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Kenny Loggins

Having Problem with SSTO

Question

Hello, I come to you all with a dilemma. I have been playing this game for a long time, but I'm having an issue. Prior to the 1.0 update, I had little problem with SSTOs, however, after the changes, I have not had much success. I was able to make a small one-man SSTO work, however, it is not of much use to me as it cannot dock, only has enough fuel for reentry after establishing orbit, and cannot carry any cargo. The main craft I have been working on, however, I cannot get to successfully establish orbit, much less rendezvous with either my station or my refueling station. I have shaved off much of the profile, reduced drag by eliminating excess external components, and played with how much fuel I load, but to no avail. If anyone has any ideas for how I can improve the craft, and hopefully make it work well, it would be greatly appreciated. 

Images Below

Spoiler

 

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dWhpiPG.jpg

7MVyjAw.jpg

zicraAN.jpg

 

 

Edited by Kenny Loggins

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It's clearly drag related, but I'm a bit confused as to how many points related to that.

I can't exactly make up how you attached the quad center rapier engines on the back of your craft. Is it attached to a quad adapter or two bi adapters?
Is the adapter attached directly to the Mk 2 tanks and moved with the move toolset into the Mk 2 fuselage? (as in clipped) I can't make that part up.
Perhaps you could detach the engines and make a picture on how it is constructed. Congrats though, most people come here first without posting pictures on their first post for help. I hope you can spare another :sticktongue:

Assuming the connection points of the adapter is directly mounted on the Mk 2 fuselage you will have major drag problems. You should use the Mk2 to 1.25m adapter or Mk2 bicoupler on the Mk2 fuselage and put 2x TWR-200 stack bicoupler on the end of the aforementioned piece(s)
Any attachment node (node=green attachment ball) when constructing in the SPH of a particular size needs to fit the same size. Otherwise you'd have a rear end mismatch and that will create major drag (yes, MAJOR!!)
Even if you moved the parts inside one another that penalty still applies. Pretty stupid system, but that is how it works.

The other problem is your choice of cabins and tanks. You used Mk 2 cabins and tanks. They are very draggy, and many people on this forum will not recommend it for SSTO flying. You can better use 1.25m Mk 1 crew cabins, cockpits and fuel tanks. Don't mix Mk 1 with Mk 2 if you don't know what your doing as the Mk 2 has more lift and DRAG but center of lift (CoT) doesn't show that at all in the SPH

Why the reactions wheels? A Mk 2 cockpit has enough torque to rotate the mass you'd ben ended up with once in orbit (whereas space is the first part you'd need them) useless mass, get rid of it ASAP.

I see a command module between the Mk 2 crew cabin and the cockpit. Why? Does it need to be remotely controlled? If no, toss it.
Struts also create drag. I see a strut part on the rear of your craft. There is a "advanced tweakables" function in the KSP menu. Enable it.
When your done, right click a part and use the "autostrut" availability to strut things.

Another important thing we need to know is which part of your flight fails. How far do you get exactly? If you needed quite a lot of liquid fuel to get out of the atmosphere to get to proper speeds it is quite likely related to drag losses in the atmosphere. So if you were to design your plane with above methods you'd probably end up with more fuel to circularize. You probably would be able to add fuel as you would need less rapier engines. I can get on average about 15 tons per rapier into orbit, and at times even less (20ton per rapier). So you would need 3, maybe 4 to get into orbit rather then 6. The fact that you need 6 rapiers kinda proves my point as per the above points. 

I'm also wondrous if you can pitch properly. If that's the problem you could use some forward canards.

 

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I wrote a guide, not very long ago in fact 

It's better if you can share the craft file itself, because something can look ok on the outside but be attached in many different ways to achieve the same look, and some methods create excess drag.

I am fairly certain drag is your main problem - six engines for a payload of cockpit only ?  

The TVR-200 stack decoupler has absolutely horrible drag, never use it on an aircraft.       Also, the mk2 fuselage parts themselves are awful for drag.

Most drag comes from the fuselage in this game, you've tried to minimise wing to reduce drag but that makes you fly lower and at a higher angle of attack, which makes the fuselage drag even more.

Note, you could just abandon the mk2 parts altogether for now and go with a mk1 design, the drag is wayy less

rw8hRBN.png

Inline cockpit, by not being right at the front of the ship, doesn't get so hot - overcomes the heat disadvantage of mk1 parts.

