SSTO to laythe and beyond

[herbal space program]

I've been messing around with Eve gravity assists to get to Jool.

For it to work you must have your periapsis inside Eve's orbit for the first assist, with a good trajectory you can get your orbit after the encounter close to a 1:2 resonance with Eve, to get a second gravity assist from Eve in order to reach Jool you need to shift your Periapsis inside Eve's orbit again (You can't get a good gravity assist when your periapsis is aligned with Eve's orbit). Burning retrograde at apoapsis until you get a second encounter is one way to do it, though if you're lucky you can probably use Kerbin, Duna or maybe Dres. A second gravity assist from Eve should be enough to get you well beyond Jool's orbit, with a bit of luck you should be able to get an encounter with Jool

That's useful information about the 2:1 resonance to get 2 assists from the same body. At the link RIC posted above, the OP did a Munar assist to get to a trajectory that encounters Eve from the inside at around 9:30 o'clock from the original position of Kerbin. This Eve encounter results in an orbit that reaches nearly out to Duna's on the major axis but has a periapsis still around Eve. The trajectory results in a Kerbin encounter that OP then used to set up a 2:1 resonance orbit with Kerbin, with apoapsis well past Duna. After the second Kerbin encounter, the apoapsis was right at Jool. OP claims it was all done with only 1000dV. In practice, I have needed around 1200dV just to get to the first Eve encounter, with or without the Munar assist, but I am doing it all manually by trial and error, not with McJeb or any online calculation tools, so there's probably considerable room for improvement. Nonetheless, I think you were right about the Munar assist not getting you much. I was mistaken about the size of the of my burn at Munar periapsis in my previous post. Anyway, I have verified that if you line up this Eve encounter correctly, you do end up with the subsequent Kerbin encounter, however I have not taken it past there yet. OP's times to each encounter appeared to be off by a factor of 2 to me for reasons I don't understand. OP said that the second Kerbin encounter was only 362 days after leaving LKO, but just one Kerbin orbit is over 400 days, so that seems plain impossible. Did they change all the orbital periods between versions somewhere? Regardless of that, my plan is to launch a fleet of 4-5 ships separated by a couple of days, in the hope that at least one of them can hit everything just right.

If I can get to Jool with under 1500dV, I'm pretty sure I can get my current SSTO to Laythe and all the way back as well. My best LKO so far leaves me with just over 3900 dV on orbit if I burn it all with the nuke engine, quite more obviously if I can use the jets, and a bit less if I burn the 250 units of Ox I have left. From the right Jool encounter trajectory, I should be able to aerobrake directly into Laythe, and in theory be able to land the ship without burning much of anything, although this brick-with-winglets won't really land acceptably deadstick. IIRC flying back to orbit on Laythe is significantly easier than on Kerbin, and I should have over a third of my takeoff fuel still on board at this point. If I can make Laythe orbit again with something like 1200dV left, I should be able to boost to a very high deltaV Tylo assist with a couple hundred to spare. Again if I do everything right, I believe I can get to some sort of Kerbin encounter from there. I seem to remember that if you eject from a Laythe-Tylo transfer retrograde and outward, you can raise your apoapsis past Jool and drop your periapsis nearly all the way down to Kerbin. From the slow top of that orbit, it also doesn't take very much dV to tweak things to the point of getting some kind of encounter. We'll see. I think it will be close, but I'm still a long way from really knowing. It's a fun challenge though!

Edited June 12, 2015 by herbal space program

[psyberduckling]

The problem I've found with the trip back (this was in an ISRU spaceplane), is managing to get an aerocapture via Kerbin's atmosphere, it cost me quite a lot of fuel to get a capture despite nearly burning most of the fittings off the ship. The dV to get a Kerbin encounter isn't that expensive (though to be fair I was coming from a refuelling stop at Pol which made things a lot easier, travelling from the outermost moon, it's fairly easy to drop your periapsis down to just above atmosphere so you can abuse the Oberth effect to it's maximum, especially at Jool which has a very deep gravity well).

