SSTO in 1.0.4 career - When are they possible?

[Two]

I've been building around an SSTO in career mode for a few hours now following Scott Manley's great tutorials and my pre-aero-update designs, and so far I got it flying almost to orbit with about 300 dV short. The problem is: my current design is at it's peak fuel/dV rating, so if I add more fuel it actually lacks even more dV afterwards because of the added weight. Since I currently only have the first 2 aircraft engines unlocked (J-X4 "Whiplash"), I wonder if it is even possible to build a SSTO so early in career in 1.0.4.

If anyone built a SSTO in 1.0.4 with only the J-X4 available I'd love to get some ideas on how to do that (pictures would be nice, too).

Edited October 22, 2015 by Two

[GoSlash27]

I've been building around an SSTO in career mode for a few hours now following Scott Manley's great tutorials and my pre-aero-update designs, and so far I got it flying almost to orbit with about 300 dV short. The problem is: my current design is at it's peak fuel/dV rating, so if I add more fuel it actually lacks even more dV afterwards because of the added weight. Since I currently only have the first 2 aircraft engines unlocked (J-X4 "Whiplash"), I wonder if it is even possible to build a SSTO so early in career in 1.0.4.

If anyone built a SSTO in 1.0.4 with only the J-X4 available I'd love to get some ideas on how to do that (pictures would be nice, too).

Two,

An SSTO spaceplane is do-able the moment you unlock the Whiplash.

Here's a small runabout design

http://forum.kerbalspaceprogram.com/threads/129374-Pro-SSTO-builder-pilot-Challenge?p=2100291&viewfull=1#post2100291

Here's a larger utility version:

http://forum.kerbalspaceprogram.com/threads/129175-Mainway-Adobe

Both of these designs are made exclusively of parts that are available once the Whiplash is unlocked.

Best,

-Slashy

[Val]

Assuming you mean Spaceplane SSTOs, then yes, they are definitely possible with Whiplash engines. But the payload fractions are quite marginal, in my opinion.

2 of the most important considerations with spaceplane SSTOs are drag and ascent profile. There's some info here:

SSTO cookbook.

"simple" rule to build spaceplanes?

You can also check out some practical examples I posted in my request thread. The Jet based craft are intended for career play when Whiplash is unlocked, like Slashy's examples. There are ascent and descent instructions with each craft, and even a picture of the tech tree unlocks required.

[Starhawk]

As Slashy says above, as soon as you unlock the Whiplash. A Whiplash and a couple of Terriers and you have a great early-career rescue spaceplane.

Here's a pic of one I built early in my career-mode game shortly after 1.0 came out.

Happy landings!

[Two]

Thank you for the links. It seems my major mistake was to include 2 Whiplash and 1 space engine (which had to be the Swivel for TWR). But then the other way around seems to be the way to go. I will try that. =)

Edited October 22, 2015 by Two

[Val]

Here's a pic of one I built early in my career-mode game shortly after 1.0 came out.

http://i.imgur.com/7tw0Nhc.png

Happy landings!

That is actually a very elegant and beautifully simple simple design. It sort of reminds me of the North American X-15. I like it.

And the landing gear placement gives me shivers, like the X-15 does, for the same reason. Landing gear should be right under CoM. It'll be much easier to take off and avoid buckling and veering sideways. The X-15 could get away with it, but in KSP it's not a good idea.

And if you gave the wings a little incidence, it should still be able to take-off and land without tail strikes.

- - - Updated - - -

Forgot this link in my first post:

Help with launch profiles for low TWR Spaceplanes

Edited October 22, 2015 by Val
Word sequence

[DaMaster_Architect]

I had the same problem in my career, and I developed the aircraft depicted below. With the Whiplash and some basic rockets you can get very far, as others already pointed out. The trick is to make the rest of your aircraft as efficient as possible, as well as the flight trajectory.

This one is now my main workhorse. It's ideal for rescue missions, space station missions, or missions involving some small probe. The craft is very stable, and easy to fly. In a 90x90 orbit I have mostly around 400 m/s left, which is enough for most LKO maneuvers. With a refuel from a space station, this plane gets you anywhere in the Kerbin system. Note: you can easily turn this into a cargo plane by swapping out the passenger cabin and docking port for a cargo bay.

[KerikBalm]

I don't bother with landing gear under the CoM most often now... with the Offset tool, you can just have the plane sit on its gear with positive angle of attack.

Full throttle until it lifts on its own.

The only downside it it can be a bit bouncy on landing if you touch down with too much speed (ie if you can pitch your plane up and still have it climb) - but it you touch down with a flare anyway, its just fine and helps avoid tailstrikes when flaring.

SSTO rockets: as soon as you have a liquid fuel rocket

The LV-T30 payload praction isn't great though

I think the LV-T45 gets a better payload fraction, although I'm not 100% sure*

Whiplashes are great, and you can get great payload fractions with them (>20%)... not marginal at all unlike what val said.

* lets do the dV calculations, assuming a 1.3:1 pad TWR

All rockets have a mk1 pod, and 0.3 tons of chutes (total mass 1.1 tons)

LV-T30: 200 kN thrust at 1 atm. 200/9.8/1.3 = 15.7 ... it can lift 15.7 tons from the pad at 1.3 TWR.

