SpaceX Fires Mars-Bound Raptor Engine (extremetech.com) 105
Elon Musk took to Twitter Sunday evening to announce the "first firing of Starship Raptor flight engine." While SpaceX has fired individual components before and experimented with various designs, this is the first time the now-completed design has been assembled and fired in its intended spaceflight configuration. ExtremeTech reports: Raptor has gone through a number of design changes -- originally, SpaceX planned to mount it to the ITS launch vehicle back in 2016 (powered by 42 Raptor engines), before changing gears and unveiling its BFR rocket concept (officially known as "Super Heavy" for the first stage, and Starship for the second). The Super Heavy mounts 31 Raptor engines, while the Starship has seven. The engine has been designed with a priority on lowering overall wear and tear and removing failure points that could limit its reusability or increase long-term operating costs. Unlike SpaceX's Merlin engine, which runs on a mixture of RP-1 and LOX, the Raptor engine is fueled by cryogenic liquid methane and LOX. The Raptor uses subcooled methane (subcooling refers to keeping the temperature of the liquid well below its boiling point). Subcooling the methane allows SpaceX to increase the amount of propellant stored in the rocket. It increases specific impulse and reduces cavitation.
The actual test burn only goes on for a few seconds, but yields tremendously valuable information about the actual performance of the rocket and its ability to ignite in a controlled fashion. The green glow in the exhaust near the end of the firing indicates the copper liner in the engine chamber burned by accident. While this should not have happened, it's precisely to find these pain points that engineers conduct test firings in the first place. There is no substitute for this kind of test-firing and, as Ars Technica notes, "any 'first' test firing of a new, full-scale rocket engine that doesn't end in an uncontrolled explosion is a good thing." Ars also states that this specific engine may be deployed for "hopper" flights this year when SpaceX attempts to fly the Starship roughly 5km high, then land it again.
The actual test burn only goes on for a few seconds, but yields tremendously valuable information about the actual performance of the rocket and its ability to ignite in a controlled fashion. The green glow in the exhaust near the end of the firing indicates the copper liner in the engine chamber burned by accident. While this should not have happened, it's precisely to find these pain points that engineers conduct test firings in the first place. There is no substitute for this kind of test-firing and, as Ars Technica notes, "any 'first' test firing of a new, full-scale rocket engine that doesn't end in an uncontrolled explosion is a good thing." Ars also states that this specific engine may be deployed for "hopper" flights this year when SpaceX attempts to fly the Starship roughly 5km high, then land it again.
Green (Score:5, Funny)
The green glow in the exhaust near the end of the firing indicates the copper liner in the engine chamber burned by accident
It's burning an engine-rich flame.
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My understanding is that methane is actually a much more potent greenhouse gas per kg, but there's vanishingly little of it in the atmosphere, so its total effect is minuscule compared to water and CO2. To make things worse, methane in the atmosphere eventually breaks down into CO2 and water, so it doesn't go away so much as just eventually transform into less potent greenhouse gasses.
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The Russians have been doing that for a long time, there's always a big green streak in the exhaust. How that works with a 'reusable" engine while it is oxidizing the combustion chamber, well, we'll see.
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I thought it was TEA-TEB but I guess that'd be at the beginning of the firing, not the end.
Moon-Bound at Least (Score:5, Interesting)
The new plan is to send the BFR on trips to the moon, early on. Later, they'll send it to Mars; this may only happen after they build their next-gen Raptor engines.
There is some sense to this. If they can cram 100 space tourists into Starship, then send it to orbit the Moon for a day (7 day space vacation), they could make LOTS of money. $10 million per ticket x 100 seats = $1beeelion per launch (prior launch of fuel into orbit required, however), and they'd only pay the cost of fuel, probably less than $1million. After a few years, once they get more super heavies/starships built, they could bring the price down to $1 million for a ticket, still make massive profits, and it'd hugely increase the number of people who would pay to go to the moon. Only a few dedicated people would be willing to spend a few years of their life to go to Mars, wait a while for a launch window to arrive, then come back. Of course, they could also offer moon landings, maybe build a moon hotel. Maybe put some Starlink satellites in lunar orbit for lunar internet connectivity, although the 1,250ms latency would be killer.
Internet access on Mars would suck (due to the half-hour latency). Bet there's a business opportunity for an orbiting data center that'd host mirrors of various sites.
