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Elon Musk Announces That Raptor Engine Test Has Set New World Record (space.com)
Iwastheone shares a report from Space.com: A test fire of SpaceX's newest engine reached the power level necessary for the company's next round of rocket designs, CEO Elon Musk said on Twitter. "Raptor just achieved power level needed for Starship & Super Heavy," he tweeted on Feb. 7, four days after he shared a photograph of the first test of a flight-ready engine. [Musk added: "Raptor reached 268.9 bar today, exceeding prior record by the awesome Russian RD-180. Great work by @SpaceX engine/test team!"
The Raptor engine is designed to power the spaceship currently known as Starship as part of the rocket assembly currently known as Super Heavy (previously dubbed the BFR). The first Raptor test fire took place in September 2016, when the company was targeting an uncrewed Mars launch in 2018. Three Raptor engines like this one are built in to the Starship Hopper, which has been under construction in Texas and which SpaceX will use to begin testing the rocket technology in real life. Eventually, SpaceX plans to assemble 31 Raptor engines into the Super Heavy rockets, with another seven Raptors on the Starship itself.
The Raptor engine is designed to power the spaceship currently known as Starship as part of the rocket assembly currently known as Super Heavy (previously dubbed the BFR). The first Raptor test fire took place in September 2016, when the company was targeting an uncrewed Mars launch in 2018. Three Raptor engines like this one are built in to the Starship Hopper, which has been under construction in Texas and which SpaceX will use to begin testing the rocket technology in real life. Eventually, SpaceX plans to assemble 31 Raptor engines into the Super Heavy rockets, with another seven Raptors on the Starship itself.
The RD-181 has the record for the highest chamber pressure for a flown engine. (And the RD-180 is only a few psi behind, so I'm not going to slam Elon for mixing them up.)
But the Raptor is currently a test-stand engine, and the record for tested engines is over 300 bar.
Testing an engine at a higher pressure than it flies in order to demonstrate a safety margin is of course completely normal. Aerospace uses a lot smaller margins than the factor of 2 used in a lot of civil engineering, but I expect a test at at least 110% of flight pressure.
So while this is an impressive demonstration worthy of praise, it is not any sort of record.
I just wish they'd hurry up and start recruiting space miners to go to the asteroid belt.
You read too much sci-fi. IRL, when miners go to the asteroid belt, they will be robots, not humans.
There is no practical reason to send humans beyond earth orbit. Robots don't need life support, they don't need expensive ultra-reliable gear, and they don't need to come back home.
https://xkcd.com/695/
If I read de Laval nozzle equation correctly an increase in the combustion chamber pressure has minimal impact on the exhaust velocity (going from 260 Bar to 300 Bar has less than 1% improvement).
Combustion chamber temperature is a far better indication of efficiency of the engine and has a far more direct impact of exhaust velocity than pressure.
Credit where credit due - design requires 170 metric tonnes of force, test fire got 172 metric tonnes (design works as expected).
The asteroid belt consists mainly of the same stuff than the Earth Moon and the Earth's crust anyway, and the later have more of it.
Just a simple comparison of 16 Psyche with our recoverable mineral reserves betrays your deception. Just because Earth has considerable amounts of iron, nickel and siderophiles in its core doesn't mean that they're easily accessible - they're in the fucking core! You're *never* getting to the core.
The energy required to move something from the Asteroid Belt to the Earth is so high that the cost will by far outnumber the possible revenue for selling the stuff. Even if you mine an asteroid consisting of pure gold or platinum, you will pay more for the fuel to get there and back than you can possible sell the gold and platinum for on Earth.
I would love to buy me some platinum from where you're buying it. Apparently it must be super cheap compared to the price of some methane and oxygen. I would, however, not wish to buy any of your math or physics textbooks, apparently they're awful.
Ezekiel 23:20
Chamber pressure is correlated to both thrust (higher chamber pressure = higher mass flow rate) and efficiency (and thus ISP, see here).
