Help with DeltaV for my Scout class

[zero]

So, it looks like the vanilla traveller campaign I planned is back on and I have built a custom 100dton scout for us all to travel in, now with added AI computer to help in the piloting etc skills we're not so good with (I only have two players).

Anyways, after writing a more hard scifi take on spaceships thanks to the Project Rho website and people here, I got to statting out the different abilities of the Scout class; Thrust in newtons, Mass Ratio, Acceleration etc just to add to the technobabble, really (I know Trav is soft scifi, but I like to rationalise stuff, you see). Plus, I dunno, it'd be impressive to know this stuff.

Now, I just need some clarification on DeltaV so I can finish my number crunching.

Leaving aside the fuel needed for Jumps, which we'll rely on more to travel (The scout is also streamlined, so I have fuel scoops built-in, plus there is fuel processing onboard too and most of the systems in my subsector have GGs), I have fuel enough for 2 weeks of interplanetary travel at Thrust 2 (An acceleration of 19.62 m/s if I'm right).

So... would the DeltaV be totalled by the Accel (19.62) multiplied by the seconds in 14 days (my gut is saying this)?

Or... is the max distance the ship could travel based on its Accel in 14 days (probs not, but you never know, and if so, someone here is going to have to do the math for me).

Either way, thanks in advance to all responses and also thanks to the forum for clarifying alot of stuff for me in the past (plus inspiring me to put in a Comp that can help with piloting, astrogation and engineering matters ).

 

[DFW]

Not sure if I understand your question (I DO understand "Delta V"). So, what M-Drive is your Scout using?

 

[zero]

Its an A-class Drive in a 100dton vessel, so it has a Thrust of 2. The P-plant is also A-class (so is the Jump Drive, but that doesnt matter for this).

So, I have a Thrust 2 vessel and it has 2 tons of fuel past that needed for Jumps, so it can accel at Thrust 2 for 14 days before it runs out of those 2 tons of fuel.

I assumed on some other comments on the forum that Thrust equals G in acceleration, so Thrust 2 would be an acelleration of 19.62 m/s (9.81 x 2)

 

[DFW]

Its an A-class Drive in a 100dton vessel, so it has a Thrust of 2. The P-plant is also A-class (so is the Jump Drive, but that doesnt matter for this).

So, I have a Thrust 2 vessel and it has 2 tons of fuel past that needed for Jumps, so it can accel at Thrust 2 for 14 days before it runs out of those 2 tons of fuel.

I assumed on some other comments on the forum that Thrust equals G in acceleration, so Thrust 2 would be an acelleration of 19.62 m/s (9.81 x 2)

Okay, using a MGT Grav M-Drive means you don't calculate Delta V at all. See here: http://www.projectrho.com/rocket/engines.php

So, you have 2 G (~20meters/sec/sec) thrust for as long as your PP is running. (You could use your J-fuel if you don't need to jump, increasing fuel time)

 

[rust]

Your scout ship has a maximum of 672 G-hours of acceleration, and can
use up to 336 G-hours to accelerate to a mid-point and the remaining 336
G-hours to decelerate to the destination, so at a thrust of 2 G this would
be up to 168 hours of acceleration and deceleration each.

I have no idea whether this helps, but at the moment it is the best I can
make of the information you provided.

 

[zero]

Okay, thanks for the help. I'm still a little confused over it (seeing as the M-Drive is a Grav engine, mainly I'm confused over which type of Project Rho engine type calulations to go with now given your link).

Looks like I may have to wing a few numbers otherwise, but thanks for clarifying how the M-Drive functions with Thrust and the fuel (and yeah, I knew I could extend acceleration with J-fuel, but we'll be Jumping alot ).

EDIT - Sorry Rust, you posted the same time as me, how do you total G-hours?
Oh and I was running for an acceleration speed for when the 2 tons of fuel run dry after 14 days (as in the chart of MGT Core for how long fuel lasts, as I have an A-class PP and M-D).

 

[DFW]

I'm still a little confused over it (seeing as the M-Drive is a Grav engine, mainly I'm confused over which type of Project Rho engine type calulations to go with now given your link).

