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1.0.2 - Any hope left for SSTOs?


panzer1b
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You know I have developed almost the same exact profile. After trying everything else I switched to 3x turbo and 1x nuke using a 40 degree rise. I usually have throttled down slightly between 10-15km as my ship tends to get pretty hot throttling up before cracking 20km. In my best run I cracked 1,350m/s before I started losing speed from low thrust.

I'm not quite getting the dv into LKO that you have but I was using MK1 so I might have to try switching, try to ensure I'm in your math for engine and I wasn't hitting the nukes as quickly as you (I was trying to coast the last gas out of the turbos).

It's a little ways away from my pre 1.0 SSTO to Duna landed and back but all in good time.

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So today I tested a rather minimalist all-liquid SSTO to see how much delta-v I can squeeze out. I used a 2 rapier 1 nuke setup with a plane that is essentially a V-shaped fuel tank. This thing can break mach 3 at sea level (and explode shortly afterwards :D ). The best I could do was a little over half fuel left in orbit, which engineer reports as 2.1km/s, although it had been acting up the entire flight showing NaN dv at times. I did the calculation myself and got around 2.65km/s using 15-tons weight in orbit and 10.7 tons empty. This is still short on anything more than a flyby on interplanetary destinations.

QkClHAa.jpg

I honestly don't know if interplanetary SSTO planes are possible anymore. Going any smaller than this would increase the relative mass of the nuke engine. I packed in as much fuel as TWR allowed. Granted I did not try 1 nuke 1 rapier setup due to thrust balancing issues. 1 rapier 2 nuke gets to orbit but had worse efficiency. My attempts at mid-sized SSTOs showed no better performance. Maybe huge SSTO's with a 30-40 rapiers and a few nukes could get more delta-v?

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I honestly don't know if interplanetary SSTO planes are possible anymore. Going any smaller than this would increase the relative mass of the nuke engine. I packed in as much fuel as TWR allowed. Granted I did not try 1 nuke 1 rapier setup due to thrust balancing issues. 1 rapier 2 nuke gets to orbit but had worse efficiency. My attempts at mid-sized SSTOs showed no better performance. Maybe huge SSTO's with a 30-40 rapiers and a few nukes could get more delta-v?

Probably possible, but not recommended. As before, the sensible way to take an SSTO interplanetary is to refuel it in LKO before heading off. This is no great hardship; if you can build an interplanetary SSTO, you shouldn't have any trouble building an SSTO tanker to establish an orbital fuel supply at negligible cost. A nuke SSTO refuelled in LKO can easily hold 4,000m/s ÃŽâ€V; design one to maximise tank capacity and it shouldn't be hard to hit 6,000m/s or more.

SSTO still works just fine. It's only SSTanywhere that has become less practical, and those were always an unrealistic exploit anyway. For the folks who want to maintain that unrefuelled SSTA ability...well, that's what the SF mods like KSPI are for.

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So today I tested a rather minimalist all-liquid SSTO to see how much delta-v I can squeeze out....

Very nice! I had not thought of using RAPIERs in jet-only mode, as I understand it they have a big advantage at high speed/altitude. Hm....

- - - Updated - - -

SSTO still works just fine. It's only SSTanywhere that has become less practical, and those were always an unrealistic exploit anyway. For the folks who want to maintain that unrefuelled SSTA ability...well, that's what the SF mods like KSPI are for.

Could not agree more with this statement. What's missing in 1.0.2 is the ability to fly an air-breathing craft at mach 6+ at 50km altitude without melting compressor blades and everything behind them. That never should have been possible. This thread proves that we can indeed get to LKO with fuel to spare in 1.0.2.... AND we don't even need to carry oxidant anymore :D

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I honestly don't know if interplanetary SSTO planes are possible anymore.

It definitely is! I just got a medium-size SSTO into LKO with 4,200 dV available. Going to fly it some place and post the pics after work!

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It definitely is! I just got a medium-size SSTO into LKO with 4,200 dV available. Going to fly it some place and post the pics after work!

I think our definition of the term 'medium-size' might be different.

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Thats a nice looking craft.

Thanks! It only barely made orbit, but I could probably replace the nuke with a 909 and have a very solid cargo hauler. What engine config are you using?

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Thanks! It only barely made orbit, but I could probably replace the nuke with a 909 and have a very solid cargo hauler. What engine config are you using?

I run a 4-man shuttle with 2 RAPIERs and a LV-909. I consider this medium sized, with a 1-person short shuttle (not shown here) as a small sized shuttle.

HPw68t4.jpg

3WsjMKL.jpg

Update: I've recently also had better success with running 3 RAPIERs in my latest shuttle, but I'll need to do more testing on it. Will post an update on that one soonâ„¢.

Edited by Levelord
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Aye... except it's not an SSTO.

"Single Stage" means you're not decoupling parts.

