Pimp my Spaceplane

[dire]

This is a generic, low-tech (mk 2) stock spaceplane. The problem I'm having with it is that while I can get to suborbital with it, and -almost- manage the last little bit to orbit, I can't quite seem to get it all the way there. Is it because I'm using Panthers, which are just not quite up to the task of going high enough and fast enough before I kick my rocket motors on? Should I just be patient and scrape a bit more tech together? Or is there a way to make this sad little plane's dreams come true?

On a side note, is there a good way to get this thing off the runway other than belly flopping off the end? I feel like maybe I put the wheels too far back

Album R9lUU5s will appear when post is submitted

Album https://imgur.com/vdI3ouN

 

And I've tried six different ways to submit this album and it turns out I have no idea how to link to imgur anymore.

Edited November 2, 2018 by dire

[Rocket In My Pocket]

To answer 2 of your questions:

Yes, Panthers are pretty under powered for making SSTO's, although it's certainly possible to do so, it really isn't practical until you have the Whiplash engine.

If you can't rotate on the runway for take off then yes; your wheels are too far back. They should be just behind the planes COM.

Finally, nothing wrong with using plain old rocket engines for your SSTO at this point in your tech tree. The Panthers may be holding you back more than helping.

Edited November 2, 2018 by Rocket In My Pocket

[AeroGav]

41 minutes ago, dire said:

This is a generic, low-tech (mk 2) stock spaceplane. The problem I'm having with it is that while I can get to suborbital with it, and -almost- manage the last little bit to orbit, I can't quite seem to get it all the way there. Is it because I'm using Panthers, which are just not quite up to the task of going high enough and fast enough before I kick my rocket motors on? Should I just be patient and scrape a bit more tech together? Or is there a way to make this sad little plane's dreams come true?

On a side note, is there a good way to get this thing off the runway other than belly flopping off the end? I feel like maybe I put the wheels too far back

Album R9lUU5s will appear when post is submitted

Album https://imgur.com/vdI3ouN

 

And I've tried six different ways to submit this album and it turns out I have no idea how to link to imgur anymore.

Would be better if you could upload the craft file itself on KerbalX or just give us a dropbox link as we've only got screenshots to go on.   

I presume this is the pic you wanted to share ?

Mk2 parts are horrifically draggy , even more so in 1.5.    That is probably why you need so many panther engines.   Panther thrust falls off a cliff above 750 m/s, so a less draggy airplane would not need so many.    Admittedly they are light for jet engines, but your delta V margin to reach orbital velocity on chem engines from a 750 m/s starting point is slim to start with. 

I understand you want a cargo bay though.   You got two choices

a)  try to make the mk2 stuff as minimal aa possible.  In front and behind the cargo bay, taper down to  mk1 size using the mk1 adapter (small).   Use an inline mk1 cockpit with a nose cone or intake ahead to absorb re-entry heat.  Swao all the other fuel tanks to mk1 size

b) ditch the mk2 cargo bay altogether,  use 2.5m parts and a fairing. - this is not my video but it's total genius,

2.5m tanks have the best drag/capacity ratio of all.        So keep all your rocket fuel in those.  I'd recommend a Poodle engine,  it has good ISP in vacuum and high altitude.     One poodle and two panthers should easily be enough on a low drag ship.

 

Here is 

a thread showing the trouble i had converting a mk1 passenger spaceplane into a cargo.

[dire]

OK I've got the craft uploaded here: https://kerbalx.com/direstorm/Spaceplane-12

I get that mk2 spaceplane parts are awful and draggy, and panthers are underpowered, but I feel like if the spaceplane is carefully manged (IE not bellyflopping it into braking 400 m/s like on the run I took pictures of), a couple tons of liquid fuel and some panthers can replace the entire first stage of a rocket, and the rest of it is significantly more recoverable even with the problems a panther has.

I get that purchasing 300-RP parts like the NERVs make life easier on the spaceplane front, and it's really interesting that the 2.5 meter profile has the best drag ratio, but honestly telling me "Just don't do spaceplanes on the 160 RP tier" or "Just don't do spaceplanes period" is, I feel, counterproductive to the spirit of the challenge. If I wanted to strap some parachutes onto a Big Orange and land it Space-X style, that's what I would be doing.

Obviously, if I'm asking for help on a basic spaceplane I don't have any right to boast but I created my forum account in 2011 and I have over 1500 hours logged on the steam version of KSP. That doesn't mean I don't make basic, dumb mistakes sometimes, but what I'm looking for here is stuff like the tip to minimize mk2 parts -- is that because they have lots of surface area relative to their volume? If you want this number of engines, are you better off with two 1.25 columns rather than one mk2 to mk 1 bicoupler? I would think you wind up with even more surface area doing it that way.

 

Edited November 3, 2018 by dire

[AeroGav]

1 hour ago, dire said:

OK I've got the craft uploaded here: https://kerbalx.com/direstorm/Spaceplane-12

I get that mk2 spaceplane parts are awful and draggy, and panthers are underpowered, but I feel like if the spaceplane is carefully manged (IE not bellyflopping it into braking 400 m/s like on the run I took pictures of), a couple tons of liquid fuel and some panthers can replace the entire first stage of a rocket, and the rest of it is significantly more recoverable even with the problems a panther has.

I get that purchasing 300-RP parts like the NERVs make life easier on the spaceplane front, and it's really interesting that the 2.5 meter profile has the best drag ratio, but honestly telling me "Just don't do spaceplanes on the 160 RP tier" or "Just don't do spaceplanes period" is, I feel, counterproductive to the spirit of the challenge. If I wanted to strap some parachutes onto a Big Orange and land it Space-X style, that's what I would be doing.

