pressure. Could work fine, but sounds like a big step up on the complexity compared to Merlin.
~Jon
SpaceX is highly vertically intergrated because of the high cost of buying technology in. But that is not really surprising while space remains a low volume (and high cost) business.
Part of the logic behind the Merlin engine is to bring down prices by upping volumes.
This also reflects into reliability.
Merlin engine already has 15 flights to its credit (14 first stage engines, 1 second stage engine) with just one loss. The first flight, after which it was redesigned and rebuilt. Since then it as flown flawlessly. The losses of Falcon 1 flights 2 & 3 were not Merlin failures.
With 10 Merlins per Falcon 9 the rate at which SpaceX will build flight experience for this engine will be amazing.
It is still very early days for the new space industry with a lot of base level R&D to go – the Merlin engine has a lot of good points but like the industry as a whole it is not technologically mature by any stretch of the imagination. It would likely be premature to design a series of RLVs around the Merlin – which also, lest we forget, was primarily designed for glorified missiles.
The performance of the Merlin is also not that great (this matters more in a RLV which does not treat engines as expendable), it is also too big for first generation RLVs which will likely be in the 10 ton GLOW range (1-2 person).
Car engines are cheap and complex, that is also where rocket engines are likely heading. Simple is not in itself a virtue. XCOR seem to be on a better development path, one towards low cost high performance engines. They are also doing their development work at small scale (cheaper) and seem to have more flexibility and plug and play ability with what they are doing. XCOR seem to be developing an engine development process that allows them to cheaply design and incrementally improve the engines the RLV market wants.
Jon,
I did not see it written or mentioned that the Raptor engine was staged-combustion cycle.
I did notice that its theoretical vacuum Isp was stated 470 seconds, which would suggest a closed-cycle staged combustion engine. The Raptor was also mentioned as having 150,000 lbs thrust.
Some of the specifications for the Raptor engine do not make sense for the markets that SpaceX is trying to serve. The thrust and Isp make it a very new, unique, expensive, and un-needed engine development program. Raptor should be a gas generator cycle 60,000-lb thrust engine that is a simple LH2 version of the SpaceX Merlin engine.
I think that SpaceX Raptor specs are not indicative of whatever they are really doing internally with their engine development programs.
“Raptor should be a gas generator cycle 60,000-lb thrust engine that is a simple LH2 version of the SpaceX Merlin engine.”
Exactly right.
Raptor should be a gas generator cycle 60,000-lb thrust engine that is a simple LH2 version of the SpaceX Merlin engine.
Simplicity is not in and of itself a useful characteristic and often over simplifies those characteristics that are.
There is yet a lot of room for improvement in rocket engines, specifically with regard to T/W and ease of use. Like rocket vehicle development, rocket engine development does not yet seem to be at the incremental development stage where innovative development should be halted and a standardized model adopted.
A rocket engine that costs a hundred times more but is flown a thousand times instead of once will have a tenth the life cycle cost – this is a cost that really matters for a RLV. An RLV rocket engine does not necessarily need to be cheap or simple for it to be economically favored – it depends.
Brad and Jon,
The original SpaceX propulsion team came from TRW and Boeing and they already have experience (from the RS-83/84 and TR-106/107 engine programs) with firing the same rocket engine in both RP-1 and LH2 versions.
I think that the maximum a closed-cycle expander-cycle LH2 engine can do is about 60,000-lbs thrust, so if SpaceX wants more thrust from an LH2 upper-stage and with an Isp higher than the Merlin-1’s current gas generator cycle, then moving to staged-combustion makes technical sense. It just does not make commercial or investment sense, because there is no market that justifies an LH2 upper stage engine in the J-2X class of thrust. SpaceX would be better off clustering LH2 versions of their Merlin-1 if they want J-2X levels of performance in a massive upper stage.
It appears that the specs given for the Raptor engine are meant to encourage NASA or DoD to fund SpaceX R&D in staged-combustion cycle engines. SpaceX (and America in general) has little to no experience in manufacturing expendable engines with staged combustion cycle (the SSME is reusable).
Elon Musk said long ago that the Falcon rockets and their Merlin engines were his first stage of technical development. I assume that staged-combustion engines would be for a new series of non-Falcon rockets 10 to 20 years from now that would be single-stage to orbit and reusable. It is common for people in the rocket industry to project 20 years into the future with their R&D plans.
A staged-combustion Raptor engine at 150,000-lbs thrust for LH2 and 250,000-lbs thrust for RP-1 fits the published specs of the US Air Force HC Boost program with Aerojet and P&W Rocketdyne pretty closely.
The SpaceX Raptor engine specs are more of an R&D wish list for a US Government R&D contract.
The performance of the Merlin is also not that great
Low cost and reliability were their goals and they seem to be hitting that target. Also note that Merlin performance has been increasing incrementally. It really could become the small block of space. Especially if you have a choice of fuels.