Re:Moon-Bound at Least (Score:5, Insightful)
Nobody is going to the moon or Mars on a tourist trip in your lifetime, try to stop being an idiot before you die.
Funny though Virgin Galactic's whole business model is based around Space Tourism and they are only planning Sub Orbital. I think Anonymous Cowards should try having dreams rather than crushing them.
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Wow, what a negative idiot. Private vs public be damned, there are resources to exploit and they will be exploited.
The difference is in direct vs indirect subsidies on what you're calling 'private sector' vs what happened with NASA in the moon shot.
Direct subsidies for specific purposes decreased by 50 fold after we landed on the moon a couple times. Indirect subsidies became the norm, and this does not encourage any sort of real evolution in tech (how many different rockets came after Saturn? How many 'ite
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You know the private sector built all of NASA's hardware, right?
And the Air Force's hardware for those ICBMs you were talking about? Private sector.
Don't be a fucking moron.
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We've waited so long for private, commercial spaceflight... sub-orbital just falls short in every way... pun not intended.
Re: Moon-Bound at Least (Score:2)
Nobody is going to the moon or Mars on a tourist trip in your lifetime
If you weren't an anonymous coward, I'd offer you a wager on that. Easy money.
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no one is going to the moon or mars in a privately funded tourist trip in the next thirty years, or ever really
space is a dead-end fantasy for powerless nerds who gobbled up sci-fi when they were 12 and never outgrew it
Every year, there are incremental improvements in both the tensile strength and maximum length of carbon nanotubes (and the related boron version, BNNTs). At some point, a space elevator will become economically practical.
Space isn't a dead-end fantasy ... zero-g offers a lot of advantages for manufacturing, and reduced-g offers longer life spans. There are many people interested in both.
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And - consequently - substantially stronger than their formed-in-a-gravity-well counterparts.
But insanely more expensive.
Re: Moon-Bound at Least (Score:1)
There are a lot of problems with the idea of a space elevator beyond the cable strength problem. At least the full length version. Donâ(TM)t forget, it still takes conventional rocketry to put it in place in the first place (and has anyone come up with an actual procedure you would use to do that? Then there are a lot of unanswered questions about maintaining stability. For me though, the biggest problem is about how long it takes to climb the cable. Geosynchronous orbit is 35,786 km above earths surf
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and reduced-g offers longer life spans. ...
No it does not, why would it? All we know it most likely reduces it
Re: Moon-Bound at Least (Score:2)
please clarify
wager that it won't happen
that is easy money
Clarification: wagering against a fool who claims that "Nobody is going to the moon or Mars on a tourist trip in your lifetim" is easy money.
this guy predicted 100 million vr goggles five years ago
It wasn't 5 years ago; more like 4 years and 6 months. He still has half a year to go in his prediction. That doesn't help him much though since the current number of VR goggles sold is somewhere in the 10-20 million range. If the current 8% growth in the market continues, it will still be a while before there are 100 million out there.
Not sure what the relevance
Re: Moon-Bound at Least (Score:2)
yet you are under the delusion that almost zero space tourism so far automatically leads to colonies on mars
Since I've never said anything remotely like that, it's now clear that you are definitely delusional. Thanks for letting me know not to waste any more time.
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With today's lightweight structural materials, goalposts are more easily moved now than ever before.
No, their "We actually never landed on the Moon" will become "We never landed on Mars." The goalposts no longer even need to be physical.
Re:Moon-Bound at Least (Score:5, Interesting)
Nobody is going to the moon or Mars on a tourist trip in your lifetime, try to stop being an idiot before you die.
You underestimate how much money some people have.
Jeff Bezos: Net worth $142 billion (before divorce)
Apollo program: $125 billion in today's dollars
Jeff Bezos could single-handedly fund the Apollo program. In fact, that should now be the new unit when describing how just how rich they are. Is there a market for $10 million joyrides to the moon? Well we know 7 tourists went to the ISS on the Soyuz when the Russians were selling seats for $20-40 million and that was a very limited opportunity. The moon sounds grander and cheaper.
Of course to normal people spending millions of dollars on this is crazy talk. But I remember passing by a TV show that was selling crazy stuff to the super rich, the store had made a gold plated $200k bicycle that was actually just intended for show. A Sheik's buyer came in, thought that was cool and that was it. That's $0.2 million for a bicycle, that sounds like the type of guy who could hire an entire flight just to throw a destination wedding.