One whiplash, two nukes.     Had to  push the nukes way up towards the front so the plane doesn't become unbalanced when empty.      Only one passenger but it's got some fuel left.....

BTW, if you want to play with that above mk1,  here's the download link.

https://www.dropbox.com/s/6r745tedeau4bnj/hunter.craft?dl=0

I tried to keep it a simple airplane, no advanced construction techniques.

Main thing, at all times keep it so the nose is not pointing more than 5 degrees above prograde or drag might stop it accelerating.

Take off,  climb to 5 or 6km, level off to accelerate supersonic.   At 440 m/s start climbing again.    Try to level off at 15-17km to hit max speed in level flight.   If you go too high,  wait till she comes back down a bit.

You should be able to reach over 1000 m/s.   When acceleration starts to fade,   press space bar to start the nukes, and ease the nose up to about 5 degrees above the prograde symbol, leave it there.

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I'm no SSTO master, but a couple things come to mind:

1) You can get a (well-designed, minimalist) 20t craft up to 25km altitude and 1600m/s on a single RAPIER, so 6 rapiers for 50 tons seems a bit excessive.  3 RAPIERs should be enough for your craft.  Dropping 3 engines means your mass also drops to 42 tons--see point 3 below.
2) Mk2 parts look pretty, but are very draggy, are heavier, and don't hold any more fuel compared to 1.25m tanks of the same length.  Also, you have lots of other draggy stuff at the back of your craft. The bicouplers are really bad for drag as well.
3) As with all spacecraft, minimizing weight is key.  Use wet wings rather than cylindrical tanks where practical. Only have as much engine as you need.  Those extra reaction wheels (4 of them!) are dead weight (400kg).  So are those precoolers (there's another 720kg you can shed).  If you lose those along with 3 RAPIERS, that will significantly improve your remaining fuel in orbit.
4) SSTOs are *very* sensitive to ascent profile, and there's a lot less wiggle room than you have with a standard rocket.  You want to be going as fast and high as possible on air-breathing mode before you switch to closed cycle.  If you switch to closed cycle at 20km and 1200m/s, you'll end up burning a LOT more fuel to get into orbit, compared to starting at 25km and 1500m/s.  That extra 300m/s at the beginning takes a LOT more fuel than the last 300m/s.  The hard part is not burning up once you're going 1500m/s and accelerating.  That's where you'll need to do a bunch of testing to determine the ideal angle at which to aim when you switch to closed cycle.
5) lastly, you *are* getting a lot of stuff into orbit with that craft--a Mk2 capsule, a Mk2 crew cabin, the Mk2 inline docking port (I think that's what I see).

so...swap out Mk2 parts with Mk1 parts, drop 3 engines, lose all the unnecessary bits (wow, lots of RCS thrusters, too!), improve your drag, and work on your ascent profile, and you should see a lot of improvement.

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I have to agree... it's a nice looking SSTO, but I think you have too many engines for what you need to do.

Here's a little 2 passenger SSTO I made a while back using 2 rapiers and 1 whiplash engines, which is more than sufficient to get her into orbit.

u5xWras.jpg

iNlow9Z.jpg

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@AeroGav I like LF only planes in general but that's a efficient little thing I tell you.

Are these wing strakes really that drag efficient as I've heard? I'm kind of in esthetics on my vessels and can't always like the wing strakes (big S) but if they're that drag resistant and it leads up to 1 whiplash for sub 30 tons. That's just gold right there.

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Thanks so much for all the input guys! I'm gonna go work on the craft now. The reason I've been using mk2 is that they are the right size for docking with my stations (I can include pics if you guys want), but if you guys think I could do better with a different part set, I can try that. The drone core is needed for missions where I need to transport more than 4 kerbals without adding too much more cargo space. I didn't realize how much extra drag the bicouplers were adding, I'm going to remove those for starters, along with some engines (3 seems to be the concensus). Also, would I be better off just scrapping the Rapiers and mixing nukes with jets?As far as intakes, is a good ratio 1 intake / engine ? Do the pre-coolers add drag? I added them thinking they would minimize it as intakes. With the reaction wheels and rcs respectively, the reaction wheels were my solution to instability in flight upon reaching thin atmosphere that I was experiencing with early versions of this craft (no longer an issue), and the rcs was my answer to manuevering slight changes to the orbit (back when this thing could *just barely* establish orbit, lots of changes to the game since then), so I will look into removing most of those. Final question, I was under the impression that less wing = less drag = better flight, but should I look into upping wing area again? It originally had much more area. 

