1.0.5, harder to make spaceplanes?

[herbal space program]

So here’s a question for the group: if the jet engine indicator says it’s getting 100% of its propellant needs, then does that mean that intake air is not a limiting factor in thrust? Because I’ve been showing way lower than ~400 kN of thrust (maybe 200 or so) on my RAPIERs when I hit Mach 3.7 at 18km, but I’m getting at least somewhere in that ballpark if I hit it at 10km. Either way though, that indicator says 100% all the time, all the way up until I flame out at 29+km. What gives?

[upsilone]

I too have found it to be very difficult to lift spaceplanes.

I have been working tirelessly over the last week or so on perfecting a single-seater SSTO with the capacity to carry fuel converters and sas thrusters for docking and refuelling on planets, as well as ion thrusters. All this provided me a space plane that was capable of travelling to every single planet in the kerbal solar system and never run out of fuel.

Strangely, the hardest part for me was to be able to orbit Kerbin using only rapier engines, avoiding the use of oxidizer upon ascent for as long as possible.

It appears that with the new update, Kerbin's atmosphere suddenly became much denser and I am unable to break past 600m/s at 10'000 meters altitude, whereas before I was able to get up to 2000 m/s before proceeding to a steep ascent.

I would like for the next update to include some major upgrades for the Rapier engine so as to provide a more powerful and more efficient engine!

[GoSlash27]

So you are saying EVEN less intakes? My craft (the HK-101A4 im working with) has 2 shock cones, one of which isnt even uses as an intake but to lower the drag the nuke engine has (since its end is exposed). So its basically one intake in the front, a fuselage, engines, and one intake to cap it off clipped far enough inside as to not block thrust (unless 1.0.5 made the whole capping the end nolonger as critical or important).

Yessir. Even less intakes.

A single engine needed about .007 m^2 of intake area to run at top end in 1.04. Now .001m^2 effective area will do.

I say "effective area" because now intakes are working under a velocity curve so their effectiveness tapers off with speed.

Is the shock cone still the best nose cone part in terms of drag, or has that now changed so that other intakes have perhaps better performance? Ohh, and what about radial intakes, are those any good now, or are they still a bad idea since before those radials had alot of drag and not so much area. Ohh, and what about the cool looking inline intake with some fuel inside, is that good at all, or worse then a shock cone (which im guessing still has to be in the front either way, unless regular nose cones are superior now to the ram in terms of raw drag values).

Well, to put it in perspective, a pair of structural intakes (now called "radial variable ramp" or some such) is sufficient for any spaceplane engine to max out it's speed and altitude capabilities, so a shock cone is pretty much overkill unless you have multiple engines.

My first spaceplane was able to max out the Panther using the engine nacelle, which is supposed to be a subsonic intake.

If I were to design an ultimate low drag setup, it would have a tailconeA at the front followed by a radial intake. This will beat the stuffing out of a shock cone.

I'm still sorting out the new physics, so I'm sure there'll be lots to follow.

Best,

-Slashy

Edited November 10, 2015 by GoSlash27

[tewpie]

Just fired up 1.0.5, it seems "peak heating" for ascending spaceplanes has moved from 12-14k to 18-20k. The upside is transsonic and supersonic drag at sea level is much reduced, so this calls for longer time spent at lower altitude building up speed and then zoom climbing at a higher angle.

It seems skin->core conduction actually works properly now so it's more important to attach things prone to skin overheating (like wings and intakes), directly to things with big thermal masses (like large, full fuel tanks).

On balance it looks like it's slightly easier now to orbit spaceplanes, we just have to use different ascent profiles.

[KerikBalm]

So here’s a question for the group: if the jet engine indicator says it’s getting 100% of its propellant needs, then does that mean that intake air is not a limiting factor in thrust?

That seems to be correct.

Because I’ve been showing way lower than ~400 kN of thrust (maybe 200 or so) on my RAPIERs when I hit Mach 3.7 at 18km

I don't think you can get maximum thrust at 18km, jet engine thrust is also affected by atmospheric pressure (the opposite of rockets... thrust decreases as you get higher).

As to body lift... I tried to make very overpowered jet-cars with little stabilizing fins, that in the past could life off due to body lift and pure thrust at high speed in thick air... no luck this time.

I wanted to use such a craft to test out the thrust reversing... oh well.

I just made a SSTO in 1.05 on my first attempt, did a successful water landing after de-orbit, and then a takeoff from the water and back to KSC... I think the changes to spaceplanes haven't been so great... certainly not like the change from 1.0 to 1.02, or 1.02 to 1.04

[fireblade274]

Yea im going to say that my favorite Multiple stage to oribit plane, that can haul up a full jumbo tank, used to cost me less then 150k to launch. On landing id get back about 115k. Since the update, i tried to launch it like normal, 20 degree assent profile, nose down to 15 degrees at 8k, nose down to 10 degrees 10k, and start rockets around 18k. It got up there every single time after many many hours of tinkering, and after the update it would start losing speed at around 14k and fail assent miserably. Ive remade the ship, but it costs 190k, and its made an efficient STO inefficient.

