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Roflcopterkklol

No more SSTO's

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Oh come now, the air-breathing engines were never balanced to begin with which was why people were fond of space planes. While they still don't chew fuel like they should, they are, at least, not as much of a cheat as before.

F22 Jet uses somewhere between 0.50-3.5 gallons of fuel per second depending on what the plane is doing.

The Space Shuttle used 1000 gallons per second on lift off.

The jet engines weren't that unbalanced fuel use wise when you see the real figures. Jets were able to go far to fast though.

There is a reason why NASA strapped their space plane to the back of a huge rocket. I don't mind if KSP has the same rules applied.

If you want an awesome plane in space get it there with a rocket.

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The jet engines most certainly were totally and completely unbalanced. They currently have, in 1.0, like 1/3 the Isp they used to and it's still nearly 10x what they have in real life. They also still have insanely high TWRs, even though that, too, has come down in 1.0.

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I do. :)

Me too. Planes are a PIA to land so its much easier and more fun to make SSTO landers.

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My apologies for not reading the entire thread (it sure did grow fast while I wasn't looking), but I disagree with OP on the basis of my SSTO rockets performing about the same as they did before. I thus have serious doubts that SSTOs are "dead" so much as perhaps a little different from what worked before.

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This graph was taken from the Skylon manual off the Reaction Engines website. Blue is the flight profile they claim the Skylon will need to follow, green is what most space-planes in KSP used to follow, and red is the current best flight profile to avoid blowing up/moving through air best. So please tell me how this new heating/aero model makes any sense.

http://i.imgur.com/sUTzTW2.png

http://www.reactionengines.co.uk/tech_docs/SKYLON_User_Manual_rev1-1.pdf

Hi everyone! First post :) This post made me curious about KSP 0.9 vs 1.0 ascent profiles compared to the Skylon hypothetical ascent profile provided by Reaction Engines. I felt that Exclipse was actually mistaken, and that 1.0 was actually closer to the Skylon model. So I tested it out!

Like the Skylon graph, the last point is roughly where I cut off the main engine, before the orbital insertion burn. Skylon uses OMS engines to circularize it's orbit, and both of these SSTO's carry OMS engines because of that. Probably not the most efficient design, but it works! Here are the results:

KSP 0.9

Mass: 18.3t

Engines: 2 Rapier engines, 2 OMS engines.

0.9 ascent was fairly traditional. 45 degree climb, leveling off between 10-20k to build up to about 1300m/s before kicking up to 45 degrees again between 20-25k to raise the apoapsis to about 75k. Circularized to a 85x85 km Orbit, with plenty of deltaV to spare.

EJuarLml.png

oD3l036.jpg

KSP 1.0

Mass: 26.6t

Engines: 2 Rapier engines, 4 OMS engines

For 1.0 my strategy was to either maintain or increase airspeed. Took off at about a 20 degree angle, lowering my climb to about 10 degrees to maintain airspeed when i hit the drag wall at Mach 1. Stayed at about 10 degrees until I started picking up speed past Mach 1 at about 5km altitude. At about 10km altitude speed started coming on fast and I started pitching up to about 30 degrees off horizon going 540m/s. Slowly pitch down in a gravity turn to about 25 degrees (Velocity vector is at 20 degrees, so 5 degree AoA) at 24km altitude and 915m/s surface speed. At this point Rapier jet mode is dying out, so I switched to rocket mode. I try to stay close to the velocity vector (5-15 degree AoA) to reduce airspeed loss due to drag, until main engine cutoff at about 45km. I forgot to take a point at main engine cut off, so that isn't on the graph below, unfortunately! Ran out of main engine fuel before the end of the circularization burn, but finished it with the OMS engines with about 200m/s deltaV to spare, I'd estimate.

A further note, reentry without airbrake spam is actually pretty straightforward with this thing! I aimed for a 40km periapsis, and came down pitched about 45 degrees. At 40-35km I started S-turning like mad while keeping the nose as high as possible, using the control surfaces and the torque wheel. By 20km airspeed was already down to about 600m/s! Then, simply glided it down, landing it at about 65m/s using wing mounted spoilers to slow me down towards the end, and the drogue chute to slow me down faster while on the ground.

2qK57sFl.png

Dw9BldRl.jpg

Conclusion

To me at least, 1.0 is much closer to Skylon. But i also think different craft might have different ascent profiles, based on mass, lift, drag, thrust, etc. EDIT: It's also notable how much quicker it is to get in to orbit now. In 0.9 it took nearly twice as long to get to the main engine cutoff point!

Edited by Binho
Forgot to mention something

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Dude... I can easily get a Mark 3 SSTO into orbit now, while still hauling a full orangie. I'd call that 'extremely significant' payload.

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The jet engines most certainly were totally and completely unbalanced. They currently have, in 1.0, like 1/3 the Isp they used to and it's still nearly 10x what they have in real life. They also still have insanely high TWRs, even though that, too, has come down in 1.0.

There aren't any SSTOs in real live. ;)

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Also, I copied an earlier poster who made something awesome. A cargo sled, can handle 2.5 tons to LKO, excellent for satellites.

SIqRZAy.png

Kind of with Wanderfound here, spaceplanes are pretty easy.

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Speaking of satellites, you don't need a Mk2...

