SSTO help to minumus/mun... Fuel/thrust balance?

[Arugela]

I modified it and added wins along with changing the control surfaces as I could figure out. I also added a bunch of weight and have two version. One with booster engines to help get up and one without. the regular one, "TheRooster," I'm not sure if can get to orbit. It may very well be my flying. But I think it can't get past Mach 1. The booster one I can get to go faster and I did with engine that can be ejected at the desired point. They should both be identical besides the boosters. And they have the same Action groups as previously. They are definitely looking weirder as they progress.(Mostly from having to pull back the COL.)

I was also thinking of dumping some fuel from the rooster and giving it a large ore tank in the center... If I'm remembering correctly and it gives twice the weight in fuel that 1500 is about 3000LF and would give it more range. Flying the version with an ore tank now(no fuel reduction). Need to see if I want/can have one or two large ore tanks. Edit: may be too heavy and mess up the COM/COL.

BTW, I saw a video that said to put small nosecones on the end of rapiers? I did this. Is that info old and does it lessen my thrust at all?

Edit: And you might need to make the front wheel "deploy shielded." Just noticed it's in the bay and gets that warning.

Craft:(Renamed to stop personal confusion as to which versions I'm using.)

TheRooster

TheRoosterBooster

Pics:

Rooster

RoosterBooster

I seem to be having a hard time getting any of these into orbit. I'll have to go back to the last version and see if I can do it finally. I think I need to reduce the fule back to it's former amount and maybe add a large ore tank for ballast if needed.

Edited October 15, 2016 by Arugela

[AeroGav]

What's your flight profile, when are you trying to go supersonic? I was able to get the duck to orbit easily once i'd stopped snapping its wings off.

1. the booster engines are aft of CG, if you attach a wing with a lift rating of 0.5 to each nacelle it reduces the effect on CG when the engine is attached.  When the engine is jettisoned, so is the little wing so it all balances up.

2. if you enable  advanced tweakables in the game options menu you can give the fuel tanks that are part of the booster engines a higher priority number than the others.  This means they empty first and you are not throwing away fuel with the engine.   Though make sure you have crossfeed enabled on the decoupler if doing this.

3. Rapiers with cones - done correctly it does not reduce thrust at all.  They just stop working completely if done sufficiently badly.   Rather than using small nose cones, use the one that are the same diameter as the engine, then use the offset tool to slide them forwards so you can't see them.  

Trouble going Supersonic - try this profile

Climb out subsonic at first.    Manage the climb angle to control speed.   By 8km or so you want to be approaching 240m/s in a climb.   Set prograde autopilot and toggle the nukes on.  The plane will arc over into a slight dive and should go sonic.   At 400 you can turn the nukes off and gently pull out.

 

[Arugela]

I've been working on the smaller version again. I'm still trying to get maximum delta V at LKO. It seems to be the better one because of the thrust amount. I saw a year old video saying that it helps to put small nose cones on the back or your rapiers. Is this still relevant or is it a waist of tonnage?

 

I think the new duck version is over weighted. It went from the one you flew with 55 tons empty to 60 tons empty and 135 tones overall. I don't think it can get to orbit at all without more engines. It can only start ascending above 20k at around 3000 total LF and it's not enough of a margin to get to orbit and get to minimus and refuel. But I'm definitely at the edge of the engine configurations limits. Without dropping nukes or something. I'm working on improving aerodaynamic on the smaller one and trying to get it to orbit faster. 8) I got it to fly really nice but it's got some problesm with keeping it's nose controled at higher altitudes. I think because I nudged it or because the weight is too balanced now. One of those problems with my nuke/rapier stacking... I'm testing fuel configuration to see if anything helps.

https://www.dropbox.com/s/tmegga34nv5himm/IDGAD Starfighter 2_7_5 Autostrut.craft?dl=0 <-Took off the junos and lightened the craft a little.

Still trying to stop the nukes from heating two of the flaps during ascent without changing the aerodynamic qualities at all.. It's looking good though.

Edit: Dropped the nose cones. I think they were lowering the thrust of the nukes. Was loosing velocity at higher altitudes on the nukes because of it. I think I solved the engine problem also.

I may change out that MK2 rocket fuselage for an LF one to see if I can get farther. And BTW I'm just about to try a potential suicidal entry into Laythe directly from kerbin. No refueling. Edit: Came in at over 9k m/s. Didn't work. But I'm going to try to use jool to slow down next time and see if I can aerobrake in to jool then laythe on one single trip.

 

Edited October 20, 2016 by Arugela

[Val]

7 hours ago, Arugela said:

I saw a year old video saying that it helps to put small nose cones on the back or your rapiers. Is this still relevant or is it a waist of tonnage?

It might have changed with 1.2, but otherwise, they only help if you have trouble breaking through Mach 1. My experience from the Stock Payload Fraction Challenge with high TWR entries, had lower performance with RAPIER-spikes.

 

7 hours ago, Arugela said:

Dropped the nose cones. I think they were lowering the thrust of the nukes.

There's no lowering the thrust. Either thrusts is completely blocked or it is 100%. There's no in between in KSP, yet. (Unless something changed, that I'm unaware of)

[Arugela]

It was definitely lower somehow. I took them off and it the trust was acting as normal. Unless It was only the two middle ones blocked... I didn't move them up like I did the side ones. So, It could have been them blocked cutting down the overall thrust. I was going by how much speed I was gaining during flight(which is very steady after using nukes after 20k.). I didn't look at the actual thrust of the engine. I assumed it was occlusion. Might have to put them back and and see if I can get rid problem with them on.

How cheaty are the nose cones on rapiers btw? Is there a real work equivalent or is it just game mechanics?

