Little help over here!

[ryan234abc]

So I've been working on this craft for a while now. Spacecraft exchange seemed the appropriate place to post this request. I need help fixing it! The plane has decent-ish looks, VTOL engines for low-G environments and is designed to carry up to 50 tonnes to Minmus' surface (in the form of a MK2 parts with wheels), refuel and return, with an IRSU for it's own use away from the base. The design is based loosely of that of Hazard-ish. Be sure to check out his youtube channel for 'Minmus Base: SSTO shipment 3' for an idea of what I'm trying to do (and also because it's amazing!) So far, however, I've been unable to even get it past normal take off.

The plane yaws horribly on the runway, completely uncontrollable as it smashes into the Spaceplane Hangar. If I do somehow manage to make it to the end of the runway, even the slightest pitch upwards sends the plane into a backflip. I've no clue as to range, its ability to get into orbit, with or without cargo, or its re-entry/supersonic handling.

 I'm relatively new to SSTO design, but I just wanted to make something that could help me build up a base on Minmus over several launches. SSTO's really aren't my thing and this is the first time I've built one on this scale, so I planned for failure but nothing THIS bad.

I'll leave a screenshot and a link to the craft file on KerbalX. I'd be grateful if someone could take a look at this, suggest (although as mentioned, I doubt I'll be good at implementing them) or even make improvements to this design. I'd like to keep the part count low, anything too high (175+) makes it difficult to use (200 parts upper limit). Thanks in advance to any and all help!

Ryan

https://kerbalx.com/Ryno/Blitzkrieg-BROKEN

 

Edited March 12, 2017 by ryan234abc

[Yukon0009]

What's the COM and COL placement?

[ryan234abc]

Just now, Yukon0009 said:

What's the COM and COL placement?

COM: Smack in the middle on the X-Axis, between the two large fuel tanks on the Y

COL: Back with the nukes, dead centre on the X-Axis

 

[Aerostar Research]

COM behind the ram intakes, between the first precoolers? It could also be the pitch-power coupling. If it's top-heavy, the COM acts as a fulcrum, and the COT throws the nose upwards. This is a common airliner thing, left in the design on purpose. What you do is just trim down a heck ton for the denser atmosphere at takeoff roll, and slowly remove the trim as you go up.

Also try tweaking rudder authority or mapping the rover steering to different keys if they're not already. It doesn't cut out tiller (nosewheel) steering at 60 like real airplanes. Even worse if it's a taildragger (lol you didn't build a taildragger SSTO did you? cwl)

Edited March 12, 2017 by Aerostar Research

[ryan234abc]

43 minutes ago, Aerostar Research said:

COM behind the ram intakes, between the first precoolers? It could also be the pitch-power coupling. If it's top-heavy, the COM acts as a fulcrum, and the COT throws the nose upwards. This is a common airliner thing, left in the design on purpose. What you do is just trim down a heck ton for the denser atmosphere at takeoff roll, and slowly remove the trim as you go up.

Also try tweaking rudder authority or mapping the rover steering to different keys if they're not already. It doesn't cut out tiller (nosewheel) steering at 60 like real airplanes. Even worse if it's a taildragger (lol you didn't build a taildragger SSTO did you? cwl)

Very in depth! The design started off with so much drag on the front that any slight yaw would cause a flat spin. Once I'd removed that, it was just a matter of adapting the wings. I've tried multiple shapes of both tail and main wing, but nothing seems to work. Centre of mass is smack in the middle of the two Rockomax X200-32 tanks on either side. Its not bottom or top heavy, and the COL is in line with the COM, albeit a bit back. The wings are actually lowered down though, alike those of the real life Space Shuttle but with no tilt. Imagine an upside down letter T. What would you recommend in terms of that? Thanks!

Ryan

[Aerostar Research]

17 minutes ago, ryan234abc said:

Very in depth! The design started off with so much drag on the front that any slight yaw would cause a flat spin. Once I'd removed that, it was just a matter of adapting the wings. I've tried multiple shapes of both tail and main wing, but nothing seems to work. Centre of mass is smack in the middle of the two Rockomax X200-32 tanks on either side. Its not bottom or top heavy, and the COL is in line with the COM, albeit a bit back. The wings are actually lowered down though, alike those of the real life Space Shuttle but with no tilt. Imagine an upside down letter T. What would you recommend in terms of that? Thanks!

Ryan

I meant whether the COM was shifted up or down relative to COT. About the drag: try delta-wing extensions ( higher-sweep delta wing protruding from the front of the main delta, sort of like a chine for the front fuselage. I see you have some already, but try making them about 20% larger. This should bring COM and COL closer. You shouldn't have them more than { 25% body length } apart. It looks like the COT is in line, so that's not it. For now, just fly with trim and fix the leading-edge extension. I don't know what else to tell you unless I download it.

[AeroGav]

The large landing gear is not steerable, that is why it veers off the runway.  I was lucky and it veered left instead of right - i took off from the grass and made orbit first try.       Swap the front gear to a Medium.

[ryan234abc]

Front gear swapped, wings edited. 95km orbit achieved with no payload and 1.5km/s dV remaining! Thanks for all the help!

