Heinlein. Chemical SSTO.

[Rune]

23 hours ago, henry quirk said:

a tad moldy

To you, mebbe...to me, she's brand-spankin' new.

KerbalX

Will take a gander...thanks.

 

You kind of inspired me to take another look at this... and yes, I do have a new version kind of done because of it! It is even simpler.

And that is the margin with a couple of flips on the way up because I wanted to test if the CoD/CoM was close enough to do all the climb without moving fuel and while ignoring your surface prograde vector and trying to hug orbital prograde, all without turning RCS on. Turns out you can only do one or two of those things at the same time (i.e: if you don't move fuel forwards during ascent, hug prograde closely if you don't want to cartwheel, or activate RCS). Reentering, tough, it is perfectly stable, capable of actually maintaining high angles of attack without RCS during most of the plunge back down (nose first, but if you go ass-first, I have no doubt it can be done, too, because "ridiculously powerful RCS" and because that open 3.75m node is a great source of drag). And when you are low and you want to flip, just turn RCS on and the autopilot to retrograde, and it should be able to flip itself to point the legs toward the ground without parachute assist.

 

Rune. That "flipping itself" part is important, because the shielded docking port has awesome temp rating, but in Duna, you have to be able to point your engines to the ground at a moments notice.

Edited July 2, 2016 by Rune

[CloudlessEchoes]

The original still works I think, although I haven't tried it in the most recent version.

[henry quirk]

I like Heinlein 2 (that's what I'm callin' her) but she has a prepubescent look to her, like she's yet to blossom into full ship-hood.

-----

A completely off-topic comment...

The 'hero' ship Rocinante, from The Expanse, gets all the press, but the little Xinglong is the that one that catches my eye...got the look of Space Cowboy's Hauler from Battle Beyond The Stars...along with vertical SSTOs, I got a weakness for space opera, bad movies, and blue collar spacers.

[Rune]

18 hours ago, henry quirk said:

I like Heinlein 2 (that's what I'm callin' her) but she has a prepubescent look to her, like she's yet to blossom into full ship-hood.

Yup, I'm still trying to see if I can make this shape work:

Much cuter. But the CoD is too far back then, and the ship can't flip itself even with powerful Vernors (they have less leverage, too) until the chutes are fully extended. That is a firm no-go if this thing is supposed to serve in Duna! Paradoxically, the simpler model with no complex fuel routing system is looking like the only thing that will work wihtout an exponential increase in weight and complexity... and I know, it does look like something that you can throw together in five minutes. Because you can. But only after you have tried things for months.

 

Rune. It's going to make refueling simpler, having just three tanks. At least there is that.

[Rune]

Victory!

Version I-don't-even-know-which-at-this-point is able to reenter shielded-pointy-end-first, then flip around once it goes merely supersonic by deploying the airbrakes, to point the engines the right way for terminal landing. And it looks like a million bucks! Short and stubby, yet all four tanks are clickable. And with the right ratio of greebles per square inch.

 

Rune. I think we could say she has blossomed into full ship-hood.

Edited July 7, 2016 by Rune

[Zamolxes77]

Very nice one Rune, can we please have a shot of the back of the ship too, or a .craft file please?

[Rune]

59 minutes ago, Zamolxes77 said:

Very nice one Rune, can we please have a shot of the back of the ship too, or a .craft file please?

Or better yet, a KerbalX link with both?

 

Rune. Ask, and ye shall receive.

[Zamolxes77]

Well I, tried it out, seems a bit unstable or my flying skills are very poor. Once I added 4 fins, it got under control easy enough. KerEngineer rates it at 3,400 dV with 4 fins added, I manage to limp in a 75 LKO, with 100 m/s left in the tanks. Any hints about how to fly it more efficiently in 1.1.3? I never thought I can get a 3,400 dV craft into orbit and circularize lol, normally I aim for a minimum of 3,700 dV for that.

[Rune]

22 minutes ago, Zamolxes77 said:

Well I, tried it out, seems a bit unstable or my flying skills are very poor. Once I added 4 fins, it got under control easy enough. KerEngineer rates it at 3,400 dV with 4 fins added, I manage to limp in a 75 LKO, with 100 m/s left in the tanks. Any hints about how to fly it more efficiently in 1.1.3? I never thought I can get a 3,400 dV craft into orbit and circularize lol, normally I aim for a minimum of 3,700 dV for that.

Well, right now it's fuel is routed so the upper and lower tanks drain at the same rate, so she does become a tiny bit unstable during some portion of the climb... but if you have the autopilot to prograde it shouldn't really be an issue. If you want to make her rock-steady, tough, either add a couple fuel lines from the upper tank into the two spikes without tanks, or move fuel manually during flight until the bottom tank is empty.

Adding fins would work for the climb up, of course, but then, on the way down, it'll be too stable to flip itself without the chutes. Which is fine on kerbin, yeah, but on Duna it might pose issues!

...And yeah, fuel margin is tight. I like to call it a challenge! But you should be able to get about 100m/s on a 100km LKO, with practice, and you very rarely won't be able to make some kind of orbit.

 

Rune. Might add the fuel lines myself, actually, and bring it up to an even 40 parts with an antenna or something.

[Zamolxes77]

The initial instability is very early, right off the pad. I normally fly everything manually, I guess I should give the old "hold to prograde" button a try.

I'm trying new ascent profiles, normally I tilt a bit late so I arrive at 45 degrees at 15km, gonna try a new one, 45 degree at 10 km and keep time to apo around 30 seconds instead of one minute, see how that goes. Thanks for suggestions.

