<ProjectThoth>
I mean, the other option is to make the first stage really long and then stuff the second stage into the intertank region and eject it during staging.
<Bornholio>
how about skeletal frame like Ruskis'
<ProjectThoth>
Bornholio: That's what I was thinking, except plus the manipulator to stuff it in the payload shroud.
<ProjectThoth>
Which has a nice bonus of giving the upper stage an RMS "for free," as it were.
<soundnfury>
wait, why would you HL the first stage and VL the second? That's a crazy way round.
<ProjectThoth>
soundnfury: WIngs are heavy, why not stick them on the first stage?
<ProjectThoth>
(where the payload penalty is lower)
<soundnfury>
but wings are useful for re-entry
<soundnfury>
and landing-fuel is heavy too
<ProjectThoth>
soundnfury: RTLS is prop-expensive, though.
<ProjectThoth>
It's nice to be able to use wings for the flyback cruise.
<soundnfury>
and trying to HL anything as big as a first stage is... interesting
<soundnfury>
what kind of size are we talking here?
<ProjectThoth>
Not if you're talking about something Delta-II size.
<soundnfury>
(e.g. HL a F9S1-size vehicle would be scary)
<ProjectThoth>
Specifically, Delta II-class with a hydrolox upper.
<soundnfury>
D-II, that's what, 96"?
<ProjectThoth>
Ish, but I'd prefer to adopt a lower aspect ratio.
<soundnfury>
okay, I guess that's not so bad
<ProjectThoth>
My plan here is to bring the first stage into operation as fast as possible (hence, reusing Shuttle aerodynamics, etc) and operate for a time with an expendable upper stage while a reusable version gets developed.
<soundnfury>
ummm, I'd be surprised if Shuttle aerodynamics were that relevant to a first stage
<soundnfury>
Shuttle has to compromise to improve its aero at near-orbital speed, S1 doesn't
<ProjectThoth>
I originally wanted to repurpose some ideas that were bounced around during the Shuttle era (i.e., a nose door that would push out of the interstage and close over the separation plane), but 'tis a bit silly, after all.
<ProjectThoth>
soundnfury: As a reference starting point, it's okay enough.
<ProjectThoth>
A solid nose would be a hell of a lot easier to deal with.
<ProjectThoth>
I wonder what kind of problems there'd be with a center-ejection stage setup?
<ProjectThoth>
I.e., putting a payload bay between the propellant tanks on the first stage and dropping it out like a bomb.
<ProjectThoth>
(alternately, flipping the first stage on its back to get an unbroken heat shield)
<ProjectThoth>
I'd assume it'd be a bastard to fly, depending on how long it turned out to be.
NomalRaptor is now known as UmbralRaptor
<ProjectThoth>
Then again, the Shuttle was pretty long and thin.
<ProjectThoth>
I'm sticking with the RMS solution... it's probably the best compromise between, well, everything.
<lamont>
mechjeb is almost working the way i’ve always wanted it to for interplanetary transfers
stratochief has quit [Ping timeout: 198 seconds]
<awang>
Anyone here used the B9 proc wings additional wing data toggle in the editor?
<lamont>
crazy i just did an interplanetary transfer burn to moho and the periapsis radius is inside the surface of moho — after a like 8 minute long nuke burn out of a parking orbit — no course correction required
<lamont>
(well i guess if i wanted to avoid lithobraking)
<awang>
Node executor has been successfully un-borked?
<Starwaster>
ok not to be a killjoy but WHY is it necessary to tie in node execution to PEG?
<Starwaster>
and are all these changes getting rigorous testing in stock conditions?
<soundnfury>
lamont: to me the crazy part of that is that the shutdown timing was precise enough
<soundnfury>
(though sounds like you're in stock — does the LV-N throttle? I forget)
<awang>
soundnfury: Do any stock engines that aren't SRBs not throttle?
<lamont>
yeah i’m in stock and it throttles, but i’m not throttling
<soundnfury>
awang: idk, so long since I've played stock
<soundnfury>
I'm sure there's _something_ odd about the LV-N; does it not gimbal, perhaps?
<lamont>
the LV-N doesn’t use oxidizer
<soundnfury>
lamont: not throttling down at the end of the burn?
<soundnfury>
lamont: well _obviously_, but _apart_ from that.
