Measure of a rocket's "goodness"

[aeTIos]

0) Does it look cool?

1) Does it go up?

2) Does it get fast enough?

3) Does it do what I want?

All answers yes?

Approved.

[cantab]

@Streetwind: To add, the delta-V for a single stage approaches a limit, since the mass ratio can never be better than that of the tankage.

For KSP that's 9.8 x ln 9 = 21.5 times the Isp with traditional tanks, and 20.6 times with ARM tanks.

More staging is thus encouraged with heavier tankage. IIRC Kerbal tankage is heavy, akin to that for LH/LOX, despite engines having lower performance closer to RP1/LOX.

[Rus-Evo]

In a big interplanetary ship I would also think about redundancy. For example my earliest big ships were made of identical ships stacked end on end as modular units, each could be a ship in its own right if plans need to be changed (ie things went wrong). Its also good to have super small efficient landers attached which can deliver a Kerbal to the surface if you accidentally kill someone down there etc etc. These things can be the difference between needing to send a rescue mission, or being able to handle it in situ.

[Thorbane]

Does it have the required ÃŽâ€v to get where I want? If yes, good.

Does it have the TWR to get off the ground? If yes, good.

Does the fiery end like to start pointing at space when I start the gravity turn? If yes, very, very, bad.

[Streetwind]

@Streetwind: To add, the delta-V for a single stage approaches a limit, since the mass ratio can never be better than that of the tankage.

For KSP that's 9.8 x ln 9 = 21.5 times the Isp with traditional tanks, and 20.6 times with ARM tanks.

More staging is thus encouraged with heavier tankage. IIRC Kerbal tankage is heavy, akin to that for LH/LOX, despite engines having lower performance closer to RP1/LOX.

Oh, good point. That's a great and simple way to look at it.

[NecroBones]

@Streetwind: To add, the delta-V for a single stage approaches a limit, since the mass ratio can never be better than that of the tankage.

For KSP that's 9.8 x ln 9 = 21.5 times the Isp with traditional tanks, and 20.6 times with ARM tanks.

More staging is thus encouraged with heavier tankage. IIRC Kerbal tankage is heavy, akin to that for LH/LOX, despite engines having lower performance closer to RP1/LOX.

Oh, good point. That's a great and simple way to look at it.

Both of you have raised some excellent points! This is now a very educational thread! Thanks