Guess what you can fit into a service bay?

yxZBsAa.png

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There aren't any SSTOs in real live. ;)

The Titan II first stage is capable of achieving orbit on its own...not with a whole lot of payload of course.

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F22 Jet uses somewhere between 0.50-3.5 gallons of fuel per second depending on what the plane is doing.

The Space Shuttle used 1000 gallons per second on lift off.

Let's tie an F-22 and a Space Shuttle together with a (very strong) rope and see how that ends up.

It would be like having a toddler have a tug of war with a Union Pacific Big Boy. With the Big Boy going down a fifteen degree incline.

Sure, an F-22 uses less fuel than a Space Shuttle or Saturn V but it produces almost no thrust in comparison (312kN vs 30,250kN or 34,020 kN). It's 286 times less fuel usage, but it's also 100 times weaker. So if you scale that up linearly, a jet should really only be about 3x more efficient than a chemical rocket engine. So uh.. change out that 19,200 isp for ...1,050? That sound good?

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There aren't any SSTOs in real live. ;)

NathenKell was speaking of the jet engines having 10x the ISP of real jet engines, he said nothing in that passage of SSTOs.

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My small test craft used to work out what changes are required to design and flight profile to get to orbit.

newssto.png

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I haven't yet managed SSTO, but I've been messing about with 2STO for a while now. I have no doubts that once I quit messing around and focus, I'll manage an SSTO. Mostly just been pulling the whole "Oh, these jets aren't useful anymore. Goodbye!" strategy. Shed a bit of extra weight, dispose of anything I won't be needing for the return trip, and I can get my butt the rest of the way to space.

Just needed to remember that, while earlier versions of KSP favored strapping 90-billion air intakes on my wings and making 70km on jets alone, 1.0 is much, much more sensible regarding air-breathing engines.

That, and I'm loving the fact that I no longer need to worry about having too many control surfaces. Seriously, the infiniglide thing, never realized how much it affected how I build aircraft until now. Now I'm not afraid to add another pair of elevons, or to toss on a set of canards.

I suppose the best way to think of 1.0 is this: Take everything you learned from the past several revisions of KSP, and throw it all away. Start with a clean slate.

After all, this is, I think, the perfect compromise for aerodynamics. It's not quite as harsh as FAR could be (I know there were a few versions in the past that made me scream and curse in rage), and it's not as ridiculous as 0.90 and previous, favoring ROFL-Jets and infinigliders and "Intakes... bloody everywhere! Cover every surface in intakes!" It comes out to be "If you know anything about airplanes, you can make a plane that flies. With a bit of tweaking, you can get that plane into space."

As for rockets, I've already done some stupid things as an excuse to try the new aerodynamics. Haven't done a single-stage rocket, but the last thing I did was trying to get to orbit using nothing but solid rocket boosters. Nearly managed it. Couldn't quite tweak the fuel load for the last handful of sepratrons, nor the thrust for some of the old RT-10's to be quite right. Always ended up either a few hundred delta-V short, or a few hundred delta-V over. Still was a fun experiment.

I actually have been having more fun in 1.0 Stock than I've had in any previous Stock version. Normally after a day or two, I put KSP down until the mods rain in, then I stuff as many as I can into the poor game and make it work. This time, I've had fun with the new aero without needing to resort to more parts to satisfy a craving for more.

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Is that an RCSTO?

Nah, it was on top of an SRB; I sent it up just to make sure that the minisat would deploy properly.

- - - Updated - - -

Might be of use to some people:

Need a low-tech stock-aero basic plane for shuttling tourists around the place?

Kerbodyne Startup. It really isn't that complicated.

Javascript is disabled. View full album

Craft file at https://www.dropbox.com/s/npi5rlt8jlxpxbu/Kerbodyne%20Startup.craft?dl=0

(BTW, as a reflection on the relative realism and difficulty of stock aero: I landed this by flying directly above the runway at 500m, putting it into a 100m/s vertical dive, pulling out of that about 20m off the deck before gently settling down without a bump and easily braking to a stop)

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Dude... I can easily get a Mark 3 SSTO into orbit now, while still hauling a full orangie. I'd call that 'extremely significant' payload.

What's your ascent profile? I am having problem achieving this with my designs. Currently using 16 Rapiers trying to get a 200ton plane to orbit. I have real trouble getting up to significant speed without doing almost a sinus curve to pick up speed above 10km.

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My first try I built a Mk2 SSTO...small payload capacity, but I do play on 50% reentry heat. KSP's heat system seems weird.

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What's your ascent profile? I am having problem achieving this with my designs. Currently using 16 Rapiers trying to get a 200ton plane to orbit. I have real trouble getting up to significant speed without doing almost a sinus curve to pick up speed above 10km.

About 160 tons at takeoff, and gets a full orange tank to 75k orbit.

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It's a quick and dirty build, there's an RCS tank but currently no RCS thrusters. There's an over-reliance on reaction wheels (there's two 2.5m ones in the back), but it will fly relatively well without those, you just can't maneuver in orbit otherwise. The only mod used on this is KJR, but if not, a few well-placed struts shouldn't adversely affect weight or handling.

Takeoff profile on this beast is dead simple, 30 degrees pitch from the runway, fly until the Rapiers switch to rocket mode, and then tip over to 20 degrees to gain some orbital speed.

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