The rods from God’s idea is insane and won’t work.
We had this back when the Russians announced they were going to drop conventional ordinance from space, and everyone pointed out that they would be lucky to hit the right continent, let alone Ukraine. In order to make this actually work, you would have to have an active aiming system. Which you know, is a missile.
this ignoring the tiny little issue of overheating during reentry
Well that’s why one of the proposed materials is tungsten, the problem with that being that tungsten is a bit heavy.
heavy is one of the advantages though. kinetic mass in a smaller morr aerodynamic package
Gram of tungsten has a mass of something like 15 grams
I’m referring to Rogozhin’s idea of putting FAB-500s as a payload, boompaste doesn’t tolerate such conditions
A gram of tungsten weighs 15 grams?
That’s not… how… weight works.
Gram of tungsten has a mass of something like 15 grams.
Yeah, probably not.
19.3 g/ cm3
The launch platform can aim it and use math to account for gravity, the atmosphere and all that jazz to hit the target at least close enough. Just like we already do to safely crash/burn up space debris.
at least close enough
To whose standards exactly? Dick Cheney’s?
No, they can’t. The atmosphere is an unknown state, different temperatures, different densities, different wind directions, none of which can be known ahead of time. That’s why weather forecasting is always approximate. You get a percentage chance that it’ll rain. You don’t get a definite time stamp with 100% accuracy.
We cannot predict atmospheric disturbances to the level necessary to make this a practical system. When they burn up space debris they do it “somewhere over the middle bit of the Atlantic” That’s about the level of definition you get. It’s not accurate at all.
From a purely physical point of view, is that realistic?
If all of its energy is kinetic, it means that the energy must result from it’s potential energy+any fuel it is propelled with. Ignoring air-friction and terminal velocity for free falling objects, that means that still the energy of a nuclear weapon is required to bring this thing up into space, or stored as fuel for its propulsion.
So unless the projectile is assembled in space, any rocket bringing it into space will contain at least the energy of a nuclear warhead. Gotta be a very nervous launch, knowing that any failure will result in a fire with the energy of a nuke.
A lot of the energy comes from orbital speeds.
The Hypervelocity Rod Bundles project proposed 6,1x0,3 m tungsten rods, weighing about 8200 kg, impacting at about 3000 m/s, meaning about 42 GJ of energy per projectile [wikipedia].
The weakest recorded nuke, the Davy Crocket Tactical Nuclear Weapon, is estimated at about twice that (84 GJ), and the largest, Tsar Bomba, at about 3 000 000x the yield (210 PJ).
That’s their point, how do you get such a heavy thing to orbital speed without spending all that energy? You can’t unless you build it from materials harvested in space.
Oh, I apologise, I suffered some curse of knowledge there, the answer is time.
A blast is a release of energy over a short time, the whole point of building weapons is to store and handle energy in safe amounts over time.
Global electric energy consumption is about 200 PJ a day, approximately the same as the Tsar Bomba, but there’s no risk for a huge explosion neither when you incinerate trash or turn off the AC.
Because time.
Although we could explode a nuke and propel things ballistically, it turns out it’s a lot easier to use rockets. A rocket, although carrying frightening amounts of fuel and exploding spectacularly when it fires wrong, has several safeguards to not expend all that fuel at once. And also gives the opportunity to correct course along the way.
Now imagine that the same amount of energy has been expended many many many times over the course of the space era, and almost any mass in orbit has serious potential for damage.
For example, the MIR was 130 tons, orbiting at about 7,8 km/s, for a kinetic energy of 4 TJ, and another 235 GJ of potential energy. Totalling about a tenth of Little Boy that levelled Hiroshima.
Edit: Specifying and correcting the global energy consumption.
One of the things that’s stuck with me during my time on Lemmy is someone remarking that the only difference between a battery and a bomb is how controlled the release of energy is. Having seen what happens when you puncture a LiPo battery, I believe it 😰
Right, and tungsten rods are dangerous because they don’t slow down and burn up in the atmosphere like most spacecraft do (like you said, spreading out that energy over time and space). As long as you can deorbit them accurately, they are devastating since they convert the entire orbital potential energy into surface kinetic energy all at once. (Oddly, orbital potential energy and surface kinetic energy are the same thing, just from different points of reference.)
Agreed. On all points.
Moreover, the Tungsten rods are quite dense and thus small, and thus very hard to spot on radar or hit with countermeasures.
The problem I remember is that it is expensive to get the rod up there in the first place.
Also every other nation would hate us and make jokes about the collective small penis of the US state.
If anyone wants some good sci-fi, I recommend The Expanse, both the books and the show. They make great use of kinetic impactors, especially Nemesis Games.
What about the Jewish Space Lasers that MTG said started the wildfires?
Magic The Gathering has a lot to answer for.