Kerbodyne SSTO Division: Omnibus Thread

[Wanderfound]

The funny thing is Wanderfound I have downloaded some of your craft to test out and compare to my designs, and I dont understand how you fly craft with such high stall speeds due to such small wings. You are essentially fling manned missiles. Have you ever considered adding a bit more wing to your craft to increase your low speed handling?

They're pretty much all intended for orbit, so I don't do a lot of low-altitude low-speed. In order to reduce atmospheric drag and post-atmosphere mass, I tend to aim for as little wing as possible while maintaining good flight behaviour from supersonic to hypersonic. While building, I'll generally check the FAR numbers at 25,000m/Mach4 and work to eliminate the reds there; I'll often also check 500m/Mach0.5.

Post takeoff, I'm climbing as steeply as possible to 20,000m or so; on reentry, I'm usually supersonic above 10,000m until I pass the mountains west of KSC, when I drop to the deck and bleed off the speed. The only part of the flight where the small wings are an issue is during final landing approach; I'm generally still substantially above 100m/s at touchdown. But that's no problem if you've got your gear set up right; half the runway is generally enough stopping distance.

With most of 'em, the canards will go into a minor stall long before anything serious happens, and I try to design for good stall behaviour. With a lot of mine, they'll happily sit in a minor stall all day long without any undesired yaw, pitch or roll.

My takeoff routine is generally to pull up hard into a minor stall, hold that posture until I've got 50+m of air under me, then drop the nose back down to clear the stall before gradually pulling up into a climb of a steepness sufficient to almost but not quite negate my acceleration. I've then got several minutes of just letting the SAS hold pitch while I climb; by the time there's any further need for manoeuvring, I'm generally over 20,000m and supersonic, and therefore virtually stall-proof.

The stalling stops once you go supersonic; even tiny-winged things can pull large AoAs without stalling once they have sufficient speed up, and the only subsonic parts of most of my flights are the bits immediately before and after the runway.

[Hodo]

So basically you have really high TWR, manned missiles.

That is a completely different design philosophy than any of my craft, fascinating.

Most of my craft have very good low speed handling characteristics and are a breeze to fly at low speeds down to 70m/s on some and yet still capable of achieving a 100km orbit with ease.

Have you ever considered increasing your wing area for more low speed handling?

Much like this craft, that is nothing more than a flying wing, and has an amazing glide slope.

[Wanderfound]

So basically you have really high TWR, manned missiles.

That is a completely different design philosophy than any of my craft, fascinating.

I like to get there fast. I generally scale the engines by "will this get me to orbit before I get bored?" rather than "what is the minimum engine to get off the runway?". It may be the case that I'm trading wing for engine, while you're trading engine for wing.

Not sure about the "really high TWR" descriptor; there are a fair few single-engine ships here, and most of the three-engine ships are doing so in order to carry multiple engine types.

The only really absurdly overpowered things are the ones that were deliberately designed to be silly (Goblin, Dementia, etc). They are nearly all intended to be "sporty", though.

[Hodo]

Most of my designs have a take off TWR of around 0.5-0.9 depending on the craft. Some of my smaller "fighters" are a fair bit more higher on the TWR scale around 0.9-1.1 again depending on the craft.

I love that your designs are different and I am just trying to find out some of the thoughts behind them. I am always erroring on the side of caution in my designs. I often have an escape system designed into them also. Granted I use it less now that I have the Kerbal Parachutes mod, so they can just eject out and deploy their individual chutes.

[eddiew]

Most of my designs have a take off TWR of around 0.5-0.9 depending on the craft.

I've never managed to get anything off the deck with less than 0.65 TWR But then I was kind of raised by the Wanderfound school of design, so I add wings like they're made of platinum and unicorn hide

I find 0.8+ the most comfortable TWR, since you tend to get a lot of leeway, particularly as the air breathers stretch their legs in the upper atmosphere

[UnusualAttitude]

I find that one of the major appeals of designing FAR spaceplanes is that there are so many different solutions to the same problem (of getting crew/stuff into orbit/to other places), rather than just applying x turbojets and y wings to an airframe of z tonnes...

