DAL59

SSTO Tylo No Refueling Or Docking

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With more thoughts, I wonder if someone could make the gyro drive stock, use the rotating core from a stock prop engine instead of the rotatrons used in the above design - then the only non stock part is the kerbal computer thing he does...

 

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On 3/19/2018 at 6:53 AM, Andetch said:

With more thoughts, I wonder if someone could make the gyro drive stock, use the rotating core from a stock prop engine instead of the rotatrons used in the above design - then the only non stock part is the kerbal computer thing he does...

 

It then depends on your definition of “stock” as the computer mod is called kOS, and with a MM patch, you can add it to any part.

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22 hours ago, Not Sure said:

It then depends on your definition of “stock” as the computer mod is called kOS, and with a MM patch, you can add it to any part.

 

22 hours ago, Andetch said:

Well if it counts as "stock" then maybe we could be onto solving this one?

You can do the gyro drive, but I'll put it in the kraken category.  I'm still hopeful for a non-glitch SSTO.

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23 hours ago, DAL59 said:

I'm still hopeful for a non-glitch SSTO.

It's not possible unless you count bouncing a fairing off Tylo's orbit at orbital velocity as "landing". I did the calculations for a 100 ton craft with one ion engine plus NERVs and RAPIERs, zero structural, wing, or battery mass, and horizontal landing and takeoff at 500 m/s. If it gets to Kerbin orbit with 80% payload fraction, the best possible mission plan with the best possible engine combination (12 NERVs and 10 RAPIERs; going any lower than 1 RAPIER/31t takeoff mass probably wouldn't yield a viable payload fraction) gives you minus 6 tons payload. Even a touch-and-go at 500 m/s yields a slightly negative payload. My math or one of my assumptions is wrong (if so, please tell me!).

The KR-2L/RAPIER/ion system is impossible by an even greater margin, and any other stock engine is inferior to one of those two. I think this is closed. Again, correct me if I'm wrong.

https://docs.google.com/spreadsheets/d/1OD7mtRem-ApGzy1eh4IsyvqDL_iB3cBtPh8KgyU_u60/edit#gid=491237559

EDIT: Accidentally doubled the engine mass the first time. Recalculated and payload fractions are positive with these assumptions: NERV/ion/RAPIER 100 ton dry mass craft, 72% payload fraction to suborbit gives a payload of about 13 tons or 3.1%.

Edited by Lirtosiast

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I think it is possible with the Wolfhound, if Making history is considered stock.  I'm using slightly different values than you as well.  In my spreadsheet the craft has a 66 ton starting mass and has 2 rapiers and one wolfhound.  It would be a bit slow getting off of Kerbin, but possible with some drag tricks?  There's even a luxury of 0.14 tons left over - enough to add a Kerbal in a command seat!

https://docs.google.com/spreadsheets/d/1sP97xSETIcLN-ntugP5VPyi_Sh-9rwwwE9URabtZRqA/edit?usp=sharing

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@sdj64 You're correct. There was a serious error in my spreadsheet; I really shouldn't be doing this late at night! Now I'm getting similar numbers. 3.1% payload fraction with nukes and slightly lower with the Wolfhound.

https://docs.google.com/spreadsheets/d/1RsHtqTvP85LdYsMRbufcYwQwO2TEs9F3RjNnSK5sqwk/edit#gid=491237559

However I think a 70% payload fraction is far too high given that @AeroGav could barely manage 50%-- and that was with an optimal SSTO engine balance, which is different from an optimal Tylo landing engine balance. Assuming 52% to suborbit and zero structural/wing mass we still have a -2.4% payload fraction (-15 tons on a 100 ton dry mass craft), or slightly worse with your engine balance.

