Crashing ships as weapons

[BwapTED]

Canonically, M-Drives don't work past 1000 diameters. (See T4 & FF&S2)

Marc seems to waffle a bit on this, but it's a reasonably good limiter to the destructiveness.

1 Do you think M drives not working past 1000 diameters eliminates or nearly eliminates the near-C rocks of doom/ suicide run planet-killer attacks? Or just makes them somewhat more difficult?

2 What do you think about all gravitics, period, not working past 1000 diameters? What would that change about warfare, trade, system security, etc?

3 Do your answers change if you assume that the M drive is some kind of torch-ship/fusion rocket that relies on gravtics to create a fusion reaction, rather than a reaction-less gravitic drive?

 

[AnotherDilbert]

1 Do you think M drives not working past 1000 diameters eliminates or nearly eliminates the near-C rocks of doom/ suicide run planet-killer attacks? Or just makes them somewhat more difficult?

The Sun has a diameter of ~1.4 Gm (million km), a thousand times that is 1.4 Tm so you can accelerate within a radius of 1.4 Tm of the Sun.

If you transect the available sphere around the Sun, avoiding the inhabited bits in the centre you might have 2 Tm to accelerate.

D = At²/2 or 2D/A = t² = 2 × 2×10¹² / 60 = 6,7 × 10¹⁰ => t ≈ 258 ks ≈ 72 h.
V = At = 60 × 258000 = 15 000 000 m/s = 15 000 km/s = 0.05 c.

You can't really get to relativistic speeds with limited space for acceleration.

Still, 15 000 km/s is quite fast...

2 What do you think about all gravitics, period, not working past 1000 diameters? What would that change about warfare, trade, system security, etc?

Commercialy very little, militarily quite a lot.

In the Solar system everything outside Saturn is more than 1000 diameters from the Sun, so basically inaccessible by M-drive. That means that Uranus and Neptune are basically separate jump destinations in the same hex as Earth. As gas giants they provide a convenient refuelling source and makes for excellent naval bases.

In effect outer system gas giants would be their own separate systems.

 

[BwapTED]

The Sun has a diameter of ~1.4 Gm (million km), a thousand times that is 1.4 Tm so you can accelerate within a radius of 1.4 Tm of the Sun.

If you transect the available sphere around the Sun, avoiding the inhabited bits in the centre you might have 2 Tm to accelerate.

D = At²/2 or 2D/A = t² = 2 × 2×10¹² / 60 = 6,7 × 10¹⁰ => t ≈ 258 ks ≈ 72 h.
V = At = 60 × 258000 = 15 000 000 m/s = 15 000 km/s = 0.05 c.

You can't really get to relativistic speeds with limited space for acceleration.

Still, 15 000 km/s is quite fast...



Commercialy very little, militarily quite a lot.

In the Solar system everything outside Saturn is more than 1000 diameters from the Sun, so basically inaccessible by M-drive. That means that Uranus and Neptune are basically separate jump destinations in the same hex as Earth. As gas giants they provide a convenient refuelling source and makes for excellent naval bases.

In effect outer system gas giants would be their own separate systems.

I wonder how T4 deals with outer system planets, then, if the 100 diameters limit on M drive was a feature of both systems?

Micro-jumps?
Not addressed?

I wonder about the effects on piracy.

 

[whulorigan]

What do you think about all gravitics, period, not working past 1000 diameters? What would that change about warfare, trade, system security, etc?

I wonder how T4 deals with outer system planets, then, if the 100 diameters limit on M drive was a feature of both systems?

Micro-jumps?
Not addressed?

Remember, it is not that they do not work past 1000 diameters, but that they drop to 1.0% efficiency past 1000 diameters (and this is explicit in both T4 & T5). Even a 1.0% efficiency acceleration can generate quite a bit of velocity over time. It is just that Jump would be much more practical.

 

[whartung]

I addressed the 1000 diameters using the stars as the gravity source earlier in this thread.

Essentially, it's not difficult to design a ship for this purpose, to wit if you want to accelerate enough, you can jump several times to where you can pass the same (or even a different star) several times, letting you build more and more acceleration before you jump in to your target.

