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SSTO Tylo No Refueling Or Docking

DAL59

By DAL59
in KSP1 Challenges & Mission ideas

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Cunjo Carl

Cunjo Carl

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2 hours ago, AeroGav said:

I've tried numerous times to create an Enterprise  and you go do it by accident when chasing a challenge !

Funnily I was trying to avoid the enterprise look, but kept needing more wings! Hopefully with the chained grandparent strut trick, you'll have the aesthetic (and extra fuel) as well.

2 hours ago, AeroGav said:

I've tried numerous times to create an Enterprise  and you go do it by accident when chasing a challenge !

I'm really skeptical this challenge can be done.    A vessel's mass divides into fuel, engine and payload.    Engine % can't be reduced too far because of the TWR requirement for Tylo,  so to get a higher fuel fraction you can go bigger in order to make the payload (probe core, KErbal in a command chair) a smaller % of the total.  But you're close to maxing that out on a 50 ton vessel, a 5000 ton monster won't do that much better.

Good estimate, and I absolutely agree. There's no more deltaV to be gained by scaling at this point, unless I really need 1.5 of some engine. It was originally a 16ton SSTO for a low weight challenge, and bringing it to its natural weight of ~50 tons bought a few hundred m/s. I wish mk2, mk3 had lower drag :/

2 hours ago, AeroGav said:

I won't enter this challenge because I can't gravity assist my way out of a paper bag. 

Right there with ya!

2 hours ago, AeroGav said:

Heavy jet engines outlive their usefulness...

Boy howdy do they. I've been dreaming ever more imaginative (read insane) ways to lower drag to ditch one of the two rapiers. So far, I'm stuck with two.

 

36 minutes ago, JacobJHC said:

I had something earlier that was just shy of being able to land. Will try again.

Ooh, looking forward to seeing it! We should definately compare notes on this one, and I'm happy to send along my work at any point you'd find it usefull.

 

27 minutes ago, sdj64 said:

So then I turned to excel, because while it only takes one success to prove something possible, only math can prove something impossible.  I'm not 100% sure on the assumptions I made, but I believe it is mathematically impossible to do a stock Tylo surface SSTO.  The spreadsheet works from bottom to top, using the rocket equation to find the wet mass after each step of the mission and finally telling you what mass you have to devote to your fuel tanks and what you have left over for stuff like wings, cockpit, and engines.

+1 for mathing a thing. There's a bunch of little improvements we can make on top of what's expected, and the hope is to solve this problem via death by a thousand cuts. For example, using BigS strakes lets you get wings and fuel in one part, and mk0 liquid fuel tanks have lower dry mass than expected. Having a sheet like this is a great starting point for figuring out which aspects need the most improvement. I happen to agree, by the way, that it won't be possible (atleast on airbreathers+LOx+nukes, I haven't run the numbers on airbreathers+LOx+nukes+ions yet). I'm gonna try anyway though :D

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DAL59

DAL59

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How about no nukes?  Make a really long plane with lots of xenon and an ion engine, and some separatrons for the tylo landing.  The add wings with 2 vasmirs.  The ions will certainly provide enough delta vee for the transfer(no need for slingshots even), though I'm not sure how the take off or lading on kerbin would go.    

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Cunjo Carl

Cunjo Carl

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5 minutes ago, KerBlitz Kerman said:

Lies! It is physically impossible but Krakenistically possible!

Hah! I have a couple kraken wheel drives in my back pocket, but I'm hoping not to bring out the dreaded beasts.

 

4 minutes ago, DAL59 said:

I still think it is possible.  With ion drive, jool aerobraking, and slingshots.  

Pace is brisk. Either something cool will happen, or it'll all explode magnificently. Win/win!

Ion drive will probably make it possible, but still holding out. One unseen disadvantage of ions is their accoutrements drag hard in atmo. I bet it'd work though.

 

6 minutes ago, DAL59 said:

... though I'm not sure how the take off or lading on kerbin would go.    

I'm bringing 'chutes :)

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Cunjo Carl

Cunjo Carl

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2 minutes ago, Ultimate Steve said:

My problem with K-drives in 1.3 is that I can't seem to get them to restart reliably. After a while, the legs break for some reason and they won't interact with the pusher.

