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SpaceX Tests Its Raptor Engine For Future Mars Flights (techcrunch.com)
Thelasko writes: Elon Musk is preparing to unveil his plans to colonize Mars at the 67th annual International Astronautical Congress tomorrow. As a tease to his lecture, he has released some details about the Raptor engine on Twitter, including pictures. Mr. Musk states that, "Production Raptor coal is specific impulse of 382 seconds and thrust of 3 MN (~310 metric tons) at 300 bar." He goes on to note that the specific impulse spec is at Mars ambient pressure. The Raptor interplanetary engine is designed for use with Space X's Mars Colonial Transporter craft. Musk notes that the "chamber pressure runs three times what's present in the Merlin engine currently used to power Falcon 9," according to TechCrunch. "Merlin has specific impulse of 282 seconds (311 seconds in the vacuum of space), and a relatively paltry 654 kilonewton (0.6 MN) at sea level, or 716 kN (0.7 MN) in a vacuum. You can view a picture of the "Mach diamonds" here, which are visible in the engine's exhaust.
In before someone comments that they can't do R&D while simultaneously sorting out the recent problems with the Falcon 9.
People can multitask, companies even more so. If they were still blowing up every vehicle on the pad, then maybe they'd have a point, but their systems are certainly working better than other programs at their stage of evolution.
Trying to become famous by taking photos. Visit my homepage please.
311 seconds of specific impulse in space vacuum is impressive. Combined with such a massive thrust of 3 Meganewtons, this certainly allows - on paper - for lifting heavy payloads onto a trajectory toward Mars. Another point to consider is the speed at which these developments are taking place. They're doing in a couple of years what took the Mercury and Jupiter programs, as preparations for the Saturn program, more than a decade. It remains to be seen, however, how much of this is just for the media and how much will go into actual rocketry and rocket-launching. Regardless of this, still quite the achievement.
Religous speak to God. Insane are spoken to by God. When all shut up, one can finally hear Shostakovich in peace
While the raptor is less powerful in terms of thrust compared to the Rocketdyne F-1 engine on the saturn (3MN vs 7.77MN), it blows it out of the water when it comes to fuel efficiency. If we use the given information for the raptor engine to estimate the isp at earth sea level, we find that it will have an isp of around 320-330s.
This in layman terms means that with a propellant flow of 1kg/s the Raptor will produce a thrust of around 325 kgf (~3.19 kN), while the mighty F-1 engine would only produce 263kgf (~2.58kN). That is a huge gain in efficiency, which primarily comes from the significantly higher chamber pressure!
Except the recent unscheduled rapid disassembly wasn't caused by the Merlin failing to contain 300psi. It was an oxidiser tank on the second stage that failed. The obligatory car analogy is that apparently Fiat shouldn't have been building the 146 Spider because the fuel tank on the Pinto could rupture.
What alternative do you suggest? ...
Using a few hundred thousand toy rockets, $10, each?
I guess from our persprctive it is best to leave rocket sciense to the rocket scientists
Cost free eBook I read (by iBook/Kobo/Amazon/ObookO/Gutenberg etc.): "The Green Odyssey" by Philip Jose Farmer.
Before someone comments that we don't need humans on Mars if robots can do the same cheaper: that's beside the point. I mean, robots are no where near performing on the same level as humans when it comes to ingenuity and ability to come up with and implement ad hoc fixes to problems that no one could even imagine before launch of the mission. But putting that question aside, the problem with robotic missions is that they will never get the same sort of funding as human missions. A human mission automatically has to have a certain size, e.g. has to develop capabilities to land payloads in the ballpark of 10 tons or more on Mars. Once we have this capability, we can easily send lots of robotic and scientific payload along with humans -- it amounts to simply using the same payload delivery system that we are developing for humans anyway.
On the other side, if there is no ambition to fly humans to Mars, then no one will develop these capabilities. There is simply no funding for a system that delivers 10 tons of cargo onto the surface of Mars, unless it can also deliver humans, and bring them back safely. So we cannot send big robotic missions to Mars.
Human missions generate lots of excitement, lots of excitement leads to lots of funding. Robotic missions can never be on par with human missions in terms of how much excitement, and thus funding they can raise.