The costs came from needed to beef up its heat resistance with delta wings instead of the largest wing set which was exploding on re entry, and add 2 more engines, and after all that my aero brakes are still not making it through re entry also when they always did. Over all, I like the update, but I feel like some things need to be balanced out now.

At the very least, I would like to see aero brakes given added heat resistance. They only have 1.2k and well landing gear is 2.7k i think? Aero brakes have always been at 1.2k but never exploded on me, and id usually come in from a 80k orbit and give myself a 20k periapsis on reentry.

Edited November 10, 2015 by fireblade274

[Franklin]

id usually come in from a 80k orbit and give myself a 20k periapsis on reentry.

this seems way too high/steep even before 1.0.5, but i'm a 70/50 sort of guy and take entry slow and long.

[fireblade274]

this seems way too high/steep even before 1.0.5, but i'm a 70/50 sort of guy and take entry slow and long.

Ah so you Slow Cosby it lol

Idk i just always hit ksc when i put that 20k periapsis on that peninsula far east of ksc, and fell into that habit. I guess I could make re entry less steep but then Id have to guess and test alllll over again: I can't wait for atmospheric trajectories to update for 1.0.5

[Deutherius]

this seems way too high/steep even before 1.0.5, but i'm a 70/50 sort of guy and take entry slow and long.

At the other end of the spectrum, I always went for a 600 m/s deorbit burn from 80 km orbits (if I had the fuel, of course). Usually done above the last desert peninsula before KSC. Never had any heating problems. Too steep is not always a bad thing

[Scarecrow88]

Well my tried and tested spaceplane that worked perfectly in 1.0.4, capable of reaching a 500x500 orbit, now explodes due to overheating during the ascent if I follow the same ascent profile as I used in 1.0.4. Will have to try something different with the ascent now I guess, as I know the craft is more than capable.

[Captain H@dock]

Same here, my ascent profile doesn't work anymore. You don't seem to cool down until 18ish km, which is fine with decent TWR/TDR spaceplane, but might prove a problem for the more optimised ones. But if you climb earlier, and settle for less air breathing speed (1400 instead of 1500 in my case), you can still do it with the same fuel load.

However, getting more than 1450 m/s from the air-breathing will probably be difficult now...

What I've been using for that quick run (fuel loads are from 1.0.2, fill everything for a lot of margin):

[panzer1b]

Not a fan of the new system 1 bit (1.0.4, realistic or not, was much more enkoyable in terms of spaceplane style builds), but i finally got my goal minus teh weight....

It gets 3K dV in LKO (and you need to ride the line with the heat as its so inefficient if you arent gunning it at high speed), its 25 tons heavy (i wanted 20, but i guess ill have to live with having excessively heavy fighters), and it carries the usual gear, docking system, RCS, and 2 internal missiles.

that said, it does beat the older model that had 7K dV in every thing that matters, its lighter, more maneuverable, better firepower, and the onboard IRSU gives it infinite range in practice (provided you are patient enough to seek out resources with the low altitude scanner (the others just wont fit inside it).

Edited November 10, 2015 by panzer1b

[fireblade274]

I call for increased heat tolerance of aero brakes, they are only 1.2k, the same as the Radioisotope thing, and landing gear have 2.7k

[herbal space program]

FWIW, I've been testing different front ends for my plane, and AFAICT the shock cone still has the least drag. At least it gave me the best takeoff speed and low atmosphere acceleration by a fair bit vs. the tail cone A or the 1.25m advanced nose cone. Not sure if they behave differently at the top end

[Bubbadevlin]

I have actually found my own SSTOs struggling in the sub-sonic zone, and accelerating enough to produce enough thrust... Its really annoying (and yes i am working with fairly low T/W ratio crafts, as its a SSTM)

[herbal space program]

I can’t seem to orbit my best long-range SSTO from 1.0.4 now either L. This used to get to LKO with almost 6km/s dV, sporting both RCS and landing struts. Now I can’t seem to get it into orbit at all. In addition to the lower velocity ceiling of the RAPIER, the thicker upper atmo makes my one nuke insufficient to make orbit from around 39km with a 45km Ap 45 seconds out, which is where I generally was with maybe 75 Oxidizer left before. Now I will have to greatly increase my TWR between 20km and 40km. I will definitely need ether more oxidizer or less weight to do that, inexorably reducing my maximum range. I don’t think the reduced intake drag is going to offset that. Bummer!

Javascript is disabled. View full album

[Pthigrivi]

Im not having any trouble getting to orbit... re-entry though... whoo! Id better shallow that .... out.

[RocketBlam]

I guess I'm not the spaceplane master like I thought I was... I feel happy if I manage to hit 1200 m/s before lighting the rockets.