Best,

-Slashy

That's why I did the SSTO/Hybrid notation. You don't have to decouple anything. It's just an option for saving DV for extra heavy cargo :)

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Did another round of testing, same basic design but with 3 RAPIERs. Managed to clock almost 500m/s which is a 100m/s improvement over the previous design.

C2UVM3D.jpg

VdBnIwz.jpg

Levelord, what do you use Terrier for? For me it looks like sabres would be enough for such a small craft...

The LV-909s? Well they weigh only 0.5 tonnes, which makes the overall craft 1.5 tonnes lighter. They also have +40s ISP greater than the SABREs in space. Because there's no drag in space, high ISP and low thrust engines can get you quite far.

Edited by Levelord
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so, like I suspected you use it for orbital maneuvering? I'm actually surprised that its extra ISP is enough to pay for extra weight you carry all the way to orbit.

A little trick which I don't think a lot of people do is that when I'm leveling out my pitch to 15 degrees at 10km up my speed is around 300-340m/s, it's almost at the sound barrier, so I fire up the LV-909 for a few seconds for that bit of thrust to push it to around to 360m/s where the RAPIERs start to pick up massive amounts of thrust on their own. Then I disengage the LV-909s. When I see the RAPIERs thrust start to go down (usually around 25Km+ up) I fire up the LV-909s again, close the intakes and switch to rocket mode.

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Hmm. my Skylon-inspired plane with just two rapiers was able to push through sound barrier just by flying lever at 10-12 km. takeoff mass was about 21ton.

Also, is there any updated info on intakes? I just used shock cones + precooler thingy, but maybe that's not optimal.

Edited by Kuu Lightwing
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I suppose that works, but I don't spend a lot of time in the atmosphere because it's a little too draggy in 1.0.2 where it becomes a TWR issue. Also because of the small size of my crafts, they don't carry a lot of fuel for cruising at altitude. I simply punch it through at max thrust to around 1400m/s at 20km before going rocket mode.

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Happy to share! What I've learned so far is that there appears to be a "tipping point" of getting enough velocity for the ramjets to develop ludicrous thrust. For my designs to date, I find I need to keep it under about 9.5 tons per jet engine and about 14 tons per nuke. The 28t craft shown above works great on 3 jets and 2 nukes; at 30t is doesn't make it.

Ascent profile for the Nooxie 6:

--Start on full throttle jet engines 1 and 2.

--Fly off end of runway, retract gear.

--Start jet engine 3 and pull up to 25-30 degrees

--Keep full throttle all three engines. Velocity should rise steadily as thrust compounds, beginning to spike around 10km

--At 18-20km you should see your velocity approaching 1200 m/s, climb rate 400 m/s or better, and jet thrust decreasing.

--Start the LV-Ns when you begin losing velocity. You may have to start early, around 18km, if TWR is low.

--When jets flame out, close your intakes.

--Depending on your TWR you will need to climb at 30-45 degrees. Watch your time to apoapsis; nose up to always keep it >30 seconds out as your apoapsis increases and your periapsis becomes less negative

--As you approach orbital velocity you can nose down to prograde, and circularize.

Good luck! There may certainly be room for improvement in the above and I would love to hear how you make out.

I think that's just it - I'm asking too much of twin turbo-nukes... I'm at 29t. And can easily, er easily enough..., get 1,200m/s, but it's that final push. So far I'm topping out around 55km.

Thank you for sharing. I'm going to get this darn thing up there. At this point, I will add a third turbo. Clearly it is the differentiator that's stopping my current design. Yet, it peters out so soon that I'm too darn stubborn to believe it will help. At times I almost miss the ol' souposphere... No, never.

Edit: Threw that third turbo on... Reduced take off weight and it makes orbit. Guess it's back to the drawing board because I had to pull fuel out to reduce TOW and subsequently only had 512m/s in a 76x76km orbit. Still don't want to believe that it was the turbo, but I guess I have to.

Edit Edit: It's not the atmospheric portion of the flight that is struggling. It doesn't need the turbo, it needs more oomph post turbo... Time to replace Third turbo with Third LV-N....

Edit Edit Edit: It seems that adding a third Nuke instead of a third turbojet is more beneficial. Would need a bigger sample size of pilots, but I think it may be the way to go. Although, I'm still short of my desired dV budget in LKO, but that means I need to reconfigure my payload to be less cargo, and more fuel. But 32t went to 90x90km orbit with two turbos and three nukes and leaves around 540m/s in the tanks when you're up there.

Some comparison photos:

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Edited by FlipNascar
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Seems to me like the drag doesnt change when you close the intakes... What does change is just a relic of the old aero. Another sign of BETA...

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Probably possible, but not recommended. As before, the sensible way to take an SSTO interplanetary is to refuel it in LKO before heading off.
I agree, it was never sensible. But when has KSP ever been about being sensible? Don't get me wrong, it's good that it's at least quite difficult now if not impossible.
It definitely is! I just got a medium-size SSTO into LKO with 4,200 dV available. Going to fly it some place and post the pics after work!
That's awesome! See this is why I come to these forums, to get ideas when I am hitting a wall myself. This definitely gave me ideas for improving medium-sized SSTOs. (I define medium sized as generally using mk2 hull with 25-75 tons wet).
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I think that's just it - I'm asking too much of twin turbo-nukes... I'm at 29t. And can easily, er easily enough..., get 1,200m/s, but it's that final push. So far I'm topping out around 55km.

