My first SSTO - please evaluate!

[Jestersage]

After some hardwork, and adjusting starting fuel level, I got my first SSTO of my own ideal:

http://steamcommunity.com/sharedfiles/filedetails/?id=797293723

Can someone comment whether the design is good?

For those that want the figures without reading my screenshot, it's on a 100x100km orbit, with 1400 dv, carrying an ISRU-125, the full-size drill, and a lab with all the science fixing. Forgot to add the rover and solar panels, but it's pretty much what I want. The starting TWR is 0.6

What I like:
-front-loading ramp and rear engine mount
-Able to carry a lab and everything needed to refuel

What I am concern with:
-Not enough delta V to anywhere else. The plan was to use it for interplanetery exploration. While it's well within reach to Mun and Minmus, it's a bit dangerous.
-Difficult to land compare to Standard landers on atmosphere-less environment (been having problem landing my mun base module on an Altair clone)
-Take so long to circulate into an orbit. My Vertical TSTO would have reach it in half the time if at all, while this design took me 20 minutes in total

Edited November 11, 2016 by Jestersage

[AeroGav]

10 minutes ago, Jestersage said:

, a standard rill

Very nice ! It's good to see you're thinking of the Kerbonaut's welfare, and have added a water feature.   

In all seriousness, you've done well.   SSTO is hard .   SSTO to Minmus harder still, doing so with a payload (mining gear) even tougher.   And you did it with all of that plus rover, ramp, cargo bay and lab.

Interplanetary SSTO pretty much requires a Minmus refuel stop.  I've got one or two that can straight shot Duna, but they don't bring the extras yours does.

Quote

-Difficult to land compare to Standard landers on atmosphere-less environment (been having problem landing my mun base module on an Altair clone)

Anything that size will be i'd have thought.   Imagine the main problem is toppling over./ landing on a slope.   lots of reaction wheels to make it more agile, is about all you can do.   You could try packing a load of Vernier engines in the belly around the CG to enable it to land horizontally on it's main wheels in low gravity.  I guess that's just trading one problem for another.

Quote

Take so long to circulate into an orbit. My Vertical TSTO would have reach it in half the time if at all, while this design took me 20 minutes in total

And your vertical TSTO would have to make a considerably larger number of launches to assemble a return mission to Laythe , for example, with lots of rendezvous and docking maneuvers.

I don't mind the 20 minutes to orbit if the spaceplane is pleasant to fly,  if  it's a twitchy beast and you're constantly fighting to keep it on track then it can be the longest 20 minutes of your life.

[Streetwind]

Spaceplanes in general take longer to fly than regular rockets do. Reentry and landing especially, since expendable vehicles don't do this at all. But ascent is also slower.

If RL time spent is a concern for you, then make sure your spaceplane is capable enough to replace multiple standard launches in one go. Otherwise, rockets might be a better choice.

[bewing]

12 hours ago, Jestersage said:

Can someone comment whether the design is good?

Any design that can get past LKO to Minmus is a very good design.

12 hours ago, Jestersage said:

-Difficult to land compare to Standard landers on atmosphere-less environment (been having problem landing my mun base module on an Altair clone)

The easiest way to land on an airless body is to come straight down vertically on your tail with wheels extended. Once you are down, hit W to make your spaceplane fall forward onto its wheels.

12 hours ago, Jestersage said:

-Take so long to circulate into an orbit. My Vertical TSTO would have reach it in half the time if at all, while this design took me 20 minutes in total

Agree with Streetwind. This is how it works with spaceplanes. Every time you launch one, it takes ages to get to orbit. They are always like that. Either take the time, or don't launch spaceplanes.

 

[Vanamonde]

Does it SSTO? Then it is a success. 

[Jestersage]

Thanks, I will work on tinkering with the design.

Another question I have is landing legs: For SSTO, is it better to use LT-2, or to use girders?

[bewing]

Wings. SSTOs need wings anyway, and wings make the best landing legs of all.

 

[Jestersage]

Have to figure out which wings... Maybe the Big-S Delta?

One more before I go back to tnkering: Should I use the Mk3 engine mounts, or use a tri/quad coupler and a Mk3-2.5m converter at the end?

[Tidus Klein]

Which ever combo is lighter

[AeroGav]

8 hours ago, Jestersage said:

Have to figure out which wings... Maybe the Big-S Delta?

One more before I go back to tnkering: Should I use the Mk3 engine mounts, or use a tri/quad coupler and a Mk3-2.5m converter at the end?

If you are using the mk3 mount, make sure you attach something to all three 1.25m nodes  AND the central 2.5m node.  If you don't want a 2.5m engine, or another 1.25m engine on a 2.5>1.25m adapter,  then put a 2.5m cone on there.    Otherwise you get an enormous flat plate drag penalty.

As for the alternative,  mk3 to 2.5m adapter followed by a 2.5m  tri/quad coupler,  I guess it comes down to looks and also whether you actually want the extra LF/O tankage the mk3 to 2.5m adapter brings.   If you put all that oxidizer at the back of your ship aft of cg,  you might want to add a similar amount up front to stop the cg shifting forwards.

[Jestersage]

1 hour ago, AeroGav said:

If you are using the mk3 mount, make sure you attach something to all three 1.25m nodes  AND the central 2.5m node.  If you don't want a 2.5m engine, or another 1.25m engine on a 2.5>1.25m adapter,  then put a 2.5m cone on there.    Otherwise you get an enormous flat plate drag penalty.

As for the alternative,  mk3 to 2.5m adapter followed by a 2.5m  tri/quad coupler,  I guess it comes down to looks and also whether you actually want the extra LF/O tankage the mk3 to 2.5m adapter brings.   If you put all that oxidizer at the back of your ship aft of cg,  you might want to add a similar amount up front to stop the cg shifting forwards.

I actually gone out and try it, and seems both would work equally in LKO. All i need to do is to remove the original LF-O tank. Also shaved some weight since the coupler is lighter then engine mount. (0.15t vs 0.7t)

So just to be clear: The central 2.5m need a 2.5m object that is aero dynamic (note the two requirements)? or can it be any (e.g flat 2.5, 1.25m, etc)? Still trying to understand how the drag model work

[AeroGav]

It really should be a 2.5m.   A smaller cone reduces drag but not by very much.  I think the game calculates the surface area of a 1.25m cone compared with a 2.5m one  (about 25%)  and gives you 25% of the benefit a properly sized one would give you.