Edited by Kenny Loggins

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9 minutes ago, Helmetman said:

@AeroGav I like LF only planes in general but that's a efficient little thing I tell you.

Are these wing strakes really that drag efficient as I've heard? I'm kind of in esthetics on my vessels and can't always like the wing strakes (big S) but if they're that drag resistant and it leads up to 1 whiplash for sub 30 tons. That's just gold right there.

All wing surfaces in KSP have the same lift/drag ratio

However Big S strakes have 1/5 the dry mass of the Big S wing, but hold 5 x 100 = 500 units of fuel instead of 300 .

So you're better off with 5 strakes instead of 1 wing if you can stand the part count (and the looks)

the drag is coming from your fuselage however.      You need to   eliminate the attachment problems causing drag if you're determined to stay with mk2,  then increase lift/wing area,  and angle the wings up  a few degrees so you can fly the plane with SAS set to prograde hold - this will reduce drag.

Edited by AeroGav

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Besides the fact that MK2 in general is very draggy unless your piloting is perfect -- to the best I can tell you have those center 4 engines radially attached, with an empty node in the middle. Very draggy.

The precoolers don't help anything either, really. You can get by with just the 2 shock cones.

So, ditch those 4 central engines. Add an MK2 bicoupler and put 2 rapiers on it. If you are willing to ditch the MK2 nacelles and go to MK1 for the nacelles, that would help a lot.

 

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3 hours ago, Kenny Loggins said:

Also, would I be better off just scrapping the Rapiers and mixing nukes with jets?

It's my preferred approach but most people on the forum say that's an "expert move".   I think it just swaps the running out of fuel problem for a "unable to accelerate on these weak nuke engines" one.  To make liquid fuel only work, you need lots of lift and low drag, and good heat tolerance.   If you can pull that off it works really well,  but the problem craft is about as far away from this as is possible to be - tiny wings, draggy  and with a cockpit right at the very front of the ship, begging to overheat.

If you want to stay purely chemical,  you could experiment with 2 rapiers 2 panthers.  The Panthers perform strong up to 750 m/s and after that the Rapiers are performing so well they won't need any help.  The panthers weigh only 1.2 tons each, much lighter than Rapiers at 2 tons.

3 hours ago, Kenny Loggins said:

As far as intakes, is a good ratio 1 intake / engine ? Do the pre-coolers add drag?

You can't go far wrong with that.    Hanging engine nacelles off the side of the ship to get more engine mounts means you need something on the front of those nacelles so might as well be a shock cone.      Of course if you go with 4 engines,  two on the main fuselage and two in nacelles, you could build the nacelles from pre coolers but put shock cones on the front.   Intakes cause drag but nothing like as much as iincorrectly attached parts or mk2 fuselages.

3 hours ago, Kenny Loggins said:

With the reaction wheels and rcs respectively,

I am actually a fan of reaction wheels , they are heavier than RCS but lower drag.   

3 hours ago, Kenny Loggins said:

Final question, I was under the impression that less wing = less drag = better flight, but should I look into upping wing area again? It originally had much more area

Press ALT F12, go to Physics Tab, then Aero, and tick the "display aero data in action menus",  that way you can see how much drag each part makes as yoGu5YdJf.jpgu fly it.

 

To clean that plane up  -

  1.  Resolve part attachment problems.     Use adapters when you connect parts of different size when using the end attachment nodes.  Do not leave any unused attachment nodes at the front or back of a stack.  Fit a cone to cover the blunt end always.   Keep fuselage parts orientated prograde/retrograde.   Don't angle them outwards like you did on the mounts for your outboard engines, this greatly increases drag
  2. swap mk2 parts for mk1 where possible.  In other words, the nacelles either side of main fuselage should be mk1 parts not mk2.     Don't use mk2 fuel tanks at all (apart from the bit of tankage you get in the adapters/bicouplers).  Put your rocket fuel in mk1 or 2.5m tanks.     Don't use liquid fuel -only tanks in any size.   Fit more Big S wing parts to increase capacity.
  3. yes , more wing area.    If a chemical fuel only ship,  one pair of big S wings and a strake or two is enough.     At least double that if you're making a liquid fuel only nuke SSTO. This lets you fly higher, so less drag.
  4. When the design is finalised and you're happy with the CoM / CoL,   angle the wings up a few degrees.  If your plane has canards/strakes ahead of the main wing, make sure you angle those up too by the same amount, or slightly more, or you can really mess up the handling.       This change lets you fly closer to prograde and still get enough lift,  which reduces drag.
Edited by AeroGav