Thank you for sharing. I'm going to get this darn thing up there. At this point, I will add a third turbo. Clearly it is the differentiator that's stopping my current design. Yet, it peters out so soon that I'm too darn stubborn to believe it will help. At times I almost miss the ol' souposphere... No, never.

Edit: Threw that third turbo on... Reduced take off weight and it makes orbit. Guess it's back to the drawing board because I had to pull fuel out to reduce TOW and subsequently only had 512m/s in a 76x76km orbit. Still don't want to believe that it was the turbo, but I guess I have to.

Edit Edit: It's not the atmospheric portion of the flight that is struggling. It doesn't need the turbo, it needs more oomph post turbo... Time to replace Third turbo with Third LV-N....

Edit Edit Edit: It seems that adding a third Nuke instead of a third turbojet is more beneficial. Would need a bigger sample size of pilots, but I think it may be the way to go. Although, I'm still short of my desired dV budget in LKO, but that means I need to reconfigure my payload to be less cargo, and more fuel. But 32t went to 90x90km orbit with two turbos and three nukes and leaves around 540m/s in the tanks when you're up there.

Some comparison photos:

http://imgur.com/a/hIz4K

Yeah, the problem in liquid-fuel-only SSTOs is the pitiful TWR on NERVAs. You can't make orbit with less than 0.5 TWR, and then only if your atmospheric climb is perfect and you leave the air at least at 1,200m/s with a high climb rate (300m/s or higher). And when you go very low TWR, you will waste a huge portion of your delta-v to gravity drag losses anyhow.

Using RAPIERs in LFO mode a tiny bit at the beginning of the push to orbit (400m/s would be more than enough to push your ap outside of the atmosphere and give you time to get orbital speed out of the nukes) will probably allow you much lower nuclear TWR, which in turn will allow higher fuel fractions in orbit, and thus greater delta-V. I'd be surprised if a LFO-only design breaks 2km/s by much, just because they can't get enough fuel up... (the italics are meant to give emphasis to the critical numbers to look at).

As to interplanetary travel and SSTOs, the sensible-er solution is to go out with a proper IP ship, that was itself carried to orbit inside one or more SSTOs, those are my two cents. Wings are worthless when you are going to and airless planet! The only reason I can think of to send a spaceplane farther out than LKO, if you are going after an efficient way to do things, is to send a shuttle to Laythe to service the ground-Low Laythe Orbit leg of the trip. Everything else is Nerva tug territory, and dedicated VTOL lander. Ok, maybe Duna rates a cool rocketplane too, but that is mostly for the looks, and in homage to Von Braun's gliders, and wouldn't use airbreathers anyway.

Rune. Rocketry is all about ratios.

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I am still stuggling to get any SSTO spaceplane with a noteworthy range into orbit (lets say Minmus or Mun-capable).

Some good ideas and hints in this thread, back to the drawing board...

To LKO it works fine, but beyond...

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SSTOs aren't supposed to be the logical choice for more than Low orbits. Think of an SSTO like a small boat. You bring the large vessel near shore and the small boat carries passengers and cargo back and forth. That's the most efficient way to do things with current technology or near future, forseeable, tchnology ( actually, current tech does not allows for SSTO's, but that's because Earth is a "little" bigger than Kerbin :P) The fun in this game is to achieve great things using the real laws of physics, if we are to break them (too much) this wouldn't be Kerbal Space Program, it would be more like a shoot'em up... Not funny at all :P

Still, you do have a point in one thing, a "turn it all off" buttom is always appreciated, whenever possible let the player costumize the game for the level of realism he/ she wants...

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As to interplanetary travel and SSTOs, the sensible-er solution is to go out with a proper IP ship, that was itself carried to orbit inside one or more SSTOs, those are my two cents. Wings are worthless when you are going to and airless planet! The only reason I can think of to send a spaceplane farther out than LKO, if you are going after an efficient way to do things, is to send a shuttle to Laythe to service the ground-Low Laythe Orbit leg of the trip. Everything else is Nerva tug territory, and dedicated VTOL lander. Ok, maybe Duna rates a cool rocketplane too, but that is mostly for the looks, and in homage to Von Braun's gliders, and wouldn't use airbreathers anyway.

^ Quoted for truthiness. This is why I haven't bothered chasing the single-stage-to-Laythe problem. I'm just building mine with high payload fraction, around 300 m/sec DV in orbit, and enough reserve fuel to cruise home.

I will need to get a shuttle in service on Laythe at some point. My plan is to piggyback a fuel tank onto it in orbit and send it on it's way.

Best,

-Slashy

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