[herbal space program]

The problem I've found with the trip back (this was in an ISRU spaceplane), is managing to get an aerocapture via Kerbin's atmosphere, it cost me quite a lot of fuel to get a capture despite nearly burning most of the fittings off the ship. The dV to get a Kerbin encounter isn't that expensive (though to be fair I was coming from a refuelling stop at Pol which made things a lot easier, travelling from the outermost moon, it's fairly easy to drop your periapsis down to just above atmosphere so you can abuse the Oberth effect to it's maximum, especially at Jool which has a very deep gravity well).

I hadn't considered how hot I'd be coming in on my final return from Kerbin, but if I actually get that far before being thwarted I'll consider it a great victory

As to leaving Jool, It's true I won't have the slow orbital velocity of Pol coming from Laythe, but I will have the awesome slingshotting power of Tylo pretty close by. I seem to recall in the past having gotten all the way to a Jool escape trajectory by swinging around Tylo from Laythe, but I guess we'll see. Again, if I even get that far I'll consider it a victory.

[herbal space program]

.....D'OHHHHH!! The new aero regime in 1.0.3 completely broke my Leythe-and-back space plane. It's basically a brick now. They were half way there, rounding Kerbin for the first time, and now I have to start over. I suppose I could revert my version to finish the job, but what's the point if that's not reality anymore? And since the change I haven't been able to get to orbit with nearly as much PF in fuel as I could before. Maybe 24% vs. a whopping 30in the previous version. It seems like the lift and engines got nerfed out of proportion to the lessened drag and air requirements. How is everybody else doing?

Edited June 23, 2015 by herbal space program

[Red Iron Crown]

It seems like the lift and engines got nerfed out of proportion to the lessened drag and air requirements. How is everybody else doing?

Not well. I tried the 1km/s route to Jool a few times, but could never get the second gravity assist right. So I went back to refining my design, which got me to 4km/s of dV in orbit, which I thought might squeak out a return if I could catch an assist from Tylo on the way out from Jool, but now I think it won't get to orbit with that much dV. I may have to give up on the return. :/

[herbal space program]

RIC: "Not well. I tried the 1km/s route to Jool a few times, but could never get the second gravity assist right. So I went back to refining my design, which got me to 4km/s of dV in orbit, which I thought might squeak out a return if I could catch an assist from Tylo on the way out from Jool, but now I think it won't get to orbit with that much dV. I may have to give up on the return. :/"

Yes, I feel about the same. I was able to thread the pork chops reasonably well after a couple of very time-consuming false starts, and although I never actually went past the second Kerbin encounter, it looked like my best launch was going to get to a Jool encounter for around 1400 dV all told. Starting with around 4Km/s at LKO, which was the best I could do in 1.0.3 after countless ascents and re-tweaks, it seemed like I could just maybe pull it off. Unfortunately, 1.0.3 has now broken that space plane completely, and with a redesigned plane I can't seem to hit orbit with more than 3-3.5 km/s using just RAPIERs. They're just too weak (and thirsty too!) at low speeds for me to do the sort of rapid ascent profile that I've found key to conserving fuel. Last night I spent a fair bit of time trying with 2 RAPIERs plus 2 TJs, and that plane's initial ascent to transonic territory looked great, but it just poops out too soon at the high end. I'm losing a good 100 m/s of speed and 50 m/s of ascent rate at a 29km switchover altitude vs. all RAPIERs in 1.0.2. The ideal ratio of engines for this rig seems to me to be 3 RAPIERs, 1 TJ, and 1 nuke, but building that is not so easy. My patience for this endless exercise is statting to wear thin, but I think maybe tonight I'll try putting 1 TJ, 1 nuke, and 1 RAPIER canted outwards on a tri-coupler in the middle, with 2 more RAPIERs on the outside. The resulting plane is sure to look ugly and fly even worse, but I think it might be able to find the deltaV sweet spot that way. Maybe I'll try a honking Mk3 design with 2+2+6 as well. At least that one won't require placing engines crookedly...'

...So after spending another evening learning how to fly my plane again, it looks like I can actually get the same deltaV on LKO I could before or maybe even better. It took lots of changes to both the design and the ascent profile, but now it seems to work pretty well again

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This plane has >4km/s dV on orbit, so I guess I can try again with this Laythe thing now...