Roll in the atmosphere seems to result in a lot of yaw for some reason and I think that an orange tank to Minmus is a bit out of it's reach, but thanks to you all I've got a viable base model for an LKO cargo transport or a Minmus crew transfer vehicle! Then again, it's got way too much drag. And prefers backwards re-entry. And flies like - y'know, we've all accepted at this point its a terrible design. But thanks to your generosity and help, it's at least something others can utilise. I think from now on, I'll stick to smaller SSTO's. I quite like the thought of making a Minmus crew VTOL.

At any rate, the help has really been appreciated. It was a broken plane to start of with so anything's an improvement!

Ryan

(And if you're feeling adventurous, give it a go yourself!) https://kerbalx.com/Ryno/Blitzkrieg-II

[AeroGav]

2 hours ago, ryan234abc said:

F

(And if you're feeling adventurous, give it a go yourself!) https://kerbalx.com/Ryno/Blitzkrieg-II

I made a version of it.

https://kerbalx.com/AeroGav/Blitzkrieg-IIg

Main changes

1.  Cones on back of engines for reduced drag
2. Triple engine mount instead of quad, for lower drag, also suits new engine config
3. Engine config swapped to 2 Rapier, 4 Whiplash, 4 NERV.      
4. 2.5metre tanks made a bit shorter since we don't need that much ox
5. Terriers replaced with 12 Vernors in bottom of the CRG 100 bay.  When the doors are closed, they are occluded by the bay and create no drag.  Press K to thrust downward with them.
6. Modular wings replaced with Big S wing and strake segments for extra LF capacity.

Also i beefed up the mining gear to a large converter and 3 big drills.   Total overkill tbh.

I should probably have gone down to dual engine mounts because 4 whiplash is too much given the drag reducing measures - it really goes nuts and likes to zoom out of the atmosphere prematurely if you're not careful.       Still carries a bit too much oxidizer, i find myself leaving empty tanks which is a waste.

Anyway this one can just about get to minmus with the irsu gear.  If not, most of the CRG 100 bay is free so you could always add more LF tanks.

 

 

 

[Rune]

3 hours ago, ryan234abc said:

Front gear swapped, wings edited. 95km orbit achieved with no payload and 1.5km/s dV remaining! Thanks for all the help!

Roll in the atmosphere seems to result in a lot of yaw for some reason and I think that an orange tank to Minmus is a bit out of it's reach, but thanks to you all I've got a viable base model for an LKO cargo transport or a Minmus crew transfer vehicle! Then again, it's got way too much drag. And prefers backwards re-entry. And flies like - y'know, we've all accepted at this point its a terrible design. But thanks to your generosity and help, it's at least something others can utilise. I think from now on, I'll stick to smaller SSTO's. I quite like the thought of making a Minmus crew VTOL.

At any rate, the help has really been appreciated. It was a broken plane to start of with so anything's an improvement!

Ryan

(And if you're feeling adventurous, give it a go yourself!) https://kerbalx.com/Ryno/Blitzkrieg-II

It's not a bad SSTO. I gave the first one a try, and the main mistake was indeed the front wheel. But apart from that, and taking out the very excessive intake are (which I solved by just taking out all the precoolers and associated intakes, gaining much drag reduction in the process), it's just a little overpowered for its weight class. Then again, perfect for adding cargo on top. I would add a bit extra liquid fuel (I 'only' got 2.2km/s out of it empty of cargo in LKO), probably by changing the wings into BigS sections to reduce part count (and frankly, ugliness), and mayhaps lengthening the NERVA pods if it'll still handle the weight, and call it a pretty decent bird for its stated purpose.

 

Rune. Oh, and the tail plane was not tweaked to yaw only, hence the yaw when rolling.

Edited March 12, 2017 by Rune

[Firemetal]

Nevermind, actually read your posts. Great SSTO!.

Fire

 

Edited March 12, 2017 by Firemetal

[ryan234abc]

Thanks For the extra help! Above and beyond my expectations! And thanks to AeroGav for the improved version. As Rune said, drag was a lot of the problem with the actual flight of the plane and the wheel was another critical error. Of course, as my first attempt at such a large scale SSTO, I expected errors.

At any rate, I'll be using the improved version to build my Minmus base. Already scoped out a location for it. I'll be using parts from your base pack, Rune!

Again, above and beyond everyone. I'm no expert on SSTO's, but if I can offer some rocket based knowledge I'll be more than happy to return the favour!

Pics will follow soon, I've gotta devise a lot of the base first.

Thanks everyone for the help with this!

Ryan

[Aerostar Research]

20 hours ago, ryan234abc said:

Thanks For the extra help! Above and beyond my expectations! And thanks to AeroGav for the improved version. As Rune said, drag was a lot of the problem with the actual flight of the plane and the wheel was another critical error. Of course, as my first attempt at such a large scale SSTO, I expected errors.

At any rate, I'll be using the improved version to build my Minmus base. Already scoped out a location for it. I'll be using parts from your base pack, Rune!

Again, above and beyond everyone. I'm no expert on SSTO's, but if I can offer some rocket based knowledge I'll be more than happy to return the favour!

Pics will follow soon, I've gotta devise a lot of the base first.

Thanks everyone for the help with this!

Ryan

I overthought this so much. I'm a fan of civilian airplanes tbh, my design method isn't any good. But yeah, I taught you aero nerd stuff so I've got that going

[nascarlaser1]

cool craft!

Edited March 14, 2017 by nascarlaser1