That's good to know, besides my ladder drives I haven't tried any since 1.2. Was it just me or did craft get wobblier in 1.3 also?

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AeroGav

AeroGav

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3 hours ago, Cunjo Carl said:

Boy howdy do they. I've been dreaming ever more imaginative (read insane) ways to lower drag to ditch one of the two rapiers. So far, I'm stuck with two

Have you considered going with one panther and one rapier instead of two rapier?   That combo is 3.2 tons instead of 4 tons.       Slightly more thrust at mach 0.8,   helping you get a larger craft supersonic,  and once the panther gives up at mach 2.8,  the rapier is now enjoying a 5x ramjet thrust multiplier.    Thrust falls off fast enough after mach 4.5 that airbreathing top speed one vs two rapier isn't much different.

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Cunjo Carl

Cunjo Carl

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9 hours ago, qzgy said:
  Hide contents

*in hushed tone* i want in.... but that link is broken...

 

 

*Cough Cough*

Spoiler

 

Whoops. Not sure how that hapenned. Link

Krakens must have eaten it. Lets go with that! Anyways, while poking about, I found @EladDv's original postings on it as well over in the spacecraft exchange: K-Drive 122

 

 

 

In other news, I tried making a mk2 version of the enterprise, and big surprise the mk2 fuselage pieces dragged so hard it couldn't leave Kerbin. I wish I took a picture of those insidious 100m long red arrows dragging me back! After reviewing the numbers, I'm going to put more work into lowering the drag (and thus airbreather drymass) on a nuke SSTO before making the probably inevitable switch to ion.

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Zhetaan

Zhetaan

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The best LFO vacuum engine is the Poodle with its Isp of 350.  However, working back through the rocket equation, when we take the tank mass ratio of 9 and that engine, the theoretical maximum delta-V for the best hypothetical rocket is about 7550 m/s.  Leaving Kerbin orbit from LKO (using the common dV map, so the values may be a bit generous) takes 950 m/s, Tylo orbit takes 1100 m/s, and Tylo landing takes 2270 m/s.  I chose these specific values because these are the critical values for which no gravity assist is possible (or practicable; a Mun assist from Kerbin orbit doesn't shave enough dV):  you have to burn.  Since you also have to return from Tylo's surface and leave Tylo's orbit on engine power (you can aerobrake at Kerbin), those latter two values must be doubled, so the combined total is 950 + 1100 + 1100 + 2270 + 2270 = 7690 m/s.  Therefore, this mission requires a nuke or an ion engine (or multiple stages, obviously, but that's disallowed).  Leaving Kerbin and making Tylo orbit can easily be done with a nuke, but landing/take-off is another matter.

However, that is not necessarily impossible:  has anyone considered a direct horizontal burn on a particularly flat part of Tylo's surface using aircraft wheels?  I'm not certain of how amenable Tylo's surface is to roving, but is it possible to get a good horizontal run before taking off and making orbit?

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JacobJHC

JacobJHC

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45 minutes ago, Zhetaan said:

The best LFO vacuum engine is the Poodle with its Isp of 350.  However, working back through the rocket equation, when we take the tank mass ratio of 9 and that engine, the theoretical maximum delta-V for the best hypothetical rocket is about 7550 m/s.  Leaving Kerbin orbit from LKO (using the common dV map, so the values may be a bit generous) takes 950 m/s, Tylo orbit takes 1100 m/s, and Tylo landing takes 2270 m/s.  I chose these specific values because these are the critical values for which no gravity assist is possible (or practicable; a Mun assist from Kerbin orbit doesn't shave enough dV):  you have to burn.  Since you also have to return from Tylo's surface and leave Tylo's orbit on engine power (you can aerobrake at Kerbin), those latter two values must be doubled, so the combined total is 950 + 1100 + 1100 + 2270 + 2270 = 7690 m/s.  Therefore, this mission requires a nuke or an ion engine (or multiple stages, obviously, but that's disallowed).  Leaving Kerbin and making Tylo orbit can easily be done with a nuke, but landing/take-off is another matter.