Basically, don't underestimate what can happen when billionaire wants something.
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Nobody is going to the moon or Mars on a tourist trip in your lifetime, try to stop being an idiot before you die.
You underestimate how much money some people have. Jeff Bezos: Net worth $142 billion (before divorce) Apollo program: $125 billion in today's dollars
Jeff Bezos could single-handedly fund the Apollo program... ...Basically, don't underestimate what can happen when billionaire wants something.
Spot on. I think people have gotten numb to just how much money some of these people have. It's not like Bezos has 142B in a bank account somewhere, I assume most of his wealth is not-as-liquid-as-cash assets, but when you have that kind of balance sheet it makes it pretty easy to convince other people to invest their money in your ideas. Space tourism isn't a million man-hour problem, it's a funding problem. I plan on living another 30 or 40 years, with the right funding there's no reason we couldn't d
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Nobody is going to the moon or Mars on a tourist trip in your lifetime, try to stop being an idiot before you die.
Blue Origin is all about tourism, and their recent product demo launch of New Shepard (first launch narration I've ever heard that was a blatant sales pitch) shows they'll be selling tickets soon for suborbital.
Their New Glenn heavy lift orbital rocket doesn't have an announced tourist business yet, as man-rating a re-entry capsule will take time, but it seems inevitable at this point.
Jeff Bezos thinks there will be a business here. He has a better track record than AC. Moon tourism is near-term at this po
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I'm only 50, so I have 30 - 50 years to go.
As I have no heirs, I would go in an instant to either of them or both, if I had the money.
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Google told me 1.25 light-seconds, I guess that was rounded.
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and they'd only pay the cost of fuel, probably less than $1million.
Until a rocket with 100 tourists explodes.
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Indeed. They'd need a live demonstration of a launch escape system (ideally with full-envelope coverage, although that should be easy due to the powered-landing capability of Starship) before many would sign on. The insurance would still be expensive, though.
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I doubt they could get 100 people on a spacecraft for 7 days, just due to the logistics. Food, water, waste management, and of course providing some entertainment because much of that time is just uneventful travel through the void. Even just the need for people to exercise and move around presents a challenge you wouldn't get on an airliner - can't expect people to stay mostly seated for a week.
There would also be issues with regulators interested in passenger safety. It's not like if someone gets sick or
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People will get out of their seats whenever the main engines are off, they're hardly going to be strapped in 7 days straight. The cargo room should be ample, so food storage will be no problem. Existing dehydration/filtration should take care of waste mass, and most of the water needs (although how many billionaires would be eager to drink water that once came out of someone's urethra? they might just use fresh water for drinking and recycled for bathing.) Entertainment is the easiest part, most people will
Re:Moon-Bound at Least (Score:5, Interesting)
There is some sense to this. If they can cram 100 space tourists into Starship, then send it to orbit the Moon for a day (7 day space vacation), they could make LOTS of money.
The budget version would be a free return trajectory where you're never in orbit, you do one flyby around the moon at a fairly long distance because you have so high relative velocity and that's it. If you first do lunar orbit, that'd probably be the two week option where you spend a week orbiting the Moon. Then neat thing is that with no atmosphere you can get real close, the LM was normally at a 110 km circular orbit but went down to 15 km for Descent Orbit Insertion, like you could get an airplane-like closeup view. That'd take at least one more tanker mission though, maybe more.
P.S. Even with some degree of re-usability it's silly to assume just the cost of fuel. There will be wear and tear parts, there will be parts that must be deprecated over 10 or 100 flights, there will be launch range/mission control operation costs and they'll never come free. Fuel is just a lower bound on how cheap it could get.
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Right on all counts. I considered a cheaper flyby ticket a possibility, but concluded it wouldn't cost SpaceX MUCH more to do lunar orbit, and the value proposition would be much higher for tourists, so they'd just skip the flyby option (at least at first, when they start doing this regularly). They'd probably have a medic/technician/security/attendant onboard, but the per-flight cost would be only say $10k per onboard employee. Insurance would be the BIG cost, at least until they'd done a few dozen flights
Apprentice Raptor (Score:1)
... and Trump told the Raptor, "You're fired!"
S,cnr
Words (Score:2)
âoerocket engine that doesn't end in an uncontrolled explosion is a good thing."