<lamont>
yeah, i’m not dribble-throttling even though stock LV-N can dribble throttle
<soundnfury>
... another "I forget what stock is like" question, is the throttle (well, shut-off) response of stock engines still immediate?
<lamont>
and starwaster, i’m going to make it selectable — for development i just replaced it since i had no idea what it would look like
<lamont>
yeah throttling is instantaneous
<soundnfury>
ok, _that_ explains why you were able to get that level of crazy precision
<lamont>
actually in RO is there delay in throttle cut off?
<awang>
I think it depends on engine
<lamont>
i know there’s spool up time, but i wasn’t aware that there was spool down time
<awang>
Does it only work one way?
<awang>
I assumed that it works both ways
<soundnfury>
there certainly should be. Heck, for maximum realism residual thrust should continue for several seconds after shutdown, just from gas after the last valve venting
<soundnfury>
(something something "recontacted the second stage" something Falcon 1 mumble)
<lamont>
sure, but is thre code that does that?
<soundnfury>
idk, I also assumed that the spool up time code applied to spool down too
<lamont>
it doesn’t make sense to me that it’d be symmetrical since you should be able to spin down a pump faster than you can spin it up
<awang>
That's true
<soundnfury>
not symmetrical, spool down should be quicker, but not infinitely so
<awang>
There's a throttleResponseRate variable
<awang>
idk if it applies to cutoff
<Starwaster>
especially for NTR... there's a prolonged throttledown to allow the core to cool
<soundnfury>
IRL, AIUI you shut the valves feeding into the preburner (or other loop-to-heat-things-for-driving-pumps-with, per expander cycle) and then just wait for the rest of the system to slow down.
<soundnfury>
Starwaster: presumably that causes the Isp to tail off as well, since the core temp. is dropping?
<awang>
There's engineAccelerationSpeed and engineDecelrationSpeed
<awang>
So maybe the game supports it, but nothing actually uses it?
<Starwaster>
presumably
<soundnfury>
It's possible that Nathan added it for RO's nefarious porpoises while he was working for Squard.
<lamont>
i can’t see in the code where shutdown / spooldown happens
<awang>
Might it have been moved to ModuleEngines?
<lamont>
well spool up is here
<awang>
idk then
<awang>
Sorry :(
<lamont>
ah i think i see, its just semi-obfuscated
<lamont>
nope, it is extremely obfuscated, i can’t tell what it does, buncha math
<lamont>
but i think throttleDownMult makes it 100 times faster to go down by default
AmbulatoryCortex has quit [Read error: -0x1: UNKNOWN ERROR CODE (0001)]
stratochief has joined #RO
<awang>
So git add has been running on my KSP install for at least an hour
<lamont>
with spinning rust and a slow CPU that might not be that implausible
<awang>
Spinning rust?
<lamont>
https://git-lfs.github.com/ might be better suited to ripping across your KSP install and all the binaries
<awang>
And git has performed alright in the past
<lamont>
not SSD
<awang>
First time it's taken anywhere this long
<awang>
I'm using an SSD
<awang>
CPU isn't that slow, I think?
<awang>
It's an i7
<lamont>
that seems slow then
<lamont>
for awhile i was running git on my KSP directories out of cron
<awang>
Oh wait
<awang>
I think I know why
<awang>
It's the Principia journals
<awang>
That and the bajillion versions of persistent.sfs laying around from quicksaves
Wetmelon has quit [Ping timeout: 186 seconds]
ProjectThoth has quit [Ping timeout: 200 seconds]
aradapilot has quit [Remote host closed the connection]
aradapilot has joined #RO
schnobs has joined #RO
aradapilot has quit [Ping timeout: 207 seconds]
ProjectThoth has joined #RO
ProjectThoth has quit [Client Quit]
aradapilot has joined #RO
aradapilot has quit [Ping timeout: 207 seconds]
ProjectThoth has joined #RO
<ProjectThoth>
Okay, here's a thought, regarding the interstage question...
<ProjectThoth>
If I had an open-frame interstage mounted around the nose of the first stage, would it be able to survive reentry?
<ProjectThoth>
Assuming it, like, could be painted with ablative paint.
<awang>
Hmmm
<awang>
Looks like B9 proc wings "show wing data" is broken in 1.3.1
<awang>
Just plain doesn't work, with a clean 1.3.1 save + MM + B9 proc wings
<awang>
Weird, since I could have sworn it was working fine...
