China plans to build a giant rail gun to launch hypersonic planes into space
China plans to build a giant rail gun to launch hypersonic planes into space
It was a project that Nasa abandoned. Now China is determined to make electromagnetic hypersonic space launches a reality.
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@yogthos So the system just accelerates to Mach 1.6, then the system had to use its own fuel to speed up to just Mach 7. But Mach 7 is just a fraction of the needed velocity to get into orbit. Mach 7 is around 8,500 km/h. But you need 25,000 km/h to stay in orbit. So you need an additional stage to accelerate to that speed. And that stage would had to be expendable, otherwise you couldn't carry enough payload.
Still you can only reach a single orbit. To reach another orbital plane, you then would had to use a lot of additional propellant to perform a dogleg maneuver to switch to a different plane.
BTW: This whole idea reminds me of SpinLaunch. Prototypes are already built by the U.S. based company with the same name. They want to accelerate small launchers in a vacuum chamber, so that in the end they can carry up to 300kg in a low earth orbit.
But the goal isn't to stay in orbit. The goal is to push the plane to upper atmosphere where there is low air resistance, and then it mostly glides to where it needs to go. The article very clearly explains that the goal is to create an alternative to long range flights instead of doing space launches. I'm also familiar with SpinLaunch, and it's a completely different purpose where they want to launch small satellites into low Earth orbit.
@yogthos The articles ends in "While SpaceX’s reusable rockets have slashed satellite launch costs to US$3,000/kg, some scientists have estimated that an electromagnetic space launch system could drive those costs down to a mere US$60/kg."
This is a comparison to a launch into an orbit.
This tech can be used for both purposes, but most of the article discusses transportation. Once China puts this tech in production, I'm sure it will be used for orbital launches as well.
@yogthos I now had more time to look into the article. The whole article is focused solely on the electromagnet technology. From here it refers to some other technology that uses electromagnet acceleration like Musk's fever dream "Hyperloop" and sea carrier catapults while in the end making a reference to orbital launch costs.
Thing is: It simply doesn't make sense. Neither in point-to-point transportation nor in space launch activities this would work out, since you could reach only a single orbital plane or flight direction. To reach more than one point or orbit, you would need to have a lot of these systems, which then would result in really high operational costs.
However, this technology is fine for a highly improved land based transportation method, especially for China, which is the forth biggest country (behind Russia, Canada and the USA).
This is literally what people said about high speed rail. The argument was that this is simply not cost effective and that's why it can't be built. Yet, China covered the whole country with HSR in a decade. Short term cost effectiveness isn't really an issue when you have a state directed economy. And costs for any new technology come down over time. Maybe China will start using it for ground based transportation first, and then start using it for other applications. We'll just wait and see.
@yogthos Which people said that about high speed rail? The country I'm living in has got high speed rail since the 90s. See also Japan or France (and some other countries).
This is a common narrative in US and Canada, meanwhile countries like France or Japan are dismissed as being small. Here's an example for you https://www.scientificamerican.com/article/why-high-speed-bullet-trains-wont-work-in-the-u-s-right-now/
@yogthos I'm not living in the US, neither I'm a fan of most of their politics. So I definitely won't defend them.
The original point was that arguments about cost efficiency have been made regarding HSR. Every new technology is expensive when it's initially developed, and it requires significant investment. One way to look at that is to say that it's not worth spending the effort on, another way to look at it is that spending the effort creates jobs, spurs innovation, and brings long term benefits to society. It's pretty clear to me that China tends to take the long view on such things, and hence I think it's very probable that they will try building such launch systems.
@yogthos Well, I've got the opinion, that infrastructure shouldn't be operated for profit, so I've got no problem with investing a lot of money in advance. My points are meant from a technical standpoint. And when I refer to the costs, then I mean this in a way that I've got the opinion that the money should be invested in other stuff as well.