I too learnt/still learn a lot from Wanderfound's designs, but I gradually drifted towards much lower atmospheric TWR (0.45 to 0.6), more wing to compensate and high rocket TWR (no nukes; ugly and heavy) and as much fuel as possible to go places from LKO, directly if possible. I was so bad at building/flying rockets that I didn't know how to launch a decent LKO fuel station. I only recently started to get into nuke spaceplanes for interplanetary missions.

I'm also just wondering if 1.0 stock aerodynamics will improve freedom of design. I'm curious to know if any of you hardcore FAR spaceplane-drivers have an opinion on this, or will consider testing stock 1.0 aero with an open mind?

[Wanderfound]

I'm certainly giving NuStockAero a try; whether I stay with it instead of FAR will be based entirely upon "which one is more fun?".

[blowfish]

I'm also just wondering if 1.0 stock aerodynamics will improve freedom of design. I'm curious to know if any of you hardcore FAR spaceplane-drivers have an opinion on this, or will consider testing stock 1.0 aero with an open mind?

Chances are FAR will be need some updating to work with 1.0, which will require a few days at least. I suspect I'll stick with FAR in the long run just because I've gotten use to the way it does things, but that's no reason not to try stock aero in the mean time.

[polan]

Hey wanderfound!

I've been downloading some of your great planes, and then I came across the Dolphin.

I just made a speedboat, so I was thinking about speedboats. And when I saw "Dolphin", I thought it was a dolphin-like speedboat.

But it wasn't a speedboat. And I was disappointed. So make a speedboat! Hopefully you're a "speedboat apprentice" xD

tootles

[eddiew]

Chances are FAR will be need some updating to work with 1.0, which will require a few days at least. I suspect I'll stick with FAR in the long run just because I've gotten use to the way it does things, but that's no reason not to try stock aero in the mean time.

Sound strategy - thinking about having a week of sandbox to get to grips with the new aero, before kicking off a career when the 'must have' mods have caught up. I shall be interested to see how things fly in stock - wouldn't mind something that let me be a little more exotic than FAR, as long as it's a bit sensible about lift and drag and doesn't allow dodgy intake clipping. Not penalising biplanes would be fun from an aesthetics point of view

Got a feeling B9 will suffer a bit though... it's very geared towards working under FAR, not sure how stock will cope with its array of parts :S

[blowfish]

doesn't allow dodgy intake clipping.

Based on the fact that jet engines will now reduce thrust with density, I suspect that any sort of intake spamming as we know it today will become irrelevant.

[Wanderfound]

Watching the previews, and happily noting that the ISRU refinery parts will fit inside a Mk3 cargo bay. Self-refuelling spaceplane with drills hidden inside the bomb bay...

[Hodo]

Watching the previews, and happily noting that the ISRU refinery parts will fit inside a Mk3 cargo bay. Self-refuelling spaceplane with drills hidden inside the bomb bay...

LOL I remember doing that back in .21...

Javascript is disabled. View full album

[UnusualAttitude]

Watching the previews, and happily noting that the ISRU refinery parts will fit inside a Mk3 cargo bay. Self-refuelling spaceplane with drills hidden inside the bomb bay...

I saw the ISRU converter is a hefty 4.25 tonnes though, plus the drills, ore storage tanks and sensors...

Several game-changers in the few previews I got to see, disregarding aerodynamics: much higher liquid fuel consumption during atmospheric flight, nukes now no longer needing oxidizer... Looks to me like nukes will reign supreme if you can get a high enough TWR, perhaps with a small chemical stage for orbital injection. Shame they're so damn ungainly on a spaceplane.

Re-entry looks benign if you're used to FAR and/or DRE.

