Is it even possible to make a <15t laythe roundtrip SSTO?

[Michaelo90]

Thank you

My thrust is mostly in-line, at least for the nuke. The Rapier not so much, but it doesn't matter since it's only used where control surfaces can compensate. The reaction wheel combined with moving fuel around is enough to keep it stable in vacuum.

I think the reason you get less dV is because you have more drag, so you use more fuel getting to orbit.

Like in real life, KSP wings only produce lift when they're at an angle to the Airflow. If you mount your wings parallel to the rest of the craft, then the whole craft has to be angled for the wings for lift. This is bad for drag.

To get around that, your wings need to be angled, in relation to the fuselage, so the leading edge is higher than the trailing edge (Angle of Incidence). Because it's better to have only the wings, at an angle to the air flow, than the whole craft.

I angle wings 5 degrees on my designs. USE Shift + W, A, S, D, Q, or E, as appropriate before mounting, or one tick with the Rotation Gizmo, while holding Shift in angle snap mode.

When that is done, you can probably reduce the wing size, too. You only need about 1 lift rating per 10 ton (not counting Control surfaces).

Mine has 2 Small Deltas (2x 0.5), 2 Structural Wing Type D (2x 0.25) = 1.5 Lift rating for 15 tons.

Control surfaces are also twice as heavy compared to the Lift rating they provide. With a few exceptions*, wings weigh 100 kg per Lift rating and control Surfaces ~200 kg per Lift rating. So try if you can do with less.

*) Swept Wings are too heavy at 257 kg for 1.37 Lift. FAT-455 Aeroplane Tail Fin, Big-S Spaceplane Tail Fin and Deluxe Winglet are lighter than other control surfaces, maybe because they are considered wing and control surface combined.

Thanks for the tips! Yeah, I guess it's a bit over-winged, I will try to make a slimmer version. Also, I found out that I looked at your first version when I thought I had more fuel, your second version has more fuel than mine. Yours is still more efficient than mine though

[Val]

I'm getting tantalizingly close to 4 km/s dV.

View full album

Only a single Control Surface for pitch. Bank and Yaw done bye Reaction Wheel.

Craft file: https://drive.google.com/file/d/0B34u1G2080ndQ0t6bmFUMmk2NEk/view?usp=docslist_api

[Val]

I did it. 4 km/s dV in a 14.874 t craft.

But it is so basic that it is mostly useless. Doesn't have any mission capacity besides Flags and Footprints.

Craft file: https://drive.google.com/file/d/0B34u1G2080ndMGZWQWh1NjNyWE0/view?usp=docslist_api

I did use a very simple ascent profile, though. Maybe that can be improved.

Edited December 4, 2015 by Val
Fix formatting

[Michaelo90]

I slimmed my plane down and used another ascent path and reached 3505 m/s in 80*80 km orbit I might be able to get a bit more out of it

Val, can you use mechjeb to measure how much delta-v you use to get to orbit? It's under the recorder tab. I managed to get to orbit with 3591 m/s with my new ascent profile

Edited August 7, 2015 by Michaelo90

[PLAD]

Val, that is impressively light for 4000m/s dV left in orbit. I think you've reached a practical limit! Is that thing landable on Laythe? Thanks again for including the craft files, those are useful.

I think the limit for an SSTO with 2 jets and an LV-N is 20.5 tons for a Laythe-and-return with no flybys, and around 16.5 tons with full flybys. I show my concept craft below along with the numbers I figure. Using Val's 1 Rapier and 1 LV-N ships strongly suggests 15 tons can be beaten with full flybys, but it might be a couple hundred kg short for no flybys.

Javascript is disabled. View full album

Here's a link to the craft file and the spreadsheet. The plane is pretty boring compared to other planes here, but if you try it set the nose up 30 degrees right after takeoff and keep it there until the apoapsis reaches 72km. (Switch to the Nuke the moment the jets flameout.) Then lower the nose as much as possible without letting the rate of climb drop below 0. The Laythe page of the spreadsheet should be self-explanatory, the 2nd page was just hacking around with the rocket equation.

https://www.dropbox.com/sh/375iamx4d94y954/AABR8mjRFaVMhtCIXDZH9nKJa?dl=0

Edited August 8, 2015 by PLAD

[MadChris48]

This thread makes me so giddy. You guys have done awesome work here.

