Satellites in Space

[publiusr]

The nuclear pulse Orion (not the current Apollo style capsule of the same name) worked better in Earth's atmosphere due to there being a shock wave to harness.

An Orion pulse unit would be good against an asteroid in that, unlike a gravity tractor that means you have a long Rosetta style matching trajectory before you can even begin a mission.

The pulse unit would be about the same size and shape of the copper impactor disk used by the Deep Impact mission--which only needed a fly-by trajectory.
http://up-ship.com/blog/?p=18971

 

[Metryq]

An Orion pulse unit would be good against an asteroid in that, unlike a gravity tractor that means you have a long Rosetta style matching trajectory before you can even begin a mission.

Huh? I get what you're saying about the Orion engine, but the above sentence does not make grammatical sense. Are gravity tractors made by John Deere or Caterpillar?

 

[Crazy Eddie]

I'm guessing you don't know anything about orbital mechanics. While a satellite can be shifted to a new orbit, this "space mines" idea would be terribly inefficient.

A nuclear powered satellite would not have such a problem. When the space mine uses it's nuclear power supply to increase the effect of the explosion, that explosion would have a large radius. Even if it does not physically cause the destruction of the enemy satellite, it could still fry the electronic circuits of the target to make it dysfunctional.

This just demonstrates that you also don't know much about nuclear detonations in space. A nuclear explosion in space is not that big, most of the energy is radiated as light and heat.

Actually, most of it is radiated in soft x-rays and infrared radiation, the latter of which is mainly emitted from the vaporized bomb casing itself. Because there's no air to absorb those x-rays (and produce the fireball you'd see in an airburst) the radiation burst falls off at the square of the distance, which means that any object within a certain radius will be superheated and/or vaporized by the radiation pulse.

Depending on the yield of the warhead, this could be anywhere between 2 and 10km. Far less than it would be in an atmosphere, but for satellites even a smaller burst of soft x-rays would be enough to fry their electronics and knock out their solar arrays and power systems.

-- This has been another random act of science --

 

[sojourner]

You would still need to target individual satellites at that radius. not very effective use of nuclear warheads considering the number needed to disable a good portion of the satellites in orbit.

 

[Metryq]

not very effective use of nuclear warheads

Well, we could always salt the ground where the enemy grows their satellites...

(That's what the SALT talks were all about, right? No? Pretzels, anyone? Beer summit? I think my train of thought has been derailed.)

 

[Crazy Eddie]

You would still need to target individual satellites at that radius. not very effective use of nuclear warheads...

THAT depends on where you choose to engage them.

For example, if you deliberately knock out all of America's communication satellites when they just happened to be directly over the continental United States and/or U.S. military bases, not only would you knock out the satellites, the resulting EMP would also zap half the computers in the country.

 

[Metryq]

the resulting EMP would also zap half the computers in the country.

"The name is Plissken!"

 

[sojourner]

You would still need to target individual satellites at that radius. not very effective use of nuclear warheads...

THAT depends on where you choose to engage them.

For example, if you deliberately knock out all of America's communication satellites when they just happened to be directly over the continental United States and/or U.S. military bases, not only would you knock out the satellites, the resulting EMP would also zap half the computers in the country.

Comsats are in geosynchronous orbit. They don't wander around. They're either over the U.S. or not. Most likely not since the whole point of a comsat is to provide signals to the other side of the planet. The other thing is that geosynchronous orbits require an altitude of 22,500 something odd miles. Would an EMP have the range to take out both a satellite at that altitude and whatever is on the Earth below it?

Remember, space is BIG.

 

[publiusr]

An Orion pulse unit would be good against an asteroid in that, unlike a gravity tractor that means you have a long Rosetta style matching trajectory before you can even begin a mission.

Huh? I get what you're saying about the Orion engine, but the above sentence does not make grammatical sense. Are gravity tractors made by John Deere or Caterpillar?

A gravity tractor is a spacecraft orbiting an asteroid and using its own gravity to pull the asteroid off couse my thrusting away from it slightly.

Not much more purchase than a gnat pushing a semi, but that's the idea. I'll take the nuke.

Comsats are in geosynchronous orbit. They don't wander around. They're either over the U.S. or not.

Yes and no. Such comsats are are over the equator. The USA is below them, down and to the northeast. From our vantage point, the comsat is up and to the southwest. That is why most if not all dishes are pointed in the same direction.

Now in terms of wandering, geosynch comsats do wander a very little bit--a halo orbit in a figure eight. http://en.wikipedia.org/wiki/Analemma

There is a difference between geosynchronus and true geostationary.
http://en.wikipedia.org/wiki/Geosynchronous_orbit
http://en.wikipedia.org/wiki/Geostationary

 

[sojourner]

Yes, thank you for splitting those hairs.

 

[Crazy Eddie]

You would still need to target individual satellites at that radius. not very effective use of nuclear warheads...

