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SpaceX's New Combustion Technologies
An anonymous reader shares this story that takes a look at some of the advances SpaceX is working on. "Getting a small group of human beings to Mars and back is no easy task, we learned at the recent GPU Technology Conference in San Jose hosted graphics chip and accelerator maker Nvidia. One of the problems with such a mission is that you need a very large and efficient rocket engine to get the amount of material into orbit for the mission, explained Adam Lichtl, who is director of research at SpaceX and who with a team of a few dozen programmers is try to crack the particularly difficult task of better simulating the combustion inside of a rocket engine. You need a large engine to shorten the trip to Mars, too....Not only do you need a lot of stuff to get to Mars and sustain a colony there, but you also need a way to generate fuel on Mars to come back to Earth. All of these factors affect the design of the rocket engine....As if these were not problems enough, there is another really big issue. The computational fluid dynamics, or CFD, software that is used to simulate the movement of fluids and gases and their ignition inside of all kinds of engines is particularly bad at assisting in rocket engine design. 'Methane is a fairly simple hydrocarbon that is perfectly good as a fuel,' Lichtl said. 'The challenge here is to design an engine that works efficiently with such a compound. But rocket engine CFD is hard. Really hard.'"
They think what they're doing is "hard"? What the hell do they know? I once had to scale a Ruby on Rails web app so it'd handle more than 8 requests per second. Let me tell you, that makes fluid dynamics and rocket engines and trips to Mars look easy-peasy!
Rocket science is soooooo hard!
The shepherds did so well protecting the flock that the sheep no longer believed that wolves existed.
It's time to stop jetting around the solar system on chemical rockets. Designers and funding should be directed towards lofting and running multi-megawatt reactors. They would be used to power multiple ION engines and once at the destination, provide power.
When Fascism comes to America, it will call itself Anti-Fascism, and tell you to give up your guns.
This is the first article I've seen that explains well how GPUs can/are being used for practical applications along with what can be achieved and some of the issues. Well worth the read even if you're not into this stuff.
I'm sure that there is a significant cost in developing this new approach to CFD (as well as pushing the envelope on GPU operation) but the result is going to be usable for different applications. TFA says there's irony in what SpaceX is doing here as it has applications with automotive Internal combustion engines but I see that as SpaceX/Musk having a secondary revenue stream for this work that doesn't mean he's helping out his direct competitors.
Along with that, they are driving the development of high speed inter GPU communications which I'm sure has value as well.
All this means is that Musk returns to his home planet, not only is the trip going to be fully funded, but he's going to have some money to throw around when he gets there.
myke
Mimetics Inc. Twitter
It's kind of the nature of research that you have to do research. Plus, if you think its hard to design rockets and "rolling your own" CFD models, just imagine how it was when you didn't have the computing power to go beyond the rudiments.
Those troglodytes designing say, the F1 might have had a bit harder of a time designing with limited knowledge and experience than now when can try rolling out likely designs based on good CFD models. Channeled explosions are not terribly forgiving of bad design in that way.
Rather, Spacex is able to make better rockets, less expensively, by using extensive CFD, modeling using models they developed. This will allow for optimization of designs, and reduce reliance on the old process dreaming up a design, building and test firing it, and if it didn't explode, analyze the parts for incremental improvements.
And rather than whine about how hard it is, maybe we should marvel at just how damn cool it is to have modern computing power and new flow and design models to work with to make better rockets. Too freaking cool!
The shepherds did so well protecting the flock that the sheep no longer believed that wolves existed.
Umm, rocket science is...rocket science?
Combustion CFD is a very difficult area. The problem is that there are so many interlinked phenomena all requiring special modeling methods that one really isn't quite certain of the accuracy of the result unless they can compare it to a physical model test, which is what is frequently done. Simply getting the correct boundary conditions can be very challenging. Failing to apply appropriate modeling and boundary situations leads to a garbage in/garbage out situation, but the numerical solution may look plausibly correct.
CFD is not use exclusively in design work except for very basic cases where the modeling accuracy is well understood. However, CFD for more complicated situations is still useful as it may illustrate behaviors and trends in performance in situations where physical observations are difficult (like in a rocket nozzle). The CFD results can be used to guide and interpret the results of physical testing.
Understanding CFD really requires PhDs who understand fluid dynamics as well as the limitations of the numerical models used. This is true in many industries, not just rocket surgery.
Left MS Windows for Linux Mint and never looked back!
Vote for Bernie in 2016!
Problems with injector design and combustion instability go back to to the Germans and the V2. They may have even been a problem for Goddard. The V2 engine is really a bunch of small combustion chambers at the top feeding into the main engine bell. I believe this was done, at least in part, to reduce the problems with combustion instability.
A much better and more efficient way to accurately simulate this process can really offer a lot in many areas, not just rocket engines.
That's not even the hardest problem they're up against. Generating fuel on Mars is a much more difficult one. As far as we know, there may be no way to produce or find and mine hydrocarbons such as methane. Mars's atmosphere lacks significant hydrogen content. If there's subsurface minable water, that could solve the problem, but only if there's plenty of it.
