Rods from God, reconsidered

[DDE]

We all know the hyped-up weapons system:

The problem is that the average depiction of such a weapon works as follows:

1. Space station magically floats in space, where there is no gravity
2. An oversized kinetic impactor is released
3. Gravity suddenly feels guilty for being a slacker, and selectively affects the impactor
4. Impactor comes down at close-to-vertical trajectory

Meanwhile, we in the Intellectual Gaming Community know that's not how space works.

Except Project Thor was also envisioned by people who know how space works, so clearly we're missing something.

The two burning questions I see are:

• What kind of a realistic deorbit "burn" (e.g. via railgun) is necessary for maximum retention of kinetic energy on impact?
• What are the effects of the considerable lateral velocity?

[Bill Phil]

Some small solid motors might be installed to deorbit each rod.

The lateral velocity is what makes it dangerous - though it’s not as powerful as a nuclear bomb/warhead it is powerful enough to take out pretty decently sized targets. 

There was some though to using them as anti tank weapons but the accuracy required and the lack of maneuvering capability rendered that impractical.

[sevenperforce]

An operational Rod from God would place the "tungsten telephone poles" in a moderately eccentric Earth orbit synchronized to reach apogee slightly west of the probable target several times per day. They would feature a small RCS pack along with a solid propellant deorbit motor. With a few dozen of these spaced equally along the orbit, you have full target area coverage and can command a strike at virtually any time. Use RCS to line up and spin-stabilize, then burn the deorbit motor to lower your perigee low enough that your entry interface includes the target. You can also perform some inclination changes to widen the target range, since the cost of inclination changes at eccentric apogee is low. Then, kablooey.

You would, however, need a different orbit (sometimes even a different orbital plane) for each collection of rods. It is also a rather significant deorbit risk......

[Guest]

Do note that the biggest problem with Project Thor is that it just isn't that effective. Such a "tungsten telephone pole" would have an energy roughly equal to its own mass in TNT, and it would go straight through the target, probably depositing most of this energy in the ground below. This is not a WMD. In practice, air drag tends to rob you of any advantage gravity gauge gives you, and deorbiting an object of this size, not to mention orbiting it in first place, are both rather expensive. Such a weapon would have some advantages, but it's a precision "bunker buster" that's also nearly impossible to intercept. To be a precision weapon, it'd need precision guidance, and entry at that speed would make it difficult to implement, especially if we consider the plasma sheath will prevent any forward-looking sensors from being of any use.

[Guest]

I don’t think you’d need to decelerate the impactor too much if at all. You could probably just alter the orbit slightly so the perigee intersects the target. This would take minute deltaV if already in a highly elliptical orbit by making the adjustments at apogee. 

Of course what you gain in deltaV savings you lose in time with this method. In combat the windows in which you can take action can stay open briefly, making weapon systems that require to be set on target months in advance less useful.

Edited October 4, 2019 by Guest

[DDE]

1 hour ago, Dragon01 said:

Such a "tungsten telephone pole" would have an energy roughly equal to its own mass in TNT, and it would go straight through the target, probably depositing most of this energy in the ground below.

The expectation is apparently to achieve flash-vaporization velocities.

Colour me skeptical.

[Guest]

you aint launching a telephone pole worth of tungsten into orbit with any launch system made in our lifetime btw @_@

[Guest]

25 minutes ago, DDE said:

The expectation is apparently to achieve flash-vaporization velocities.

Colour me skeptical.

In that case, and we're looking at about 3km/s, even with a low drag design. My feeling is, it'd punch a hole. APFSDS rounds travel at a bit less than 2km/s, and they do just that. 

Just now, Dale Christopher said:

you aint launching a telephone pole worth of tungsten into orbit with any launch system made in our lifetime btw @_@

Actually, you are. Each penetrator was supposed to weight about 11 tons. A Titan IV could boost one, plus a hefty propulsion bus, into LEO. Tungsten is heavy, but not that heavy.

