New Rocket Jockey SSTO Problems

[TheDarkMechanic]

I am thoroughly enjoying this discussion on struts. It's kind of nice not having to strut EVERYTHING down these days. As far as the spaceplanes go, with minimal consultation I was able to make a very primitive plane exceptional, so I'm not going to take issue with the difficulty of their creation/use in game (as said, especially considering the difficulty of reality). It would be nice to have an aerodynamics system that is a little more natural and accounts for things like the drag models we were talking about earlier. I'm thinking about trying out FAR for the first time ever. I'm a little afeared though.

Related, I reentered "Toothless" today and it was beautiful. Aside from an action group failure with the air-brakes at high altitude (easily fixed manually) she floated right down over KSC, which I over shot because I'm a crap pilot. I'm not quite used to the descent of an actual space shuttle so falling that vertically was scary and I screwed it. My planes before this were a little more f14. Went right over the tower, like 4 meters. Gene might have had a heart attack. I easily fired the jets and came around though. My final variant is sans the vertical wingtips.

Has anyone thought that someone might be using game-theory to have us solve actual spacecraft problems?

[Streetwind]

I don't want to hijack this thread with back-and-forth about how game mechanics should work but the simple fact is SSTO space planes don't exist in the real world, so who's to say how they should actually work in the game.

The thread has been off topic for a long while already, we're just talking about interesting stuff now

The thing with spaceplanes not existing IRL isn't a problem of aerodynamics, though. It's one of speed and dV.

Consider this:

- Planes IRL and in KSP can fly at roughly the same speed on airbreathing engines: roughly 1000 to 1500 m/s.

- Orbital velocity in KSP is 2200 m/s.

- Orbital velocity IRL is 7500 m/s.

Can you spot the problem?

(There's also the issue of heat, which KSP largely ignores, but the primary issue we have not been able to solve is how the heck to get to orbital velocity without staging at least once.)

[GoSlash27]

That's a great attitude and I'm sure it has served you well but unfortunately the new young players that I've introduced this game to don't feel the same. They look at the space plane mechanic as overly complicated and difficult and quickly get frustrated and lose interest. Don't get me wrong, I love space planes I just think the aerodynamic model needs to be adjusted to take into consideration the more junior players - and basically it just needs to be fun again. For all those hard-core space plane aficionados, there's the FAR mod (which is still used by many), for the rest of us the aerodynamics should should be enjoyable.

JR,

The problem with that approach is one of gameplay balance. Back in .90 and earlier spaceplanes were so efficient that it didn't make any sense to use chemical rockets. We were doing all sorts of outlandish stuff with spaceplane parts. I had a vertical lifter that could carry a duplicate of itself into orbit as payload (LifterCeption) and I had a spaceplane that could do 3 round trips with passengers between LKO and the KSC without refueling (Groundhog Day). It was really pretty silly

They've toned it down to the point where rockets make sense again. Personally, I think that jets are still a bit OP (see the leaderboard in the payload fraction challenge), but overall I think it's a reasonable compromise for balance and accessibility.

Best,

-Slashy

[KerikBalm]

I present the x1.3 final, re-designated "Toothless." Yes...

http://img.photobucket.com/albums/v304/tdm/Toothless%201.3.jpg

Well, there is still room for a little more improvement - but now we're looking at some pretty small improvements

#1) I see you have fuel lines going both ways from the FL-T800 tanks (on the whiplashes). This is not needed. Airbreathing engines do not need fuel lines. In fact, you don't need any fuel lines of you don't mind doing a manual transfer during flight.

So that is -2 or -4 fuel lines depending on your preference.

#2) you have a cargo bay, use it:

Move your solar panels from the outside, to inside the bay, you won't want them extended in an circumstance where you wouldn't be able to open the cargo bay anyway

[DancesWithSquirrels]

You can probably leave the cargo bay RCS tanks (and their 0.63 mass) behind. They add 120 units of monopropellent, but the Mk-2 docking adapter carries 75 and the cockpit another 15 - more than enough for most docking missions.

[TheDarkMechanic]

You can probably leave the cargo bay RCS tanks (and their 0.63 mass) behind. They add 120 units of monopropellent, but the Mk-2 docking adapter carries 75 and the cockpit another 15 - more than enough for most docking missions.

I didn't even notice the docking adapter has monoprop. Yeah, I can definitely ditch those then. There have been a couple other tweaks since then as well but I can lose one set of fuel lines and accomplish what I want. Hadn't occurred to me, thanks

[GoSlash27]

I didn't even notice the docking adapter has monoprop. Yeah, I can definitely ditch those then. There have been a couple other tweaks since then as well but I can lose one set of fuel lines and accomplish what I want. Hadn't occurred to me, thanks

That was my bad. I pulled the extra fuel lines and forgot to mention it. If you check the pic you'll see they're gone.