The industry thinks âoeexplosionâ is a unspoken word and prefers âoerapid unscheduled disassemblyâ
Double whammy (Score:1)
Mistake in the summary (Score:3)
In an unthinakbly rare mistake, particularly given the laser-accurate reporting on Musk's antics in the space buff community, there is a mistake in the summary.
Supercooling the methane don't increase the ISP, it increases the density, making the tanks slightly smaller for a given volume, slightly reducing the weight of the tanks. Technically, it increases the mass ratio (ratio of fueled to dry mass) very slightly. That's still good, as good as if it had increased the ISP, but the effect (which, as all things Musk "invents", has been used for about 60 years or more) is not to change the ISP.
Once you start burning it, you need exactly the same amount per unit oxygen and use the same mass of it per unit impulse you would have had anyway.
The rest of the concept is marginal, Methane is only slightly better than RP-1 (refined kerosene) in terms of ISP in an ideal situation for both, and even supercooled methane is still less dense than RP-1. So the effect is that the effect you are creating with supercooling is more effective if you went to RP-1 - still smaller tanks for a given amount of energy.
The same effect is why hydrogen makes a bad fuel, particularly for a first stage (or even worse, an airplane). Giant tanks for a given energy and the difficulty of handling outweigh the very large increase in ISP aside from special cases like upper stages.
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The advantages of methane aren't really in its ISP, which as you noted are marginal. The advantages are it is much nicer to your engines (no buildup or metal fatigue) and you can make it on Mars/other places without too much difficulty. Both of which will be very helpful in our initial forays into truly reusable spacecraft and interplanetary travel.
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Exactly- the possibility of in-situ generation is a potentially important advantage. This assumes, almost certainly incorrectly, that you will ever be able to get to Mars in the first place using such an arrangement. Someone might try to weigh 31 Raptor engines and comparing that to the weight of the extra tank needed for methane over kerosene.
There is *nothing new* here, all of this stuff was studied extensively over half a century ago, it's well-known what the optimum parameters are, every idea, crackpot
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"Practical" involves more than specific impulse. Liquid hydrogen has not proven to be an economical booster propellant. Its low density makes tanks huge and hurts mass ratio while making it difficult to achieve sufficient thrust, typically requiring the cost and complexity of additional boosters to get off the ground. It works better as an upper stage propellant, but handling multiple propellants is also costly, and it's difficult to store in liquid form for any length of time. SpaceX has achieved major red
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Were you really responding to me? Because I made mostly the same points above.
The varnishing/coking/non-volatile residue is a real issue as well, but cleaning it is relatively simple matter. There are F1s that had 30+ runs, which is more attempts than you will ever get with a flight unit, so it's not an insoluble (get it...) problem.
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The F1 is a gas generator engine, one that operates at even lower temperatures and pressures than the Merlin 1D. Nobody's ever done a fuel-rich staged combustion engine with kerosene fuel because of the severe coking that would occur downstream of the preburner.
SpaceX could have pursued oxygen-rich staged combustion with kerosene fuel as is used in numerous Russian engines, but it results in lower specific impulse than full-flow staged combustion (the kerosene-fueled ORSC RD-180 only gets 338 s in vacuum, r
Re:Mistake in the summary (Score:4, Insightful)
The main attraction of methane is that you can make it on Mars, and only have to send up hydrogen. Secondarily, pumping fuel is a big part of rocket engine deign, and that's just easier with cryogenic fuels than fuels that are liquid at room temperature. It also has slightly better ISP, and you get less coking, than RP-1, but I'm not sure those differences are compelling.
Mars? (Score:1)
Great picture (Score:2)
I saw that yesterday on Twitter and thought it was an especially impressive looking flame, so you should actually both to click on the link... the shape of the flame is really interesting.
Re:Great picture (Score:4, Informative)
the shape of the flame is really interesting.
Mach diamonds. It's what happens when the exhaust is at a slightly lower pressure than the atmosphere. (What happens when the exhaust is at a much lower pressure than the atmosphere is far more exciting, briefly.) Atmosphere-optimized engines are usually optimized for a higher altitude, since the engine will spend more time there.
When the exhaust is at higher pressure than the atmosphere you can still get Mach diamonds (assuming enough atmosphere to matter) but the flame will expand larger than the nozzle before coming back.
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Anything with supersonic exhaust in an atmosphere, unless the exhaust pressure exactly matches atmospheric pressure (which never stays true for long).
Please stop (Score:2)