Space Thread!

cannabineer

cannabineer

Ursus marijanus
Doer said:
Thanks for the explain!

For luna transportation, won't a simple Holzman orbit take us there and back in 30 days
or so? It's been proposed for Mars, an 18 month orbit.

If there is any place else, it might be found in exo-planet research. Then a one way
trip, indeed.
Click to expand...
Apollo followed a Hohmann orbit between LEO and LLO (low lunar orbit). That took three days coming and the same amount going. It's the most efficient transfer orbit.
A Hohmann trajectory from Earth to Mars takes nine months indeed. Serious crewed exploration of the solar system will benefit mightily from a drive with an abundance of delta V, so that we needn't be confined to Hohmann orbits and their years of coasting. Such a drive exists ... but there is a pollution issue. It's called Orion - not the recent "Apollo on steroids", but a design from the 60s that uses nukes as a pulsed reaction mass. Isp in the tens of thousands ... Saturn and return in a year!! cn

<edit> I recommend the science fiction novel "Footfall" by Niven and Pournelle. Asteroid impacts, alien invasion ... an Orion-type warship ... plucky monkeys might yet prevail ...
 
Doer

Doer

Well-Known Member
Yep, read all the sci-fi. Integral Trees, I think is my favorite, if I have to choose, which I don't. :)

I believe we need to think of space as an origami problem. How to
fold the surface?

Oh, another favorite. Red Mars.
 
Doer

Doer

Well-Known Member
What exactly is the problem with tethers in space? Hasn't worked so far and
we seemed to have stopped trying for the time being.

It would buy us so much, elevators, propulsion, power, catapults to the moon....
 
cannabineer

cannabineer

Ursus marijanus
Doer said:
What exactly is the problem with tethers in space? Hasn't worked so far and
we seemed to have stopped trying for the time being.

It would buy us so much, elevators, propulsion, power, catapults to the moon....
Click to expand...
Two basic problems, Doer.
1) Take the classic Beanstalk/space elevator. We have NO materials with enough tensile strength, and no prospects for making them.
2) Even if a Beanstalk were put into place by an amused deity ... we'd still have the problem of powering and controlling the traffic of the trolley-type vehicles going up and down. I don't have a ref handy, but someone put out a request for design of a beanstalk rider. Didn't get any useful ideas back. cn
 
Doer

Doer

Well-Known Member
I don't know if the company stayed in business. Space Elevator, Inc? IAC, they were
starting with carbon nano-tubes.

No, earth tethered is a special problem. I mean space tethers. Seems you can't
un-reel a line more than about 100 feet. It's a micro-gravity problem of some kind.
 
cannabineer

cannabineer

Ursus marijanus
Doer said:
I don't know if the company stayed in business. Space Elevator, Inc? IAC, they were
starting with carbon nano-tubes.

No, earth tethered is a special problem. I mean space tethers. Seems you can't
un-reel a line more than about 100 feet. It's a micro-gravity problem of some kind.
Click to expand...
The unreeling problem is "fixable" by a bit of research imo. In LEO there should be enough tidal force to hiold one straight Didn't the Italians andor the japanese try this, but the reel jammed? I think that was a local problem, not something systematically screwed. In complete microgravity, just impart a bit of spin ... it'll unreel straight and true.
Tethers in space could ultimately be very useful "momentum banks" for transferring payloads between orbits. But in the meantime, achieving orbit from earth's surface remains the ouchie. cn
 
Doer

Doer

Well-Known Member
You think you could even have a little motor on the end to provide some friction for
the reel. I don't know if that was the problem. I saw a picture and the snarl on
the reel certainly looked like a mico-grav problem. Not seen that on earth, though
snarled winchs are not unfamilar. There is one in my grow right now. And other
snarling wench in the house. (woops, outloud?) :)

Not earth tethered, but perhaps the same material problem is an LEO pinwheel.
It's drags along for a few miles on the earth in some number of places.
Low side to low is earth transport. Low to high is obital trajectories. High
to low is earth delivery.
 
cannabineer

cannabineer

Ursus marijanus
Doer said:
You think you could even have a little motor on the end to provide some friction for
the reel. I don't know if that was the problem. I saw a picture and the snarl on
the reel certainly looked like a mico-grav problem. Not seen that on earth, though
snarled winchs are not unfamilar. There is one in my grow right now. And other
snarling wench in the house. (woops, outloud?) :)

Not earth tethered, but perhaps the same material problem is an LEO pinwheel.
It's drags along for a few miles on the earth in some number of places.
Low side to low is earth transport. Low to high is obital trajectories. High
to low is earth delivery.
Click to expand...
Don't tangle with her ... cn
 
Doer

Doer

Well-Known Member
Huh? A Space Fountain. Was unaware of this tech. Solves propelling, but not the material problem?



And another thing...

Sky Hooks and Rotavators
 
Doer

Doer

Well-Known Member
cannabineer said:
Unfortunately space fountains etc. are not tech ... they're pipe dreams. cn
Click to expand...
A pun, I get it. 100 mile vacuum pipe dream. Yeah, not tech, indeed. I'd like to see a working model that could
hold itself off the table. Then it'd be tech.
 
cannabineer

cannabineer

Ursus marijanus
Toy mfrs? Not following. I reserve "technology" for that which has been proven at a working scale. There were some folks who were working on a laser-pumped air rocket, for example. They built a small model that could go a few hundred feet. But since they never progressed to something beyond a <cough!> toy, I don't call that tech, but a principle demo.
We had a nuclear-thermal rocket demonstrator in the 60s, but never took it to the point where there was a field-ready unit. So ... no tech, quoth the 'neer. cn
 
cannabineer

cannabineer

Ursus marijanus
Very cool vid, Ryan!
I went into immediate nerd mode and estimated their acceleration relative to the station at two milligee (two cm/s²). I then found a link that stated that the actual acceleration was 1.6 milligee ... close enough! ~grin~
I looked up the station's mass, 450 tonnes, and finally figured that the rocket was producing 71000 newtons (about 15900 pounds) of thrust. It fired for about 114 seconds, imparting a delta vee of 1.8 meters per second to the entire structure.
The rocket was most likely the orbital maneuvering unit aboard a Progress module, essentially a stripped Soyuz used as a supply mule. Figuring an Isp (specific impulse, a measure of how efficiently a rocket uses its fuel) of 310 seconds, typical for hypergolics in a vacuum, the Progress consumed about 2.6 tonnes of propellant for this boost.
I wonder if they performed an antipodal circularization burn ...
cn
 
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