Unless Musk figured out a way to make going to Mars profitable or thinks he'll be able to wring out some amazingly fat government subsidies, actually doing it will be a huge cost with essentially no near-term return (unless you find some rich loonies willing to pay out the ass to be the first people to die on another planet (if they're lucky)), and that's not how capitalism works. There's a reason the government has to pay for 99% of scientific research not directly related to certain highly profitable industries.
And even if you believe Musk is willing to ditch a lifetime of business experience for this one goal, even he's not rich enough to fund it personally. New Horizons alone cost almost a billion.
tl;dr: Nice engine, but that and a cult of personality ain't enough to land anything on Mars. At least Jobs was smart enough to stick to phones.
Because the United States so far has no decent engine worth speaking of?
Ezekiel 23:20
"So they figured out how to get an engine to run on Mars, but they can't figure out how to <Uneconomical goal on Earth>. Will they find intelligence on Earth"?
>"Production Raptor coal is specific impulse of 382"
Isn't coat a poor choice for fuel? Even for a solid fuel rocket? What about the greenhouse gases?
The recent Falcon 9 accident has been traced to a Helium COPV tank in the oxygen tank. It runs at more like 5,500 PSI, not 300 PSI. Delamination of COPV in cryogenic applications is a longstanding problem which they must have thought they'd conquered, having used them successfully so many times.
And this article is about an engine, not a composite helium tank. The engine runs on cryogenic methane, which is a new fuel for Spacex, replacing kerosene. They are running scaled tests during the design phase of their new engine - so not exactly building it faster now and hoping to get lucky that it doesn't blow up. The new engine is supposed to be much more efficient than current incarnations and is specifically tuned for use in a vacuum. Plus it has the advantage of using a fuel that can be harvested or manufactured from several locations around the solar system.
""Production Raptor coal is specific impulse of 382 seconds and thrust of 3 MN"
That's impressive, considering they are using coal as the fuel!
To be fair, we don't know that it was a COPV failure (although that would be most likely) - all we know at this point is that the failure was in the helium system and was unrelated to the strut failure in CRS-7.
While technically you can also produce other fuels off-world methane is indeed the highest throughput and efficiency, as sabatier synthesis yield by far the highest mass fraction as methane, so you don't have to do a lot of recycling of the methane to try to get your desired fraction as an output. Yet the mass is still mostly carbon, which is much easier to get than hydrogen (to the point that even a lot of in-situ production concepts have still called for bringing the needed hydrogen from Earth (reliable/sustainable fuel cell decomposition of CO2 to CO and O2 is pretty much a solved problem; reliable/sustainable permafrost brine mining and purification in Mars conditions, not so much). Methane is also cleaner burning, aka less likely to clog up your injectors and the like. Its disadvantages compared to RP-1 are its cryogenic nature and much lower density (increasing rocket bulk/cross section/mass and decreasing thrust). The lower density does however have its advantages as well - by virtue of requiring bulkier launch vehicles, you inherently increase fairing diameters, which allows for bulkier payloads.
"You abandoned me! You abandoned my hatred!" "I... I have cuttlefish..."
You have stolen the words from my mouth. Exactly that. For the same money we could explore more and do more science than spending it to send a useless piece of meat with no embedded measurement capabilities to grab some knowledge from the worlds it explores.
First off, if we only send probes or only send humans that would be idiotic. There are things that each can do that the other cannot. For example it is basically impossible to study human or animal physiology away from Earth unless we send a human. Similarly there are some environments that are simply too hostile to life to send a human. Use the best tool for the job. Sometimes that a robot, occasionally it will be a human. It should never be a case of only one or only the other. We should be working towards both.
Second, there is no robot or probe that we could send that would be even a fraction as scientifically productive per unit of time as an on site human. We send robots solely because they are currently the only practical option available to us. That will remain the case for a while as we lack the technology to send a human safely to anywhere beyond the moon at this time. But once the technology to send a human is available there are a LOT of missions where it would be much preferable to send a human if that were a feasible option. A geologist on the surface of Mars would be far more scientifically productive than 100 probes. We just can't get one there safely or economically... yet.
