Need help with SSTO's

[Noname115]

This has been the bane of my existence for as long as I can remember.

Rockets? No Problem.  Planes? Piece of cake.  But SSTO's? HOW DO THEY WORK?

Getting it to fly is no big deal. I can get it into the upper atmosphere. My problems stems from the fact that I can't get to orbit. I've been using combinations of "Whiplash" and the LV-N nuclear engine. The whiplash being used to get off the ground, the nuclear engine being used to get into orbit (with the added benefit of high ISP). I can never seem to get out of the atmosphere though. Always edging JUST behind that allusive 70km mark.

So I ask YOU, fellow kerbonauts: Teach me your ways!  

[regex]

Use a RAPIER.  They work higher up and faster than anything else.  That'll get you started.

[Nich]

Nuke sucks for learning TWR is too low. Try anything else spike is nice

[Gaarst]

^ This, the Nuke is way too heavy for your average small SSTO so not only it has terrible TWR, but it also reduces your TWR when in jet-powered flight.

The one of very few SSTO spaceplanes I ever built (2 actually) used a combination of 2 Whiplashes and 2 RAPIERS. While it is probably not the best thing you could come up with, it might be a good start.

(Pic in spoiler)

Spoiler

 

Edited April 23, 2016 by Gaarst

[Alshain]

The best thing you can do for an SSTO is avoid unnecessary weight.  That includes the LV-N, but also try to limit unnecessary wing segments, also sometimes people try to take too much fuel.  Often adding more fuel just makes the problem worse, not better, while taking away fuel will get you to orbit.

Start with a passenger plane, cargo way way later.

Edited April 23, 2016 by Alshain

[Noname115]

20 minutes ago, Gaarst said:

^ This, the Nuke is way too heavy for your average small SSTO so not only it has terrible TWR, but it also reduces your TWR when in jet-powered flight.

The one of very few SSTO spaceplanes I ever built (2 actually) used a combination of 2 Whiplashes and 2 RAPIERS. While it is probably not the best thing you could come up with, it might be a good start.

(Pic in spoiler)

  Hide contents

 

I actually tried replicating that exact design. Yet, I still couldn't get into orbit. Is there something I'm doing wrong on the ascent?

[lobe]

If you want to build SSTOs, you also have got to know how to fly them. I would suggest practicing with the Ares 4 SSTO stock provides and build from there.

[PanzerAce]

In my experience, SSTOs are easiest when you either go as small as possible (like...11 parts total small) or go huge and massively overpowered. I try to set mine up with tons of atmospheric thrust. Vac thrust doesn't matter as much if you've built up a ton of horizontal velocity while in atmosphere.

 

The other big thing I see people doing is pitch up maneuvers while in atmosphere. This is a bad idea. You want to essentially get on a ballistic arc while in atmosphere, while thrusting to get your apo to about 50K. The. Use rockets to push the apo further down range, and thus out of the atmosphere. When I switch to rockets I only burn professed.

[Broco]

Nuclear Engines are very bad for the orbit burn. They have a great specific impulse but very low thrust and a very high weight. As others said before, go with the Rapier engine for beginning, or a combination of Whiplash + Aerospike (2 each).

You can build an SSTO purely with 1 Rapier engine, just dont add too much weight (aka fuel + passenger cabins...).

A FL-T800 and a Mk1 Liquid fuel fuselage + a Rapier engine should do the trick. Don't forget wings and Intakes

It takes a while till you figure it out but at some point you'll get bigger and bigger and then your framerate drops to 2 with stuff like this:

 

Yes, this thing made it into orbit and it just took 1 hour This was 1.05 though.

Edited April 23, 2016 by Broco

[Atlas2342]

I can build SSTOs but they can't go anywhere because by the time i've made it to orbit, i will have spent almost all of my fuel...

[AeroGav]

Whiplash / LV-N should work actually.   I build with 1 nuke per 15T of vehicle weight.  1 whiplash per 30T vehicle.  

Two concepts for you -

Tiny ship

Mark 1 cockpit.

Fuel tank behind

1 LVN

Decoupler behind the LVN

Intake and Whiplash behind decoupler. 

Attach wing segment with sufficient lift ratings to the whiplash/intake so as to  offset it's weight, so that your centre of lift/centre of gravity is unaffected whether whiplash is on or off.

Jettison the whiplash once it's unable to take you higher and continue to climb on nuke.

Not 100% reusable but it's a lot of delta v and whiplashes are cheap compared to nukes, rapiers and more exotic rockets. under 3000 kredits per launch is  still good.

Bigger ship 

2 nukes in wing mounted pods

1 whiplash in rear fuselage.

I tend to disagree about keeping the wings small.   At angles of attack greater than 4 degrees drag goes up drastically.  You need decent size wings to  keep AoA down at the sort of altitudes we'll be at where the nuke is on its own. And the nuke doesn't have enough power to overcome a lot of drag, nor forget the wings and provide "thrust borne" flight like a VTOL.   Low drag and large wings are absolutely key to making an LV-N ship work.