[eddiew]

Ok, so... just for grins I took the Kerbodyne Dolphin out for a few joyrides with 1.0 stock aero It's a bit... different... to FAR.

1) Reaching a 40k apoapsis on air breathers is a doddle, but not useful.

2) Turbojets conk out really easy now... way before the rapiers.

3) Too much thrust makes explosions. I took the turbojet off because it was lethal... Dolphin still climbs at 45 degrees, gaining speed, on just the rapiers.

4) All air breathers give up really early... the rapiers pegged it by 22km with 30km AP. Speed/altitude? Cause uncertain...

5) There is negligible drag past 45km. You can easily coast to orbit from here.

6) I got a 76x72km orbit out of the Dolphin with a mere whisker of fuel left that was just enough to get to 75x50km.

7) I had 70 units of oxidiser to spare.

8) This shallowest of shallow re-entries exploded the plane from the heat... really?

Overall, I think there's a lot of new data points to collect and stuff that flew under FAR is probably not guaranteed to work under 1.0 stock... I dunno yet whether I like it or not. It seems more forgiving during flight, and the crazy stock craft kind of work... but it's also harder to get a bird to orbit, and I can't figure out how to get them down again...

*edit* On the up side, there's a re-entry heat slider I'm going to bed now, but I expect you chaps will have figured it all out by the time I get up for work Good luck!

Edited April 27, 2015 by eddiew

[Kagame]

My report on the 1.0 aerodynamics:

Wow, this is the most fun I've had in a while. And that was with a low-tech-level jet trainer I cobbled together using a CM and a V-tail. No tuning, no nothing, it just got up and went. Granted, all the wings were facing the right direction, so I'm not sure if any of your more awesome building techniques would work. Still, it's very, very cool. I can now control my craft instead of just hoping it doesn't tumble all over the place. And Eddie's sort of overestimating the atmo- I found that control surfaces stopped working past 20-ish km. Granted, though, that was with a rocket, and rockets don't tend to hang in the air that well.

I'm off to sandbox mode to cobble something new up. *giggles*

[Wanderfound]

Squee!

http://forum.kerbalspaceprogram.com/threads/20451-0-90-Ferram-Aerospace-Research-v0-14-7-4-2-15?p=1870281&viewfull=1#post1870281

[blowfish]

Squee!

http://forum.kerbalspaceprogram.com/threads/20451-0-90-Ferram-Aerospace-Research-v0-14-7-4-2-15?p=1870281&viewfull=1#post1870281

What do you make of the new heating system? It seems to make spaceplanes start exploding before Mach 3, even though the RAPIERS for instance are good to Mach 5.5 at least. Perhaps DRE's update will make it a little more sensible?

[Wanderfound]

Ok, so... just for grins I took the Kerbodyne Dolphin out for a few joyrides with 1.0 stock aero It's a bit... different... to FAR.

1) Reaching a 40k apoapsis on air breathers is a doddle, but not useful.

2) Turbojets conk out really easy now... way before the rapiers.

3) Too much thrust makes explosions. I took the turbojet off because it was lethal... Dolphin still climbs at 45 degrees, gaining speed, on just the rapiers.

4) All air breathers give up really early... the rapiers pegged it by 22km with 30km AP. Speed/altitude? Cause uncertain...

5) There is negligible drag past 45km. You can easily coast to orbit from here.

6) I got a 76x72km orbit out of the Dolphin with a mere whisker of fuel left that was just enough to get to 75x50km.

7) I had 70 units of oxidiser to spare.

8) This shallowest of shallow re-entries exploded the plane from the heat... really?

Overall, I think there's a lot of new data points to collect and stuff that flew under FAR is probably not guaranteed to work under 1.0 stock... I dunno yet whether I like it or not. It seems more forgiving during flight, and the crazy stock craft kind of work... but it's also harder to get a bird to orbit, and I can't figure out how to get them down again...

*edit* On the up side, there's a re-entry heat slider I'm going to bed now, but I expect you chaps will have figured it all out by the time I get up for work Good luck!

