Gravity assist

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paltrysum
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Gravity assist

Postby paltrysum » Sun May 06, 2018 5:11 am

Have any of you employed gravity assists in starship maneuvering in your games? I'd like to find a way to add gravity assist rules to starship operation that don't entirely feel like hand-waviness and I'd like to know if anyone has any suggestions.
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Reynard
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Re: Gravity assist

Postby Reynard » Sun May 06, 2018 11:24 am

I'm not sure my computer has the capacity to calculate the complexities of orbital slingshotting about a system. Might be useful to save fuel if you're doing a reaction drive only universe.
phavoc
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Re: Gravity assist

Postby phavoc » Sun May 06, 2018 3:25 pm

With constant thrust M drives you don't need it. Even the lowly 1g drive can do amazing things just by turning it on and letting it run constantly.

The amount of time spent maneuvering to do the slingshots is generally not work it when you have constant high thrust. A ship adding a slingshot maneuver to its base velocity also has to expend the energy to slow down on the other side of its course. With constant thrust you do a turnover half way to your target to decelerate. You would need to do the math to determine if your initial slingshot speed increase would actually be more efficient. Adding more baseline speed at the beginning means you may have to use a similar maneuver at your destination, assuming you can. Otherwise you may overshoot your target.
phavoc
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Re: Gravity assist

Postby phavoc » Sun May 06, 2018 3:25 pm

With constant thrust M drives you don't need it. Even the lowly 1g drive can do amazing things just by turning it on and letting it run constantly.

The amount of time spent maneuvering to do the slingshots is generally not work it when you have constant high thrust. A ship adding a slingshot maneuver to its base velocity also has to expend the energy to slow down on the other side of its course. With constant thrust you do a turnover half way to your target to decelerate. You would need to do the math to determine if your initial slingshot speed increase would actually be more efficient. Adding more baseline speed at the beginning means you may have to use a similar maneuver at your destination, assuming you can. Otherwise you may overshoot your target.
Rikki Tikki Traveller
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Re: Gravity assist

Postby Rikki Tikki Traveller » Sun May 06, 2018 6:32 pm

Phavoc is right. Gravity Assist works mostly because the ship leaving has a lower mass than the ship entering the planetary area. Since M-Drives basically don't use fuel, you don't get nearly the benefit.
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Nobby-W
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Re: Gravity assist

Postby Nobby-W » Mon May 07, 2018 7:02 pm

paltrysum wrote:
Sun May 06, 2018 5:11 am
Have any of you employed gravity assists in starship maneuvering in your games? I'd like to find a way to add gravity assist rules to starship operation that don't entirely feel like hand-waviness and I'd like to know if anyone has any suggestions.
If Kerbal Space Program counts I have.

Gravity assists are useful if you don't have a lot of Delta-V to play with in your manoeuvre drive. Folks running probes have used gravity assists to get their craft on grand tours of the solar system and can be incredibly stingy with reaction mass if you're prepared to take 10 years on your trip. For the sort of things a Traveller party might want to do they're probably not relevant as Traveller ships have so much Delta-V available that it's going to be more economical to just blast your way to the destination quicker.
Nobby-W
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Re: Gravity assist

Postby Nobby-W » Mon May 07, 2018 7:05 pm

Reynard wrote:
Sun May 06, 2018 11:24 am
I'm not sure my computer has the capacity to calculate the complexities of orbital slingshotting about a system. Might be useful to save fuel if you're doing a reaction drive only universe.
May I suggest you try Kerbal Space Program. You can learn more about orbital mechanics than you ever thought you wanted to know.

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Condottiere
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Re: Gravity assist

Postby Condottiere » Wed May 09, 2018 8:56 pm

It's something to consider for orbital or limited range thrusters.

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