> To fly Orion you have to put hundreds of nuclear explosives in orbit and pinky-swear that you're not going to use them to obliterate your enemies.
To reiterate berntb's point: Every nation who has the ability to do this already has ICBMs that can deliver nukes anywhere on the planet in 20 minutes. So what difference does this make?
From a strategic point of view, what's the difference between building on Mars and building it in orbit? Obviously there is a difference because the hostile faction has to seize control of it and move it to Earth, but once they do that, the calculation becomes the same. Do you commit to obliterating them the second they start moving it to Earth?
Best case scenario, Mars is 55 million kilometres from earth. Even using a ridiculous engine going full blast the whole way (in which case your payload will probably disintegrate when it hits the atmosphere) you won't get the transfer time under a month. If you want to actually deliver your payload in a useful manner you'll need twice that at the very least. 2+ months is a long lead time, and the engine you'll need will make the craft impossible to miss.
What's the difference to building it in orbit? Building it in earth orbit you're dropping it from under 500km and your assembly makes 10~20 orbits a day, you can deliver it quickly at pretty much any time.
The former allows countermeasure, the latter not really.
I'm talking about just flying the entire Orion ship to Earth, loaded with propellant bombs. Sure, you can try to take it out during the journey, but that may be complicated by it being the highest g ship in existence for the Mars-Earth distance. Once/if it arrives, you have the same strategic problems you have if you build it in orbit.
> I'm talking about just flying the entire Orion ship to Earth, loaded with propellant bombs.
Er… yes?
> Sure, you can try to take it out during the journey, but that may be complicated by it being the highest g ship in existence for the Mars-Earth distance.
That's not really a complication, it's still taking months to make the trip, and while it might be "the highest g ship in existence" that's linear acceleration, it's not a nimble ship performing a tailside in space to avoid projectiles.
> Once/if it arrives, you have the same strategic problems you have if you build it in orbit.
With the pretty damn big difference that you've had several months head start knowing the think was incoming at high speed instead of it just dropping of your head more or less instantly.
Since Orion doesn't need to accelerate constantly, it's in principle quite possible to turn it and fire bombs in the direction of any interceptor, and the thick pusher plate makes it actually pretty durable from some aspects. What happens when two Orion ships duel, I don't know, but shooting it down isn't quite as simple as for most other spacecraft.
If you're crashing it into the atmosphere you're not delivering anything, the ship and its payload will just disintegrate, possibly bouncing back in the process. Even if the payload does detonate on impact, the only purpose an explosion at atmospheric boundaries would have would be EMP.
Indeed, I didn't understand why you thought I would suggest something pointless. I wasn't suggesting it.
If you want to argue that crashing into the atmosphere would be an inevitable result of the trip, okay, but I don't understand what else it would have to do with my initial comment.
> If you want to argue that crashing into the atmosphere would be an inevitable result of the trip
That's not what I'm arguing FFS, I'm saying that'd be the result of going with the fastest possible trip, which would still leave the target significant time to set up countermeasures.
Here's the rest of the paragraph of my original answer since you apparently stopped at the first period:
> If you want to actually deliver your payload in a useful manner you'll need twice that at the very least. 2+ months is a long lead time, and the engine you'll need will make the craft impossible to miss.
The point is that no matter how you slice it, "the difference between building on Mars and building it in orbit" is the target gets a warning several months in advance in the former case, a few minutes or seconds in the latter. One gives ample opportunity to set up and deploy countermeasures, the other not so much.
Because there's no way you'll be able to detect the launch and deploy your countermeasures, even assuming said countermeasures actually work which is unlikely: it's doubtful we can counter ballistic missiles as-is, a payload starting from orbit can launch much closer to the target (rather than half a world away) and is not fighting gravity for half the trip.
To reiterate berntb's point: Every nation who has the ability to do this already has ICBMs that can deliver nukes anywhere on the planet in 20 minutes. So what difference does this make?