[Test Results] How much wing does your SSTO spaceplane need? Answer: Maybe none at all.

[Captain H@dock]

Agreed. Adding flaps doesn't really hamper performance, but deploying them does.

Like you said, KSP doesn't model camber, so flaps will obviously hurt drag a lot (since they just are metal plate you put against the airflow). Deploying them quickly puts you quite behind the power curve, so it's powered landing required.

From my personal experience with low TWR take-off, where flaps are needed the most, they seem to create more drag than lift. So I never use flaps for take-off.

But I do find flaps quite useful for bleeding off speed at a steep approach to the runway. And if I have fuel left I may do a powered landing with flaps deployed. It lowers touch down speeds a bit and is especially useful, if landing in terrain.

I had opposite experiences. See my link above (though the main wings were mounted with zero incidence): Take off was really improved (shortest distance to lift-off), and deploying them too fast produced excessive wind loading (RUD) and ballooning (not great when you're trying to follow the glide path).

Except for the touchdown speed: I agree this is obviously improved too. I'd guesstimate you can reduce your landing speed by about 30% with a proper flap setup.

Edited September 22, 2015 by Captain H@dock

[Val]

...

I had opposite experiences. See my link above (though the main wings were mounted with zero incidence): Take off was really improved (shortest distance to lift-off), and deploying them too fast produced excessive wind loading (RUD) and ballooning (not great when you're trying to follow the glide path).

...

Seems we agree on all points. For high-TWR flaps can shorten take-off runs. I didn't mention this specifically, though.

My experience with flaps was very low-TWR. So low that you need the full runway to gain enough speed for lift and only just able to avoid splashing into the sea. ~30 t per RAPIER or ~50 t per Whiplash.

I that scenario, deploying flaps made me lose speed and *splash*.

[Captain H@dock]

Seems we agree on all points. For high-TWR flaps can shorten take-off runs. I didn't mention this specifically, though.

My experience with flaps was very low-TWR. So low that you need the full runway to gain enough speed for lift and only just able to avoid splashing into the sea. ~30 t per RAPIER or ~50 t per Whiplash.

I that scenario, deploying flaps made me lose speed and *splash*.

Would deploying them at the very last second help, or is your TDR (Thust/Drag Ratio) in dirty wing configuration that bad?