None of those calcs are applicable to the MGT grav m-drive. There is no exhaust velocity, etc. The "m-drive" thrust isn't based on the mass of the ship but, on the volume of space the ship takes up. It is a constant. The "drive" imparts 2 G's of accel on every bit of mass within that volume independent of the amount of mass. http://whatis.techtarget.com/definition/0,,sid9_gci549408,00.html

IE: The 100 Ton (volume) ship could be loaded with gold bricks or, almost empty and you get the same rate of acceleration.

 

[zero]

Fair does. That makes the technobabble much easier for me in the long run, though I must say I enjoyed doing all the other calculations for the Scout.

As an aside, and more for my non-Trav hard scifi writing, if a spaceship didnt have a Grav engine, would I be right in saying that to get the max deltaV of a vessel, I multiply the acceleration (in m/s) by the amount of seconds it can accelerate by?

So, as a really simple and non-realistic example, if a ship only had 2 seconds of fuel on it and accelerated at 9.81m/s, it has a Delta V of 19.62m/s?

 

[rust]

Sorry Rust, you posted the same time as me, how do you total G-hours?

With fuel for 14 days of 24 hours each at an acceleration of 2 G you have
14 x 24 x 2 = 672 G-hours.
You can spend these as 672 hours at 1 G or 336 hours at 2 G, with a 3 G
drive you could spend them as 224 hours at 3 G, and so on.

Oh and I was running for an acceleration speed for when the 2 tons of fuel run dry after 14 days (as in the chart of MGT Core for how long fuel lasts, as I have an A-class PP and M-D).

I hope you do not intend to use more than half of the fuel / G-hours for
acceleration, because then your ship would drift at high speed and unable
to decelerate again - a kind of "Flying Dutchman" fate.

Unfortunately the formula I use to calculate speed from G-hours of acce-
leration is somewhere in the Traveller New Era material, which I do not
have right now, and I hesitate to write a formula from memory - mine is
far from reliable.

Edit.:
I just found a rough estimate of G-hours used for acceleration and time
required to travel 1 light-second.

1 G-hour = 3 hours per light-second
2 G-hours = 1.5 hours per light second
3 G-hours = 1.0 hours per light-second
4 G-hours = 0.75 hours per light-second
5 G-hours = 0.6 hours per light-second
6 G-hours = 0.5 hours per light-second
7 G-hours = 0.43 hours per light-second
8 G-hours = 0.375 hours per light-second
9 G-hours = 0.333 hours per light-second

 

[DFW]

Fair does. That makes the technobabble much easier for me in the long run, though I must say I enjoyed doing all the other calculations for the Scout.

As an aside, and more for my non-Trav hard scifi writing, if a spaceship didnt have a Grav engine, would I be right in saying that to get the max deltaV of a vessel, I multiply the acceleration (in m/s) by the amount of seconds it can accelerate by?

So, as a really simple and non-realistic example, if a ship only had 2 seconds of fuel on it and accelerated at 9.81m/s, it has a Delta V of 19.62m/s?

Figuring Delta V for a rocket is more complex and involves fuel mass, burn rate and declining fuel mass. (see link I gave you for formulas.)

As far as figuring speed and distance for your Scout with the Mdrive, see this very handy link. http://www.cthreepo.com/lab/math1.shtml
and http://www.transhuman.talktalk.net/iw/TravTime.htm

EDIT: simple Delta V calculator http://www.strout.net/info/science/delta-v/

 

[locarno24]

IE: The 100 Ton (volume) ship could be loaded with gold bricks or, almost empty and you get the same rate of acceleration.

Also bear in mind that there's no point in not using the drive; traveller starships are burning fuel as long as the reactor's on, which you need for such trivial fripperies as life support and the computer systems, so you might as well be burning your drive as well.

As a result, you don't get the same "delta V reserve" effect as you do with a reaction drive - unless suitably equipped (solar panels) there's no advantage to coasting on inertia. The big reason that traveller ships are so fast around a star system (compared to NASA) is not that they accellerate that fast (civilian ships, anyway), but that they're under power for the whole trip.

 

[AndrewW]

Also bear in mind that there's no point in not using the drive; traveller starships are burning fuel as long as the reactor's on, which you need for such trivial fripperies as life support and the computer systems, so you might as well be burning your drive as well.

With the exception if one is using solar panels.