That is a weapon, not a teleporter. -Samuel Hayden (Doom Eternal)
this post was submitted on 15 Mar 2024
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Not the Onion
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Finally, a worthy ~~successor~~ contemporary companion to the great trebuchet.
Why is this in NTO?
There are a great many methods to lowering costs for launch vehicles, this is just one of them.
Honestly this isn't nearly as "crazy" or out there as putting a super fast spinning arm in a vacuum chamber (think super sized centrifuge on its side) and letting go when it will launch the payload upward.
As to whether this will work with human passengers and let them survive the trip? I'm sure with a long enough track, sure.
I'm sure plenty of abandoned projects from the past have merit now that relevant tech has improved.
Hell, just look at electric planes. Axial flux motors. That stuff wasn't around when I was a kid, and people dubbed such things impossible.
Indeed, especially if you have favourable geography, incl. being as high as possible near the equator.
You need consistent sustained force to combat air resistance as you exit the atmosphere. If you go too fast too quickly you'll put too much stress on the vehicle and you'll lose a lot of energy. I don't see this working well. Powerful 2-stage reusable rockets are the way to go until we have a space elevator.
It'll have to be VERY big to accelerate the planes up to escape velocity without killing the passengers and crew.
That’s actually pretty cool.
Metal gear?
I need someone else to watch this phenomenal redub of the scene with Liquid and Snake on top of Metal Gear: https://youtu.be/srTqxL_6Ysg
There’s nothing oniony about this ?
Actually it could be an interesting idea. Instead of rockets carrying their own propulsion in the form of fuel, which adds to the weight of the rocket. External propulsion, which is what rail gun basically is, could work.
Or it might just fling your mom down to the nearest gas station, that’s a lot of mass.
1: you need to launch something at 8200m/s to get into low earth orbit. That's not counting air resistance, or equatorial benefits, so let's ignore both.
2: gravity acceleration is 10 meters per per second. So 5 time gravity is 50 meters per second per second (50m/s^2)
3: to launch something into orbit, from a railgun at 5g, you need to accelerate for 8200/50=164 seconds. Your average speed will be 4100m/s for 164 seconds.
4: a 5g orbital railgun will have to be 4100x164=672km long. And probably still crush any sattelite you want to put on it.
How did you calculate 8200 m/s?
the gravitaitonal constant is only constant at one specific height in the gravitaitonal field. But the gravitaitonal force is reducing, the further away from earth you get. So what you actually have to do is calculate U1 = -GMm/r1 for the LEO and U2 = -GMm/r2 for surface level. leaving out the objects mass already you get as difference
(U1-U2)/m = 6.67e-11 x 5.97e24 x (1/6,73e6-1/8,73e6) = 13,555 Now that is your specific energy from the starting velocity = 1/2 v² from the kinetic energy. So at ground level you actually need 5,206 m/s ignoring air friction.
Also your length of the railgun exceeds the atmosphere, so not only for the friction, but also for the distance to earth you will need much less speed at the end of that railgun. Furthermore g will get less as it gets higher, so you can accelerate faster towards the end of it.
http://hyperphysics.phy-astr.gsu.edu/hbase/gpot.html
I'm not claiming the concept is viable by default, but your calculation is not including crucial aspects of how gravitaitonal force changes in a gravitaitonal field.
How did you calculate 8200 m/s?
I looked at a delta-v chart, which mostly list 9000-10000 for 250km orbits. I subtracted 10% from the one on Wikipedia for an absolute minimum.
Also your length of the railgun exceeds the atmosphere,
That rather speaks against the concept, wouldn't you say?
China has always been about weird projects on a large scale. For one there's the desire to show off its greatness and second, the incompetent or fearful mid-level management unable or unwilling to say no. So every once in a while, a project gets announced, gets made shoddily, embarrassment ensues and heads roll.
And the thing is, we see it happen in the US all the time. That company that promised launching a rocket every other day is a recent example.
And the thing is, we see it happen in the US all the time. That company that promised launching a rocket every other day is a recent example.
Oh, but they're DEFINITELY doing well. They're totally on schedule for an unmanned moonlanding in... checks notes... Q1 2024.
The electronics within an artillery shell can survive tens of thousands of gees just fine. The Sprint missile accelerates at a hundred g. A launch system will only need to be several kilometers long.
Neither artillery shells nor missiles tend to be packed full of fragile scientific instruments, solar panels, people, or liquids.
If your goal is only to launch solid cubesats, this might work, otherwise it's nonsense.
People will never be launched this way for sure. As for scientific equipment, that's a very nebulous term. Almost all solid state hardware can be launched this way. The efficiency of the launch system will allow for heavier, more robust payloads. Even a JWST can be modified for launch in this manner.
what do geese have to do with this?
Honest question, that might be answered in the article but I’m a little lazy (also not so great at physics). Is the energy efficiency the same for traditional rockets and a rail gun getting into space? I assume it’s the same amount of energy needed regardless of the method
It needs less energy overall because you don't carry the fuel with you. The vast majority of the energy needed for a rocket launch is used to carry a bit more fuel a bit faster.
So in theory a railgun could send a payload in space for only a fraction of the cost.
The problem on earth is the atmosphere, travelling through the atmosphere at orbital speed will instantly vaporize any object due to friction. In the article they are talking about sending objects at mach 1.6 which is close to 2 000km/h. Orbital speed is around 29 000km/h so they would still be far from reaching orbit.
travelling through the atmosphere at orbital speed will instantly vaporize any object due to friction
You’re aware that re-entry is possible and is done at speeds around 28,000km/h right?
A railgun will have vastly greater efficiency. Think of propelling yourself on a skateboard by farting vs using your feet.
Even if it would be the same in theory (which makes sense to me), there's the matter of not needing so much fuel on board.
Even if we assume the cost of the fuel is equal to the electricity cost (though I imagine rocket fuel is pretty pricey), you're also saving on the cost of the larger fuel tank, and the cost of propelling the full fuel tank.
That's my entirely amateur opinion, anyway. Plus, it's cool as hell, which has got to count for something.
You don't have to carry a huge amount of rocket fuel so I assume that the energy requirement would be less. But this is just a laymens guess.
Didn’t think of this, very good point. Sounds like it might allow for “better” payloads reaching space (supplies for building or food whatever) without needing to worry about huge fuselages.
What about this is onion like?
Is it just because it is about China doing something neat?
If that is the case this just comes off super racist.
It's a giant rail gun that shoots stuff into space
Yeah but that has been conceptualized for a century. It's actually one of the oldest hypothetical methods of breaking earth orbit (a giant cannon that fires a rocket to the moon being depicted as one of the early silent films).
It is also a very practical solution to the fuel and weight limitations of solid rocket boosters.
It just seems weird to put in this comm because it is not at all an absurd or even far fetched idea.
Once again only seems like it is here because China.
Dunno what to tell you. I just found the concept funny to think about. You can report the post if you want, or just ignore it.
Already did. I was just curious what you thought was funny about it. It should have just gone in any of the space or science comms, putting it here just feels like typical lib china bashing is all.