Which is why shrapnel is sort of fragile, the quantity of shrapnel that actually enters a stable orbit is pretty small, so you are dealing with a pretty brief effect or very small odds. And whole actually stopping something is sort of hopeless, if you are making some extremely favourable assumptions about the practicality of getting armour into space, some sort of deflection design(remember that you only need to protect against a fairly narrow range of angles), possibly with reactive armour, could probably survive an impact with smaller objects. Of course, if you can get that much armour up, then you can presumably get some very large scatter bombs, but still, you are basically looking at something that works similarly to a 40mm armour-piercing shotgun. Very scary, but not completely futile to resist and very difficult to actually get into a useful position...
The idea is that your bomb is already in a stable orbit before, you detonate it. In that case, almost all shrapnel will remain in a decent orbit. After all, that's how orbits work.
And really, you don't deflect objects moving in at 15 km/s. Reactive armor will be equally useless, because reactive armor doesn't blow away the incoming projectile. Reactive armor deforms a particle, but this is a shrapnel bomb, so that doesn't matter.
And we're not looking at a 40 mm shotgun. The Mercury capsules weighted 1.4 tonnes. You're thus looking at a 1.4 ton shrapnel bomb at the very least. The fact that we don't need many complicated systems allows payload to increase dramatically.
On a second note, your armor is also going to be your heat shield, so your choice of armouring is extremely limited, and any hit is likely to result in desintegration. You could turn around your spacecraft mid-flight to use the aft as armor, and the front as heatshield, but then you have to add a significant weight in front in order to ensure that the ship remains stable on re-entry, which dramatically reduces payload.
I suspect that our automated systems are extremely primitive, probably all mechanical. So they cannot reasonably be expected to react at all to the enemy, so you need to accurately predict your enemies. Your vehicle will pretty much need to be manned until it is in space... Nothing stopping us from prioritising automation though, but it'll be a big project...
No it won't. Orbital trajectory of the bomb is strictly ballistic and perfectly predictable. Sure; the bomber can change course, but we know it's destination, and we should know it's launch trajectory, so we know where it will have to be.
Besides, shrapnel stays up there forever.
You can go around the long way...
You won't be fast enough. The only way to gain on them would be to make your orbit lower than theirs. Since they're trying to bomb us, their orbit won't be very high. Thus our orbit, in order to have sufficient speed, will have to be in atmosphere, which is untenable at such speeds.
Assume the enemy starts in low Earth orbit (altitude 2000 km*), they have a 127 minute orbital period. Now, the lowest you can be without orbital decay is 160 km, at which your orbital period is 88 minutes. Now they have to travel 1/4 of the globe, while you have to travel 3/4 (roughly). You can see where this is going.
*They have no reason to be this high. Should be at altitude of 200 km or so.
Of course, we can station forces in space to intercept any upcoming craft, but then we would need to have craft over the entire orbit, in range to pounce on an enemy within half an orbit. At that point, the range of a fighter is smaller than the range of our shrapnel cloud.
Well that is all dependent upon communication and detection.
Nope, it's dependent on orbital mechanics.
Rockets are kind of obvious, especially if you know where they are coming from. And assuming that getting mass into orbit is easier in the game, you can pack a decent supply of manoeuvring fuel and regularly reposition...
If getting mass into orbit easier, so is getting a kinetic kill vehicle. The shrapnel bomb still wins.
You simply can't beat a kinetic kill vehicle in space.
Kinetics are way too obvious and slow, you need L.A.S.E.R.s... Well, that or fighter craft, well, okay, unmanned fighter craft, but something with more autonomy than the average missile and you will almost certainly want submunitions...
First, lasers were invented only in the 1960. Secondly, lasers are much, much easier to defend against than a kinetic kill vehicle. Anything that can afford to armour itself against a shrapnel bomb will be impenetrable to a laser.
As said, fighters are largely useless due to orbital mechanics.
Shrapnel is the king of submunitions.
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