Val, your design is the shiz, over the top. 4k dV is ridiculous for <15 ton SSTO. Way to go, pushing the limits, maximizing. I applaud you!

So, thanks for being kick-ass kerbonauts.

[Val]

Val, that is impressively light for 4000m/s dV left in orbit. I think you've reached a practical limit! Is that thing landable on Laythe? Thanks again for including the craft files, those are useful.

...

...

Val, your design is the shiz, over the top. 4k dV is ridiculous for <15 ton SSTO. Way to go, pushing the limits, maximizing. I applaud you!

So, thanks for being kick-ass kerbonauts.

...

Val, can you use mechjeb to measure how much delta-v you use to get to orbit? It's under the recorder tab. I managed to get to orbit with 3591 m/s with my new ascent profile

Thank you, All, for the praise. Made my day

I did another ascent and took screenshots at strategic places with the dV info that Michaelo90 requested.

Starts here.

---

Edit: @PLAD it should be theoretically possible to land at Laythe. Though from experience with my Nano Jet, the narrow wheelbase does make it easy to fall over when landing in uneven terrain.

Edited August 8, 2015 by Val
Answer to PLAD

[Michaelo90]

I tried replacing my cockpit with a mk1 pod and got 3900 m/s in orbit. I tried a mk1 lander can too, but it was waaay to draggy.

But then I tried dumping the pod completely and putting jeb in a chair in a service bay and success! 4291 m/s in 80*80 orbit

[Val]

I tried replacing my cockpit with a mk1 pod and got 3900 m/s in orbit. I tried a mk1 lander can too, but it was waaay to draggy.

But then I tried dumping the pod completely and putting jeb in a chair in a service bay and success! 4291 m/s in 80*80 orbit

http://i.imgur.com/4VsjreP.png

Awesome! Poor Jeb, though. Spending many years in a Service Bay on the way to Jool.

[Michaelo90]

Awesome! Poor Jeb, though. Spending many years in a Service Bay on the way to Jool.

Yep, pretty cramped in there, and it feels a bit cheaty too. And the probe core torque is pretty much nonexistent, which is probably the main reason it took 3900 m/s to get it to orbit. But it's possible to fit two chairs in there. It's so cramped they fuse into one but at least he would have some company Their eyes actually line up so it looks like one pair of eyes with two pupils each

[selfish_meme]

Are you using Rapier Spikes at the back? Either a small nose cone turned around on the back of the rapier or a shock cone at the back, clip it inside so only the point sticks out.

[I_Killed_Jeb]

Are you using Rapier Spikes at the back?

what's that?

[Val]

Are you using Rapier Spikes at the back? Either a small nose cone turned around on the back of the rapier or a shock cone at the back, clip it inside so only the point sticks out.

I am, yes.

[selfish_meme]

what's that?

The explanation is right after the bit you quoted.

[Michaelo90]

Are you using Rapier Spikes at the back? Either a small nose cone turned around on the back of the rapier or a shock cone at the back, clip it inside so only the point sticks out.

I don't, I have a nuke behind the rapier and an rtg behind the nuke, and then clipped everything together.

Maybe I could put my rtg in the service bay instead so I could clip a shock cone in the back too.

[Michaelo90]

A rapierspike did help a little bit, I got 4317 m/s. Jeb didn't seem to mind having an rtg inside his head

[I_Killed_Jeb]

The explanation is right after the bit you quoted.

I saw the explanation, I'm just not sure what it accomplishes?

[Val]

I saw the explanation, I'm just not sure what it accomplishes?

It reduces drag, because it there's no longer an unused stack node on the Rapier.

[Red Iron Crown]

The science behind the Rapierspike, all credit to Levelord for the discovery and testing.

[ManEatingApe]

So I'd thought I'd try the Rapier/Ion combo to Laythe and also have a stab at an SSTO to Eeloo.

First up was the Laythe mini-SSTO. Kept the design as minimalist as possible.