Third, your argument that humans are "a useless piece of meat with no embedded measurement capabilities" is an idiotic statement. Humans are the most useful, flexible, and productive tool we have. Our probes and tools are crude mockeries of what humans can do given adequate resources. Yes humans are hard to keep alive in hostile environments. So what? We aren't designed to go sailing on or under the oceans and yet we figured that out. We aren't designed to go into space either but we've figured out that as well. It's going to take a while to figure out interplanetary travel but there is no objective reason why we shouldn't go there too eventually. We're not going to stop sending probes. They're terrifically useful. But it is short sighted to believe that there is no value in sending a human to explore space or that humans would be no value there. Sometimes the best tools are the most fragile ones. Sometimes what seems fragile is actually incredible robust.
There isn't a large pent-up demand for "big stuff" in orbit, at least nothing that anyone's willing to pay even $5000/kg for.
What is your evidence that there is no demand for large objects in orbit? I'd imagine there is lots of demand if the price can be reduced to something that doesn't require the resources of a nation state. You have no idea what the actual demand for large satellites is because it's not presently economically feasible to get very large objects into space in a single piece. It's a chicken vs egg problem.
Very occasionally the US spy industry wants to put a unitary big-mirror observation satellite up and that can run to 20-25 tonnes. In those cases the Delta Heavy is used, the only time it is ever launched as far as I know.
That's a economic problem, not a technical one and certainly not an indicator of potential demand. It's like arguing that there is no demand for supercars because only the really rich can buy them today. Bring the price down to something affordable and there will be people doing all sorts of clever things you didn't begin to imagine.
The human race has got very good at throwing up small lumps of stuff into orbit and putting them together there afterwards -- the ISS is over 400 tonnes of small lumps, none of them over ten tonnes in mass when they were on the ground.
That's because we had no other options at the time we launched those components. Given a larger and economically viable launch vehicle and the ISS likely would have been designed differently and probably would have cost less to lob into orbit.
The proposal is so miserable. Using chemical rocketry for interplanetary travel is like using steam engines for rail travel. Thomas the tank launcher and his friends!
Before embarking on a person-rated trip to Mars or Venus, humankind needs some better space tech. Not necessarily warp drives or Cannae drive, but practicable large scale ion thrusters or solar sails or Moon based laser push-beams, etc.
My evidence is that there is actually, in reality, no demand for large objects in orbit
That my friend is the very definition of begging the question. Your premise assumes the conclusion.
SpaceX is a for profit business. If there were no demand or market for a heavy lift vehicle then why would they bother developing one? That's a huge expense if there is no expected ROI. I'm pretty sure they have a better feel for the market than either of us. Is it possible they are building a figurative bridge to nowhere? Maybe but that would be inconsistent with their prior behavior and economic sanity. Elon Musk has been accused of many things but stupidity has rarely been among them. It is difficult to gauge demand for very large objects in space until you have a realistic means of getting them there. Given that SLS is subject to the whims of congress and that SpaceX hasn't brought their heavy lifter to market yet why would anyone seriously plan a very large satellite today? Simple logic would dictate taking a wait and see approach. Once the lift vehicle is available then and only then should we expect to see very large objects getting designed.
> What alternative do you suggest?
Even if there is an 80% chance that the money is wasted, doing the development might be the smart choice in order to establish market share while the private space industry is in it's infancy. So I wouldn't *suggest* a change.
The other *option* they should consider finding and fixing the significant existing problems before investing so much in a new platform that will likely have the same problems again. Figure out how to build an pressure tank before you build an even bigger version, for example. Maybe one problem is the quality control of the materials that one of their subcontractors is using. Example, maybe the material lining their tanks has more impurities than specified. Find out and get a different, better source for the material before you build another rocket with the same substandard lining . Or figure out how to build a tank that still work with the lining material, maybe by making it twice as thick. But don't just build another rocket with the same type of lining, which have the same type of failure.
SpaceX will be streaming Elon Musk's presentation live on their website.
One of our competitors trademarked the term "hypothesis". From now on, we will call them "boneheaded ideas".