Isn't the combustion chaotic?
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
The same issue is a challenge to internal combustion engine design and a number of other applied physics problems. Combustion is a chaotic process and thus a hard challenge for computational modeling. Developing better simulators for combustion would reduce the cost of developing reliable and safe systems.
Last year the National Research Council and National Academy of Science released a damming report on the prospects of the USA or any other country/society on Earth to mount a human space mission to the Moon or Mars. The verdict, 50 years at least and likely 150 years needed. Why? The humans/economy/society/education-training system/infrastructure/GDP do not currently exist and will not, until very likely 150-years from now.
As a matter of economic pragmatism, all current efforts, even writing code, will fail, so it is better to kill-off all national/state Federal departments engaged in the continuing failures that will persist until the humans/economy/society/education-training system/infrastructure/GDP exist and are capable to support such missions to the Moon or Mars. Using the savings from the Federal/State divesture and re-assinging the monies into banking/economy/education/finance/society would be better spend in order to build the national economy/society/education-training system/infrastructure/GDP in anticipation that in the future the humans not yet born will be able to use and figure out a solution.
Hmm, CH4...so methane is 1/4 H2 by mass, and 3/4 C...
Which means, absolute worst case, that we have to carry the H2 to Mars, thus giving us only a factor of four improvement over having to carry ALL the fuel to Mars.
If, as seems moderately probable, Mars has frozen water under its surface, you produce all the fuel there. Or, if our moon has H2O, as seems probable, then it's actually easier to ship fuel from Luna to Mars than to put the same fuel into Mars orbit FROM Mars.
Note that a mass-driver, a la "Moon is a Harsh Mistress" (which would also be workable on Mars, if you built one on steroids) would make the process even more efficient, in that all the H2O from Luna could be sent to Mars or LEO without having to burn any of it to get it off the moon.
"I do not agree with what you say, but I will defend to the death your right to say it"
Nope. Unpowered flight already existed by the time the Wright brothers headed to Kitty Hawk, and powered flight was right on the edge of possibility. The drives you propose, aren't. The problem is, you don't grasp that fundamental difference and thus assume that people who aren't as egregiously ignorant as you are the ones in the wrong.
True. But those solutions must fall within the bounds of physics and chemistry - and nuclear reactors and ion engines, for the reasons I outlined, don't. Absent new physics, they never will.
Only to someone who doesn't grasp physics in general as well as the mathematics behind orbital mechanics. Absent new physics, all vehicles in space are going to spend far more time coasting than under power.
Go to Mars. *Stay there*. Don't return the Presbyterian astronauts back home to Ohio. Keep lobbing supplies at the colonists until they can sustain themselves. Why on earth do we keep trying to re-enact the Apollo fiasco? Colonize, or don't go. Plenty of older folk such as myself who would be glad of a few years of low G before we die while we build up the place for later arrivals. Dying there? The horror! Um, of course you'd die if you stay on Earth anyway. Dying on Mars would be more scenic, and your knees wouldn't hurt when you stand up.
Of course, Mars won't pay for itself as far as Earth is concerned, the way orbiting terraria and factories would. Less room, less opportunity, and yet another gravity trap on any planet. Mars is a place to colonize. It can't produce wealth for the old country. And colonies don't care about the old world much, so we're building a suburb that will home-rule faster than a town next door to a impoverished city.
Well, limited vision, but at least we'd have two baskets to put our eggs in.
I hope they simulate propane too, not just methane. Propane has some really interesting properties as rocket fuel but have (like methane) never gotten much research. But now there's a big rush to research methane as fuel based on the concept of generating it on Mars - so propane still gets left in the dark.
Methane's ISP is only very slightly better than propane's - 364,6 vs. 368,3 at a 100:1 expansion into vacuum and 20MPa chamber pressure. But propane at around 100K (note: not at its boiling point, 230K) has far higher density (782 kg/m^3), closer to that of room temperature RP-1 (820 kg/m) then that of boiling point methane (423 kg/m^3), which reduces tankage mass and cost. 100K propane's ISP is of course better than RP-1's 354.6 in the same conditions as above. Plus, its temperature is similar enough to your LOX that they can share a common bulkhead, which reduces mass further and simplifies construction.
Hydrogen generally is the easiest fuel to synthesize offworld. Methane is generally second, and propane third. Hydrogen is often rejected as a martian fuel because of the tankage and cooling requirements. Methane can be kept as liquid on Mars with little cooling in properly designed reflective / insulated containers - but so can 100K propane, in similar conditions, but with significantly smaller tankage requirements.
It seriously warrants more research, I tell you what.
"99 dead duelists of Dios on the wall. 99 dead duelists of Dios! Take one's ring, pass it around..."