Edited by Lirtosiast

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19 hours ago, Lirtosiast said:

@sdj64 You're correct. There was a serious error in my spreadsheet; I really shouldn't be doing this late at night! Now I'm getting similar numbers. 3.1% payload fraction with nukes and slightly lower with the Wolfhound.

https://docs.google.com/spreadsheets/d/1RsHtqTvP85LdYsMRbufcYwQwO2TEs9F3RjNnSK5sqwk/edit#gid=491237559

However I think a 70% payload fraction is far too high given that @AeroGav could barely manage 50%-- and that was with an optimal SSTO engine balance, which is different from an optimal Tylo landing engine balance. Assuming 52% to suborbit and zero structural/wing mass we still have a -2.4% payload fraction (-15 tons on a 100 ton dry mass craft), or slightly worse with your engine balance.

The difference is that he counted only the mass of the ore tanks detached in orbit, while I count the mass of the SSTO itself upon reaching orbit.  His SSTO, by my quick estimate from looking at the video, has at least 42 tons dry weight so it would be a 72% payload fraction, even better than the optimistic number in my spreadsheet.

Edited by sdj64

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Ah, I missed that too. My spreadsheet gives zero overall payload fraction at 60% total MF to Kerbin orbit, so theoretically we only need a little more than that. It goes up by 5% for every 100 m/s slower than 500 m/s we land at, but if someone can get a SSTO with your engine balance to orbit with 60% total MF we're on our way to a Tylo SSTO.

Maybe batteries would help? Bradley Whistance has a large percentage of batteries on his Laythe-Eeloo and two-trips-to-Eeloo SSTO as well as a general long range SSTO. Tylo isn't the best use of batteries, because the high gravity means the additional ion engines we need are heavier during the landing. Nevertheless we could use battery power 3 times when we're desperate for thrust: during Kerbin circularization, at the end of the Tylo landing, and at the start of the Tylo ascent. It would also make burns easier. Haven't done the math, but maybe the better mass ratio of the ion tanks makes battery power useful in situations like these now.

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On 24/03/2018 at 7:24 PM, Lirtosiast said:

@sdj64 You're correct. There was a serious error in my spreadsheet; I really shouldn't be doing this late at night! Now I'm getting similar numbers. 3.1% payload fraction with nukes and slightly lower with the Wolfhound.

https://docs.google.com/spreadsheets/d/1RsHtqTvP85LdYsMRbufcYwQwO2TEs9F3RjNnSK5sqwk/edit#gid=491237559

However I think a 70% payload fraction is far too high given that @AeroGav could barely manage 50%-- and that was with an optimal SSTO engine balance, which is different from an optimal Tylo landing engine balance. Assuming 52% to suborbit and zero structural/wing mass we still have a -2.4% payload fraction (-15 tons on a 100 ton dry mass craft), or slightly worse with your engine balance.

You might be able to get more than 50% of your craft's launch mass into orbit as liquid fuel, as the mk3 cargo bay that carried all that ore has a lot more drag than a bunch of wing strakes carrying an equivalent weight of liquid fuel.    So you could get by with fewer jet engines.   The part count would punish your PC though,  and whilst wing strakes are better than any fuselage tank on Kerbin,   in a vacuum non wing parts have better wet/dry mass ratio.    Plus, the amount of NERVs you need is predetermined by the TWR needed to land on Tylo,  so better aerodynamics won't allow you to cut back on the NERVs.

Ion engines seem like they would only be useful for the transfer burns, both flights to orbit and the powered Tylo landing would require NERV  TWR.  

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Using such low TWR engines like bikes and ion isn't is probable that you will miss the encounter? It's an issue I've had sending my rcs powered (place anywhere thruster, not monoprop throttle controlled engine) to the mun and minimus - the burn takes so long maneuver nodes become pretty meaningless!

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Okay, it's time to start putting actions behind my words.  I whipped this plane together in about 15 minutes based on my spreadsheet.  It weighs 68 tons at launch.  On the first time I reached orbit, it weighed 47.223 tons once in orbit, for a 69.44% mass fraction!  I haven't actually played KSP in quite a while and I forgot to use LF tanks or bigS wings instead of LFO.  My flying skills could also use a tune-up, so I'm sure I can do better with this plane.

