Open Twr somehow still exists in high orbit

[Jebediah Kerman]

My space station to mars moves slowly in high and low orbit when other lighter crafts with the same amount of fuel escape Earth faster send help

 

[Pink]

That's physics for you, it's a bug with the real life universe.

 

[Jebediah Kerman]

Oof, guess ill need more thrust then.

 

[Pink]

Yes.

 

[Pink]

And you need more fuel for the station to have the same dV as the smaller rocket.

 

[Horus Lupercal]

My space station to mars moves slowly in high and low orbit when other lighter crafts with the same amount of fuel escape Earth faster send help

Why do lighter things move faster....?

You've really just asked that.

TWR exists everywhere, even in deep space.


You don't need more thrust, you need a lighter dry mass, more efficient engine

 

[Jebediah Kerman]

Pardon for my stupidity, but, since my station is in high orbit and my other light spacecraft are also in high orbit, shouldn’t the twr of both them do be almost the same?

 

[Pink]

TWR doesn't determine how fast you will be going when the fuel goes.

 

[Horus Lupercal]

Pardon for my stupidity, but, since my station is in high orbit and my other light spacecraft are also in high orbit, shouldn’t the twr of both them do be almost the same?

Nope. The TWR is determined by the thrust and the weight. The orbit height doesn't matter in SFS. At all.

If your 300ton space station and a 50t space craft are racing, then unless your spacecraft is powered by an ion engine and the space station has a bank of 3 frontiers powering it, the space craft will accelerate faster because it has more thrust and less weight.

However as Mooncrasher has said, the overall speed attained by the end of the burn (or delta velocity) will be higher on the craft with the most fuel and most efficient engine on board.

 

[Jebediah Kerman]

Nope. The TWR is determined by the thrust and the weight. The orbit height doesn't matter in SFS. At all.

If your 300ton space station and a 50t space craft are racing, then unless your spacecraft is powered by an ion engine and the space station has a bank of 3 frontiers powering it, the space craft will accelerate faster because it has more thrust and less weight.

However as Mooncrasher has said, the overall speed attained by the end of the burn (or delta velocity) will be higher on the craft with the most fuel and most efficient engine on board.

I see. Thanks.

 

[Horus Lupercal]

I see. Thanks.

Space stations aren't supposed to be fast.

If you're going to move one, making it fast means it's only going to run out of fuel quickly and not actually get very far. Be efficient rather than quick and maybe it will escape Earths SOI.

 

[Roger Jolly]

In a nutshell, figuring equal efficiency, twice as much mass requires twice as much fuel and twice as much thrust to do the same thing;
But as long as you start in vacuum you can exchange the twice thrust for twice time which is why ions are so great in space but useless for an atmospheric launch

“Twice mass” is of course compounded by the rocket equation and “vacuum” has a surface gravity escape limitation if we’re talking moon launch rather than from orbit

 

[Jebediah Kerman]

I see. Again, pardon for my stupidity. I tried applying my poor understanding of n body physics in this.

 

[Pink]

All you need is F=ma and V=u+at for rough calcs
Where t is how long until the fuel runs out.

 

[Earl]

Pardon for my stupidity, but, since my station is in high orbit and my other light spacecraft are also in high orbit, shouldn’t the twr of both them do be almost the same?

Even in a high orbit you are under the influence of gravity. That's why you don't just fly out to space, but stay in orbit. Heaver objects need more force to accelerate than light ones, even in orbit. That's why larger rockets need more powerful engines.

 

[Lt. Snakestrike]

It's the same reason why we need absolutely enormous rockets to get bigger payloads into orbit.

 

[Roger Jolly]

Weight is the measure of mass in gravity,
Weight is lessened as its distance from the COG is increased,
or disappears if it is in free fall at or around a COG

Mass is a constant measure of a material composition, its (volume x atomic density) and so is not affected by gravity

Mass is what determines the needs of fuel and thrust in moving an object;
During launch there are additional secondary considerations, particularly from inside an atmosphere, namely escape velocity to create an orbit (always) and atmospheric drag;
But outside a gravity well or in orbit outside an atmosphere Mass is always directly proportional to Thrust and Velocity, increasing Mass requires more Thrust/Fuel to achieve the same Velocity in the same Time;
The same Velocity can be achieved by extending the Time and reducing Thrust, this ignores efficiency ratings which are largely what make this desirable in space (ion engines in particular)

 

[SPQRALAN]

All you need is F=ma and V=u+at for rough calcs
Where t is how long until the fuel runs out.

Only problem is that acceleration must be constant for the second equation. But for short burns it works perfectly fine. For long burns you need the rocket equation(which is why there is a ln from the calculus).

Again, what you said is perfect for short burns.