Obviously, if I'm asking for help on a basic spaceplane I don't have any right to boast but I created my forum account in 2011 and I have over 1500 hours logged on the steam version of KSP. That doesn't mean I don't make basic, dumb mistakes sometimes, but what I'm looking for here is stuff like the tip to minimize mk2 parts -- is that because they have lots of surface area relative to their volume? If you want this number of engines, are you better off with two 1.25 columns rather than one mk2 to mk 1 bicoupler? I would think you wind up with even more surface area doing it that way.

 

Yeah mk2 rocket fuel fuselage long holds 800 units of lfo,   but has over twice the drag of the ft-800.       So yes, you are better off with two mk1 stacks instead of a bicoupler usually at least on the side stacks if not on the main fuselage (since you got to have a mk2 there anyway for the cargo bay).     I can make small tweaks to the design that will  reduce drag a bit,  but i suppose due to the high thrust of the Swivel engine drag might  not be the main problem.

 

The main issue with panther / chemical rocket ssto is that the air breathing top speed is only 1800 vs orbit velocity of 2200 which  requires a lot of rocket fuel to bridge.      With a panther/nerv the large amount of rocket delta v is not such a problem nut you have to keep drag down,  so you're better off with fairings or just bilding passenger/interplanetary craft only and forgetting about cargo.

BTW nervs are 300 tech but that can still be researched on the tier 2 R&D building.   Whiplash and rapuer are 500 and 1000 science points, both of which require the tier 3 building which is hugely expensive.

Also,   the poodle engine and the procedural fairing are 90 tech parts.

I'v never gotten much more than 5% payload fraction out of a panther / terrier design on a mk2 cargo bay,  but i'll see if your ship can be optimised at all.

 

[AeroGav]

OK I got your airplane to orbit first try with 80 m/s to spare.   I have a screenshot but IMGUR been playing funny buggers all week and the pictures are failing to upload.

I made a version with as many parts as possible swapped over to mk1 size,  4 terriers and 2 panthers.  I angled the wings up where they attach to the fuselage so you can fly on prograde hold for less drag.

It weight 6 tons less and makes it to orbit with less pucker factor on the fuel gauge.    However, I had to reroot the ship to change the cockpit,  and that seemed to make RCS build aid loose it's $##4  ,  it kept telling me my dry CoM was too far aft,  i put forward swept wings on,  moved the panthers out to the tips and ended up sliding them so far forward they were alongside the cockpit, before realizing it was broken and stopped listening to it.

So,  you could probably have done this with a planform that looks more like your original.

RCS  action group deploys this nose down trim flap which i installed to try stop it climbing above 14km before hitting mach 2.5.    Even with that,  on the test flight, i overshot this slightly,  ended up coasting to 29km (!)

then it does 5g pullout, bottoming out at 830 m/s and 9.5km.    Started the Terriers at 13km and just stayed on Prograde hold.

 

 

Edit  -  this 77kb image took 10 minutes to process by IMGUR apparently.  Nothing else will upload at all.  Need to send Dilbert i think.

https://www.dropbox.com/s/krtigx263gr5wnv/kLUDGER 1_3.craft?dl=0

Edited November 3, 2018 by AeroGav

[dire]

Working on a version based on your input. I did dedicate the entire science payload of a trip to Minmus on my career to getting the two prereqs for NERV rockets and an actual nucular engine, so the plane is a bit more high-tech than the last one, but now the mission profile is to dock with an orbiting station and onload/offload tourists, then return them to the space center. 

It can still accomplish the original mission of launching satellites by hooking the satellite onto the docking node in the nose and then covering it with the fairing.

Is it still an SSTO if I use a fairing? I think most people say yes but I'm not 100% sure actually.

[dire]

I need a name for my Spaceplane 4 vessel. Pretty sure I'm only using the USI-Kolonization mod for the supplies in the payload, aside from the payload and the Engineer drive I think the rest is stock. It is suggesting that the spaceplane has about 1600 delta-V once in orbit, which is enough to push its payload into a munar orbit and return. If the payload were a mun lander you could do an apollo-style munar landing, although if, like me, you are not very good at hitting your dV targets the margins might be a little uncomfortably slim.

https://kerbalx.com/direstorm/Spaceplane-4

 

Edited November 8, 2018 by dire

[dire]

Finally flew another adapter drone up to the space station and was able to dock to the station with the payload. Those konstruction dockers are a PITA, they don't seem to work with the stock dockers and they're pretty grouchy even when you're trying to dock another konstruction port to them. It was a huge mistake to make my main docking nodes (four of them!) with the konstruction ports.

 

Whuffed the descent. It turned tail first and was doing fine until I decided I still had so much fuel (after topping off the station, which can only hold half an orange tank at the moment) I should try to complete one of those "Get science data from below 16 km" missions I had lying around instead of just landing wherever I fell.

As it turns out, one of the nuclear reactors survived. We aren't telling the natives about the other one >.>

[AeroGav]

@dire

 

Haha ouch,   with engines at the back weight and balance gets tricky when returning with no fuel and payload.

BTW it looks like you're mounting the panthers with tri couplers that are designed for 1.25m rocket stacks.   These 1.25m bicoupler and tricoupler parts are incredibly draggy ,  and will be more so because you are mounting them on the back of 2.5m fuel tanks.    Use  the 2.5m trcoupler - the one that has a 2.5m parent node and three 1.25m engine mounts on the bottom, it is the most drag efficient engine mount in game,  and you are saving drag from the mismatched attach surfaces (back of tank to front of adapter) as well.

Have a look a this design perhaps - payload in the middle,  engines split front to back so neutral CG shift, and  very low drag 

https://www.dropbox.com/s/v0g8bz5wu1xkp68/Fat Fairy.craft?dl=0

Also,   have you had a look at my Panther/NERV SSTO tutorial ?