[RocketBlam]

OK, I just made a spaceplane in sandbox, and... if anything, it has more Delta-V in orbit than I usually got in 1.04.

I just put this dirty boy into orbit. He has more D/V than I usually have with a one-engine design.

I do have to mention though, that the Mk. 1 cockpit is much more prone to overheating now. You're probably not going to want to come barreling in from Jool and try to aerobrake with this.

[Goomblah]

I don't think it's the cockpit so much as nose cones in general. I've found my spaceplane noses (regardless of if it's an intake, cockpit, or structural part) get much closer to the explodey zone than they did in 1.0.4.

[Alshain]

Way way way way way better than 1.0.4. (way... way way). I thought my plane building days were over, but I just tried it in 1.0.5 and I love it.

Introducing the Shrike Mk2 (click here if you want to compare to the Mk1 from 0.90/FAR)

Edited November 12, 2015 by Alshain

[Streetwind]

I can’t seem to orbit my best long-range SSTO from 1.0.4 now either. This used to get to LKO with almost 6km/s dV, sporting both RCS and landing struts. Now I can’t seem to get it into orbit at all. In addition to the lower velocity ceiling of the RAPIER, the thicker upper atmo makes my one nuke insufficient to make orbit from around 39km with a 45km Ap 45 seconds out, which is where I generally was with maybe 75 Oxidizer left before. Now I will have to greatly increase my TWR between 20km and 40km. I will definitely need ether more oxidizer or less weight to do that, inexorably reducing my maximum range. I don’t think the reduced intake drag is going to offset that. Bummer!

Holy saint in a camper van, what kind of mess of font and size and color tags is this post?

Anyway: check that silent patch that was applied tonight (see announcement forum). It fixes a bug in 1.0.5 where body lift isn't being applied. If you plane relies a lot on body lift, this migh tbe the reason why it can't reach orbit anymore. Perhaps the patch will fix things for you.

[Warzouz]

Ascending overheating is more an issue than before (especially the MK2 cabine). Other than that, I don't see much difference.

The ramjet seems to be much less efficient at low altitude. My SSTO has 2 Rapier and 1 ramjet. When returning home, only the ramjet is used, and usually at 1/4 thrust. In 1.0.5 I had to throttle at 100% just to keep speed above 200m/s.

[rodion_herrera]

No problems. Actually feels easier now. My ascent angle was 35-40 degrees, built up V to around 950 m/s (using both RAMjets and RAPIER) at an altitude of around 28,000M, then switched modes on the RAPIER, and voila, orbit. Orbited once, and landed back at KSC with fuel (both fuel and oxider) to spare.

Javascript is disabled. View full album

Incidentally, this is not a demonstrator SSTO, it's fully capable of delivering small satellites into LKO (see cargo bay). Ergo, it is an economically efficient sat delivery system.

Edited November 11, 2015 by rodion_herrera

[herbal space program]

Holy saint in a camper van, what kind of mess of font and size and color tags is this post?

Anyway: check that silent patch that was applied tonight (see announcement forum). It fixes a bug in 1.0.5 where body lift isn't being applied. If you plane relies a lot on body lift, this migh tbe the reason why it can't reach orbit anymore. Perhaps the patch will fix things for you.

As to the post, Sorry about that. I'm having all kinds of weird problems with the editor interface here and nowhere else. I’ve taken to pasting text in from a word processor, and no matter what everything posts in that tiny font. I don’t see any color tags when I look at it, but it wouldn’t surprise me if it was messed up in other ways. I guess I need to switch browsers for this forum.

Anyway as to the plane, I’ll see how it works now. By the time that patch was applied, I had already given up on Mk1 fuselage-based stuff and was working with Mk2. There were a fair number of us in 1.0.4 working on high dV spaceplanes for long-range missions, and based on this thread none of them seem to be very happy. The thick atmosphere high up makes trying to circularize on the nuke engines quite a bit harder. Doing that is always a narrow-margin exercise, and that little bit of extra drag up there made it seem to me like I would have to increase TWR a fair bit, i.e. boost less fuel and/or ship more oxidizer. On top of that, while I could just get to 1500 m/s on air plus the nuke, I couldn’t sustain that speed to nearly the same altitudes as I could in 1.0.4, so I had to switch to bipropellant quite a bit earlier. It will be interesting to see later how getting the body lift back may mitigate all these problems. It also seems like they fixed the intake air situation with that patch, as I noticed I needed significantly more intakes to keep flying up high afterwards, but OTOH my range seemed higher once I had enough. If they’ve fixed it so that this thicker air now sustains combustion in proportion to its drag, then we might be in a different movie...

...So I went back to my old plane and tried it, and it’s definitely better than it was before the patch. Nonetheless, it still can’t make orbit the way it is and will need to ship more oxidizer. I suppose with the cheaper transition to supersonic flight, that might actually work out to more or less a wash. We’ll see...

Edited November 11, 2015 by herbal space program