THAT depends on where you choose to engage them.

For example, if you deliberately knock out all of America's communication satellites when they just happened to be directly over the continental United States and/or U.S. military bases, not only would you knock out the satellites, the resulting EMP would also zap half the computers in the country.

Comsats are in geosynchronous orbit. They don't wander around.

Civilian satellites, yes. A surprising number of military datalink satellites are still operating at lower altitudes (I'm not entirely sure why).

Would an EMP have the range to take out both a satellite at that altitude and whatever is on the Earth below it?

Hard to say, because the EMP is generated by the interaction of the warhead's radiation with the Earth's ionosphere and not by the bomb itself. The Starfish Prime tests demonstrated that the EMP actually gets STRONGER the higher up you go; an airburst at 100km produces an EMP that covers a smaller area and is less intense than an airburst at 500km or higher.

But nobody's ever tested a nuclear weapon at intermediate/satellite orbits above 5,000km. Could be the radiation pulse is too weak to produce a significant EMP, or it could create reactions in the Earth's magnetic field that fries all of our brains like so many eggs.

 

[publiusr]

I don't think it would be that bad. I know here is this idea that early on people thought shooting off the first nuke down here would ignite the atmosphere, or something--but, as Sagan would say, we are star-stuff. There is another word for that though--stellar fallout. Once a star "burns" down to iron, that's all she wrote. It collapses. That collapse allows one final forging of elements allowing for heavier elements (that and neutron star collisions for gold it seems)

So we are nuclear ashes. Matter is tough. Now if nature allowed all these over-unity devices the conspiracy-believers think are out there--forget shooting off a nuke--I'd be scared to light a match.

In terms of satellites, it looks like they keep getting bigger:
http://www.space-travel.com/reports...most_sophisticated_telecom_satellite_999.html

http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385&plckPostId=Blog%3A04ce340e-4b63-4d23-9695-d49ab661f385Post%3Aa7cb6aee-1c4e-406a-a022-7b7fb65dee07

Optics, the size of antennas, all these limit the real utility of small sats, which just clutter up LEO.

There have been even larger concepts: http://www.astronautix.com/craft/globis.htm

The largest was the orbital antenna farm (OAF) called for by Director of COMSAT Labs, Burt Edelson:
http://www.permanent.com/space-products-and-services.html


Large antennas allow for better reception, but I think we still are addicted to the Smaller faster cheaper mantra of Goldin.

Ironically smaller circuits in some ways led to larger comsats anyway.


Early on, Clarke wanted manned communication platforms, not unlike--I hate the acronym-- OAF, thatwere large affairs. The idea is that you re-use the dish and solar power systems, but just slide in and out different breadboards.


The Soviets just used off the shelf electronics and made big pressurized, air-conditioned housings for their early systems. The electronics and early nukes were heavy, allowing their space advocates to say--don't shrink the payload--make the rocket bigger.

They still make the Vostok hull to this day, it is just used for research craft like FOTON
http://en.wikipedia.org/wiki/Foton_(space_programs)


Our warheads were small, and our sats were small. So our craft had to be space-rated...rad-hardened..vacuum proof...shock-proof...


Now simple solid state systems, while still better than room sized computers like ENIAC what with vacuum tubes, were rather hardy due to their primitive natures.

Early integrated circuit chips didn't have a lot too them, and only a hadfull of people worked with computers on the ground.


But once microchips were used in numbers down here--a funny thing happened. Computers here evolved faster than what could be put in space. By the time the 486 was space-rated, it was already obsolete. I think it takes eight transistors to hold one bit of data with authority IIRC. Now everyone down here has faster computers than many systems in space.Asia-Pacific uses who don't have fiber-optic trucks or other land-line infrastructure demand more and more data.


So comsats have gotten larger, not smaller. Since Russian rockets were already over-powered, they picked up the slack. Ariane 5 was going to launch the Hermes, and was considered overlarge. Now, it straines a bit and had to be up-dated with the ECA and other life-extensions. Musks rockets are overpowered with regards to EELVs, but that allows him more payloads.

Now some comsats have had to use electric drives since their hydrazine thrusters became stuck, so there is a trend towards all electric propulsion now, and that allows a lower "wet mass" as it were. But there are still adherants to the cubesat movement. I on the other hand think we need to embrace the gigantism, and go farther, with smaller numbers of larger, perhaps shielded systems.


One more note. I rather like primative electronics. To me, the circuits on the viking spacecraft are about what any spacecraft bus needs. Not as sensitive as some of todays circuits, but smaller than Apollos. Some happy medium needs to exist for hardy systems that can last. Voyager seems to be doing quite well after all.

 

[publiusr]

Some other large concepts
http://arsastronautica.com/article.php?news_id=4

Dwayne Day talks about satellites that "would have 300-meter diameter dishes"
http://www.thespacereview.com/article/1691/1