Helps to have a friendly system to do it in. Helps to have a suicidal crew (assuming you don't simply automate it), since it will be very difficult for them to slow down if they want to get off before impact. Because by it nature, not only do you need the gravity well to accelerate the M-Drive, you need it to decelerate as well.

It could probably be done with a large ship. 1000+ tons, with a special life boat that's all jump drives and fuel and power bars that the crew leaves the larger ship with.

I mean, if you're going to do this, you're not going to take some off the rack scout ship. Do it right, build something specific. What's a few million Cr for a planet killer.

 

[AnotherDilbert]

Essentially, it's not difficult to design a ship for this purpose, to wit if you want to accelerate enough, you can jump several times to where you can pass the same (or even a different star) several times, letting you build more and more acceleration before you jump in to your target.

That does not help all that much. In my example above the first acceleration pass gives 15000 km/s, the second pass gives an additional 7000 km/s, and the third pass less than 5000 km/s, since each pass is faster so the ship has less time to accelerate.

Since each pass consumes at least 10% of the ship for the fuel for the micro-jump, you can't do all that many passes.

 

[BwapTED]

What about:

1 M drives are not nearly so powerful.

They are also not reaction-less, but something like atomic rockets, fusion torches, HEPLaR.

It takes a considerably longer time to reach 100 diameters. I mean days or weeks, not hours. Of course the exact travel time depends on a number of factors.

2 Jump is near-instantaneous.
You still retain vector.

Consequences?

Yes, I know this is definitely ATU territory.

 

[Condottiere]

Approaching the transition point at speed should increase the chance of a misjump.

Since the point of astrogation is to calculate the optimum point for said transition.

 

[mike wightman]

What about:

1 M drives are not nearly so powerful.

They are also not reaction-less, but something like atomic rockets, fusion torches, HEPLaR.

It takes a considerably longer time to reach 100 diameters. I mean days or weeks, not hours. Of course the exact travel time depends on a number of factors.

2 Jump is near-instantaneous.
You still retain vector.

Consequences?

Yes, I know this is definitely ATU territory.

If you want to use fusion torches, atomic rockets etc fuel use has to go up. Swap jump fuel % for maneuver fuel, and limit drives in delta V by fuel carried.

Move the jump point so it takes a week to reach it and make jumps instant and you maintain the trade system.

In such a paradigm you could remove artificial gravity and rely on constant thrust or spin habitats for pseudo-gravity - instant Traveller harder sci fi without having to rip up the whole setting if you don't want to.

 

[mike wightman]

Approaching the transition point at speed should increase the chance of a misjump.

Why? Everything is in relative motion even if you are stationary with respect to the planet you departed.

Since the point of astrogation is to calculate the optimum point for said transition.

I think you mean the generate program or the course cassette - navigation/astrogation may help but the jump program still requires generate or a course cassette.
It's why you need a supercomputer instead of an i-pad...

 

[whartung]

So, I got my napkin and magic marker out and did some fiddling.

Given a star the size of the Sun to work with for the example, a 6G ship making 3 passes will accelerate to ~34,000 km/s, or roughly 0.1C. It accelerates for about 157 hours. I did not compensate for any additional acceleration or drag caused by the star itself.

That was my initial estimate.

That does not help all that much. In my example above the first acceleration pass gives 15000 km/s, the second pass gives an additional 7000 km/s, and the third pass less than 5000 km/s, since each pass is faster so the ship has less time to accelerate.

I got 34000, you got 27000. not dramatically different.

for a kinetic energy of about 10 000 000 × 17 000 000² / 2 ≈ 1.4 × 10²¹ J ≈ 360 gigaton.

So, following your math: 10 000 000 x 34 000 000^2/2 = 5.78E21.

Now, for contrast the Dinosaur Meteor/Comet is estimated at 1E23 Joules.

So, can't say if one of these ships is "enough" of a hit or not.

Thankfully, for only a few million CR more, you can make another!

 

[kilemall]

Big concern then would be ramming into orbital/space facilities, no atmo to buffer or burn up (but no pressure wave either).