Apologies,

-Slashy

[Nich]

sadly slash I can not rep you anymore but I 100% agree

[Jett_Quasar]

JR,

The problem with that approach is one of gameplay balance. Back in .90 and earlier spaceplanes were so efficient that it didn't make any sense to use chemical rockets. We were doing all sorts of outlandish stuff with spaceplane parts. I had a vertical lifter that could carry a duplicate of itself into orbit as payload (LifterCeption) and I had a spaceplane that could do 3 round trips with passengers between LKO and the KSC without refueling (Groundhog Day). It was really pretty silly

They've toned it down to the point where rockets make sense again. Personally, I think that jets are still a bit OP (see the leaderboard in the payload fraction challenge), but overall I think it's a reasonable compromise for balance and accessibility.

Best,

-Slashy

So space planes were OP before and they're OP now and game balance is a matter of opinion. People will continue to do crazy silly things no matter what game mechanics you put in place (I have created several different types of infinite range SSTO's myself - which means 100% payload capacity and the ability to launch and land as many times as you want). But I think it would be a mistake for Squad to accept the status quo ahead of a major release that will put the game out to a much wider market. Complacency has never been a good approach to game design and ignoring constructive criticism is not the path to broader acceptance.

If you think it's OK to have strut-nubs keep a space plane from entering orbit I simply have to disagree with you.

JR

[FyunchClick]

Been lurking these SSTO threads a while now. Thanks to the tips in this and other threads I've finally got my 1.004 SSTO planes working again and with a decent payload. My mistake was pulling up 45 degrees directly upon flameout on the jets, which really dropped my horizontal speed too much; I should've stuck at half that pitch a while longer and slowly worked my way up to 45 (low fuel guages are because I stuck at 20 degree untill I noticed an Apoapsis coming on in 5 secs ).

Thanks to all involved for the great tips (and questions).

Lovely rosy hue on my precoolers thanks to the pair of LV-Ns (so I don't have to worry about the mix of lf and ox). I'll try my hand at rapiers next.

Question: if you're looking for carrying the most dV to orbit, is there anything to be said for going with rapiers for the higher kick in the airbreathing phase and not carying a set of unused engines in either phase, or mix whiplashes with efficent rockets of some sort for a beter ISP in the none-breathing phase?

[Vegetal]

Fyunch, the configuration I see having the most success in this regard is Rapiers + Nukes. You carry just enough oxidizer for the Rapiers to give you the final kick on closed cycle, and then the nukes carry you to LKO and beyond.

I usually don't pitch up much when going closed cycle, but due to the nuke's low thrust, that might be necessary for the plane in your pic. Try not pitching up too much with rapiers though.

[Jett_Quasar]

Your on-orbit delta-V will depend quite a bit on how you fly in addition to how your craft is designed. Vegetal's approach is good but I find a combination of Rapiers and Whiplash to be more efficient coupled with the LV-N. The Whiplash reach a peak efficiency and have higher thrust at lower altitudes and weigh less than the Rapiers. And then of course the nukes will be used to get you the last way to LKO and beyond. The ratio I use is about 3:2:1 - Rapiers:Whiplash:Nukes but my style is to over-design these things.

What I like to do is right-click on one of the Whiplash engines and keep an eye in the thrust while maintaining a constant increase in velocity and altitude. When the thrust drops to around 30kN toggle them off. Then right-click on the Rapiers, and as the thrust begins to drop kick in the nukes. How low you let the Rapiers thrust drop before you toggle to closed cycle mode will depend on your TWR. I usually check on my velocity and if the acceleration starts to slow too much I toggle to closed cycle.

If you're planning on only using the nukes beyond LKO use up all your oxidizer getting to orbit - beyond that it's just dead weight. My design philosophy is to include an on-board ISRU so that the craft can refuel and fly to multiple destinations.

JR

[Vegetal]

Using the Whiplash is just wasteful in my opinion, if the objective is the most dV in LKO, you need the least amount of atmospheric parts weighing your spacecraft.

That's about efficiency of course, if you like over-engineered things, that's another story...

[GoSlash27]

If you think it's OK to have strut-nubs keep a space plane from entering orbit I simply have to disagree with you.

JR

JR,

I'm afraid we're starting to go around in circles now

I'm really not in a position to declare what's "OK" and what's not. I just try to figure out what "is" and how to make successful spaceplanes in accordance with that. What "is" is that struts (even nubs) make a lot of drag so they're best avoided in spaceplane designs in KSP 1.04. Maybe they could figure out a way to better- compute the drag, but then again maybe they can't without overloading the game engine. I don't know. I'm not a coder.