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So I threw something together this evening, with your "payload" of cockpit, crew cabin, docking port, etc.  I got rid of all the rest of the Mk2 parts, cut it down to 3 engines, no bicouplers, no empty node attach points (except on the back of the RAPIERs), no extra intakes or anything.  I didn't take a whole lot of care on my ascent, but got to orbit with 1000LF and 800OX left in the tanks.  KER says I have 1,300 m/s left.  Launch mass is about 33 tons

gVnir6z.png

It doesn't have solar panels, and its CG moves probably a bit too far forward when it's empty (hey, I was rushing it!), but it *is* quite overpowered.  I could probably cut it down to 2 RAPIERs and have it still work.

 

EDIT:  I did a bit more tweaking, and here's the 2-engine version:

vACApet.png

It would have more dV in orbit, but I forgot to fill the wing tanks before takeoff. Gross take off weight (with all fuel) is a hair under 30 tons.  Because it has less thrust, I had to switch to closed cycle a few thousand meters lower and 100m/s slower than with the 3-engine version.

One thing worth noting is that this design could really use more wing area.  I have to get well over 125m/s for it to leave the ground.

Edited by zolotiyeruki

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1 hour ago, zolotiyeruki said:

So I threw something together this evening, with your "payload" of cockpit, crew cabin, docking port, etc.  I got rid of all the rest of the Mk2 parts, cut it down to 3 engines, no bicouplers, no empty node attach points (except on the back of the RAPIERs), no extra intakes or anything.  I didn't take a whole lot of care on my ascent, but got to orbit with 1000LF and 800OX left in the tanks.  KER says I have 1,300 m/s left.  Launch mass is about 33 tons

gVnir6z.png

It doesn't have solar panels, and its CG moves probably a bit too far forward when it's empty (hey, I was rushing it!), but it *is* quite overpowered.  I could probably cut it down to 2 RAPIERs and have it still work.

 

EDIT:  I did a bit more tweaking, and here's the 2-engine version:

vACApet.png

It would have more dV in orbit, but I forgot to fill the wing tanks before takeoff. Gross take off weight (with all fuel) is a hair under 30 tons.  Because it has less thrust, I had to switch to closed cycle a few thousand meters lower and 100m/s slower than with the 3-engine version.

One thing worth noting is that this design could really use more wing area.  I have to get well over 125m/s for it to leave the ground.

6

huh, I might just cut it down to two then. Ill get back later with an updated craft file and pic. 

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Alright. This is what I've got so far, it can technically establish orbit, and so far is more successful than my other designs. However, I'm having trouble getting it to orbit with enough extra fuel to do anything productive. I'm thinking it's flight path problems, as I always seem to have a significant excess of liquid fuel left in my craft when I run out of oxidizer. Any advice?

Spoiler

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Craft File 

 

Edited by Kenny Loggins
added craft file

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2 hours ago, Kenny Loggins said:

Alright. This is what I've got so far, it can technically establish orbit, and so far is more successful than my other designs. However, I'm having trouble getting it to orbit with enough extra fuel to do anything productive. I'm thinking it's flight path problems, as I always seem to have a significant excess of liquid fuel left in my craft when I run out of oxidizer. Any advice?

That's a big improvement !

Without nukes, there is only so much liquid fuel you can make use of.  However, you should be getting to 1400 m/s air breathing before switching to rocket mode.    

From the wiki -

400px-CR-7_R.A.P.I.E.R._Engine_velocity_

You can see that if you had enough power to bust mach 1, you should be able to manage mach 5.5 at sufficiently high altitude.      Which altitude ? On the RAPIER, 20-22km , beyond that, power falls off more quickly with increasing height than drag.

If you do that however, you might find things getting hot up front.     It might be less stressful with an inline cockpit.