Edited June 25, 2015 by herbal space program

[Red Iron Crown]

Ship just got real:

This is not particularly tweaked, and the ascent was...uh...suboptimal. The Isp of the Rapiers has been nerfed, but fewer of them are needed for ascent (initial TWR of this thing is only about 0.5) so there is much less dry mass affecting the delta-V. Plus the Mk1 fuselage has an excellent mass ratio now. I think a return mission is possible now with direct Hohmann transfers, so I'm going to tighten up the design and hopefully put together a mission this weekend.

[herbal space program]

Ship just got real:

...Plus the Mk1 fuselage has an excellent mass ratio now. I think a return mission is possible now with direct Hohmann transfers, so I'm going to tighten up the design and hopefully put together a mission this weekend.

Wow, that's a lot of dV on orbit! With 5 km/s, I think you could do it going straight there, although the ejection burn with that one nuke is not going to be very efficient. One useful thing about doing the multi-assist route for a plane like this is that you can do a much smaller initial ejection burn. It was looking to cost me about 1400 dV to get to Jool that way, which is only a 600 m/s savings over a direct route nominally, but I suspect that with that long last burn a direct route will cost significantly more than 2km/s. It will be interesting to see how cheaply you can pull it off.

I also note that you have no oxidizer left. Do you think you can make Laythe orbit again without burning the RAPIERs at all in rocket mode, or do you intend to trade off some dV for oxidizer in the final version? I've always assumed I needed to be shipping at least a couple hundred units of oxidizer on LKO for that purpose.

[Red Iron Crown]

Wow, that's a lot of dV on orbit! With 5 km/s, I think you could do it going straight there, although the ejection burn with that one nuke is not going to be very efficient. One useful thing about doing the multi-assist route for a plane like this is that you can do a much smaller initial ejection burn. It was looking to cost me about 1400 dV to get to Jool that way, which is only a 600 m/s savings over a direct route nominally, but I suspect that with that long last burn a direct route will cost significantly more than 2km/s. It will be interesting to see how cheaply you can pull it off.

If I could do it with exactly 2km/s the final ejection burn after three periapsis kicks would be about 7 minutes, longish but not overly bad. Still, I expect the ejection to be significantly more than 2km/s, but I think I'll be able to build in enough dV to fit it in the budget.

I also note that you have no oxidizer left. Do you think you can make Laythe orbit again without burning the RAPIERs at all in rocket mode, or do you intend to trade off some dV for oxidizer in the final version? I've always assumed I needed to be shipping at least a couple hundred units of oxidizer on LKO for that purpose.

That's the big question. The ascent from Laythe should be a bit easier than Kerbin, due to better TWR from lower gravity and less mass as well as LLO speed only being ~1,880m/s. I use LFO mode on Kerbin ascent to push the Ap far enough ahead for the LV-N to have time to finish raising Ap and circularize, I'm hoping that airbreathing mode alone will be sufficient on Laythe to do the same. We'll see, I guess.

[Red Iron Crown]

Wow, that's a lot of dV on orbit! With 5 km/s, I think you could do it going straight there, although the ejection burn with that one nuke is not going to be very efficient. One useful thing about doing the multi-assist route for a plane like this is that you can do a much smaller initial ejection burn. It was looking to cost me about 1400 dV to get to Jool that way, which is only a 600 m/s savings over a direct route nominally, but I suspect that with that long last burn a direct route will cost significantly more than 2km/s. It will be interesting to see how cheaply you can pull it off.

A quick update, as I have finalized my design and completed the ejection burns. I went with three kicks plus ejection, similar to the precomputed ones linked in my signature but starting from a lower orbit. The transfer window I used was at Y2 D257 1:58:12, nominally 1,989m/s according to Transfer Window Planner. I got lucky with my timing, making the final burn only 4 minutes off the ideal window (lucky given that the timing is about +/-15mins depending on initial orbit) and caught a small gravity assist from the Mun on the way outsystem. Final ejection burn was under 7 minutes, total dV spent for the Jool encounter was 2,037m/s. Hopefully I'll have time to get down on Laythe and try the ascent this week.