Especially so if you got tech access to wings that hold fuel, since they weigh no more than fuel tanks of the same capacity rating, and they hold liquid fuel which is exactly what your engine selection needs.

The drawback of large wings is that once in orbit,  they form dead weight and make it harder to get to minmus on the same quantity of leftover fuel.

If you're that bothered, you could always construct in a way that lets you undock from the rest of the airplane in orbit and come back to it later, so you 're not dragging a load of wings up from low orbit to minmus and back - kinda like this

Anyways give me an hour, i'll rustle up a quick Whiplash / NERV ship to show it can be done.

Ps.  Rapiers are better, but i'm assuming OP dont have access to one.

 

 

EDIT - HERE you go 

craft file here

Edited April 23, 2016 by AeroGav

[RCgothic]

Jettisoning engines is not Single Stage To Orbit, btw.

[Grumman]

1 hour ago, Atlas2342 said:

I can build SSTOs but they can't go anywhere because by the time i've made it to orbit, i will have spent almost all of my fuel...

One solution to this problem is to use two craft - one that can get from Kerbin to LKO and one that can carry an ISRU and tanks from LKO to Minmus and back again. The single-stage-to-LKO is the hardest, most time-sensitive part of the mission, so having a tanker make refuelling runs to and from Minmus is an easy way to extend the range of a fully reusable space program.

[AeroGav]

1 hour ago, RCgothic said:

Jettisoning engines is not Single Stage To Orbit, btw.

Cost of complete vehicle 30,561 Kredits.

Cost of vehicle minus the Whiplash stage 25,951 Kredits.

Therefore loss of 4,610 per mission - to put a MK1 cockpit in orbit with >2800 dV remaining.  Sorry if that's not good enough  but I'm just demonstrating the technique.  Not discarding the Whiplash would cost a bit of that delta V but not so much we can't make orbit.

 

The main reason for engine dropping in this case is because I can't think of any easy way to mount them in a 1 NERV 1 Whiplash vehicle and not get into asymmetric thrust problems.

As I stated in my previous post he could build a larger vehicle with 1 whippy in the tailpipe and 2 nerv pods under the wings , that would be nice n symmetrical and would not require engine dropping.

Edited April 23, 2016 by AeroGav

[Nich]

Here is an SSTO with enough oomph to get to minimus.

 

 

[Red Iron Crown]

Moved over to Gameplay Questions.

[Starhawk]

1 hour ago, AeroGav said:

Sorry if that's not good enough  but I'm just demonstrating the technique.  Not discarding the Whiplash would cost a bit of that delta V but not so much we can't make orbit.

It has nothing to do with not being good enough.

If you drop anything on your way to orbit you have staged.  Once you stage on your way to orbit you are using a vehicle which is at least two-stage to orbit.  Thus not single stage to orbit.

There are spaceplanes that are not SSTO's.

There are SSTO's that are not spaceplanes.

 

On topic:

Here's a fairly simple SSTO spaceplane.  Empty half the oxidizer out of each tank.  Fly up to about 15 km.  Level out and activate SAS in 'Stability Assist' mode.  This will allow the pitch to slowly climb as you build speed.  Adjust as necessary allowing speed to build over 1400 m/s before you lose thrust (you begin to lose thrust quickly over 20 km).  Once you've wrung everything from the air-breathing engine that it's willing to give, switch to rocket mode.  Proceed to orbital altitude and circularize.

Happy landings!

Edited April 23, 2016 by Starhawk

[AeroGav]

15 minutes ago, Starhawk said:

It has nothing to do with not being good enough.

If you drop anything on your way to orbit you have staged.  Once you stage on your way to orbit you are using a vehicle which is at least two-stage to orbit.  Thus not single stage to orbit.

 

Maybe I'm just being cranky because i haven't eaten today,  but I feel as though this is being used as a weapon to put devalue the points i was making* and the ship i designed.    It's not a K-prize entry but people seem to want to disqualify me for "cheating". 

I will state for the third time that it is not necessary to drop engines to make orbit but it looks like i got to go build a non engine discarding version to keep everyone happy.               

*what was the points i was making?  I was just wanting to contest the assertion that you cannot get a working design with the whiplash/nerv combo, someone else said you need to make the wings as small as possible, which is not how i do things generally.

Nice looking ship.    I like how you've put some fuel ahead of and some behind the CoG to avoid unwelcome shifts.   BTW what's on the front of the cockpit, circular intake? Docking port? Heatshield?

[Starhawk]

12 minutes ago, AeroGav said:

Maybe I'm just being cranky because i haven't eaten today,  but I feel as though this is being used as a weapon to put devalue the points i was making* and the ship i designed.    It's not a K-prize entry but people seem to want to disqualify me for "cheating". 

