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Message Subject Rods from Orbit
Poster Handle darth
Post Content
Dan Bongino, who is normally totally reliable, linked to an article about penetrators from space:

[link to www.wearethemighty.com (secure)]

However, their math is off. A 20 foot long, 1 foot diameter rod of pure Tungsten will weigh NOT 24,000 lbs. as stated, but about 180,000 pounds! The Specific Gravity of Tungsten is 19.25, therefore, a cubic centimeter of the metal weighs 19.25 grams. Incredible density plus very high melting point.

We would need a heavy lifter to get even one of these on orbit which makes it a very expensive weapon system.

However, the rod could be much smaller. Yeah, a twenty footer weighing 90 tons would be great for attacking deep underground structures, but much smaller rods could be used for targets on or near the surface.

IIRC, each pound of material coming in at 7 km/sec. has kinetic energy equivalent to 28 lbs. of TNT. In other words, a 100 lb. rod would pack the punch of a 2800 lb. bomb. Somebody please check my maffs!

Back over 30 years ago there were open source papers on using windows on the front of hypersonic projectiles so that the missile or bomb could steer itself directly to the target, even a moving target like a truck. The windows were made out of gem material and sometimes cooled to withstand the high heating rates.

A cheaper alternative is to simply put into orbit reentry vehicles like we use for nukes now and fill them with either Lunar or asteroid soil. It's the MASS that makes the weapon effective. That mass would be far cheaper than any boosted from Earth.

Space based penetrators would work best if stationed in highly elliptical orbits. At apogee (the top of the orbit), very little energy or delta V is required to make the penetrator hit any point on the globe. It would take longer to arrive at the target than if stationed in low Earth orbit but be more versatile in targeting. It would take a lot of energy to get a low earth orbit vehicle very far off its orbital track.

In case you all are not aware, most of the Chicom leaders are ENGINEERS and they know full well that off-world resources would make dandy weapon systems.

All the more reason we have to control the High Ground.

Ad astra

P.S. For those thinking that the Nashville attack was a DEW, the amount of energy required would be mind boggling. Most lasers are not very efficient and such a laser shot would require many, many megajoules of energy.

Lasers from space COULD take out high altitude aircraft, other satellites, or nukes in space. However, hitting something at ground level would lose a lot of that energy traversing the atmosphere. Probably could fry an enemy though!

Note that I grew up reading SF with my slide rule in my hand, so I naturally ended up working on Star Wars systems.
 Quoting: darth


What accelerates the rod to 7km/sec that’s 25,200km/hour. Gravity alone would not do this due to friction? Help me understand this!
 Quoting: Anonymous Coward 79772691


YES, gravity alone does this.

Achieving low Earth orbit takes over 7 km/sec. Getting to a high orbit can take nearly 10 km/sec.

That potential energy goes into the projectile when the orbit is diverted to one that impacts the Earth.

YES, there is air friction, but that is why a rod shape works. Low cross section = less air drag.

For example, nuke RVs can retain about 6 km/sec. when they hit the ground. They are usually cone shaped to maintain accuracy.
 
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