Another M-drive variant

[Apache]

So, I was pondering different M-drives after reading this thread, and I came up with the following.....

Instead of a vector-movement drive (whether its reactionless or not), how about a non-vector drive?

Remember the old TFG game Starfire?

The ships there used an 'ion drive' that capped out at roughly 10% lightspeed. It also included a nuclear dampener effect, and if the drive was turned off, you stopped.

So what if the M-drive in Traveller was the same way?

A 1-G drive doesn't accelerate you by 1G....it just gives you the velocity of 1G....and thats it.

And if you turn it off, you stop. And yeah, there is a built-in nuclear dampener effect. Large enough to make using nuclear-tipped missiles useless (altho bomb-pumped xaser warheads would still work just fine, probably).

How would this affect travel times assuming nothing else changes (100D, etc.)?

[far_trader]

Originally Posted by Apache

So, I was pondering different M-drives after reading this thread, and I came up with the following...

It's a common enough sci-fi trope that it should be an option.

Not saying it's a bad idea, just needs more work on specifics :)

Such as...

Originally Posted by Apache

A 1-G drive doesn't accelerate you by 1G....it just gives you the velocity of 1G....and thats it.

...but 1G IS an acceleration (GURPS and Traveller rounded 10m/s/s iirc)... and NOT a velocity (such as 1000km/s). So, we need to pick a number.

And is that speed also instantly applied? What happens to everthing "inside" that "velocity" envelope? And "outside" it? Can you engage it in a medium denser than deep space? With what effects (again inside and outside)? A sudden velocity of that type in atmo is going to at the very least make one hell of a vortex(?). How does gravity affect it (if it does)? Especially if you suddenly turn it off and come to dead stop at great height over a hard place.

Not at all familiar with the game noted so maybe this was already covered in it.

[malloyd]

Originally Posted by Apache

A 1-G drive doesn't accelerate you by 1G....it just gives you the velocity of 1G....and thats it.

You need a time unit in there: 1 G-second or 1 G-week or 1 G-year would be a velocity, 1 G by itself is not. Without that, any questions about effects are undeterminable. 1 G-second is 36 kilometers per hour, space travel becomes effectively impossible with this drive, 1 G-year is about the speed of light, and insystem distances become almost trivial.

[Apache]

Well, right now Traveller drives are rated in G-accel.

IIRC, both GURPs and Trav round this to 10 m/s/s (as noted above) per G-factor.

So lets work with that.

Instead of accellerating you at 10 m/s/s per factor, the M-drive simply gives you a maximum speed of 1000 m/s per factor, period.

Assume accelleration time from zero to max takes about 5 seconds.

In all other aspects the M-drive works exactly as it does now.

Discuss.

[jeff_wilson]

Originally Posted by Apache

Instead of accellerating you at 10 m/s/s per factor, the M-drive simply gives you a maximum speed of 1000 m/s per factor, period.

Relative to what? LEO is 7800 m/s relative to Earth, but 140,000 m/s relative to planets around Barnard's Star.

Originally Posted by Apache

Assume accelleration time from zero to max takes about 5 seconds.

20g's, per factor? Ouch!

[Apache]

Originally Posted by jeff_wilson

20g's, per factor? Ouch!

Good thing inertial dampener/contragrav technology comes with the M-drive, huh?

As for 'what its relative to', use your head. Last time I checked, it's going to be 'relative' to your origin point.

[jeff_wilson]

Originally Posted by Apache

Good thing inertial dampener/contragrav technology comes with the M-drive, huh?

Does it?

Originally Posted by Apache

As for 'what its relative to', use your head. Last time I checked, it's going to be 'relative' to your origin point.

If by origin point, do you mean the earth if the trip originates at the earth? What about the earth's acceleration toward the sun? Do you mean relative to the earth's hypothetical velocity as if the sun's gravity had ceased to accelerate it? Or if the particular launch point on the earth as if the earth had ceased to rotate, instead of continuously accelerating toward its center?


And regardless of which of these are picked, ships from Earth and from Barnard's star will need a combination of [EDIT M200] to dock reliably, and about M80 to dock at all, ever, because their origin systems are already moving 140,000 m/s relative.

[malloyd]

Originally Posted by Apache

Instead of accellerating you at 10 m/s/s per factor, the M-drive simply gives you a maximum speed of 1000 m/s per factor, period.

OK. It's almost worthless as a spacecraft drive. 1 km/s is a pathetic delta-v even for a chemical rocket. It takes you 4.5 days to get to the moon, almost 15 days to get to Earth's 100D limit, and nearly 5 *years* to cover 1 AU, a fairly typical interplanetary distance. The 6G version is almost useful compared to current launch vehicles, though you'd need 8 or 9G versions to reliably outperform them.

It's equivalent to a 100 second "burn" at the G rating, so it's not surprising it's pathetic compared to maneuver drives that normally operate for much, much longer than that. Give them a hour maximum burn (36 km/s per "G") and they start looking sort of OK - 3 hours to the moon, half a day to 100D, 50 days per AU is really good compared to realistic space drives, and not a disaster for Traveller economics or typical adventure plots. You're probably better off doing this as a maximum burn duration rather than an instant jump to a high fixed velocity - it solves the relative to what issue for one thing. All you need is a reason the drive can't operate more than an hour without, well, something - more fuel, discharging technobabble particles into a strong gravity field, resting the hamsters for a week, whatever.

[Mike Wightman]

Originally Posted by jeff_wilson

Does it?



If by origin point, do you mean the earth if the trip originates at the earth? What about the earth's acceleration toward the sun? Do you mean relative to the earth's hypothetical velocity as if the sun's gravity had ceased to accelerate it? Or if the particular launch point on the earth as if the earth had ceased to rotate, instead of continuously accelerating toward its center?


And regardless of which of these are picked, ships from Earth and from Barnard's star will need a combination of [EDIT M200] to dock reliably, and about M80 to dock at all, ever, because their origin systems are already moving 140,000 m/s relative.

I'm intrigued.

You take all of that into account when using the manoeuvre drive as presented in Traveller?

[jeff_wilson]

Originally Posted by Mike Wightman

I'm intrigued.

You take all of that into account when using the manoeuvre drive as presented in Traveller?

No, because as presented in Traveller, velocity relative to "the origin" is immaterial. Which is a good thing, because the velocity of the earth changes by 60,000 mps over the course of a year and it would look weird for your ship to start moving backwards on a seasonal basis.