How do YOU spaceplane?

[Cynor]

So I know the general basis behind making and flying/landing them to a degree, but at the same time I know I'm missing a lot. For example designing my own feels sluggish/"standard" (aka following a design like from Scott Manley). I also struggle to figure out good flight plans and how much fuel to include for said flight. Oh and landing at the KSC (or even with the nose up) seems to be an issue with my designs atm.

For example one I have I can get to orbit by basically staying at about 10 degrees the whole time, but if I throttle down to avoid some mach/heat effects I don't have enough fuel left. If I stay at mostly full throttle I get up and circularized around 80k with about 400 DV (4x rapiers) leftover. However I almost blow up the MK2 cockpit in the process, the temp gauge bar get so close to the end I feel like there are less than 10 pixels left. Other than that it flies and lands pretty well, though I feel it may be nose heavy when empty  as I had to do a fairly steep dive to be able to get enough speed/lift to pull the nose up for landing. Not to mention knowing where exactly to aim for the deorbit... last time I wound up in the far desert despite aiming for the sea past the KSC with my orbit path.

Anyways, the point/end of this is I'm wondering how everyone else likes to do things like design spaceplanes, fly them in terms of ascent paths, etc.

[Wanderfound]

Some demonstrations...

Small passenger SSTO:

Lower tech cargo SSTO:

SSTA:

If you click through to the Imgur albums, you'll get an idea of the flight profile.

Edited December 29, 2016 by Wanderfound

[KevinW42]

For deorbit aiming, if you're willing to use mods I would highly recommend Atmospheric Trajectories.

 

[Cupcake...]

This is an example of a high T/W space-plane I made recently.

By keeping weight down to a minimum (no extra engines), and using streamlined parts you can still get a very respectable 2.5k in orbit or 1.9k without the drop tanks.

Ascent is 5* rising to 10* with the drop tanks or a straight 10* climb without. Hope this helps.

 

Cupcake...

Edited December 29, 2016 by Cupcake...

[KroShan]

I can recommend you the MK3 SSTO Guide from Kerbal Space Command. Also watch Part2. I built an MK3 SSTO with 4 Rapiers one ShockCone Intake which gets more than 22ton into a 85km Orbit based on this design.

The best hint i got from him is the 10° tilted Probe core - by activating 'Control from here' and 'Point Prograde' SAS you have a very nice reentry...

 

[Leafbaron]

For landing at the ksc with a spaceplane I will lower my periapsis to about 30-32km above the peninsula to the east of the KSC. I hold at roughly 30 degrees and watch my orbit. Pitching down if I'm decelerating to quickly or pitching up if I'm not decelerating fast enough. I try to aim to be around 1500 m/s or less @ and altitude of 20-26km when coming over the top of the mountains to the west of the KSC.

For your pitch problem, being nose heavy is good for a space plane i have found, because even if you CoL is behind your CoM slightly, its not enough to keep you nose forward during reentry. Before you try to adjust anything on your plane, the first thing I would try is increasing the authority control limit on your control surfaces for pitch.  

As for my flight profiles, they differ from spaceplane to spaceplane because of drag characteristics and TWR's. But climbing at 10-15 degrees until about 9-12000m then leveling out and building speed to about 18-22km is usually what i aim for. When i switch to closed cycle engines i like to pitch up and get to 30-40km as quickly as I can without decreasing my speed. At this point gravity losses are negligble because of the speed you have and also the wings on the craft, What your really fighting is drag, so the quicker you can reduce drag the more fuel you'll have and also it decreases the amount of heating you experience. Staying at 10 degrees until orbit means youre pushing through a lot of thicker atmosphere at quick speeds, burning a lot of fuel to over come drag as well as cooking your kerbals. 

However some of my designs, because of low TWR and "high" drag must climb to about 13-14km level out and actually slowly fall back down to 10-11 km before over coming mach 1 and building serious speed. All it takes is just regular flying of the craft and you will tease out all of its idiosyncrasies and learn what it's best flight profile is. But all you can do is fly fly fly and try different things. 

 

-Leafy

[Aegolius13]

8 hours ago, Cynor said:

For example one I have I can get to orbit by basically staying at about 10 degrees the whole time, but if I throttle down to avoid some mach/heat effects I don't have enough fuel left. If I stay at mostly full throttle I get up and circularized around 80k with about 400 DV (4x rapiers) leftover. However I almost blow up the MK2 cockpit in the process, the temp gauge bar get so close to the end I feel like there are less than 10 pixels left.

As you say, throttling down is generally not a good thing for efficiency.  If your cockput is burning up, consider switching to the inline cockpit and putting something that's robust to 2400k, like a shock cone or NCS adapter + small cone, in front.  Apart from exploding parts, I would ignore flame/mach effects.  You want to be going absolutely as fast as possible on jet power.

You may also look at removing one engine if that's feasible.  Better to run on, say, 3 Rapiers full-throttle than to bring 4 and throttle down.  

 

As for my SSTOs, I've started building kind of Skylon-style, with engine nacelles out on the wingtips around the middle of the ship.  Then maybe a couple engines in the back if necessary.  As with cars, the midship engines really help with weight distribution.  I also cannot seem to avoid using the Big S wing in every single build.  Wish they'd give us some more wing designs with built-in LF storage and decent heat resistance.