Generational Dynamics Forum - New Site

[quote="psCargile"][quote]I even wrote a simulator that runs as a Java applet. It can simulate orbits, space tethers, reentry heating and drag, and lots of stuff. [/quote]

Have you ever played around in Orbiter? [url]http://orbit.medphys.ucl.ac.uk/[/url]

Space tethers . . . would those be the momentum exchange tethers?[/quote]

I have not tried Orbiter but it looks very nice. Might get my boys to play with it this summer.

Yes, rotating momentum exchange tethers. Also electrodynamic tethers that thurst against the Earth's magnetic field, and hanging tethers that rotate once per orbit so the same side is always down.

[quote]I even wrote a simulator that runs as a Java applet. It can simulate orbits, space tethers, reentry heating and drag, and lots of stuff. [/quote]

Have you ever played around in Orbiter? [url]http://orbit.medphys.ucl.ac.uk/[/url]

Space tethers . . . would those be the momentum exchange tethers?

[quote]True, but weapons, especially kinetic energy weapons, want to do the opposite of "matching speed and position". They just need to attempt to occupy the same point in space at the same time as the target. There are literally an infinite number of possible orbits that would do that. Matching speed and position of the target is the last thing you would want to do with a kinetic energy weapon. It is the matching speed and position that takes all the time.
[/quote]

No argument there, but If I have the delta V budget to change my orbit upon detection of your kinetic energy weapon, I avoid a collision.

[quote="Reality Check"]
The mathematics of such orbital mechanics is much more complex, but modern micro-computers can do such math nearly instantaneously.[/quote]

I even wrote a simulator that runs as a Java applet. :-) It can simulate orbits, space tethers, reentry heating and drag, and lots of stuff. It is free and at:

http://spacetethers.com/spacetethers.html

[quote="psCargile"] If you are 160 km above seal level, you are traveling at 7.8 km/s and circle the Earth once every 88 minutes. Slowing down will shrink your orbit causing you to reenter, and speeding up will put you into a higher orbit that will have a longer period and slower velocity. 500 km up gives a velocity of 7.6 km/s with a period of 95 minutes. At 10,000 km, that gives 5 km/s and a revolution of 5.8 hours..[/quote]

While an orbit can be circular, there are infinitely more orbits that are not circular. Elliptical orbits have many, many advantages over the type of circular orbit you describe above. They can pass very near the upper atmosphere at extremely high rates of speed. They can dip into the atmosphere to slow down rapidly, or skip off the atmosphere to change orbit suddenly.

The mathematics of such orbital mechanics is much more complex, but modern micro-computers can do such math nearly instantaneously.

[quote="psCargile"] Even while traveling 17,500 miles per hour in low Earth orbit, getting to the ISS ( International Space Station )takes a few days of maneuvering using phasing orbits to match the speed and position of the target. [/quote]

True, but weapons, especially kinetic energy weapons, want to do the opposite of "matching speed and position". They just need to attempt to occupy the same point in space at the same time as the target. There are literally an infinite number of possible orbits that would do that. Matching speed and position of the target is the last thing you would want to do with a kinetic energy weapon. It is the matching speed and position that takes all the time.

Physics determine what happens when two objects traveling at very high relative rates of speed attempt to occupy the same space at the same time. The result is the same, even if one of the objects is very small.

"Analysts" always hype new foreign military technology. Always have. They look at in on paper and pee themselves. Even if the threat is actually capable of penetrating the Aegis unbrella, the Air Wing unbrella, the Sea Sparrow unbrella, and then the CWIS (phalanx)unbrella, it will not be a show stopper. Your Navy, as well as the rest of your military forces, have a very long history of overcoming new challenges.
Years ago, these "analysts" saw a particular model of Russian tank and came to the conclusion that the world as we know it was about to end. As Tom Clancy pointed out, these tanks were indeed deathtraps. For the Russians. We popped hundreds of these things open in Iraq. The match-up was not even close.

Orbital combat will be governed by physics whereby the period of revolution around the Earth is associated with a certain speed, and for a satellite or spacecraft to alter their speed alters their altitude or distance from the Earth. ([url]http://www.braeunig.us/space/orbmech.htm#motions[/url]) If you are 160 km above seal level, you are traveling at 7.8 km/s and circle the Earth once every 88 minutes. Slowing down will shrink your orbit causing you to reenter, and speeding up will put you into a higher orbit that will have a longer period and slower velocity. 500 km up gives a velocity of 7.6 km/s with a period of 95 minutes. At 10,000 km, that gives 5 km/s and a revolution of 5.8 hours. Also, spacecraft and satellites can't get from one orbit to another in a straight line as gravitational acceleration forces everything to move in arcs--although, if a spacecraft or projectile weapon is traveling fast enough-- beyond the escape velocity of its orbit--it will be in a hyperbolic trajectory and close enough to a straight line. Even while traveling 17,500 miles per hour in low Earth orbit, getting to the ISS takes a few days of maneuvering using phasing orbits to match the speed and position of the target. Even at the high speeds, nothing happens fast in space.