Edit -  I like to disable "auto switching" on the RAPIERs,  it's really easy to accidentally fly too high and trigger a premature switch to rocket mode - then you're committed.    If it's on an action group instead, you can just wait till you get her back down to the proper speedrun altitude and switch over when you want to .

BTW,   you could try a  version of that ship with one centreline rapier and a pair of panthers out on the nacelles.

 

Edited by AeroGav

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Here's a 2R 1P version of your ship.   https://www.dropbox.com/s/w0hpyfxrjva8dlp/Wyvern Mk3a.craft?dl=0

Climb out at 35 deg on takeoff, then set Prograde Hold.         Use action group 3 to toggle afterburner on / off and  damp out oscillations in acceleration and climb rate.

3nrP79d.jpg

Burners on for transonic acceleration 250m/s to 430 m/s.          After that back to dry power or we'll climb too steep.         Burners back on above 700 m/s.

bfEK3qP.png

Switching to close cycle ..

FZWJtNu.png

About 500 m/s delta V in orbit.    If you want more, chemical SSTO not really optimal.

The ideal panther / rapier ratio is probably 1:1, but something this size doesn't need 4 jet engines.    The main thing is busting the sound barrier.  If a RAPIER ship can do that, it has enough thrust to reach space... the only question is if the fuel is sufficient.

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5 hours ago, Kenny Loggins said:

I'm thinking it's flight path problems, as I always seem to have a significant excess of liquid fuel left in my craft when I run out of oxidizer. Any advice?

you could replace the 2 mk1 liquid fuel tanks behind the shockcones with same size LFO tanks. the 600 liquid fuel from the wing strakes should be enough for the whole airbreathing phase of the flight anyway.

simply take off, set the nose somewhere between 8 and 15° above horizon and keep it that way until you're in orbit. if you can't break the soundbarrier, either change to a more elaborate ascent profile or simply add a 3rd rapier into the mix. if you accelerate to fast and the nose explodes, use a higher angle. 

 

it's just a simple passenger plane to get some people to a low orbit station - a task you could handle with a rocket quickly thrown together and launched in only a few minutes. so the plane shouldn't require an elaborate ascent profile that takes 15 minutes to orbit. that would kinda defeat the purpose, imo. just make it a little overpowered and enjoy a quick ascent - you probably won't need more than maybe 500 m/s left in orbit to dock to your spacestation (and for the retro burn to get back to KSC) anyway.  

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https://www.dropbox.com/s/exlkyurpwhq2hf7/Wyvern Mk3b.craft?dl=0

...and here is a 1R 2N version.    Actually, I ended up adding 2 Junos, because it took 14 minutes to get to 7km and go supersonic with just one RAPIER.     By 4km sheer boredom had driven the crew to autoexrotic asphyxiation,  by 6km, cannibalism,  and by 7km the crew had started worshipping Cult of the Kraken and had converted the passenger cabin to an occult temple, with ritual sacrifices.        Anyway, with 2 Junos it only takes 7 minutes to get to the same point, so you should be fine with a bit of Tolstoy.

Action group 2 toggles some trim flaps that force the nose down slightly, helps to manage climb rate when flying on SAS prograde hold.

Action group 3 toggles nukes, obviously you want to put them on for a bit when crossing the sound barrier.

Didn't get much more than 1200 without having to restart the nukes, but the RAPIERs didn't flame out till over 1500.

1hSH1XV.jpg

YMhRUZv.png

>2300 dV but takes 27 minutes instead of 18 to reach orbit.   Also a bit ugly, I'm afraid the force is not with me today.

Like I say, my favourite jet engine layout is 1R 1 P,  but unless you fit them in pairs (2R 2P) asymmetric thrust is a problem, and a craft this size doesn't need that much power.  You could just  go 1R 1P and clip the engines into each other to solve the asymmetric thrust, but then everyone starts calling you a cheating scumbag. 

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example of a simple crew plane similar to the one OP asked for:

https://imgur.com/a/9NRZv

quickly thrown together. very simple handling - basically just throttle up, take off, set nose to ~10° and let it soar. engine cutoff after about 4 minutes, then fast forward to AP and circularize after ~10 minutes game time (maybe 5-6 minutes real time due to physics warp/normal time warp after engine cut off)

still plenty of fuel left for some rescue missions in low orbit or docking to a space station somehwere in LKO.