Total weight: 12.4t on the runway and 8.2t in LKO.

TWR on Ions 0.24 and dV (on paper) ~ 5,400 m/s

Kerbin to Laythe was straightforward (if slow) with a direct Hohmann transfer, although I did use Tylo for a Jool capture orbit.

Returning from Laythe was when it all fell apart horribly, had to use a Tylo-Tylo-Tylo-Kerbin-Kerbin-Kerbin gravity assist sequence to get home.

So back to the drawing board. I suspect the TWR was just too low to use the dV effectively, the burns took so long that most of it was wasted. I'm thinking of trying again with at least 2 ions and less Xenon, the increased TWR should be more efficient, so even with less dV on paper it might be possible to use direct transfer both ways.

Craft File: https://www.dropbox.com/s/dygg5r1cw4quyly/Space%20Minnow.craft?dl=0

Album: http://imgur.com/a/3LnRe

Had more success with the SSTO to Eeloo. A slight tweak to the Space Whale Mk3/LV-N based design gave a craft with 7000 dV in LKO and a reasonable TWR.

Used a single Jool assist, this reduced the dV for an Eeloo capture orbit to 330 m/s. Dropped the orbit to 5km, followed by a massively entertaining suicide burn for touchdown.

On the way back used a single Jool assist, then was able to aerocapture and brake into Kerbin orbit without any further shenanigans. Even had a bit of fuel left over.

Craft File: https://www.dropbox.com/s/wn8gwth2uk47ou7/Eeloo%20Experiment.craft?dl=0

Album Part 1: http://imgur.com/a/CXTqz

Album Part 2: http://imgur.com/a/8pX1I

(I forked the game at the Jool assist point to chance my arm at trying a Laythe landing as well, managed to touch down and get to LLO before running out of fuel. I'll post that version of the attempt into the "SSTO to Laythe" thread)

[Val]

So I'd thought I'd try the Rapier/Ion combo to Laythe and also have a stab at an SSTO to Eeloo.

First up was the Laythe mini-SSTO. Kept the design as minimalist as possible.

http://i.imgur.com/24poYBD.png

Total weight: 12.4t on the runway and 8.2t in LKO.

TWR on Ions 0.24 and dV (on paper) ~ 5,400 m/s

...

That is indeed minimalist

Very efficient design

... Mk3/LV-N based design gave a craft with 7000 dV in LKO and a reasonable TWR ...

Impressive

[ManEatingApe]

That is indeed minimalist

Ha, thanks for the feedback.

Did you ever take your SSTL U-9 Mk 2 design to Laythe?

It seems like it has the potential to make a return journey with no flybys.

[Val]

Ha, thanks for the feedback.

Did you ever take your SSTL U-9 Mk 2 design to Laythe?

It seems like it has the potential to make a return journey with no flybys.

No, I did not.

I'm fairly sure I can go to Laythe orbit and back, but if I want to land on Laythe, I need flybys. At least judging by what I was able to do with the Mk3 attempt I did, which had similar dV budget.

[Pecan]

...a stab at an SSTO to Eeloo

Why don't you leave all that excess baggage in Kerbin orbit before going to Eeloo and back? That would save a lot of mass.

[ManEatingApe]

Why don't you leave all that excess baggage in Kerbin orbit before going to Eeloo and back? That would save a lot of mass.

You're absolutely correct, dropping the Rapiers would give an extra 2,000 m/s dV at least.

However I was interpreting the challenge here to see how far you can go with zero staging or "no mass left behind", deliberately lugging all your initial parts across the Kerbol system, as in this challenge http://forum.kerbalspaceprogram.com/threads/117415-SSTO-to-laythe-and-beyond

I found that the no staging constraint forced me to be more creative, as otherwise it's pretty straightforward to just add more stages/boosters to solve any problem.

There were 2 areas it really improved my KSP playing:

* SSTO design and piloting - You really have to hone your ascents to eke out as much mass fraction into orbit as possible.

* It also made me really appreciate the beauty of gravity assists. I'd regarded them as a kind of curiosity before, but with limited dV they're an immensely useful tool to slingshot your way around on the cheap.

Edited November 9, 2015 by ManEatingApe