[Rune]

22 minutes ago, Zamolxes77 said:

The initial instability is very early, right off the pad. I normally fly everything manually, I guess I should give the old "hold to prograde" button a try.

I'm trying new ascent profiles, normally I tilt a bit late so I arrive at 45 degrees at 15km, gonna try a new one, 45 degree at 10 km and keep time to apo around 30 seconds instead of one minute, see how that goes. Thanks for suggestions.

That's pretty much what I do, and what a high TWR like this one as calls for. Minimize those gravity losses!

 

Rune. Let it climb to one minute once you are below 45º, tough, you can go horizontal too early and waste dV on drag.

Edited July 8, 2016 by Rune

[Zamolxes77]

SUCCESS !!!

100 LKO and 200 m/s to spare. Instability trick was the fuel pumping, I actually just disabled the tanks and enabled them later. With that, you don't even need hold to prograde, is stable enough for manual.

[henry quirk]

"I think we could say she has blossomed into full ship-hood."

Yes, indeed!

[Rune]

11 hours ago, Zamolxes77 said:

SUCCESS !!!

100 LKO and 200 m/s to spare. Instability trick was the fuel pumping, I actually just disabled the tanks and enabled them later. With that, you don't even need hold to prograde, is stable enough for manual.

 

9 hours ago, henry quirk said:

"I think we could say she has blossomed into full ship-hood."

Yes, indeed!

Glad you guys like it! I went ahead and updated the file, now it is an eye-pleasing 40 parts, and those fuel handling/piloting issues should be gone with the addition of the two fuel lines, with a trivial amount of dV lost to the mods.

 

Rune. Who knows, we might actually get to use the antenna for something useful when 1.2 comes.

[DDE]

Hm. Not nuclear. I suppose Heinlein would be slightly disapproving.

I've been toying around with Nertea's hydrogen and nuclear motors for some extra I_sp and hence better mass ratio; admittedly, the pebble beds I had high hopes for have thus far proven disappointingly weak.

What's with the use of Mk 3 fuselages? Shouldn't you try to escalate to the 3.75 m tanks to cram more fuel into less craft length and less drag?

[Rune]

On 11/7/2016 at 1:34 PM, DDE said:

Hm. Not nuclear. I suppose Heinlein would be slightly disapproving.

I've been toying around with Nertea's hydrogen and nuclear motors for some extra I_sp and hence better mass ratio; admittedly, the pebble beds I had high hopes for have thus far proven disappointingly weak.

What's with the use of Mk 3 fuselages? Shouldn't you try to escalate to the 3.75 m tanks to cram more fuel into less craft length and less drag?

Well, there ain't no decent nuclear torches in KSP like the ones he wrote about, but given the kinds of fire we do have access to in KSP, at least it lands the way he always saw spaceships landing.

As the the fuselages, you will find that adapters add quite a bit of weight to offset the better payload fraction of 3.75m tanks, and most of all, looks. Because looks matter.

Speaking of which, the new Heinlein inspires me more and more the idea of just sticking it on top of something. Something big. And get something cool out of it like, say, a Duna mission where all you throw away are a few SRBs and some tankage.

 

Rune. Would you guys be interested in something like that?

[Majorjim!]

Are those two recoverable boosters connected? I don't think you can recover both of them so as you make these for career would it not be better to just have a core booster with chutes and do a chute/motor landing saving everything.

Edited July 12, 2016 by Majorjim

[Rune]

3 hours ago, Majorjim said:

Are those two recoverable boosters connected? I don't think you can recover both of them so as you make these for career would it not be better to just have a core booster with chutes and do a chute/motor landing saving everything.

Both of them make orbit (3,700m/s before burnout,supposing the payload stays connected), and are fully capable of independent orbital operations and return to KSC (Vernors, Fuell cells, and a probe core, basically). Runway landing for 100% recovery, of course. The rest is just a big drop tank to handle the transfer to Duna and, most likely, have enough fuel left over for Duna insertion and/or Duna escape (2.2km/s on top of the heinlein's 4km/s), in case you burn the Heinlein dry landing and taking off from Duna.

 

Rune. The idea is the couple hundred m/s in margin becomes a huge asset when you release the payload.

[Majorjim!]

Just now, Rune said:

Both of them make orbit (3,700m/s before burnout,supposing the payload stays connected), and are fully capable of independent orbital operations and return to KSC (Vernors, Fuell cells, and a probe core, basically). Runway landing for 100% recovery, of course. The rest is just a big drop tank to handle the transfer to Duna and, most likely, have enough fuel left over for Duna insertion and/or Duna escape (2.2km/s on top of the heinlein's 4km/s), in case you burn the Heinlein dry landing and taking off from Duna.

 

Rune. The idea is the couple hundred m/s in margin becomes a huge asset when you release the payload.

Right so you can just de-orbit them one by one? Any chance to add a small payload to the Heinlein? Maybe a small rover?

[Rune]

1 minute ago, Majorjim said:

Right so you can just de-orbit them one by one? Any chance to add a small payload to the Heinlein? Maybe a small rover?

That is what the LackLuster is there for! They are basically the same ship, but with two different payloads. And yes, the LackLuster also lost its wings in order to be able to flip itself when reentering in a recent redesign.

 

Rune. I.E: the Lackluster was supposed to superseed the Heinlein, but people liked the 3-person cabin too much for me to let it go.