[Guest]

11 tons of tungsten does not a telephone pole make

Residential telephone poles around these parts start at 10m tall above ground. That would have to weigh a hell of a lot in tungsten

Edit* my bad seems like a telephone pole made of tungsten would be roughly 3m3 in volume = approx 58 tons. so i guess you could launch one (i had an extra zero in my guestimate somehow)

Edited October 4, 2019 by Guest

[kerbiloid]

Thinking about the rawds-of gawds in KSP/RSS context, I made a conclusion that this project is actually a full bull, unless you push the impactor by nuke, like a single-use orion.

I.e. I believe it should be a separate satellite with one impactor, one small nuke, and a crashable dampener in between. Actually, it's absolutely like an Xray laser but with impactor instead of the bunch of parallel rods which generate the parallel bunch of beams.

[DDE]

3 minutes ago, kerbiloid said:

Thinking about the rawds-of gawds in KSP/RSS context, I made a conclusion that this project is actually a full bull, unless you push the impactor by nuke, like a single-use orion.

I.e. I believe it should be a separate satellite with one impactor, one small nuke, and a crashable dampener in between. Actually, it's absolutely like an Xray laser but with impactor instead of the bunch of parallel rods which generate the parallel bunch of beams.

Yeah, the idea of just using the gravity gauge is pretty ridiculous. The only two options are a massive ortillery gun that depends on cheap solar energy, or actually dropping the orbit bit altogether and use a conventional-tipped ICBM.

[Guest]

16 minutes ago, Dale Christopher said:

11 tons of tungsten does not a telephone pole make

Residential telephone poles around these parts start at 10m tall above ground. That would have to weigh a hell of a lot in tungsten

A USAF report states 6.1m long and 0.3m (30cm) wide. That easily qualifies as a telephone pole. This particular report had rods with a mass of about 9 tons, which checks out. Here's a hint: do yourself (and everyone else) a favor and do some research before you say something stupid. Rockets, turn out, can lift that much, and even if you made it the size of your local telephone poles, there is (or was, at the time) a lifter than could take it to LEO. I'll leave the elementary school level calculations involved in finding that out to you.

1 minute ago, DDE said:

Yeah, the idea of just using the gravity gauge is pretty ridiculous. The only two options are a massive ortillery gun that depends on cheap solar energy, or actually dropping the orbit bit altogether and use a conventional-tipped ICBM.

Which is why Thor was never launched. A conventional artillery rocket loaded with good old TNT works just as well if not better.

[kerbiloid]

When just a rod masses 11 t, plus systems, plus fuel, then what rocket should be spend to put it in high orbit?..
Every such rod of several tens tons of TNT equivalent should use a rocket as heavy as a whole pack of ICBM with tens of nuclear warheads.

But if put a sat with such impactor in orbit, and push it with a mini nuke, it will have hyperbolic velocity and either pierce the atmo at arbitrary angle, with no side maneuvers, or hit an orbital station.
More of that, it will be by default an interplanetary impactor, so you can hit Mars.
In proper direction it will actually be an interstellar impactor.

Another case: release rods from interplanetary ship without (or with minor) acceleration, so they will hit a Martian fortress before your dropships land.

[Guest]

Just now, kerbiloid said:

When just a rod masses 11 t, plus systems, plus fuel, then what rocket should be spend to put it in high orbit?..
Every such rod of several tens tons of TNT equivalent should use a rocket as heavy as a whole pack of ICBM with tens of nuclear warheads.

Again, do remember the ultimate fate of project Thor. This, undoubtedly, was part of the reason. You can lift a rod+systems into a decently ecliptic orbit using a Titan IV or the Space Shuttle (the latter could possibly carry two rods, or three 9T ones). You can also use a Titan ICBM to lob a 9MT nuke at the enemy.

Quote

Another case: release rods from interplanetary ship without (or with minor) acceleration, so they will hit a Martian fortress before your dropships land.

That is a more solid way of doing this, especially on Mars, which doesn't have nearly as much of an atmosphere problem. Anything without atmosphere would be very vulnerable to orbital bombardment. 

[Guest]

Edits, especially after someone else responded, are generally not very effective at being noticed. I wrote my reply before you did the edit. 