In LKO, best of five ascents and about as good as I seem able to do. Craft was initially 39.5t, so TWR was pretty marginal and I used the nuke to help with the transsonic region:

Transfer burns completed:

KER seems to have glitched out here (and was giving erroneous readings on node burn times, too), but calculating manually gives 3,420m/s of dV remaining.

[Starhawk]

Final ejection burn was under 7 minutes, total dV spent for the Jool encounter was 2,037m/s. Hopefully I'll have time to get down on Laythe and try the ascent this week.

Nice.

In LKO, best of five ascents and about as good as I seem able to do. Craft was initially 39.5t, so TWR was pretty marginal and I used the nuke to help with the transsonic region:

https://dl.dropboxusercontent.com/u/61004449/KSP/1.0.4/LSSTL/screenshot325.png

Transfer burns completed:

https://dl.dropboxusercontent.com/u/61004449/KSP/1.0.4/LSSTL/screenshot350.png

KER seems to have glitched out here (and was giving erroneous readings on node burn times, too), but calculating manually gives 3,420m/s of dV remaining.

It always takes me aback a little bit when I see the navball off to the side like that. Is that Enhanced Navball that allows that?

Looking forward to seeing the rest of the mission. What's your plan for insertion?

Happy landings!

[Red Iron Crown]

Yes, Enhanced Navball. I make it a bit larger for better legibility and precision, and move it off to the side for more useful screen real estate.

Haven't finalized the insertion plan yet, probably either a gravity-assisted capture with Tylo or a direct aerobrake at Laythe if it will stand up to the heat. I'll see which makes more sense when I refine the encounter.

[Val]

Ship just got real:

https://dl.dropboxusercontent.com/u/61004449/KSP/1.0.4/screenshot280.png

This is not particularly tweaked, and the ascent was...uh...suboptimal. The Isp of the Rapiers has been nerfed, but fewer of them are needed for ascent (initial TWR of this thing is only about 0.5) so there is much less dry mass affecting the delta-V. Plus the Mk1 fuselage has an excellent mass ratio now. I think a return mission is possible now with direct Hohmann transfers, so I'm going to tighten up the design and hopefully put together a mission this weekend.

Very nice looking design. Looks really sleek. And nice dV, too.

Here's my humble attempt. Still haven't gone beyond LKO with it.

Depends on pure Airbreathing to take off from Laythe, but I think that should be doable. Can reach 1350 m/s on Airbreathing, taking off from Kerbin.

I think it looks like a coldwar relic. A mix of a B-58 Hustler and Myasishchev M-50. I'm quite happy with that.

[Red Iron Crown]

Nice plane, Val, I love the B-58. What are you using for propulsion?

Off-topic, but which skybox are you using? I'm in the market for a new one and that looks pretty. Also, I'm envious of your 21:9 1440p monitor.

[Val]

Nice plane, Val, I love the B-58. What are you using for propulsion?

Thank you

Propulsion is 3 Rapiers and 2 Nervs. Total mass at launch is 49.61t

The craft file.

1. Take-off and accelerate with nose 5^o above horizon.
   
2. At 200 m/s nose up to 10^o and continue accelerating.
   
3. At 400 m/s nose up to 15^o and keep it there until coasting to Ap. Should hit 830+ m/s at 10km.
   
4. At 20km you should be going at 1200+ m/s and be very hot. Engage Nervs.
   
5. When Rapiers run out of air switch Mode. Rapiers should boost you from ~1350 m/s to ~2050 m/s.
   
6. Keep going on Nervs til Ap is at 81km.
   
7. Coast to space and circularize. Should be around 80km.
   

Off-topic, but which skybox are you using? I'm in the market for a new one and that looks pretty. Also, I'm envious of your 21:9 1440p monitor.

I'm using Rareden's Real 8k Skybox for Texture Replacer

Monitor is LG 34" and, yeah, I'm very happy with it.