You're forgetting that you need oxygen as well, which is derived from the CO2 taken from the atmosphere. So yes, bring hydrogen to Mars, but it's 1/20th the total mass; not 1/4th. 95% of the mass is found in situ.
http://en.m.wikipedia.org/wiki/Sabatier_reaction#Manufacturing_propellant_on_Mars
"Getting a small group of human beings to Mars and back is no easy task, we learned at the recent GPU Technology Conference in San Jose hosted graphics chip and accelerator maker Nvidia.
It hardly gets spammier than that, congrats.
This guy walks into SpaceX.
Elon Musk says "You here for the interview?"
"Naw... just here to put in the Brawndo fountain."
E
just make sure you have a huge chem rocket engine firing at the same time...and you can leave orbit using an ion engine, a steam engine, or a bunch of hamsters.
My God can beat up your God. Just kidding...don't take offense. I know there's no God.
So I think we've found Hank Hill's /. account.
Very insightful. It would seem that you could build a simple processing facility to distill out propane from the hydrocarbon muck. Yeah would need a similar facility for purified methane anyway, so what's the diff? Not much.
Was ULA making any investment in propulsion technology? Well they started using the Russian RD-180 in 2000 and didn't start looking for a replacement until 2014. This was after SpaceX starting to compete with them for heavy launch contracts and everyone realized that Russia could stop deliveries because of political considerations.
Meanwhile, Space has been continuously investing in new rocket technology, primarily with their own money. They haven't made any profit yet, it's ongoing reinvestment.
As this article shows, they are even working on extending the state of the art by extending CFD technology so that rocket engine design can benefit from advanced computation capabilities.
So how much new technology did ULA produce? What did the taxpayers get for the $1 billion per year above and beyond paying for actual launches? Sound of crickets...
Welcome to our post capitalism system. Entrenched special interests get guaranteed profit and government subsidies, obscene tax breaks and use government regulation to keep out any competition. SpaceX just got hit by the regulation trap: US Air Force Overstepped in SpaceX Certification. The report came out about two weeks ago well after the damage was already done. Business as usual. No one will be held to account.
This obvious sabotage resulted because the USAF/Lockheed/Boeing are for all practical purposes a unified conglomerate. They are all insiders, The military and government employees know that as soon as they leave the US payroll they will go to the (not really) civilian side and make even more money. When they retire from their civilian jobs they get two retirement packages: double dipping.
Why is Snark Required?
Man, I hated that class. One equation taking up half a page, with the audacity of including an error range of +/- 500%
Do you get enough extra delta v from converting 4 kilos of hydrogen to 16 kilos of CH4 to make that worthwhile?
The boiling point of CH4 is only 111.66 K (258.68 F; 161.49 C) while liquid H2 needs to be cooled to 20.28 K (423.17 F; 252.87 C). It's far easier to refrigerate liquid methane than liquid hydrogen. Trying to reach 20 K on Mars will require much more equipment than that needed for 111 K. Liquid hydrogen is about 25% more efficient (455 vs. 363 vacuum Isp) but is much less dense than liquid methane; so a hydrogen rocket needs to be larger and insulated. A smaller lighter rocket helps makes up for the lower specific impulse.
Thank you Slashdot for removing the negative signs from the temps :-(
Waa.... waaa... waiitttt! Where are the adults hiding in this game? OK, I get it April 1st only two days off.
I'm an employee with Bagaveev Corporation. We're a very small startup that is developing a launch vehicle for nanosatellites. We've designed our engines for propane from the start. The higher density of RP-1/LOX is offset by propane's higher ISP and the ease of a shared bulkhead. It's surprising that more people haven't done any serious development with propane; I guess there is a lot of inertia in the choice of RP-1 as a rocket fuel which prevents people from trying other fuels unless absolutely required (e.g. in-situ methane for Mars ascent vehicle).
That sounds like an argument for shipping purified methane or some other liquid fuel from Earth.
Wow, this is great to hear - I'd never heard of you guys before. :)
And looking at your site, I like what you're doing even more - direct 3d printed aerospikes? Pretty darn cool. What sort of 3d printing tech are you using? Have you looked into the new hybrid laser spraying / CNC system that's out there (I forget the manufacturer)? The use of high velocity dust as source material gives you almost limitless material flexibility and improved physical properties that you can't get out of plain laser sintering, and the combination with CNC yields fast total part turnaround times.
And you're working on turbopump alternatives? Geez, you're playing with all of my favorite things here.... ;)
What sort of launch are you all looking at - is this ground launched (and if so, do you have a near-equatorial site) or air launched? I'd love to see more details about your rockets, what sort of ISP figures you're getting so far, how you're manufacturing your tanks, and on and on. But I guess I'll have to wait just like everyone else ;)
I wish you lots of success! And even if you don't make it, at the very least you'll have added a ton of practical research to the world :)
"99 dead duelists of Dios on the wall. 99 dead duelists of Dios! Take one's ring, pass it around..."
Air launch usually isn't so much about the (small) extra delta-V as it is the greater flexibility on launch sites. Which is why I asked as to whether you have an equatorial site. :)
I'll definitely keep my eyes out! :)
"99 dead duelists of Dios on the wall. 99 dead duelists of Dios! Take one's ring, pass it around..."