AFAIK, thrust density is the more key factor here, at least for Super Heavy (the first stage). There's a sort of "maximum height" to a rocket stage which relates to the thrust density. Your ability to pack more engines into the rocket corresponds to the rocket's cross section at the base. These engines in turn have to lift a column of liquid sitting above them; each engine can be viewed as having to lift the portion of the column of liquid directly above it (in addition to dead mass and payload). Eventually you get to a height where the mass of liquid (plus overhead) above each engine equals the thrust, and you don't move at all. The higher the thrust density of your engines, the taller you can realistically make that stage, the more fuel it can carry, and - for a given ratio of lower stage mass to upper stage mass - the heavier the payload it can launch (for a given dV). Other options to increase rocket upper stage masses come with disadvantages, such as making the rocket higher diameter (more air resistance) or adding strap-on boosters (more air resistance, more complexity, more work in recovery for reuse).
Thrust density is primarily of importance for lower stages (which is why you don't see many hydrolox lower stages without boosters), and why strap-on boosters (incl. very high thrust density solid rocket boosters) are commonly added to the first stages of large rockets. Thrust density limits are also why small rockets tend to be shaped like pencils (very high aspect ratio) while large rockets tend to be fatter, particularly at the base. For upper stages, ISP is of greater importance.
Also, for a rocket of a given (constant) height, improving its engines' thrust density comes with another advantage: they burn through their fuel faster and deliver the stage's dV faster. While there are limits to how fast you want to do this in the lower atmosphere, once you're past max-Q, more thrust is better (up to the G-force limits of your payload/passengers), as it means lower gravity losses.
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More accurately, you have twenty times more widely dispersed low-grade oxides that would require fucking up the whole crust and atmosphere that we live on/in to get to than 16 Psyche has 90% pure metallic material. How much of your stuff is practically recoverable?
Ezekiel 23:20
The Saturn V's first-stage engines were crude and inefficient due to problems scaling up the engineering of smaller rocket motors, with bodges added to solve difficulties with the flow of oxidiser and fuel into the engine. The Soviet solution was to use multiple smaller injection systems in separate combustion chambers.
By the late 1960s the Isp figure for LOX/RP fuels was about what we can get today, 300s-plus at sea level for well-designed engines like the RD-170 derivatives (the F1's sea-level Isp was 263s by comparison). The big steps made in rocket engineering are design and materials. The structures are lighter but stronger since the CAD tools allow better understanding of where to add mass and where to remove it without lessening strength, rigidity, resistance to vibration, heat dissipation and other factors. The engines are modelled and tested in simulation a long time before any metal is bent or additively-fabricated, the shapes and structures can be more complex thanks to new manufacturing processes, new alloys and composite materials are available etc. etc.
I love the various hacks that have been used in rocketry over the years to deal with "difficult problems", which throw away a bit of performance in order to not have to deal with them. One of the most recent ones that springs to mind is that North Korea "dealt with" the stability problems on their missiles by adding a ring of stationary (no axial rotation, aka non-maneuvering) grid fins around the base. They deliberately increase the drag of the first stage in order to keep it stable (like a shuttlecock).
Anchor: "We take you now to our Chief Meteorologist, Paris Hilton." Paris: "It's hot." Anchor: "Thank you."
The $60 per barrel argument is correct, but that's not why fracking shale became popular. In the late 70's/early 80's the price per barrel was over $100 but nobody was fracking. It became popular because of technological advances in horizontal drilling in the late 90s. The shale layer is frequently tight - 5-500 ft thick at depths of 5000-15000 ft (http://www.marcellus.psu.edu/resources-maps-graphics.html) The only way to make the effort of fracking economical is if your well bore can run down, and then along the shale layer for 1000's of feet or miles. That requires horizontal drilling.
It also helps that there's a lot of natural gas in shale, making fracking all that much more economical outside of the price-per-barrel of hydrocarbon. In some areas (eg Marcellus) that's the only reason to frack. In other areas the methane is of minor value compared to the heavier hydrocarbons that come out (like natural gas liquids).
I remember talking to an engineer from a drilling company a few years ago that said with current drilling technology they could drill down, under the Grand Canyon, then back up on the other side and hit a target at the surface only a few feet wide. There are major negative environmental impacts of fracking and the subsequent use of the produced fuel, but the the horizontal drilling capability on its face is an engineering marvel (to me at least).
The best way to predict the future is to invent it.