[Val]

In LKO, best of five ascents and about as good as I seem able to do. Craft was initially 39.5t, so TWR was pretty marginal and I used the nuke to help with the transsonic region:

https://dl.dropboxusercontent.com/u/61004449/KSP/1.0.4/LSSTL/screenshot325.png

Transfer burns completed:

https://dl.dropboxusercontent.com/u/61004449/KSP/1.0.4/LSSTL/screenshot350.png

KER seems to have glitched out here (and was giving erroneous readings on node burn times, too), but calculating manually gives 3,420m/s of dV remaining.

BTW, what are those cones sticking out of the Rapiers?

[nicky4096]

aerospikes that have been clipped slightly in, i think,

[Val]

aerospikes that have been clipped slightly in, i think,

If that is the case why don't they show in the Staging?

[nicky4096]

good point.

it turns out they are shock cone intakes. in his resources tab, he has 3.8 intake air. the 2 visible rams each give 1 intake air, and the 2 semi-hidden shock cones produce 0.9 each. 1+1+0.9+0.9=3.8, so yay!

[Teilnehmer]

BTW, what are those cones sticking out of the Rapiers?

It’s RapierSpike  a Small Nose Cone stacked to a Rapier without any clipping for drag reduction.

Edited July 1, 2015 by Teilnehmer

[nicky4096]

now *that* is interesting...

edit: but then where is the extra 1.8 intakeair coming from?

Edited July 1, 2015 by nicky4096

[Val]

It’s RapierSpike  a Small Nose Cone stacked to a Rapier without any clipping for drag reduction.

Interesting read. Thanks.

Going to see if I can improve my SSTL with this new info.

And here I was just using Shock Cone Intakes for that B-58 Hustler look. Seems they were actually the best choice, too. Woot.

[herbal space program]

A quick update, as I have finalized my design and completed the ejection burns. I went with three kicks plus ejection, similar to the precomputed ones linked in my signature but starting from a lower orbit. The transfer window I used was at Y2 D257 1:58:12, nominally 1,989m/s according to Transfer Window Planner. I got lucky with my timing, making the final burn only 4 minutes off the ideal window (lucky given that the timing is about +/-15mins depending on initial orbit) and caught a small gravity assist from the Mun on the way outsystem. Final ejection burn was under 7 minutes, total dV spent for the Jool encounter was 2,037m/s. Hopefully I'll have time to get down on Laythe and try the ascent this week....

but calculating manually gives 3,420m/s of dV remaining.

Looks like you're on your way! My progress unfortunately got interrupted by the demands of real life, but I'm going to go back to trying now. I got rid of those bicouplers and it really helped. With a 4-engine, 60.5 ton ship I'm getting on orbit no with right around 5km/s dV in fuel now plus 250 units of oxidizer. I think I can probably improve that by adding just a bit more wing area, but the returns of hauling more fuel to LKO are starting to diminish as its own weight starts to exceed 20t. Those air brakes you have have gotten me thinking too. They might come in handy if I ever want to use Jool's atmosphere to slow down. Word on the street seems to be that aerobraking at Jool is pretty broken.

Edited July 1, 2015 by herbal space program

[Val]

I made a new design. Still with 3:2 Rapier/Nerv. 5.5k m/s dV, but only 0.3 TWR at LKO.

Inspiration for the look should be obvious. I call it SSTL A-12 Ghosthunter.

I also tried 2:2 Rapier/Nerv layout, but I couldn't get enough dV without overwhelming the Rapiers.

Will try making some designs with other Rapier/Nerv layouts. Then select the best and try to complete the challenge this weekend.

More pics http://imgur.com/a/nWUaf

Edited July 2, 2015 by Val
More pics

[herbal space program]

I made a new design. Still with 3:2 Rapier/Nerv. 5.5k m/s dV, but only 0.3 TWR at LKO.

Nicely done. I suspected that with the new Mk1 fuselages making your plane out of only those would be the best move, and it looks like you've proven that to be correct. It looks also like having the 2 nukes instead of 1 offsets the extra weight by giving you enough vacuum TWR to burn the RAPIERs closed only a wee bit getting to LKO. I expect the 2-nuke design will also have a much better chance of getting you off Laythe without oxidizer than only 1 nuke would. I'm tempted to just scrap what I have and copy your design, but that wouldn't seem right.