I will state for the third time that it is not necessary to drop engines to make orbit but it looks like i got to go build a non engine discarding version to keep everyone happy.               

*what was the points i was making?  I was just wanting to contest the assertion that you cannot get a working design with the whiplash/nerv combo, someone else said you need to make the wings as small as possible, which is not how i do things generally.

Your point is made and taken.  It's all good.  I was just being needlessly pedantic, I suppose.

12 minutes ago, AeroGav said:

Nice looking ship.    I like how you've put some fuel ahead of and some behind the CoG to avoid unwelcome shifts.   BTW what's on the front of the cockpit, circular intake? Docking port? Heatshield?

It's the shielded docking port.  Although it's not very good on drag, it has almost magical overheat prevention capabilities.

Happy landings!

[Wanderfound]

Start small, start simple, walk before you run.

Single-RAPIER designs are probably the easiest to start with. So long as you don't overload it with excess gear, one Mk1 LF tank and about an FL-T800 of LFO should be enough fuel. Possibly add a bit extra LFO if you're unused to making an efficient SSTO ascent.

For example:

 

Edited April 23, 2016 by Wanderfound

[AeroGav]

OK, quickly thrown together mk2 with 2 NERVs, one Whiplash and it's 100% recyclable.  Runs on Biodiesel,  has 2 cargo bays for vegan snacks and the LV-Ns only use ethically-sourced Uranium.

I couldn't be bothered angling with wings so it has no incidence or dihedral.  There's a small heatshield behind the nosecone to save the aircraft if you drive too fast and burn it off.     There's even a pair of bitty parachutes on the tips of each engine nacelle, so Health and Safety will be happy.

We're down to just 1000 delta V on orbit though which is not so good.  With only one whiplash to push all of that, we maxed out at 20km and mach 3 airbreathing.  I'd set the nukes up to custom action group 1 since i had to use their help to get through the sound barrier at 10km

Edited April 23, 2016 by AeroGav

[Vanamonde]

I've been playing this game for about 4 years and still can't consistently get SSTOs to orbit, but I have learned one bit of advice to pass along. Building a plane that can can do it is easier than figuring out the ascent profile for the plane to fly. I would suggest downloading a design someone else has made, so that you know that it works, and practice flying it to orbit. Once you get that technique figured out, making a plane of your own that can do it really isn't all that difficult. 

[Jarin]

I got my first spaceplane to orbit just this week. The Aeris 4A is a great learner ship. Though for re-entry, it really needs to become the custom "Aeris 4B" with some radiators strapped to the cockpit (you can use the translate/rotation tools to make them look aerodynamically nice) and maybe a battery and a couple solar panels. 

Everyone recommends learning on the rapier, and it is indeed the easiest way to work, but that's not all that helpful for diehard career players. What's the earliest in the tech tree that you can manage a proper SSTO?

Edited April 24, 2016 by Jarin

[Wanderfound]

1 hour ago, Jarin said:

I got my first spaceplane to orbit just this week. The Aeris 4A is a great learner ship. Though for re-entry, it really needs to become the custom "Aeris 4B" with some radiators strapped to the cockpit (you can use the translate/rotation tools to make them look aerodynamically nice) and maybe a battery and a couple solar panels. 

Everyone recommends learning on the rapier, and it is indeed the easiest way to work, but that's not all that helpful for diehard career players. What's the earliest in the tech tree that you can manage a proper SSTO?

As soon as you get your first jets and wings:

(advanced canard tailfin just for aesthetics; it'd work just as well with an AV-R8 or similar instead)

However, that's an extreme example. Juno-based SSTOs are novelties. A Wheesley SSTO might be useful for crew transfer, but not much else. Once you've got Panthers, you can manage a bit more, but they don't become truly useful until the Whiplashes arrive.

Once you've got Whiplashes, though, you can annihilate the career game economics. Minimal-cost fuel delivery to LKO makes everything else much, much easier. When refuelled in LKO, a RAPIER/LV-N spaceplane can go pretty much anywhere.

Edited April 24, 2016 by Wanderfound

[zeekkay]

It's usually best to do a mock-up of the craft first using kerbal engineer mod. This is my method.

1) Create a mock-up of your craft. Include all command modules and test cargo mass. Then add some rocket fuel and engines, as well as your jet engines. Your goal is to find out how much rocket fuel you need to haul to 12km to start your run. Make sure your rocket engines have a TWR of at least 1, or you're not going to make orbit. You should want at minimum 1800m/s dV.

2) Now that you know how much rocket fuel you need to reach orbit, begin assembling and laying out your aircraft. Also add some fuel for your jet engines. The trick is to keep that center of lift just behind the center of mass. (Try to keep your fuel towards the middle of the ship if you can)

3) Lastly make sure your jet engines also have a TWR between 1-1.5. It makes things a lot easier. SSTO's are more late game, panther engines might be able to get your craft into orbit if the ship is very lightweight.