<ProjectThoth>
I'd assume pneumatics on an interstage is a bad idea.
<awang>
Why?
<ProjectThoth>
awang: As the load-bearing structure.
<ProjectThoth>
Because it'd be nice to just retract the damn thing.
<ProjectThoth>
awang: Basically, I'm imagining six or eight or some number of pistons that would serve as the load-bearing structure between the two stages. (They'd have to have some sort of fault-tolerant system onboard so that any leaks could be accommodated by driving up the pressure in the healthy cylinders).
<awang>
I see
<awang>
Sounds... complex
<awang>
Maybe you could hack something together with infernal robotics?
<ProjectThoth>
*shrug*
<ProjectThoth>
Okay, another thought, is there any reason why heat shields aren't purely hemispherical?
<awang>
Might some of the early Soviet capsules count?
<awang>
Since they were spherical
<awang>
Otherwise, idk
<ProjectThoth>
awang: Probably. The only hemispherical heat shield/conic aft body I can think of is Hyperion.
<awang>
"Here, we demonstrate that this generic shape ['blunted-cone'] can be derived mathematically and yields the maximum stabilizing aerodynamic torque of all possible shapes"
<awang>
Doesn't take into account expected heat load and craft volumetric efficiency, according to them
<ProjectThoth>
Yeah, and isn't blunted-cone like missile warhead shaped?
<awang>
Maybe a non-hemispherical shape makes it easier to stuff things inside?
<ProjectThoth>
I would assume that it might have to do with drag, because the spherical segment ones are more flat.
<ProjectThoth>
Think ferram might know? (plz no ping)
<ferram4>
What is the question?
<ferram4>
Oh. Why blunted cones.
<ferram4>
They're more stable, for one.
<ferram4>
They also have lower drag, which when you're working with warhead reentry vehicles is actually desireable.
<ferram4>
Less drag lets it get there slightly faster and means less error from drag in the trajectory. As long as it survives to go off, who cares about how fast it's going when it detonates?
<ProjectThoth>
ferram4: Shit, sorry, I hope I didn't wake you. Any reason why pure hemispheres aren't used?
<ProjectThoth>
(for regular old capsules)
<ferram4>
For regular capsules, because the whole hemisphere is a waste.
<ferram4>
The blunter parts are more important for drag and stability, and making it flatter results in lower heat transfer, higher drag, easier manufacturing, and more volume.
<ProjectThoth>
ferram4: If I had a magic inflate-a-ball, would there be anything wrong with that shape?
<ProjectThoth>
I'd assume it might tend to wobble.
<ferram4>
Wrong? Nah, it'll work. I mean, Vostok and Voskhod were that.
<ProjectThoth>
Er, magic inflate-a-hemi-ball.
<ferram4>
With an offset CoM to keep it oriented right and not get killed from bad G-loading orientations.
<ferram4>
That'll work the same if it's oriented right.
<ProjectThoth>
CoM inside the inflate-a-hemi-ball, I'm guessing?
<ferram4>
It'll actually be worse if it's oriented flat-end first, because (assuming it has a sharp corner around the edge) there will be harsh heating at that edge and it'll start melting away there.
<ferram4>
Also, it would have no stability in that orientation without any cone or rounding to produce a good re-orienting moment.
<ProjectThoth>
I'm basically imagining a regular capsule shape (15 degree sidewall), but with the heat shield replaced with a half-sphere.
<ferram4>
It would work, but the CoM would need to be deep in the hemispherical portion to be stable and it would have worse drag and thermal resistance than an equivalent size Mercury cpasule.
<ferram4>
It would probably be more reliant on the "Oh shit, make sure it's oriented right" drag fin that Mercury had to keep things from going bad.
<ProjectThoth>
ferram4: Ah, so it's kind of a pain in the ass to design around?
<ferram4>
It is inefficient.
<ProjectThoth>
In case you're curious why I have this question, I'm investigating a reusable TSTO that has an unfortunately long interstage.
<ferram4>
And you would like to have the interstage turn into a hemisphere.
<ferram4>
Yes?
<ProjectThoth>
ferram4: Well, I wanted to pack an inflatable heat shield around it (the interstage is ~1/2 the diameter high) and make it into a crude approximation of a hemisphere.
<ProjectThoth>
My choices are to 1) throw it away, 2) use an RMS to stuff the interstage into the payload shroud for recovery, or 3) this abomination.