I just had a play with new aero, taking a basic single RAPIER Mk1 up and down.

It's easy to accidentally pop above your jet altitude, and stock aero makes it hard to pull out of a dive without losing huge amounts of speed so a FAR-style climb & bounce doesn't work. So, take it to 15,000m and then flatten off to cut your climb rate to 10m/s or so.

Stock ships can casually pull extended 15+G manouevres, but they lose a lot of speed in doing so. It's possible to lose control if you try very, very hard to do so, but it's easy to regain control. Stock ships cannot easily fly at low speed and high altitude; they lose too much speed at high AoA to manage it.

Reentry is easy, but you have to do it stock-style: huge AoA and high-G S-turns.

Stock aero ships still glide like bricks; if you run out of fuel, you're coming down fast.

The newly increased jet fuel consumption is noticeable, but it's not a huge issue.

I love the new landing gear (although you can't unlock the steering on it...) but it's annoying that the new wing parts aren't designed to be modular and don't come with a full set of matching control surfaces.

- - - Updated - - -

What do you make of the new heating system? It seems to make spaceplanes start exploding before Mach 3, even though the RAPIERS for instance are good to Mach 5.5 at least. Perhaps DRE's update will make it a little more sensible?

It's very altitude dependent (as it should be). Get up over 20,000m and you can go as fast as you like.

- - - Updated - - -

Also noticed: RAPIER glow stays on when the throttle is off.

Edited April 28, 2015 by Wanderfound

[blowfish]

It's very altitude dependent (as it should be). Get up over 20,000m and you can go as fast as you like.

Without flameouts and while still maintaining enough thrust to accelerate (as jet thrust is now altitude dependent)?

[eddiew]

Squee!

Ooo... do want

Reentry is easy, but you have to do it stock-style: huge AoA and high-G S-turns.

...

It's very altitude dependent (as it should be). Get up over 20,000m and you can go as fast as you like.

Will try these tips tonight - didn't have much time yesterday. Although I blew up around 25-30km on ultra-shallow re-entry, which seemed a bit unfair

Just playing with the atmospheric stock ships, I found them relatively easy to glide and land - my problem was stopping the little buggers. I got the Albatross (big wide glider) down on the old airfield at 70 m/s, and ran off the far end! Not to mention the amount of flex and bend during flight is ridiculous... they have not learned from the existence of KJR at all.

- - - Updated - - -

Without flameouts and while still maintaining enough thrust to accelerate (as jet thrust is now altitude dependent)?

Some of the preview vids I've seen had spaceplanes lighting their rockets before 20km Which may be viable, given that drag more or less stops at 45... but it's decidedly a bit of a shock when you're used to FAR, and probably worse for the stock players.

[Wanderfound]

Not to mention the amount of flex and bend during flight is ridiculous... they have not learned from the existence of KJR at all.

It's just bad building; the stock ships are awful. I don't use KJR, and my stuff doesn't flap.

[Kagame]

Hey Wander:

How much LFO am I gonna need to get two tons into orbit from Mach 2 @ 30K? (let's say getting pushed by a TV45)?

I've been struggling with figuring out how to do proper spaceplanes. Spacecraft I have no problem with. Aircraft I have no problem with. However, my spaceplanes always run out of dV before the periapsis even hits 70K...

[Wanderfound]

Stock, NuStock, NEAR, FAR or NuFAR?

Why from Mach 2? That's an extremely slow speed for that altitude. You want to be over Mach 4 before you light the rockets.

[Kagame]

NuStock, because I love it to bits. And it's Mach 2 because that's the top speed my best micro-SSTO design achieved before switching to closed-cycle. Granted, that was back in 0.90 with FAR and B9's nerf o' doom, so my newer designs may be able to hit three plus. I'll just need to download KER for 1.0 because I can't calculate Mach numbers on the fly...

Rule of thumb for dV, if any exists?