Tylo Landers

[Der Anfang]

This is prolly silly to ask, but, is a single stage lander and orbit vehicle for Tylo possible? Landing on the evil rock and taking off back into orbit without losing any parts?

[Sovek]

Yes, but then you probably get into the tyranny of rocket equation, quite heavily.

[Foxster]

There was a challenge with just this a little while ago. Have a search. 

[Mastikator]

The ISRU is your friend in this.

Tylo has an escape velocity of 3km/s. Lets say 3.5km/s because inefficiency. A transfer burn to let's say Vall is another 1.4km/s, plus Vall has an ecape velocity of 1.1km/s. 3.5+1.4+1.1 = 6. So in theory a 6km/s d-v SSTO with an ISRU can take off from Vall, land on Tylo, go back to Vall an arbitrary number of times.

You'll probably want nuclear engines for everything but the last seconds of landing and taking off. A 6km/s d-v with an ISRU plus other stuff would be quite a heavy craft though.

[problemecium]

I've done it.

Sadly, despite the lack of atmosphere, I find LV-N engines are still no good. They simply don't have the TWR for an effective lander. It can theoretically be done, but it ends up being more economical to just use chemical rockets. In that department I recommend the Poodle or a cluster of Terriers. If you keep the accommodations conservative (read: Mk1 Lander Can) it isn't too hard to achieve the needed dV.

[Geschosskopf]

4 hours ago, Der Anfang said:

This is prolly silly to ask, but, is a single stage lander and orbit vehicle for Tylo possible? Landing on the evil rock and taking off back into orbit without losing any parts?

Sure, this is quite possible, even without ISRU.  The thing is, though, that just building the necessary dV and TWR into the ship is only the 1st and least tricky step in the process.  The real work is figuring out the proper descent profile for the thing.  This is really what separates Tylo from other airless bodies.  Many people design something that, on paper, has the stats for the job, then try to land it any old way like they would on another moon and it goes splat.  Then they tweak the design but not the descent profile and it still goes splat, so they get frustrated and give up.

So, what you do is, design something that carries the desired payload and has the necessary stats.  Then HyperEdit to Tylo at whatever altitude you think best and give it a try.  If it goes splat, revert and try again from a higher altitude.  If it runs out of fuel before it runs out of altitude, try a lower alittude.  Or try changing how you manage your speed during the descent, and the angle you come down at.  Keep tweaking your descent profile until you find something that works and that you can do repeatedly.  Remember, Tylo's surface altitude varies somewhat, so, once you get it to work once, try it again but land in a different place to see if it still works.  It might be that you can land only at certain terrain elevations but not others.  And if where you want to land has a different altitude, you'll have to tweak your descent profile again.  But eventually you'll find something that works because, after all, the lander DOES have the on-paper stats to do the job.

The upshot of this is that there is a huge number of possible 1-stage Tylo lander designs, but each will require a different descent profile.  Because there are so many possible designs, you should be able to make something with the on-paper stats to do the job.  Then it's just a matter of figuring out how to land it.

Once you're down, however, the rest is easy.  Because Tylo has no atmosphere and not much in the way mountains, taking off again is a doddle.  Just lean over immediately as far as possible and burn out as horizontally as possible.  Because there's no air drag, you accelerate quickly so can get even more horizontal.  And remember, you only need to reach 20km or so to be safe and await a tanker or tow truck to come get you.

[LordKael]

5 minutes ago, Geschosskopf said:

Once you're down, however, the rest is easy.  Because Tylo has no atmosphere and not much in the way mountains, taking off again is a doddle.  Just lean over immediately as far as possible and burn out as horizontally as possible.  Because there's no air drag, you accelerate quickly so can get even more horizontal.  And remember, you only need to reach 20km or so to be safe and await a tanker or tow truck to come get you.

With this in mind, I would recommend using the "Surface Info" tab of MJ to give you a more accurate idea of what you're doing on your descent profile. Potentially with a customized window to show as many relevant data as you would benefit from. The other thing I would recommend, beyond what has been said above, is to try at the two extremes of terrain height. 

[Geschosskopf]

9 minutes ago, LordKael said:

With this in mind, I would recommend using the "Surface Info" tab of MJ to give you a more accurate idea of what you're doing on your descent profile. Potentially with a customized window to show as many relevant data as you would benefit from. The other thing I would recommend, beyond what has been said above, is to try at the two extremes of terrain height. 

And to this I would add that if you have MJ, you'll no doubt be using (or desirous of using) its landing autopilot.  This thing is rather unimaginative--it has its favorite general descent profile that it uses for all occasions.  Thus, the only way to change your descent profile with MJ is to vary your starting altitude--you can't tweak the angle of descent.  But OTOH, this does reduce the number of variables involved, making it easier to end up with a design and a starting altitude that works.