Popular science fiction is dreadfully inaccurate concerning orbital combat. For instance, if the Battlestar Galactica is in orbit around Caprica and launches its Vipers in response to a Cylon threat, since they are all in the same orbit, the Galactica and the Vipers will be traveling at the same speed, regardless of their sizes and masses. If the Vipers accelerate away from the Galactica, depending on the direction of travel, they will either increase their orbit's eccentricity, putting them into a higher orbit, or do a inclination plane change, or a combination of both. And it could take several hours to a couple of days to reach the Cylon base star on the other side of the Caprica, that would be doing its own orbital maneuvers to thwart a rendezvous that would allow an exchange of weapons fire, the missiles too acting as separate spacecraft under the influence of orbital mechanics. Since a missile launched from an orbiting platform will behave predictably by its direction of travel and speed, a target that sees the missile coming can change its orbit to avoid destruction. Unless it's out of propellant. That's the other problem, the number of maneuvers one can make is determined by the amount of propellent available.

ICBMs could be taken out with relative ease as they aren't meant to evade, provided an orbital weapons platform in LEO is in the right position and has adequate time to react. Or you have hundreds of such platforms. We can't use geostationary orbit to launch warheads against ICBMs because we don't have the propulsion technology to get from 35,786 km to LEO in a matter of minutes. Microsatellites could do damage, but what orbit do you put them in that doesn't jeopardize you or your allies own space interests? Are the microsats maneuverable, or are they simply kinetic impactors? A wide cloud of microsats are not going to stay perched over the hostile country in LEO and they are useless in GEO. If we want to deny Iran the capability of launching ICBMs, then we would need a minefield of microsats at least as wide a Iran banding the entire Earth. Space is pretty damn huge and to cover an effective range of orbits with individually cheap microsats is still going to be costly; the field density has to be such that a rocket can't slip through--we could be talking one microsat for every 125 to 8000 cubic feet, spread over a distance several hundred miles wide, in a band much larger than the Earth's circumference. I don't think it's a practical defense shield. You simply can't deny access and use of all orbits. And there are ways to punch holes in a microsat blockade.

If there is any orbit worth denying it is geostationary orbit and beyond, as it is here were the communication, navigation, and some surveillance satellites are parked.

And for the obvious reason, microwave and laser weapons are best suited for orbital combat.

[quote="psCargile"]While spacebased munitions have the advantage of gravity boosted kinetic energy, they lack tactical immediacy due to each orbit having its own defined speed.[/quote]

Interesting conclusion. But there are a lot of variables that would have to be considered in reaching that conclusion.

For example:

1. How fast is the target relative to the spacecraft that would attack it, and,

2. How maneuverable is the target relative to spacecraft that would attack it, and,

2. How many micro-spacecraft are in how many different orbits vs how many targets can attempt to climb into orbit at the same time, and,

3. How much do a thousand micro-space craft already in orbit cost vs the cost of a thousand targets capable of climbing up the gravity well, and,

etc., etc. etc

The bottom line here is a battle ship is much slower, has much shorter weapons range and can be destroyed by a few airplanes.

Airplanes, that is craft that fly through the air at high speed ( compared to ships ) made the most expensive, and must survivable ocean based weapon system obsolete because of the cost differential, range differential, and speed differential that were all in favor of aircraft over battleships.

Any weapon system that has the same advantage over land/sea based ballistic missiles will make such ballistic missiles obsolete.

Ballistic missiles require between 10 and 30 minutes ( depending on range ) to climb up the gravity well, out of the atmosphere and reach the top of their ballistic arc, high in outer space, before falling back to earth.

Micro spacecraft cost a tiny fraction of the cost of a ballistic missile and many of them can be deployed per low cost rocket launched from a high flying airplane months or even years before any conflict.

Space is the high ground, and any country that can place enough micro spacecraft in orbit to deny the use of space to any earth based enemy will control space.

Short range Ballistic missiles, medium range Ballistic missiles, and long range Ballistic missiles all require access to space to work. The side that controls space will be able to use Ballistic missiles, the side that does not will be denied the use of Ballistic missiles.

While spacebased munitions have the advantage of gravity boosted kinetic energy, they lack tactical immediacy due to each orbit having its own defined speed.