Best,

-Slashy

- - - Updated - - -

Been lurking these SSTO threads a while now. Thanks to the tips in this and other threads I've finally got my 1.004 SSTO planes working again and with a decent payload. My mistake was pulling up 45 degrees directly upon flameout on the jets, which really dropped my horizontal speed too much; I should've stuck at half that pitch a while longer and slowly worked my way up to 45 (low fuel guages are because I stuck at 20 degree untill I noticed an Apoapsis coming on in 5 secs ).

Thanks to all involved for the great tips (and questions).

http://i1031.photobucket.com/albums/y379/jorreholland/screenshot3_zpssnbxeqt4.png

Lovely rosy hue on my precoolers thanks to the pair of LV-Ns (so I don't have to worry about the mix of lf and ox). I'll try my hand at rapiers next.

Question: if you're looking for carrying the most dV to orbit, is there anything to be said for going with rapiers for the higher kick in the airbreathing phase and not carying a set of unused engines in either phase, or mix whiplashes with efficent rockets of some sort for a beter ISP in the none-breathing phase?

FyunchClick,

For tips on maximum DV in orbit, I'd recommend the "single stage to Eeloo" challenge thread. Those folks are assassins.

From what I'm seeing there they go with vertical launch designs, overpowered RAPIERs, weak LV-Ns for vacuum, and maximum streamlining.

I personally don't have experience at that approach, since I only design for maximum economy and reliability to LKO and back.

Good luck,

-Slashy

[FyunchClick]

Fyunch, the configuration I see having the most success in this regard is Rapiers + Nukes. You carry just enough oxidizer for the Rapiers to give you the final kick on closed cycle, and then the nukes carry you to LKO and beyond.

Interesting. That would mean you'd just need to have little ox on board. Do you use a rule of thumb for the ratio of liquid fuel tanks vs rocket fuel tanks?

The ratio I use is about 3:2:1 - Rapiers:Whiplash:Nukes but my style is to over-design these things. [...]

My design philosophy is to include an on-board ISRU so that the craft can refuel and fly to multiple destinations.

Hehe, I was thinking that ratio was more likely 6:4:2 or it'd be hell to balance so it'd have to be big. Is that enough with an ISRU on board (tucked in a MK3 bay?), or do you end up even doubling that again? I can see how this setup would help smoothen those drops in efficiency at several stages, and you and Vegetal both offer a nice solutions for that awkward drop in power after flameout that was concerning me most. Thanks both.

- - - Updated - - -

For tips on maximum DV in orbit, I'd recommend the "single stage to Eeloo" challenge thread. Those folks are assassins.

Good grief I haven't even made it there multi stage... I gotta see that.

[GoSlash27]

FyunchClick,

Sorry, I screwed up the challenge name.

Here's the linky:

http://forum.kerbalspaceprogram.com/threads/117415-SSTO-to-laythe-and-beyond

Best,

-Slashy

[FyunchClick]

Tnx, checking it out.

[GarrisonChisholm]

http://hdwallpapersfit.com/wp-content/uploads/2015/03/f4-phantom-wallpapers.jpg

Proof of concept

The old running joke for the F-4 Phantom was very similar; "You can make a barn door fly if you put a big enough engine on it".

Best,

-Slashy

I loved that plane. Looks like it was designed by a committee, but rugged as heck. That and the F-105. Has anyone built an F-105 in KSP?

[Jett_Quasar]

Slashy, you're way more Zen than I could ever be. I'm all about pushing the envelope and doing things that other people don't - must be my space pirate nature. I love this game but there are still some things that are broken and need to be fixed, and I think the V1.1 release is a good opportunity to do that. I've never spoken up before but I feel some things just need to be addressed.

JR

[Val]

... I was thinking that ratio was more likely 6:4:2 or it'd be hell to balance ...

On a winged craft with a bit of control authority, it really isn't a problem to have your Jet Engines thrusting off-center. It can even be an advantage, if your your nose is heavy, because of far back CoL for stability reasons, then thrusting below CoM can be used to counter act that. Even better if it can be combined with a CoM that moves forward as fuel is used, while the engine thrust increases, keeping the craft nice and balanced during the whole airbreathing ascent. (Not that I've managed that level of synergy yet)

It can also be done with Rapiers, if they are only used to give a short closed-cycle boost, low enough in the atmosphere that control authority can still keep them in check.

Here is an example of off-center air breathing thrust, I built for the Single Stage to Laythe challenge

[KSP 1.0.4] SSTL U-5 Dart Mk.6 [stock]

---

Take-off weight 24.935 t.

In my experience, Rapiers and Jets usually also need slightly different ascent profiles. Jets can usually start climbing for 10 km straight off the runway, while Rapiers need to build speed up to 400-450 m/s at sea-level, before starting the climb to 10 km. At least with the loading I put on my designs, ~25 t per Rapier/Jet.

