Advanced Question What is the acceleration of the delta glider?

[Ctein]

Dear folks,

I want to use the delta glider (in unlimited fuel mode) for some orbital modeling. I need to know what acceleration full thrust on the main engines corresponds to. I *think* I've done some correct experiments to measure this-- it looks like it's either 20 m/sec per second of thrusting or perhaps it's 2 gees (19.6 m/sec/sec).

I'm not concerned with the 2% difference, I just want to know if I've got it basically correct.

IOW, in free space, 50 seconds of maximum thrust will impart 1 km/sec delta-vee-- is that right?

Thanks!

Ctein

 

[BrianJ]

Hello,
using "Acceleration = Force/Mass"
Deltaglider has mass of 24500kg (with maximum fuel)
Deltaglider main engines are 320000N max thrust.
So, Acceleration = 320000/24500 = ~ 13.06 m/s^2

 

[Ctein]

Dear Brian,

... and that's what I thought... and what I used in my modeling so far.

But... now I have a ship sitting out in deep space (~1 billion km from the sun). Not near any planets. As close as you can get to a zero-gee field, so potential vs kinetic energy doesn't mess up the test. I have it sitting at rest with respect to the sun. If I kick the thrust up to maximum, either towards or away from the sun, I get a velocity change (relative to the sun) of 20 m/sec/sec or very close to that.

I'm getting the velocity by having the display in orbit view mode, sun as reference and looking at the "Vel" readout (the one just above inclination).

(20 m/sec/sec several orders of magnitude larger than the acceleration caused by the sun at that distance-- I checked that. So that ain't the source of the error. Confirmed that by seeing that it's symmetric-- same result thrusting towards or away from the sun.)

So, I need to figure out what I'm doing wrong. Either my test is invalid, or I'm reading the screens wrong, or the 13 m/sec/sec isn't right.

I'd *really* like it to be a test error (save me a lot of rework), but I need to understand the error in my test.

Got any thoughts?

Thanks!

pax / Ctein

 

[Ctein]

Dear Brian,

Solved it, with the help of your data!

Older simulations I inspected showed the correct acceleration, only the most recent set of runs were off. So, I sez to myself... could something be off in a config file-- thrust or acceleration?

I start poking around: Main menu (F4) -> Custom... -> Scenario Editor -> DeltaGlider -> Edit... -> Propellant.

(including these steps for someone else, if they need to find their way there)

Lo and behold, the propellant tanks are only 35% full! Which cut the total mass of the ship enough to account for the acceleration I saw.

Reset them to 100%, checked to make sure "unlimited fuel" was still on (it was), and it all works like it's supposed to.

I have no idea how that got changed (I don't muck with those settings intentionally), but it's OK now.

Thanks for your assistance. Much appreciated.

pax / Ctein

 

[jangofett287]

The on-orbit starting scenarios were probably made by flying a DG up there, rather than spawning it in and adjusting its orbit though the scenario editor, so the tanks start the scenario part empty.