Help with launch profiles for low TWR Spaceplanes

[GoSlash27]

Dances With Squirrels,

Back in .90 I had a vertical lift SSTO as well...

http://s52.photobucket.com/user/GoSlash27/slideshow/KSP/Lifter-Ception/Flight

It could orbit more than it's entire fueled mass on the pad.

As good as that was, it was still nothing compared to what could be achieved with spaceplanes.

http://s52.photobucket.com/user/GoSlash27/slideshow/KSP/DoubleDipper

This little bugger could make the round trip to LKO with passengers 3 times without refueling and didn't even need airhogging.

Those were the days...

Best,

-Slashy

[Stoney3K]

Yes, they are more draggier because you can't have incidence on them. Mk2 parts used for lift will always have the extra drag because they are also regular parts with regular drag, which increases a lot more than the lift drag when they're not pointed prograde.

Mk2 part lift is only good for high alpha maneuvers, such as re-entry, takeoff and landing, where the regular drag is low or not a problem.

You CAN have incidence on Mk2 parts if you surface attach them but you need a big ship for it to become practical.

Also, the Mk2 parts usually have engines attached to them so angling them means you mess up your center of thrust.

[Bomaye]

You CAN have incidence on Mk2 parts if you surface attach them but you need a big ship for it to become practical.

Also, the Mk2 parts usually have engines attached to them so angling them means you mess up your center of thrust.

It will never be really practical........but never say never, show me your design

[Val]

You CAN have incidence on Mk2 parts if you surface attach them but you need a big ship for it to become practical.

True, you can mount them with incidence, but it doesn't have the same drag reduction benefit, because they're also fuselage parts.

The point of incidence is to have different AoA on wings and fuselage. Enough AoA on the wings to provide lift and as close to zero AoA as possible on the fuselage, respectively.

[Stoney3K]

True, you can mount them with incidence, but it doesn't have the same drag reduction benefit, because they're also fuselage parts.

The point of incidence is to have different AoA on wings and fuselage. Enough AoA on the wings to provide lift and as close to zero AoA as possible on the fuselage, respectively.

Think along the lines of an MK3 main fuselage (pointing nose forward) with Mk2 side pods (mounted at incidence) which support the wings and act as fuel tanks/service bays.

[Val]

Think along the lines of an MK3 main fuselage (pointing nose forward) with Mk2 side pods (mounted at incidence) which support the wings and act as fuel tanks/service bays.

It would create proportionally more drag than lift, compared to mounted it with no incidence, because of their dual nature in regards to KSP physics. Unless you're building a subsonic craft. Below 250 m/s it would probably be feasible.

Edit: Well, at 0 AoA Mk2 parts wouldn't create any lift. What I mean is, it would be more beneficial to add a little extra wing with incidence, than mounting mk2 parts with incidence, with regards to lift-to-drag ratio.

Edited October 20, 2015 by Val

[Bomaye]

Val is correct, think of F-16 and its design

[GoSlash27]

^ Val is *definitely* correct.

You should always get your lift from wings, not fuselage parts. Wings create the necessary lift with a lot less drag and minimizing drag is the secret to efficient spaceplanes.

I personally prefer to use more wing area and less incidence because it makes the spaceplane more stable during launch and more forgiving during landing. This approach carries a mass penalty, but it's relatively miniscule since wing mass is such a tiny fraction of the total. *BUT*...

If given the choice between less wing area or more wing area with struts, I recommend going with less wing area. Struts are the devil for spaceplanes.

Best,

-Slashy