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Spacepoanes are not exactly my area of expertise but I'd like to adress a few points.

-Too many engines can easily lead to stability problems. That because putting engines at open nodes at the rear seems natural tendency and consequently the CoM is shifted toward the rear. This make more difficult to keep the Aerodynamic Center behind CoM (to make things worse, ulike CoL, we don't hage Aerodynamic Center indicator). Often that results in a barely controllable spaceplane that struggle to keep the correct attitude on the ascent and happily flip on reentry.

-there is not a 'right amount' for wings. Much like in real life (F-104 vs U-2) , also in KSP both approaches can result in effective planes. Each approach will also rely more or less in different other characteristics of the craft to produce a balancef craft

-Nerv is well know for its strong and  weak points.  I think the decision to use it or not should be based mostly on how far one want to go. If you just want to go to a station in LKO and back to Kerbin nervs are a bit of overkill but for a interplanetary spaceplane they turn out more of a necessity.

-weight is sometimes a neglected factor for spaceplanes, but cutting some deadweight can often turn a 'good' craft in an 'excellent' one. Its particularly common to not take the opportunities to Improve overall performance when it will have a negative effect (even if slight) in the atmospheric flight or deltaV budget. 

 

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One other thing I'd like to point out to the OP... and if I'm ninja'ing someone else I apologize.

SSTOs are one of the biggest challenges in the game, and even some of us more experienced players can spend days, or even weeks, tweaking a design until it's finally right. So don't give up or let it get to you if it doesn't work right off. :wink:

This is my most famous SSTO in Emiko Station, the Diamondback:

mzMAxW7.jpg

GAXXt9t.jpg

I spent over 2 months working on this one, until I got it where it can make it into orbit and back.

 

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2 hours ago, Spricigo said:

there is not a 'right amount' for wings. Much like in real life (F-104 vs U-2) , also in KSP both approaches can result in effective planes. Each approach will also rely more or less in different other characteristics of the craft to produce a balancef craft

I think the tradeoff depends on whether you're chemical or nuclear.    Wings keep you up until you hit orbital velocity.   When air breathing, you need to stay below 22km so there's no advantage having larger wings than the OP's Wyvern mk3.    Once you go closed cycle,  larger wings get you up into the thinner air earlier, or let you run a lower angle of attack.  Less drag and heat.      But,  wings add to your dry mass.        On dual rapiers,  you got 360kn thrust,  so it won't make much difference to you whether drag is 30kn or 45kn.   But every gram you can take out of the craft makes your ISP go further.  Also, you got no need for the extra liquid fuel tankage anyway.

On liquid fuel only, each nuke weighs 3 tons and only makes 60kn - one third of a RAPIER in closed cycle.     So if total thrust is 120kn and drag losses are 80kn, it's a lot more economical to add wings to reduce the drag than to fit more nukes.   One nuke has the dry mass of three pairs of Big S wings.

3 hours ago, Spricigo said:

-Nerv is well know for its strong and  weak points.  I think the decision to use it or not should be based mostly on how far one want to go. If you just want to go to a station in LKO and back to Kerbin nervs are a bit of overkill but for a interplanetary spaceplane they turn out more of a necessity.

I used to think that, till I built this thing, https://kerbalx.com/AeroGav/partridge

Spoiler



 

the payload mass fraction of 43.7% is pretty  competitive.    Though if you're after making the highest possible delta V SSTO ,  build a chemical one since it'll have lower dry mass, and use one nuke and a bunch of mk1 liquid fuel tanks as the "payload to orbit".  I max out at around 6k delta v on liquid only, but people building huge rapier powered ships with a single nerv can get 8k or 9k.      Not very useful outside of a competition though,  120ton craft with 1 nerv makes for awful burn times, and it won't actually have the TWR to land anywhere.    Even on Laythe the lack of wing area could make landing tricky

2 hours ago, Just Jim said:

SSTOs are one of the biggest challenges in the game, and even some of us more experienced players can spend days, or even weeks, tweaking a design until it's finally right. So don't give up or let it get to you if it doesn't work right off. 