[cantab]

Since the engine efficiency nerf in 1.0, it's harder than it used to be. On the other hand I suspect it's still possible. IMHO it wants a combination of excellent efficiency and good TWR which makes the Rhino the leading candidate, but that does make for a large lander. The increase in TWR as you burn off fuel is important - you can easily be starting your landing burn with a TWR of 1.0 or even lower, it will rise by the time you touch down.

Some versions ago I did my Tylo landing in this: https://flic.kr/p/qK65LP

I was using a custom engine nerf at the time, which brought performance down to a level similar to what we now have. Now that lander was deliberately overbuilt, I could easily have done it with a single engine. In the event I didn't make it back to orbit but had to bail out and use the jetpack.

[MaxL_1023]

The problem is gravity losses. With a starting TWR near 1.0, you pick up a considerable amount of vertical velocity in the time it takes to cancel your orbital speed. Then, you need to cancel this vertical speed by the moment of impact. This forces additional gravity losses proportional to 1-TWR. If your TWR is high enough to make an efficient landing (think 5-6g suicide burn at least) then you will tend to have a lot of lander weight tied up in engines. 

You want to do a reverse gravity turn type situation, where you have a PE near the surface and you burn progressively more normal as you cancel orbital velocity, just enough to keep you from hitting the ground. The higher your starting TWR, the sharper this turn is and the closer you get to the ideal "instant suicide burn at a PE of 1m cancelling all orbital velocity."

It might be possible to do this with a single stage and return to orbit, but I suspect your payload fraction would be close to zero.

[LordKael]

8 minutes ago, MaxL_1023 said:

I suspect your payload fraction would be close to zero.

And thats the real kicker, ain't it?

[MalfunctionM1Ke]

LV-N's seem to be a great choice for this but they are not.
I landed on Tylo before with a behemoth of a ship utilising 24 Nervas and one Skipper Engine.

The Nervas were jettisoned once the tanks were dry, only then the framerate was smooth enough to go for a landing.
Allthough this all was back in .25 I believe, but I never would build a ship/lander this complex without multithreading.

I cant even imagine what a single staged lander would look like, but the way I approached it was probably the opposite approach.

But what I wanted to say is the following:

LV-N's are great for everything in a vacuum but 60kn of thrust is barely enough to keep your head over "water" on Tylo and then it still depends on your ships Overall mass. Better go with a huge fueltank and a mighty Engine. 
 

Spoiler

 

Edited January 2, 2016 by MalfunctionM1Ke

[Warzouz]

9 hours ago, Der Anfang said:

This is prolly silly to ask, but, is a single stage lander and orbit vehicle for Tylo possible? Landing on the evil rock and taking off back into orbit without losing any parts?

Back in beta 0.9, I did it with a SSTO rocket. The lander was brought into low Tylo orbit from Laythe station by a tug. The lander had to land once and get back to the tug (the Tug would do the rendez-vous), Then, the whil ship returned to the station.

The SSTO lander had a low TWR (0.98/tylo when deorbiting) but it raised up to 1.3 (if I'm not mistaken) when landing. The suicid burn was not possible (it resulted in crash every time) even the retrograde trajectory was deadly every time. I had to hover by keeping the vertical velocity under control (nio more than 100 m/s) and concentrating on slowing down the horizontal velocity until TWE was reasonable enough to land. Take off was easier. The ship, had 6050m/s before deorbiting (not counting the tug), it had 50m/s left back on the 30km orbit.

The Tylo lander was 14 tons (the Vall/Bop/Pol lander was 15 tons and the Laythe lander was 16 tons)

Sadly I don't have many pictures of the lander

 

 
SSTO lander at Tylo : Success ! / SSTO reaching orbit !

The whole Jool station orbiting Laythe (this was not a Jool-5 challenge because the station was assembled around Laythe (13 flights). The Tylo SSTO lander is hidden below the tanks. It's on the opposite side of the alternative staged lander for tylo you can see below the return vehicle which is docking. I wasn't sure I would be able to land the SSTO lander so I brought another lander ( and 6 pilots !)