Its mass is 1.25 tons, the 1.1 tons of pod and chutes leaves 13.35 tons for tanks and fuel.

.. * 8/9 = 11.865 tons of LFO. 15.7-11.865= 3.835

Vacuum dV is thus: 9.81*300*ln (15.7/3.835)= 4,148 m/s

Yea... assuming you need ~3,500 m/s vacuum dV to get to orbit... that will do it, and give you about 600 m/s for maneuvers (sadly, not enough for a Lunar flyby)

LV-T45: 168.75 kN @ 1 atm. 168.75/9.8/1.3 = 13.25 tons total mass @1.3 pad TWR

-1.5-1.1 for pod and chutes and engine = 10.65 tons of fuel and tanks = 9.46 tons of LFO

Dry mass is thus 13.25-9.46= 3.79

Vacuum dV is thus 9.81*320*ln (13.25/3.79) = 3,929 m/s .... yea, it gets you to orbit too, and does it with more control, but the payload fraction will be lower

Anyway... either liquid fuel engine should be enough to get you a SSTO ride to orbit without upgrading launch facilities.

If you want to add a science payload... just recalculate with its dry mass added). For example, the LV-T45 will get 3,767 m/s dV with a 0.2 ton science Jr added, maintaining a 1.3:1 TWR

If you use the LV-T30, you'll definiely want to add extra fins because gimbal can't save you (if you don't add at least some fins on the LV-T45, you have to be very careful during the gravity turn). I'll note a set of 3 basic fins is only 0.03 tons.

Time your deorbit right, and you can get to orbit fairly cheaply early on.

[Val]

I don't bother with landing gear under the CoM most often now... with the Offset tool, you can just have the plane sit on its gear with positive angle of attack.

Full throttle until it lifts on its own.

The only downside it it can be a bit bouncy on landing if you touch down with too much speed (ie if you can pitch your plane up and still have it climb) - but it you touch down with a flare anyway, its just fine and helps avoid tailstrikes when flaring.

That is all true.

The point I expressed so poorly, is that landing gear right under CoM, gives much more benign ground handling and is able to carry much greater loads, because the landing gear won't buckle.

Tail strikes can be mitigated by wings with angle of incidence, which means you don't need to lift the nose as high at take-off or when flaring. Angle of incidence also has the added benefit of greatly reducing body lift drag, regardless of landing gear placement.

Another way to mitigate tail strikes, is to add a small landing gear on the tail that doesn't touch the ground, but will hit the ground before the tail does. I usually do that if I can't design my way around a long low tail.

[Two]

I definitely have to check a few more rocket designs. I so far never made it to orbit with a single liquid engine.

[Starhawk]

That is actually a very elegant and beautifully simple simple design. It sort of reminds me of the North American X-15. I like it.

Thank you very much!

And the landing gear placement gives me shivers, like the X-15 does, for the same reason. Landing gear should be right under CoM. It'll be much easier to take off and avoid buckling and veering sideways. The X-15 could get away with it, but in KSP it's not a good idea.

Wow, is the X-15 gear placement ever like my 'Rescue 2'. I'm quite surprised actually.

I'm afraid I have a tendency to use that sort of gear placement quite often ever since I had an unfortunate series of tail-strike incidents early in my spaceplane building career.

I've never had a problem with buckling or veering sideways. The one big problem I tend to have with it is if I am not lined up well on the runway and need to veer after touching down there is a strong tendency for craft with such gear placement to tip to the side like a wheelbarrow.

And if you gave the wings a little incidence, it should still be able to take-off and land without tail strikes.

Yeah, I built that way before I began using wing incidence. I would also swap the type B nosecones for type A's.

Happy landings!

[Mesklin]

You can create usefully SSTO very early in carrier, almost from start:

Download link: http://kerbalx.com/Mesklin/SSTO-Spaghetti-Low-tech-Sc

[Vegvisir]

This is what I've been using, also early career. I'd like to find a way to increase it's range. Once it's achieved orbit there's not a lot left for maneuvers, in orbit or back in atmos. Here it's gliding down because not enough to get home. I'm not sure if more fuel is the answer, since that's just more weight. A better executed launch perhaps.

[g00bd0g]

This is the lowest tier tech minimal SSTO I could come up with. Initial climb and boost to 75m apogee in less than 2 minutes. Full orbital insertion about 3 minutes from cold start on the runway

Javascript is disabled. View full album

Edited October 23, 2015 by g00bd0g

[Signo]

I'll add my 2 cents.

[SpacedCowboy]

I had the same problem in my career, and I developed the aircraft depicted below. With the Whiplash and some basic rockets you can get very far, as others already pointed out. The trick is to make the rest of your aircraft as efficient as possible, as well as the flight trajectory.

This one is now my main workhorse. It's ideal for rescue missions, space station missions, or missions involving some small probe. The craft is very stable, and easy to fly. In a 90x90 orbit I have mostly around 400 m/s left, which is enough for most LKO maneuvers. With a refuel from a space station, this plane gets you anywhere in the Kerbin system. Note: you can easily turn this into a cargo plane by swapping out the passenger cabin and docking port for a cargo bay.

http://i.imgur.com/hf0wQIx.jpg

"This is how you do it" DaMaster. Awesome craft