<ferram4>
You could inflate it into a conic-with-spherical-center shield.
<ferram4>
That's what most inflatable designs inflate to.
<ProjectThoth>
So basically a really, really big Corona-ish shape.
<ferram4>
Just because it's inflateable doesn't mean it can't have some rigid parts inside to force the shield into a particular shape.
<ProjectThoth>
Ah, though the engines tend to get in the way of that.
<ProjectThoth>
I currently favor option 2 out of the list, even though it's a bit silly.
<ferram4>
Hmm, is this for the upper stage or lower?
<ProjectThoth>
Upper.
<ProjectThoth>
Lower stage is a regurgitation of the old flyback S-IC designs, except sized around an NK-33/Delta II.
<ferram4>
Because there is the most abominable option possible, which is, "put the heat shield on the front and do a convoluted parachute-involving flip maneuver"
<ProjectThoth>
ferram4: I thought about that, but I like having a more-or-less unlimited payload length (blame Gary Hudson for that).
<ferram4>
Hmm, the engine being in the way is a serious problem.
<ferram4>
I assume this engine isn't being used for landing or has a rather small nozzle if it is?
<ProjectThoth>
No, the TWR is way too high.
<ferram4>
Alright, my dumb idea then is to have the heat shield in several parts.
<ferram4>
On a fixed part around the engine nozzle, extending nearly as wide as possible.
<ProjectThoth>
Landing engines are going to be kind of dinky. Probably peroxide/kerosene for storability and due to volume constraints.
<ferram4>
A bunch of fold-out/inflatable stabilizer parts attached to the edges of that.
<ferram4>
And then a single solid part intended to be hinged down to cover the nozzle exit when all is done like a lid.
<ProjectThoth>
I'm wary of heat shield doors, don't they tend to be heavy?
<ferram4>
It is amazingly... overcomplicated.
<ferram4>
Hmm, I dunno. Never did much research into that.
<ProjectThoth>
My solution thus far has been to just use one inflatable heat shield and radially mount the engines (maybe 2 or 3 RL-10s).
<ProjectThoth>
So there's a void in the middle where the heat shield can be mounted on a jackstand.
<ferram4>
That is a feasible solution, so long as the engines are at the bottom of the tank still.
<ferram4>
Just offset.
<ProjectThoth>
Yup - no structural weirdness.
<ferram4>
On the bright side, you completely dodge the question of whether to send one propellant feed pipe through the other propellant's tank.
<ProjectThoth>
So under option 2, the interstage would be removed after insertion (it'd probably be one of the Russian lattice types) and would be stuffed in the payload shroud by the RMS after deployment (or, for crewed/tanker variants, the cabin/tank diameter would be just small enough to allow the fairing to pass around it).
<ProjectThoth>
*interstage, not fairing
<ProjectThoth>
And then it'd deorbit, puff up the heat shield, reenter, and land (probably not in exactly that order).
<ferram4>
Why not keep the interstage on the first stage?
<ProjectThoth>
ferram4: VTHL stage.
<ferram4>
Yeah, so?
<ProjectThoth>
Wouldn't a lattice structure around the nose present... issues?
<ProjectThoth>
What about during reentry? Would painting it with ablative paint be enough?
<ferram4>
How fast is it coming in?
<ProjectThoth>
Uhhhh...
<ProjectThoth>
I unno, total delta-v *shoud* be around 2 or 3 km/s, at most.
<ProjectThoth>
Maybe 4.5 in the absolute worst-case scenario?
<ferram4>
Around 2-3 km/s with good ablative paint should probably be doable.
<ferram4>
4.5 km/s is far more qquestionable.
<ProjectThoth>
Yeah.
<ferram4>
I'd put more of your dV in the upper stage. It'll still need to take the same abuse on reentry, but you can give the lower stage an easier time.
<ProjectThoth>
I haven't actually done delta-v calculations yet, the last couple days were spent figuring out the volume of everything.
<ProjectThoth>
But, by mass, the first stage has about 3x the propellant of the upper stage. (S1 is kerelox, S2 is hydrolox).
<ProjectThoth>
I could get away with stretching it some, if needed.
<ferram4>
...that's probably going to give you a nice low speed for first stage reentry.
<ProjectThoth>
I literally ripped that data off of Saturn-Shuttle.