This is the Tylo tug carrying the Laythe SSTO lander on it's final approach in his flight from Kerbin. The design was a bit different (ram jets + Swivel instead of double LVN) but the general shape and mass was nearly the same

 

Of course, this lander should have to be heavily redesigned in 1.0.x due to LAN mass increase and physicless parts having no mass at that time. But that was a very nice multiple mission which I played during 3 weeks

Edited January 2, 2016 by Warzouz

[KerrMü]

Is ISRU allowed? Then this was my Tylo SSTO a few months ago:

(And the Kerbals had a LOT of time exploring the surface while the fuel was processed)

Edited January 2, 2016 by KerrMü
added a pic

[selfish_meme]

See my signature, aerospikes seem the most efficient small lander engine

[GoSlash27]

Figuring a 1 tonne payload and starting t/w of 1.5, it's a matter of how much DV you want on top of the theoretical minimum.
+50% for landing is an 83t monster powered by 5 Aerospikes.
The theoretical minimum would be 13.5t on a single Aerospike.

The "tyranny of the rocket equation" rears it's ugly head. This would definitely be a job for ISRU.

 

Best,

-Slashy

 

[bewing]

Do you consider prepositioning a space station in permanent orbit to be "losing a part"?

 

[Hcube]

The spark would have been perfect for a minuscule tylo lander before the patch. It was so OP you could SSTO super-small probes on Kerbin easily. Now it's not worthless but nearly not as good, and probably wouldn't do the job

[cubinator]

See my Jool-5 entry. I did it with a Mammoth engine cluster to boost TWR, and it worked well for almost everything I did.

[KerikBalm]

Well, I just did it with a full science package, 2x lander cans, and a KR-2L (seemed to be the best combo of vacuum Isp and TWR), very generous electrical capacity (5130 charge, 4x RTGs), and a docking port Sr. to allow it to be towed.

The landing could have been a little more efficient, and a little softer, and 4 of 8 struts needed repairing, but I had 630 m/s to spare after inserting into a 18km x 10km orbit.

The starting mass was 154 tons though....

And just tried a 3x aerospike 1 kerbal lander (again full science complement, 865 EC, 1x RTG), 415 m/s to spare into a 10km by 26km orbit (and I found that there are mountains near the equator over 9km high... my coast to a 10km apopasis got really close to the terrain...). 42 tons starting mass

And again a full science + electricity+probe guidance+ docking port for towing + 1 kerbal capacity, this time poodle powered, fits in a mk3 cargo bay, had 178 m/s left over after achieving a 10x11km orbit... this design had the lowest starting TWR, and the lowest dV... but its only 23.7 tons and 25 parts. I landed in a low area, and the difference between orbital and surface velocity is only 40 m/s on tylo, so in theory it should be able to land anywhere, if it starts in a low polar orbit.

Next I'm going to try a vector powered design... it will surely be more massive though. I think if I accept lower TWR and dV margins (as I did with the poodle design), I can get by with 2x aerospike, or maybe even 1.

FWIW, every design so far has worked without requiring any modifications(KER really is great), and I've landed them all successfuly on the first try except for the KR-2L design, which required a quick load

Edited January 3, 2016 by KerikBalm

[Foxster]

It really doesn't need to be huge for a manned hop down to the surface of Tylo and back.

This is just 1125 LF+O, a lander can, a Dart (clipped up so that the craft can land on the bottom tank) and a handful of solar cells, weighing in at a little over 15t. Does a landing from and a return to a 40km orbit with about 200 dV to spare...

Or if you want to do it without clipping and use some radial intakes for legs then this works too...

Edited January 3, 2016 by Foxster

[KerikBalm]

Well, I was a bit overconfident... my next 4 attempts fall into two categories:

*Failed to adequately control descent rate -> 2x high speed impacts with terrain

*Failed to remain upright after landing ->2x tip-overs... which would strand a kerbal but not kill them outright... A tall laner, as aways is tipping prone... I just wanted it to be able to fit in a mk3 cargobay..

 

Foxster... nice... but it still lacks certain things that many would want... like a docking port (yes, I know they fixed most of the issues wit te claw) and science equipment... For me, I dont even like the intake part clipping... and it seems gimicky to use intakes as landing legs... would using some landing leg parts render the design unworkable? I like to have probe cores (and in anticipation for 1.1, an antenna) on all my vessels so tey can be maneuvered even when uncrewed... which makes me wonder if those ox-stats are sufficient out at Jool (not that RTGs are so heavy)

Also, how does it handle? I'd think you may want more torque (ie add a SAS).

[Foxster]

Ah, that's all requirements drift from the OP's specification . 

 

[MaxL_1023]

Your payload fraction there is about 5% if you include the solar panels and potential science gear. I would personally just stick the small ISRU and a mining drill on a lander - it cuts your delta-v requirement in half and lets you hop from moon to moon.

[Temstar]

Since Tylo is an airless body why not just use command seats to cut the weight from capsules? That should cut the  payload fraction by a lot.

Edited January 4, 2016 by Temstar