I think it might be worth it to switch to turbojets for higher thrust and efficiency and lower dry mass.  The wolfhound was enough to take over without any closed cycle on the rapiers, so I think it can make up for slower airbreathing top speed.

Anyway here are some pictures.

5AuJJtv.png

L7FIIq8.png

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This is... actually happening.  Huh.

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On 4/9/2018 at 3:32 PM, DAL59 said:

This is... actually happening.  Huh.

I actually stopped trying after getting less than halfway to the Mun in 2 hours (real time) of ion burning.  I then went back to my spreadsheet and tried to make it work with nukes, but I don't think the TWR and DeltaV can both work out.

Does somebody else with more time and experience with ion ships want to try?

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On 6/26/2018 at 1:07 PM, DAL59 said:

Any progress?

The ion stage didn't have enough TWR.  I set no minimum for it, thinking it was fine for in-space maneuvers, but Mr. Oberth was not happy with my decision.  I did create a new craft that has much lower drag and the proper ratio of LF to Ox, and even raised to 4 ions but I still don't think it will be enough.  I got about 75% mass fraction to LKO but didn't really want to try the ion part again.

I revisited the spreadsheet and it looks impossible without ions.

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1 hour ago, sdj64 said:

The ion stage didn't have enough TWR.  I set no minimum for it, thinking it was fine for in-space maneuvers, but Mr. Oberth was not happy with my decision.  I did create a new craft that has much lower drag and the proper ratio of LF to Ox, and even raised to 4 ions but I still don't think it will be enough.  I got about 75% mass fraction to LKO but didn't really want to try the ion part again.

I revisited the spreadsheet and it looks impossible without ions.

If you can get it into orbit and give me a flight profile to follow I could take a shot at flying the thing. But I can't efficiently launch an SSTO even if my life depended on it.

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AND THE IMPOSSIBLE HAS BEEN DONE YET AGAIN!

You sir, are now a god.

Is there anything left to do, that anyone can be the first to do? Because you have done 2 impossible missions back to back and now all us inferior players bow down in your presence.

giphy.gif

Also, Wolfhound OP AF NEVER NERF

Edited by Xurkitree

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6 hours ago, EvermoreAlpaca said:

I cast my wand of necromancy on this challenge with:
 

 

Just... AWESOME :)

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21 hours ago, EvermoreAlpaca said:

I cast my wand of necromancy on this challenge with:
 

 

cIeKBZG.gif

On 12/10/2017 at 9:53 AM, Matt Lowne said:

Another impossible challenge. There really needs to be a rule that OP has actually verified that what they're asking is possible without mods.

This post didn't age well :wink:

 

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59 minutes ago, DAL59 said:

This post didn't age well :wink:

OTOH - do you think it could be done without wolfhounds?

@EvermoreAlpaca, I think you might have an interesting response to this question.

Edited by qzgy

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Good point, there.  Just to spell it out: The switch from Rhinos to the Wolfhound engine (from the Squad part-mod expansion 'Making History' from March 2018) was cited by Bradley as one of the enabling factors to what he also concluded was impossible in November 2017.

Given the benefit of considerable hindsight, Matt's assessment of December 2017 is looking very good.

Edited by OHara
speling

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3 hours ago, qzgy said:

OTOH - do you think it could be done without wolfhounds?

@EvermoreAlpaca, I think you might have an interesting response to this question.

The wolfhound resulted in a ton of gained dV.  I suspect it is possible without the wolfhound, but it would require one to land and takeoff from Tylo at even higher speed, and possibly further optimize the Kerbin ascent as well.  One could throw in an additional Mun assist to save some ion fuel, but that is extremely minimal savings.   That being said, all of these things are doable.  The landing gear on this thing could probably take as much as 120 m/s on a different landing zone that was less rugged.

I would say that this is most likely possible, but it would require landing at absurd speeds.

Edited by EvermoreAlpaca

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