[Nuke]

i think the idea was that the satellite would be in a highly eccentric orbit. so only a small kick motor would be needed at appogee to intersect the earth. this also buys time for the rod to accelerate. however i think the real exaggeration is the yield of the impact, something achievable with more conventional ordinance. 

[kerbiloid]

54 minutes ago, Dragon01 said:

You can lift a rod+systems into a decently ecliptic orbit using a Titan IV or the Space Shuttle (the latter could possibly carry two rods, or three 9T ones). You can also use a Titan ICBM to lob a 9MT nuke at the enemy.

Titan IV is as heavy as ~6 Titan ICBM.

***

And a purpose of such rods is still unclear.
If hit a nuclear country, they can react with mass launch.
If hit a non-nuclear one, why these efforts.

Hundreds of invisible deorbit burns at well-known satellites?

Edited October 4, 2019 by kerbiloid

[mikegarrison]

It's just one of the many, many ideas that sounds better* than it really is.

* assuming you allow for "better" to mean "able to kill people"

[sh1pman]

What kind of accuracy would these rods have? 

[Gargamel]

Some posts have been removed after a spontaneous outbreak of accidental bickering.   Just remember to play nice with each other, and to tip your waiters.   

[Nuke]

2 hours ago, sh1pman said:

What kind of accuracy would these rods have? 

same kind you get with any other reentry vehicle. fins could allow for last second course correction but you would probably be dependant on an inertial reference since getting targeting data through the wall of plasma is going to be difficult. laser guidence might be possible if you use a wavelength not being emitted or blocked by the plasma (do those even exist). the target would have to be laser designated from another satellite over the target area at the time of reentry. i don't know if machine vision systems would be reliable enough for ordinance delivery, but if a human can guide the weapon visually (assuming it had a cockpit and a kamikaze pilot) then you could probably train a neural net to do it. 

Edited October 5, 2019 by Nuke

[Nothalogh]

4 hours ago, kerbiloid said:

I believe it should be a separate satellite with one impactor, one small nuke, and a crashable dampener in between. Actually, it's absolutely like an Xray laser but with impactor instead of the bunch of parallel rods which generate the parallel bunch of beams.

This is the Cold War practical lunacy I come here for

[magnemoe]

An bomber version of starship would be useful. An 100 ton long rod penetrator  hit pretty deep. 
Yes you would need to screw it together in space but this is not an major issue. 
Main purpose would be to get fools to dig deeper to bury their dark secrets. 
 

[Spacescifi]

36 minutes ago, magnemoe said:

An bomber version of starship would be useful. An 100 ton long rod penetrator  hit pretty deep. 
Yes you would need to screw it together in space but this is not an major issue. 
Main purpose would be to get fools to dig deeper to bury their dark secrets. 
 

 

Haha... there are no secrets. Since all of them boil down to abuse of other lives or themselves or both. Or at least the attempt.

Edited October 5, 2019 by Spacescifi
Attempt

[kerbiloid]

4 hours ago, Nuke said:

same kind you get with any other reentry vehicle

Several kilometers accuracy is too low for a 0.1 kt yield.

4 hours ago, Nuke said:

fins could allow for last second course correction

As the fins get effective somewhere at ~10 km, and it moves at ~10 km/s speed, it has about a second for the last corrrection.
And as you say, it needs a guidance system which works not perfect in a cloud of plasma inside a 10 km/s heat-protected nose. Pershings were just ~1.5 km/s fast, their nose was much thinner.

The best of the best inertial guidance of Peacekeeper is ~100 m accurate, while cruise missiles and Pershings with radars have ~10..20 m.

So, imho all corrections should be orbital.

4 hours ago, Nuke said:

if a human can guide the weapon visually (assuming it had a cockpit and a kamikaze pilot)

Riding the rod is true Kerbal, we need this in KSP.

4 hours ago, magnemoe said:

An bomber version of starship would be useful. An 100 ton long rod penetrator  hit pretty deep. 

An Orion-derived flechette booster with multiple rods.
Wait... KSP-2...

Edited October 5, 2019 by kerbiloid