However, that is not necessarily impossible:  has anyone considered a direct horizontal burn on a particularly flat part of Tylo's surface using aircraft wheels?  I'm not certain of how amenable Tylo's surface is to roving, but is it possible to get a good horizontal run before taking off and making orbit?

I'm pretty sure anything over 300 m/s would get too bouncy to control, Tylo isn't the flattest place.  It could potentially be done though.

Edited by JacobJHC
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Vanamonde

Vanamonde

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If a post is a problem, please just report it, okay guys? Quoting it REPEATS the problem and commenting on it adds to forum clutter for others to click past to get to the actual content of the thread. 

That being said, we had to remove your pic link, @DAL59. Sorry, but it was causing page loading problems. 

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DAL59

DAL59

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27 minutes ago, Vanamonde said:

If a post is a problem, please just report it, okay guys? Quoting it REPEATS the problem and commenting on it adds to forum clutter for others to click past to get to the actual content of the thread. 

That being said, we had to remove your pic link, @DAL59. Sorry, but it was causing page loading problems. 

Thank you, @Vanamonde.  It was really lagging out my computer too!  

What's worse is, the link was broken!  :confused:

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sdj64

sdj64

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On 11/8/2017 at 8:49 PM, KerBlitz Kerman said:

Lies! It is physically impossible but Krakenistically possible!

So, I did see one error in my calculation: When I assumed the SSTO payload fraction of 35%, it didn't include any engines or wings used for Kerbin ascent (because the payload fraction challenge specified an inert payload).  My test craft had a mass of about 45 tons full and 30 in orbit, for 66%, which puts chemical engines back in the realm of possibility for the Tylo landing and ascent.

You can also use your efficient (ion or nuclear) engine in conjunction with your more powerful engines for Tylo, which could maybe save you some more.

 

23 hours ago, Zhetaan said:

The best LFO vacuum engine is the Poodle with its Isp of 350.  However, working back through the rocket equation, when we take the tank mass ratio of 9 and that engine, the theoretical maximum delta-V for the best hypothetical rocket is about 7550 m/s.  Leaving Kerbin orbit from LKO (using the common dV map, so the values may be a bit generous) takes 950 m/s, Tylo orbit takes 1100 m/s, and Tylo landing takes 2270 m/s.  I chose these specific values because these are the critical values for which no gravity assist is possible (or practicable; a Mun assist from Kerbin orbit doesn't shave enough dV):  you have to burn.  Since you also have to return from Tylo's surface and leave Tylo's orbit on engine power (you can aerobrake at Kerbin), those latter two values must be doubled, so the combined total is 950 + 1100 + 1100 + 2270 + 2270 = 7690 m/s.  Therefore, this mission requires a nuke or an ion engine (or multiple stages, obviously, but that's disallowed).  Leaving Kerbin and making Tylo orbit can easily be done with a nuke, but landing/take-off is another matter.

However, that is not necessarily impossible:  has anyone considered a direct horizontal burn on a particularly flat part of Tylo's surface using aircraft wheels?  I'm not certain of how amenable Tylo's surface is to roving, but is it possible to get a good horizontal run before taking off and making orbit?

Good analysis, it's nice to see similar delta V figures.  You might be able to save 200m/s by landing at speed and braking, and your first 200 m/s could use your most efficient engine to build up speed across the ground?

 

I tried incorporating these changes into a craft, but I'm still coming up short.  It has about 1000 m/s too low delta V on the "high thrust" part, and its TWR is only 0.5 where it needs to be 0.8 at Tylo landing.  It also is missing electrical systems to run the ions and was tested with infinite electricity on.  My spreadsheet says I can devote 5 tons to non-tank stuff, and I'm sitting around 6.5.  How to increase the thrust and decrease the engine mass?  I think it might be better to just use the rapiers on closed cycle - the engine mass savings might make up for the lower efficiency.  If I use those, my non-tank budget drops to 4 tons, but I also lose 1 ton of Terriers, so it's an even trade and I get higher thrust for the Tylo landing.

W8YouFz.png

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