Honestly, my first orbit in KSP came from a spaceplane.   I've been messing with flight simulators since the 1980s and used to have books on the F-15, B1-B lancer etc. in my bedroom as a kid.   Read a book about gliding as a 14 year old too, went up in one a few times.         Fast forward 20 years, got KSP.     My rockets kept flipping, wobbling and blowing up and i couldn't figure out why (hadn't figured how to adapt what i knew about aerodynamics to rockets, which don't have wings).     After scaring and killing jeb umpteen times, went to SPH and stuck a pair of airliner wings on a mk1 fuselage, flew around the space centre.   Jeb was smiling, not freaking out.    Landed, decided to try a space plane.    

Discovered that just because you can put the canards at the front, it's not a good idea to put the tail fin there as well, even though it looks like it might save space.   Rebuilt the SPH.  Try again with the vertical stabilizer at the back.  Think I got to orbit in my first 2 or 3 attempts.     Took me another week to learn how to gravity turn the tutorial rocket. I'm still not much good with delta V calculations or sizing stages.

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Well... Oh boy.. SSTO's..... Me and these beasts go way, way back. I remember when I first got KSP, I spend hours on the old.. I think it was T40? The thingy with the engines mounted to drop tanks with the forward-swept wings? Yeah; that thing. Well anyways, I spent a ton of time just messing around, trying to land that thing on the grass with a 90% success rate (Stupid hill :angry:). So, I watched Duna Attacks (Great movie by the way) and I tried to replicate the SSTO's. I spent many-a-day trying to get those RCS ports in just the right spot (You know, that move where you spend an hour flight, only to find out that an RCS port is half a centimeter too far forward? Yeah; those kinda moves), and finally, I had it. Then, the save got corrupted, so I lost it. Go me, right?

Anyways, I'd just like to say; keep on trying! Basically, build a regular plane, and just go from there! Use your instincts! Try, fail, and revert flight again! KSP is meant to challenge your abilities. Even if it takes what seems like forever, you'll get it. And I promise, when you do, you'll feel like you own the world :wink:

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12 hours ago, Kenny Loggins said:

Alright. This is what I've got so far, it can technically establish orbit, and so far is more successful than my other designs. However, I'm having trouble getting it to orbit with enough extra fuel to do anything productive. I'm thinking it's flight path problems, as I always seem to have a significant excess of liquid fuel left in my craft when I run out of oxidizer. Any advice?

This is the correct response:

6 hours ago, mk1980 said:

you could replace the 2 mk1 liquid fuel tanks behind the shockcones with same size LFO tanks. the 600 liquid fuel from the wing strakes should be enough for the whole airbreathing phase of the flight anyway.

In my experience, 300 units of LF per RAPIER is plenty for the air-breathing part of the ascent, and that much is being provided in your strakes.  So the rest of your fuel tanks can be LF/OX.  Or, you could simply delete the two Mk1 LF tanks, saving 4 tons of takeoff weight. Going from 27 tons down to 23 tons will make a big difference.

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1 hour ago, AeroGav said:

I think the tradeoff depends on whether you're chemical or nuclear.

More like it exacerbates some of those factors: thrust/drag and thrust/weight. (Also maybe not directly applicable for different combinations of engines) 

Regarding the other point, I think your comments kind of corroborate my opinion. For one side, on the short range, chemical can offer similar peformance than the weak, heavy and expensive nerv.  On the long range you want the high Isp. Nonetheless,  good point about using chemical propulsion for mass saving purposes.

 

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41 minutes ago, DarkOwl57 said:

Well... Oh boy.. SSTO's..... Me and these beasts go way, way back. I remember when I first got KSP, I spend hours on the old.. I think it was T40? The thingy with the engines mounted to drop tanks with the forward-swept wings? Yeah; that thing. Well anyways, I spent a ton of time just messing around, trying to land that thing on the grass with a 90% success rate (Stupid hill :angry:). So, I watched Duna Attacks (Great movie by the way) and I tried to replicate the SSTO's. I spent many-a-day trying to get those RCS ports in just the right spot (You know, that move where you spend an hour flight, only to find out that an RCS port is half a centimeter too far forward? Yeah; those kinda moves), and finally, I had it. Then, the save got corrupted, so I lost it. Go me, right?

Think that's the Stearwing D45

I tried to recreate it actually, and make it work in KSP 1.2+   https://kerbalx.com/AeroGav/Stearwing-D45N-Lite

 

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