[Nothalogh]

On a winged craft with a bit of control authority, it really isn't a problem to have your Jet Engines thrusting off-center. It can even be an advantage, if your your nose is heavy, because of far back CoL for stability reasons, then thrusting below CoM can be used to counter act that. Even better if it can be combined with a CoM that moves forward as fuel is used, while the engine thrust increases, keeping the craft nice and balanced during the whole airbreathing ascent. (Not that I've managed that level of synergy yet)

It can also be done with Rapiers, if they are only used to give a short closed-cycle boost, low enough in the atmosphere that control authority can still keep them in check.

Here is an example of off-center air breathing thrust, I built for the Single Stage to Laythe challenge

[KSP 1.0.4] SSTL U-5 Dart Mk.6 [stock]

http://i.imgur.com/Sqa61p2.png

---

http://i.imgur.com/I22Wosd.png

Take-off weight 24.935 t.

In my experience, Rapiers and Jets usually also need slightly different ascent profiles. Jets can usually start climbing for 10 km straight off the runway, while Rapiers need to build speed up to 400-450 m/s at sea-level, before starting the climb to 10 km. At least with the loading I put on my designs, ~25 t per Rapier/Jet.

That's ugly as sin, but I like it

[TheDarkMechanic]

Coolest first thread ever.

Question: if you're looking for carrying the most dV to orbit, is there anything to be said for going with rapiers for the higher kick in the airbreathing phase and not carying a set of unused engines in either phase, or mix whiplashes with efficent rockets of some sort for a beter ISP in the none-breathing phase?

Oooo... good question. Sounds like my next ssto is going to be rapiers and nukes. How integral are the intercoolers to more advanced designs?

[GoSlash27]

Slashy, you're way more Zen than I could ever be. I'm all about pushing the envelope and doing things that other people don't - must be my space pirate nature. I love this game but there are still some things that are broken and need to be fixed, and I think the V1.1 release is a good opportunity to do that. I've never spoken up before but I feel some things just need to be addressed.

JR

JR,

Ain't nuthin' wrong with that. I'm kinda the same way. The folks who have been around for a while know the "impossible" things I managed to accomplish in earlier iterations of KSP.

It's just that I tend to go the opposite way when I find and demonstrate the loopholes. It's important that KSP be accessible to keep the frustration down, but it's equally important to avoid breaking the game by making certain techniques and parts too good or too bad in comparison to others.

Whenever you buff one part or approach too much, you effectively nerf all others. This has to be done carefully to avoid obviating a large portion of the parts and/ or techniques, rendering the game one dimensional.

Conversely, you don't want everything to be equivalent (different looking parts that are all equal) or else you destroy the challenge because it no longer matters how you go about it.

All of this needs to be balanced to make a game that's engaging and educational without being too frustrating or too easy.

I don't think we've perfected the balance yet, but I do think that 1.04 is the best I've seen so far.

Best,

-Slashy

- - - Updated - - -

Coolest first thread ever.

Oooo... good question. Sounds like my next ssto is going to be rapiers and nukes. How integral are the intercoolers to more advanced designs?

My opinion: Totally worthless. They were helpful in 1.02, but they don't seem to do squat these days. Intercoolers don't add any thrust whatsoever. They do help spaceplanes run cooler, but they don't overheat without them. All they add is mass, drag, and cost.

Best,

-Slashy

[Nothalogh]

They were helpful in 1.02, but they don't seem to do squat these days. Intercoolers don't add any thrust whatsoever. They do help spaceplanes run cooler, but they don't overheat without them. All they add is mass, drag, and cost.

Best,

-Slashy

I still add them on principle.

In fact I think the rapier should require them

[Jett_Quasar]

...

All of this needs to be balanced to make a game that's engaging and educational without being too frustrating or too easy.

I don't think we've perfected the balance yet, but I do think that 1.04 is the best I've seen so far.

Best,

-Slashy

- - - Updated - - -

Slashy, on that I will agree with you 100% - I always try to use as many parts as possible on my designs... even when they are infinite range SSTO's.

It's not Zen and it's certainly not minimalist but it will take you where you need to go... in style!

Interesting. That would mean you'd just need to have little ox on board. Do you use a rule of thumb for the ratio of liquid fuel tanks vs rocket fuel tanks?

Hehe, I was thinking that ratio was more likely 6:4:2 or it'd be hell to balance so it'd have to be big. Is that enough with an ISRU on board (tucked in a MK3 bay?), or do you end up even doubling that again? I can see how this setup would help smoothen those drops in efficiency at several stages, and you and Vegetal both offer a nice solutions for that awkward drop in power after flameout that was concerning me most. Thanks both.

That's the idea but it's still a WIP so those ratios are just a rule of thumb. You got it exactly right on the ascent profile though.

JR

Edited September 28, 2015 by Jolly_Roger