 

[Condottiere]

While most aspects of Traveller technology tends to be kept deliberately vague, I would assume if you miss the optimum jump point, the transition is more likely prone to a misjump.

You have to charge up the capacitors and the astrogator brew a cup of tea to the right temperature, for the Captain to drink at the correct moment.

Kinda hard to do while pressed against the bulkheads during overdrive.

 

[AnotherDilbert]

That was my initial estimate.

Sorry, I didn't read the entire thread.

I got 34000, you got 27000. not dramatically different.

Agreed, not significant.

It seems you used the entire diameter of a 1000 d sphere around the star to accelerate, unfortunately that line passes through the star so I rounded the distance down.

 

[whartung]

It seems you used the entire diameter of a 1000 d sphere around the star to accelerate, unfortunately that line passes through the star so I rounded the distance down.

Yea, I figured you would just fly "over" (or by) the star. Perhaps it's 998 diameters * 2 to make up the margin. It's why I use crayons and thick markers for math like this -- that extra precision that they give.

 

[aramis]

While most aspects of Traveller technology tends to be kept deliberately vague, I would assume if you miss the optimum jump point, the transition is more likely prone to a misjump.

You have to charge up the capacitors and the astrogator brew a cup of tea to the right temperature, for the Captain to drink at the correct moment.

Kinda hard to do while pressed against the bulkheads during overdrive.

The optimum point is the one that intercepts nothing in-between at the moment it's initiated, except the 100D limit of the target.

Looking at the T5 6/2018 draft...
Fantastic Drives (Hop, Skip, Leap, Bound, Vault, etc) do not have increased diameters any more... but the astrogation difficulties are still 1D per parsec... with hop having a minimum 10 Pc plot (and thus 10d6). Skip's gonna be 100 Pc, so 100d6. There's an interesting bit in the task mechanics: even if you don't make the target number, as long as your 1's exceed your 6's and at least 3 1's are showing, you succeed spectacularly. (Example on p.361, rules on p.109)

Those uber-drives are going to be either dead on the money, or WAY WAY off course.

 

[BwapTED]

Maybe jump space is the absolute frame of reference for the physical universe?

 

[Condottiere]

 

[Sifu Blackirish]

Sifu strolls by, stops in his tracks

What's the usual answer for the problem of ships accelerating to near-C speeds and smashing into cities on planets?

If you have meson weapons, great. If not? Is it really that easy to obliterate an entire civilization by ramming a reasonably small starship into a planet at 0.9C?

Yeah. I am still in the midst of writing my SF trilogy, which is heavily TRAVELLER inspired. I have an item called a 'tau shunt power tap' which is basically free energy.

I thought about combining them with the high powered ion drives they use IMTU and almost immediately the 'near-c rocks' issue raised its head. I still haven't decided how to resolve it. Now I guess I have to read the thread!

 

[Quint]

The more I've thought about this the more I've pretty much decided that around any inhabited system there is enough "space junk" that it simply doesn't work - especially the highly inhabited higher tech worlds.

Sure, everyone knows it is technically possible, and it's been tried, perhaps even succeeded once or twice - but the vast, vast majority of ships simply run into something large enough to shred themselves before ever getting to the main planet.

Plus, in all honesty, I think that the real problem with this is that Jump navigation isn't actually fine enough to let this happen. If normal variation is variable within hours of the predicted exit point of time, even if the time is taken to fine-tune that, were still down to quarter-hours or minutes - which is going to change the actual vector of approach to the main system pretty significantly - and at near-C speeds there won't be any chance to.

That assumes that Jump navigation is *only* inaccurate in time and not only in space - I'd posit that it also has the ship show up a with a similar variable in space (it certainly seems reasonable enough when extrapolating the rules). It's not a factor in normal operations because it's simply not a large enough amount of space (maybe only hundreds or thousands of km) to matter for transit times - but again, vectors and speed make actually targeting a planet when moving that fast more a matter of luck than any actual plan.

That's before it flies into some leftover sandcaster ammo, or an old satellite part, or defensive mines, or whatever...


D.