<ferram4>
And besides, you should make it upper-stage focused with that anyway.
<ProjectThoth>
Yeah, the upper stage does the lion's share of the work, that's what I intended.
<ProjectThoth>
I believe that the mathematical ideal (for minimum MTOW) is about 5:1 in favor of S1, considering the pmf of both stages and including recovery hardware.
<ProjectThoth>
But, of course, that's not what I'm worried about.
<ferram4>
FWIW, I think a properly reinforced (read: really heavy) wire interstage could take reentry.
<ferram4>
I'd be less concerned with raw heating and more concerned with it being weakened by heat and then ripped apart by forces.
<ferram4>
I mean, it's brute force and stupid.
<ferram4>
But it'd work, and your system is already complicated enough.
<ProjectThoth>
Are you talking reentry from orbit, or from suborbit?
<ferram4>
From suborbit.
<ferram4>
Frankly, as far as parts to throw away go, the interstage is literally the best candidate.
<ProjectThoth>
Yeah, it's cheap to throw away, but I'm stubborn.
<ProjectThoth>
Do you have any specific qualms with the RMS strategy?
<ferram4>
At is likely a steel frame, which is cheap.
<ferram4>
What's RMS stand for exactly?
<ProjectThoth>
Remote Manipulator System.
<ferram4>
Oh. Then here it is:
<ProjectThoth>
So there'd be a non-structural robotic arm stuck to the side of S2 that would grab and stick it in the payload box.
<ferram4>
The weight, extra complication, and cost to save a bit of steel.
<ferram4>
I admire the single-mindedness towards reusability, but as a practical idea it might actually be worse than the space shuttle.
<ProjectThoth>
I mean, it already would have use on-orbit, this is basically just repurposing it for something else.
<ProjectThoth>
ferram4: Ah, you're more interested in r-selection rockets?
<ferram4>
Not so much that. Just towards the unimportant bits of them.
<ProjectThoth>
I'm approaching this from the perspective of "the rocket as a product" instead of "the launch as a service."
<ferram4>
I mean, sure, it gets in the way having to replace the interstage each time, but in the grand scheme it's not too big a deal.
<ProjectThoth>
Yeah, just a shame that I can't come up with a clever way around this.
<ferram4>
You could have the interstage set up so that it left part of it on the upper stage to come down with that, and the remainder on the first stage could fold flat against the first stage hull.
<ProjectThoth>
Folding interstage?
<ProjectThoth>
Is that even, uh, safe?
<ferram4>
If it can only fold inward, it should be fine.
<ferram4>
The upper stage would force it outward and braces could be put in place to keep things in check.
<ferram4>
It would require a fair bit of extra reinforcement to keep it from deforming the first stage tank, but that shouldn't be too bad.
<ProjectThoth>
I thought about folding it, it just seemed kinda crazy.
<ProjectThoth>
But then, of course, it needs thermal protection and all that jazz.
<ferram4>
It is far more sane than the other ideas.
<ferram4>
But it will actually need slightly less than just leaving it hanging out there.
<ProjectThoth>
If only there was a way to cap it off.
<ferram4>
I was imagining that you had put quite an aerodynamic nose cone at the top of the first stage.
<ProjectThoth>
It's kinda boring thus far, just a hemisphere.
<ProjectThoth>
ferram4: I originally wanted to do what they planned for the flyback S-IC and have a moveable nose/"cowl flaps" to cover the attachment hardware on the interstage.
Wetmelon has joined #RO
<ProjectThoth>
Anyway, sleeps.
ProjectThoth has quit [Quit: +++out of cheese error+++]
Shoe17 has quit [Quit: Connection closed for inactivity]
TM1978m has joined #RO
stratochief_ has joined #RO
stratochief has quit [Ping timeout: 198 seconds]
aradapilot has joined #RO
TM1978m has quit [Remote host closed the connection]
aradapil_ has joined #RO
aradapilot has quit [Ping timeout: 186 seconds]
stratochief_ has quit [Remote host closed the connection]
schnobs has quit [Ping timeout: 383 seconds]
Rokker has quit [Quit: Connection closed for inactivity]
BasharMilesTeg has joined #RO
BasharMilesTeg__ has joined #RO
BasharMilesTeg has quit [Ping timeout: 207 seconds]
BasharMilesTeg_ has quit [Ping timeout: 383 seconds]