Edited October 20, 2016 by Arugela

[Val]

4 hours ago, Arugela said:

How cheaty are the nose cones on rapiers btw? Is there a real work equivalent or is it just game mechanics?

I don't find them cheaty at all, but that's only because they don't provide any benefit on most of my designs. Look at the link I posted above to see some of the discussion we had about it back then.

The best argument for using them, I can come up with is that KSP doesn't model how drag on the end of a stack is affected by exhaust. RAPIER spikes is way to compensate for that. It still reduces drag when there's no exhaust, though. So not a perfect argument.

[AeroGav]

On 20/10/2016 at 0:31 AM, Arugela said:

 

https://www.dropbox.com/s/tmegga34nv5himm/IDGAD Starfighter 2_7_5 Autostrut.craft?dl=0

I played with your ship for a few minutes.    The biggest problem is instability in pitch. This makes it hard to fly an optimal ascent profile.

Your ship does have loads of power in air breathing mode. Starfighter easily reached mach 4.5 at 20km,  then started overheating.  SAS was on.   I tapped the UP key. It was a very short tap, the shortest key press that I could manage.  Unfortunately, due to the instability problem, one the nose started going up it kept going up, despite SAS trying to correct with down elevator.   When angle of attack got too high we exceeded 15g and broke up. 

Other problems -

• The mk2 cockpit overheats easily when it is used as the nose.   Inline cockpits are best.  Also they are more crashworthy !
• There's a vertical stabilizer up at the front of the ship.   When placed ahead of CG they reduce yaw stability !
• The game thinks your drill bit is outside the cargo bay.   Therefore it is generating huge drag.  If you right-click on the drill, "Shielded : False"  even when the cargo bay is closed.

 

Honestly, I think the smaller drill is better anyway.  With 4 RTGs,  your ship will never run out of electricity when mining.  Mining will be slow and take weeks, but you can use 10,000 time acceleration and this will pass in seconds.  

The bigger drill will make the converter work harder, and your batteries will go empty often.   Every time this happens, the drill stops.  The drill will not restart automatically when the batteries recharge ,  you have to click on the drill to restart it.  This will be really annoying !

TrueCoL  is a mod available on CKAN.  It includes lift and drag from fuselage parts when calculating Centre of Lift.  The stock game does not, so the CoL indicator in SPH can be wrong. 

I decided to make a "diet" version of your ship, with half as many engines

It still has enough pitch authority to do this  however -

Spoiler

 

Subsonic climb - lift to drag ratio of 9:1 - decent

going supersonic

Just before the Rapier switches to closed cycle.   To avoid upsetting the balance of the ship with a mad rush of power, only the centreline engine switches.  I just let it switch over by itself when the air breathers flame out at 29km.

After our burst of oxidizer fuelled acceleration,  we've gone from mach 5 and 28km to mach 6 and 33km.   I use action group 2 to kill the rapier while there's still some oxidizer left - want to save that for our Vernier engines, which are in the rear cargo bay.  

As you can see we can easily reach Minmus.

 

Screenshot of the underside..

Spoiler

 

 

Diet Version of the starfighter here

https://kerbalx.com/AeroGav/Diet-Starfighter.

 

Edited October 21, 2016 by AeroGav
simplified/international english

[AeroGav]

I've just edited my last reply.   I've tried to write in "simplified / international english" .  It seems a lot of people in this forum are from Europe/ South America

[Arugela]

Here is my latest version of the Starfighter. I made some improvments. Not sure how much else needs to be done. It can land on duna with some good flying and management. It can also make it to Laythe, but it needs to know where to refuel... It also have mini juno engines so you can land on water and get to shore. It takes a while but you can go a decent distance if needed. Just make sure you are close to shore as possible to avoid issues.

IDGAD Starfighter 2.7.7

I went back to those weird tail fins that are angled to get the COL back far enough. I found a place to put them to get more stability in flight(It's not perfectly inline but back and up in the corner of the farthest back possible weight.). But I often use the "Tumble Weed" method of reentry.... Although it's pretty easy to nose up 5 to 10 degrees to aerobreak. I think it has some limits in that area though.

I even fixed the ladder. Go to the highest point where it says "climb out" then press "f" and he will go onto the wing!! 8)

South Pole landings are nice. You can see Jool on one side and the sun on the other:

And there always seems to be ore on the poles no matter what. Which is nice if you bothered to scan the planet coming into land. 8)

Mining:(Friiiieeennndd!!)<- I need to stop watching crappy game play videos when I'm bored!! ><

 

Anyone notice how all of laythes minerals are generally underwater? I'm betting when we get proper buoyancy stuff we will be able to mine on the ocean floor! 8)

 

Edit: Just left Jool. Now on a 33year trip to Eeloo! 8d ..... This is going to be a while. So how much RL time will the 33year max warp to next maneuver trip take...?! I hope they add another level of warp at some point. Edit2: 21 11 years left! So, what is everyone else doing. 8p

 

Captured Eeloo coming from laythe... Just need to land. It's not any where near as fast spinning coming from laythe. I think you could do an equitorial landing if you start there. I came in at only 1km/s.

I'm not coming in correctly for it, but has anyone used their spaceplanes breaks to simply break on the surface of Eeloo on an equatorial landing to stop themselves instead of aerobreaking? 8) It would be a nice advantage for wheeled vehicles. *add meme about marties mom having done it.*

 

 

BTW, there are no marties mom memes for lythobreaking on the internet.... You have all failed me!!!!! THE INTERWEBS IS DEAD!!!

Laythe to Eeloo was pretty easy. I'll have to try Kerbin to Eeloo at some point:

Friend!:

BTW, I missed a problem with the Docking bay and the front wheel overlapping. The wheel needs to be moved or the Docking bay flipped back over.

Edited October 31, 2016 by Arugela