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.

Comments

R&D versus production

[bruce_the_loon]

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.

Human missions = funding

[saibot834]

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.

Re:Human missions = funding

[KeensMustard]

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.

Without humans, the mission is less complex so the risk of some problem occurring is much less.

But putting that question aside, the problem with robotic missions is that they will never get the same sort of funding as human missions.

But that just begs the question: why should we fund such a mission in the first place? The robotic mission is justified by science and our desire to explore new places. Arguable, of course, not everybody agrees that those goals are worth the spend, but let's say we agree that they are. Having the exploration craft carry a human along does nothing to further that cause, anymore than the cause is furthered by having the craft carry a bag of random meats, or a monkey that urinates on everything. Good for a laugh maybe - but we could explore more, and longer, and also go to far more interesting places for the same amount of spend.

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.

But again, why send a human? Why not a cow, or a peacock?

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.

We can if we want. But honestly, Mars is a bit boring, and we also know a great deal about it already. We have the opportunity to go to interesting places instead, why not do that?

Human missions generate lots of excitement, lots of excitement leads to lots of funding.

No, they don't.

There is a little excitement but it's confined to a small circle that happens to hang around in places like Slashdot. That might trick you into thinking this is a bigger deal than what it is. In the end, I think human spaceflight has been largely defunded because nobody can explain why we are doing it in terms that don't sound religious. Sorry, but perhaps the lack of funding is rational and not some mistake because congressman are fat and lazy.

Robotic missions can never be on par with human missions in terms of how much excitement, and thus funding they can raise.

You are presupposing the people who currently don't care one way or the other will suddenly get excited for some reason.

Perhaps, in the end, we need a better reason than a dog and pony show.

Re:Human missions = funding

[frnic]

There is no need to bring them back. That is a nice thing if it can be afforded, but if we would stop concentrating on 100% safety the entire process would be less expensive and there would be no short of volunteers willing to take a reasonable risk instead of guaranteed safety.

Haha no.

[Anonymous Coward]

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.

Re:Haha no.

[Rei]

Indeed. Part of the reason that satellites are so expensive is how light you have to make everything; there's a huge amount of engineering that has to be done in order to achieve mass goals, as well as make use of the most expensive materials on the planet. An example is the use of things like top-end Spectrolab multi-junction solar cells, which get the highest efficiencies, but since they're basically lab-scale production hardware they cost two orders of magnitude more than what slightly less efficient panels on Earth cost (about $400/W).

Beyond the simple cost effect on engineering, there's the size effect. Look at James Webb and the massive expense they had to try to make it "origami" itself to fit into smaller launch vehicles. Or how many parts ISS had to be built out of in space, dramatically escalating both ground engineering / production costs and in-space assembly costs (the latter costing nearly $10m per man-day). There are serious expenses to trying to compensate for a lack of space or payload capacity when you really need it.

Then there's the size of the market. As launch costs have been dropping, the number of companies looking to launch payloads has skyrocketed. The skyrocketing launch demand has been reducing average payload development costs, as designs get more reuse. Both of these trends will continue as costs continue to decline. Meanwhile, new markets will continue to open up. Space tourism has always been hindered by the absurdly high launch costs, limiting it to only the wealthiest individuals. While it will remain a "small" market for the forseeable future, it can expand by orders of magnitude with reduced launch costs. Which again makes more demand..

Lastly, there's economies of scale. It's generally recognized in the rocketry world that - at least up to a point - larger rockets get a better cost per kilogram than smaller rockets. So wherein you can launch a lot at once - multi-satellite launches, large geo launches, large interplanetary probes, fuel depots for tugs/boost stages, shielding mass for manned missions, etc - you tend to save a lot of money by going big rather than using multiple smaller launches. The caveat is that just simply going big is no guarantee of a price reduction. Just like you can make an absurdly-expensive smaller craft, you can also make an absurdly expensive large craft. And even a "moderately priced" large craft isn't generally a "win" - if you can sell payload space for $5k/kg on a 10 tonne payload rocket and for the same price per kilogram on a 100 tonne payload, the vast majority of customers will choose the former. But if you're a company like SpaceX that's been delivering cost reductions on the small scale, and you can carry it over to the large scale, it gives you the potential to take the cost reductions even further.

If you can pull it off.