# Tag Info

7

I recreated your scenario using Wolfe's Spreadsheet. Here's a screen capture: The numbers you cited match mine fairly closely. A very nice tool Hohmann fan has made available. I intend to link to his page from several of my tether blog posts. The bottom of the spreadsheet answers some of the your questions. I called 70 kilometers the altitude where the ...

7

I'm going to say "no". I thought of a lot of objections but realized I was overlooking a fundamental one, namely: What's the most important difference between a kilogram of oxynitrogen in the upper atmosphere and that same kilogram in an air tank in low Earth orbit? The difference is the speed that it is moving at. Eight km/sec! No matter how your ...

6

There are some real hurdles here. They include: Drag. Some portion of the "hose" will experience drag which will have to be compensated for by some sort of propulsion. Angular momentum. Regardless of how you pump the gas up to a higher orbit, you will have to increase that mass' angular momentum. More propellant... Rarefied gas. In order to be able to ...

5

Ralph Kramden and Ed Norton were two characters in a very early (1951-1955) TV sitcom called The Honeymooners. Bonus: The New Horizons satellite that flew past Pluto almost two years ago sported two experiments named Ralph and Alice, named after Ralph and Alice Kramden.

4

Yes. Given the radii of the upper and lower moons and knowing their angular velocities, there are simple expressions that give the periapsis and apoapsis radius of the Zero Relative Velocity Transfer Orbit. The specific angular momentum, h, of an orbit is constant. At any point on the orbit the specific angular momentum $\overrightarrow{h}$ is the cross ...

4

tl;dr Everyone will die within five minutes. Your plan is a non-starter. You must consider letting go from a much lower altitude, or higher forward velocity, or convert your capsule into a spaceplane the likes of which do not yet exist. Here is some physics. To get an approximate idea what the re-entry would be like, I've used a simple scale-height model of ...

4

Nice question; it's gedankenexperiment time! Let's assume the Earth's gravitational field is spherical (no oblateness or other lumps) and stick with the OP's draglessness. Let's also assume the cable has some finite mass. If we place just the two satellites in the same circular orbit but phased differently, then they would continue in that orbit spaced by ...

4

Indeed, it doesn't work. What you are proposing is fundamentally the same as a chain. The main issue is that gravity will apply to every single link. While the mass of the links is equally distributed on the chain (ie each links have roughly the same weight), each link will need to carry the weight of each link below it (or your chain would just fall on ...

3

Firstly, while the idea sounds good, it turns out it can't work at all even if we did have the materials for the tether and a plane. The reason is that a space elevator doesn't just have one counterweight! It has two. The first one is the obvious one, out beyond GSO. The second one is the earth! In order for our space elevator to be effective with a plane, ...

3

Employing Wolfe's spreadsheet I'm getting numbers similar to Hohmann fan's. That's reassuring. With tether center balance point at 3000 km altitude and tether foot at 10 km altitude I get: Foot speed: .375 km/s Acceleration at foot 1.52 m/s^2 Zylon taper ratio 1.43 Tether mass/payload mass ratio: 1.63 With tether center balance point at 10000 km ...

3

On the right are the equations. On the left is an example based on LEO around Terra. 5.97E24 kg Mc = Central mass 900000 kg Mb = mass of tether base 100000 kg Ms = mass of shuttle Assume tether mass is negligible 6.67E-11 m^3/(s^2*kg) G = Newton’s constant 3.986E14 m^3/(s^2) mu = G*Mc 7000000 m Rb = ...

2

It can be done if you back up and change some of your ideas about what you're building. Forget the space elevator per se, Quietghost demolished that. Space elevators must have a net upwards pull or they fall down and that upward pull is only generated by mass beyond synchronous orbit. However, there is also the concept called the rotovator. Take a cable ...

2

There are potentially many forms of oscillation, all of which would require some form of damping. Any offset from straight is a higher energy state, and the system won't die down without some damping. There is however already a natural form of damping. The extension and contracting of the tether will damp some of that energy. Its worth noting that that won't ...

2

Parsing information from Wikipedia. Space tethers are extremely slow, and are somewhat unweildly. The main thought has been for use to deorbit them. In order to make them work, one has to have a very long tether. Just to give a few numbers, as seen from this site, a tether to raise the ISS would be about 25 km long. It would produce a continual 0.5-0.8 N of ...

1

In the linked AIAA article, the bottom of page 4 (excerpted below) estimates numbers for a 250 m x 0.28 m tape. When 700 km high, electrodynamic drag and aerodynamic drag are both about 15 μN. Higher up, electrodynamic drag dominates. To generalize this, into equation (4) plug in values for tape width w, a bunch of numbers ∆V me mi that I don't know how ...

1

If you are going specifically for the issues, here are some: Orbital stability Your tether is in reality orbiting in a two-body system, as the Earth's gravity have a significant influence when getting far enough from the Moon. The altitudes you are talking about is well within the Hill sphere of the Moon though, so this disturbance is pretty minor. Mass-...

1

Concern 1: as the ship crawls up the tether, the tether is pushed downward. You can have a counterweight crawling the other way to balance it, but you ultimately need as many kilogram-trips from top to bottom as bottom to top, or spend stationkeeping thrust, or something. Concern 2: all the spacecraft rendezvous we've done thus far have been in free fall ...

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