I just clicked the temperature thingy in annoyance because I don't use Fahrenheit and to my delight, it just switched to Celcius
Doesn't work on the the "meters" display, though!
Space Elevator
281–290 of 414 posts
Re: Space Elevator
#282Very cool. One thing I wish was better shown: space is close, it's just hard to go up. Our liveable breathable atmosphere is razor thin compared to the size of earth. In most cases, 100km is less than the distance between sizeable metropolitan areas. It's a day long bike ride. Air runs out less than a bus ride across town. A 15k jog/hike would put you in the stratosphere. Those jet aircraft that seem so high are clos…
> Our liveable breathable atmosphere is razor thin compared to the size of earth.
If earth were a grapefruit, our atmosphere would be ~1mm thick!
Re: Space Elevator
#283Earlier quoted context omitted.
The issue of the line falling back to earth is solved by putting the base of the elevator on water. If the top part of the elevator was cut of you could even detonate charges along the line to make sure all pieces fall into water.
I don't understand why you think that where you put the base of a 35000km cable makes a difference for where the rest of it would fall. I also don't understand why you think that a 35000 km long cable falling in the ocean from space would cause any less damage to the planet than it falling down on solid ground, or at least why the difference would be significant.
> why you think that a 35000 km long cable falling in the ocean from space would cause any less damage to the planet than it falling down on solid ground
They’re not obviously wrong.
A lot of the cable is moving at escape and orbital velocities. Tensile strength is all that holds it together.
If, as the cable fails, you sever the parts above from below around escape velocity, you’ll significantly reduce the length of cable that will ever hit the surface.
Re: Space Elevator
#284I like how the height is measured in metric but the temp is measured in imperial.
Re: Space Elevator
#285Earlier quoted context omitted.
I don't think there are any physics reasons why it'd be impossible, but certainly we can't do it with existing technology. You'd need an air breathing jet that could get a vehicle to go about five or six times faster than any current such engine has ever achieved (i.e. around mach 20-30), which is perhaps ridiculous, but I don't think it's necessarily impossible, just something we don't know how to do. There have bee…
Can an air breathing jet actually attain those velocities? I thought most supersonic aircraft use rockets after a certain point
"Most" supersonic aircraft are fighter jets and other military aircraft that use jet engines, not rockets. They may have afterburners that are much like a rocket that just injects jet fuel in the exhaust stream, but that's still using atmospheric oxygen.
The issue, I think, is more about balancing drag and air intake at appropriate atmospheric densities for different speeds. An SR-71 Blackbird could fly at 85,000 feet continuously, and a MiG-25 set what I believe is still the air-breathing record max altitude by pulling a "zoom climb" (accelerating in higher-density air that the engines could use effectively, then pulling the stick back and coasting up through rarefied air too thin for the engines) to 38km or 123,000 feet.
Most experimental hypersonic aircraft use rockets because that's what works.
Re: Space Elevator
#286I love this page and I donated, but I was (naively) expecting it to get to geosynchronous altitude, which is the actual top of a space elevator. Of course, that would require a page 420 times longer, and I don't know if a browser would even support it.
actually geosync isn't the top. You need to extend beyond that & have a counterweight that balances the weight of everything below the point of geosynchronous orbit. Otherwise it would fall down.
Re: Space Elevator
#287Earlier quoted context omitted.
You can reach space using air breathing jets. You can’t stay in space using air breathing jets.
I don't think there are any physics reasons why it'd be impossible, but certainly we can't do it with existing technology. You'd need an air breathing jet that could get a vehicle to go about five or six times faster than any current such engine has ever achieved (i.e. around mach 20-30), which is perhaps ridiculous, but I don't think it's necessarily impossible, just something we don't know how to do. There have bee…
Basically when you cut thrust you must pass through that altitude again or escape orbit.
So either fire a rocket in space to circularize the orbit or reach more than Earth’s escape velocity 25,020 mph (11.186 km/s, 40,270 km/h) ~ Mach 32.6, due to some drag in air to thin for any kind of air breathing engine to work.
X-30 was aiming far lower ~Mach 20. Nuclear could make it more realistic than any form of chemical combustion. It might be physically possible using Hydrogen but you’re talking generating extreme thrust at vastly more extreme conditions than the space shuttle’s retry.
Re: Space Elevator
#288Amazing work! One minor correction: > As particles from the sun hit the atmosphere, they excite the atoms in the air. These excited atoms start to glow, creating brilliant displays of light called auroras. The process is a bit more nuanced than that. The modern mainstream understanding is that the growing pressure of the solar wind makes the tail of the magnetosphere "contract" (sort of pushing it inwards from the si…
Any discussion of aurora which do not mention space tornados: https://en.wikipedia.org/wiki/Space_tornado Is inherently incomplete. Not necessarily because they're needed to explain it, but they do need to be brought up at any time possible because they're cool.
These are cool. I wonder how much they screw with satellites etc.? How predictable are they? It seems like it's just a deadly, mostly-invisible wall of energy flying around at unbelievable speeds!
Re: Space Elevator
#289TIL it's estimated that over 48 tons of meteors hit the atmosphere every day. Regarding actual space elevators though, while they're not sci-fi to the extent of something like FTL travel - ie. they're technically not physically impossible - they're still pretty firmly in the realm of sci-fi. We don't have anything close to a cable that could sustain its own weight, let alone that of whatever is being elevated. Plus,…
> while they're not sci-fi to the extent of something like FTL travel - ie. they're technically not physically impossible
On Earth.
Zylon or M5 [1] could build an elevator on Mars. Kevlar on the Moon.
To drive this home, it’s estimated we could build a lunar space elevator for less than what Bechtel fleeced NASA for a mobile SLS launcher [2][3].
[1] https://en.wikipedia.org/wiki/M5_fiber
[2] https://opsjournal.org/DocumentLibrary/Uploads/The_Lunar_Spa...
[3] https://oig.nasa.gov/wp-content/uploads/2024/02/IG-22-012.pd...
Re: Space Elevator
#290TIL it's estimated that over 48 tons of meteors hit the atmosphere every day. Regarding actual space elevators though, while they're not sci-fi to the extent of something like FTL travel - ie. they're technically not physically impossible - they're still pretty firmly in the realm of sci-fi. We don't have anything close to a cable that could sustain its own weight, let alone that of whatever is being elevated. Plus,…
While a space elevator doesn't contradict any fundamental limits of physics, that doesn't mean it's actually possible to build one. There is no reason to be certain that it's actually possible to create a material that has the required characteristics in terms of tensile strength to support it's own weight, plus the weight of the elevator, plus the weight of all the additional cabling. It also has to endure the huge…
I'm wondering if it's one of those paradoxes where by the time we are technologically capable of building one, we won't actually need it.