Lauching some guys into orbit with a plane device --> OMG, HELP.

[Smalish]

Planes.

Ho.. planes.

Here is me, showing you what I created and trying unsuccessfully to launch it to space :

http://puu.sh/kmPqt/8a7b5559ed.jpg

It's a little cabin that should be able to bring up to 4 people into space, and everything behing the decoupler is the launcher that is supposed to take the cabin to low orbit. I thought it could be useful as a fast way to get people out of the atmosphere and operationnal in space (dacking to other spacecrafts and stations etc).

I looked at scientifically accurate designs for such things to get inspired and built that thing pretty quickly. But what I don't get is why it's so SLOW. It takes forever to reach a descent speed for lifting-off and starts loosing speed as soon as its in the air, until it end up crashing right back to the surface miserably.

All I need is speed. I tweeked the damn thing for weeks now, and there's no way I could change it for the better... I don't just know what is SO wrong.

It looks stupid like that I know. You're going to think : "why did he started to do that in the first time", and seriously, I just had this idea and I wanted to try it out... But now I fell into the dangerous pit of the game : I want it to work.

I'm new to the game, and especially to the Spaceplane Hangar, so please be indulgent :C

Thanks !

[eataTREE]

Spaceplanes are hard. Big spaceplanes are much harder. Do not feel bad about having trouble with them.

Okay, so, the performance of air breathing engines is proportional to the amount of air they are able to suck through their intakes. The higher you go, the less air there is. So, if your speed remains constant, you will slow down further and further the higher you go.

The way around this is to go faster. The faster you go, the more air gets pushed through your intakes, and the better your engines perform. This effect becomes very pronounced starting at around Mach One (350 m/s, more or less).

So, if you are slowing down instead of speeding up, it means you are climbing too fast. It is much more important to maintain your acceleration than is to climb quickly -- set your pitch angle to where your speed is always increasing, and take your time climbing through the atmosphere. Once you hit Mach One or so (depends on which engines you are using) you will have all the thrust power you need and you will be more worried about going so fast you explode before you exit the atmosphere.

Remember, spaceplanes are hard. (After all, NASA tried to build one and couldn't, which is why we got the neither-fish-nor-fowl weirdness that was the Space Shuttle.) Keep trying and don't give up.

[Korizan]

The larger the plane the more mass you have to move.

Think Smaller especially for a crew transport.

Here is one example from another thread.

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You also need to change the way you fly when using a SSTO.

For example to get the above one into orbit do the following.

Engage SAS

Full Throttle (it will auto take off no action required)

Pull up to 10 Degrees pitch hold till 500 m/s

Pull up to 20 Degrees and let it go.

It will kick in the rockets around 30km do nothing.

When your AP is at 80 Km shut off the engines and from there you are done other then your orbital burn.

This is only one example and it is not the smallest SSTO out there.

I also tried to make it a bit realistic, based on current tech and designs to keep true to heat shielding that would be required.

I have seen some designs for even smaller planes as well.

At any rate hope this gives you some ideas.

PS - Your ship is cool looking don't give up on it, it might just need some tweaking and a change in flight profile.

Edited September 24, 2015 by Korizan

[SpeedDaemon]

I'm no spaceplane expert, but one thing I learned from reading some really good posts by people who are is that drag is the devil!

That thing of yours looks awesome, but it's got bits sticking out all over the place that are probably killing you.

Here's only my second successful spaceplane (which Val managed to actually land on the runway about 20 minutes ago!):

The only bits stuck on the outside are things that absolutely have to be: lift/control surfaces, RCS, and landing gear (and airbrakes, which I sort of forgot to add for that flight). Another important detail that's hard to see is that the wings are angled up very slightly. This allows them to generate lift while the fuselage is pointing directly prograde (when it's not directly prograde, it generates a lot of drag).

I made that one to ferry smallish amounts of fuel to LKO (and possibly to ferry science back from Minmus - I think it could make it), so those two long tanks in the back could be replaced with two short ones and two crew cabins

[Snark]

The thing to bear in mind about jet engines is the faster they go, the more thrust they have (completely unlike rockets, which generate the same thrust regardless of speed)-- up to a certain optimum speed for that jet engine, then it starts to drop off.

So what this means is that it's vitally important for a spaceplane to have enough engine. It's different from rockets. Rockets are okay with lower TWR (as long as it's not too low)-- "hey, I have half as much thrust on this rocket, so it'll just take me twice as long to get going as fast as I need." But with jets, they don't get their full power until they get going fast, and they can't get going fast unless they have enough power to start with.

So there's very much a "threshold" on a jet-- below a certain amount of engine power, they just kind of mope along and never really go vavoom, but once you pass that threshold, suddenly they leap off the runway like a bat out of hell and quickly slam themselves up towards their max speed.

How much is enough? Well, I dunno a good rule of thumb (I'm mostly a rocket guy, not a spaceplane guy). But my simple-minded trial-and-error technique is this: If the plane takes off and immediately starts going faster and faster and faster and I hit Mach 1 pretty damn quick after takeoff, then it's a go. If that doesn't happen right away, then there's not enough engine power and it's back to the drawing board.

So yes, spaceplanes are hard. But at least they fail fast-- you find out pretty quick if there's enough engine or not.

[n.b.z.]

I'm no plane expert, but have built quite a lot of space-worthy MK2 stuff. Looking at your pictures I would say:

- the 4 Rapiers should be enough for something of that size

- a number of parts seem to be more decorative than functional, such as the steel plates or the flap parts oriented length-wise. (I may be wrong.) Try to remove those, and test again.

- you don't need anywhere that much lift: I would guess that this much wing area causes too much drag.

But I really like the concept, and also the look. I'm myself "guilty" of always adding less-than-necessary parts just for the looks. I'm just saying that you should start out with a design as clean as possible, then carefully add the luxury items later.

[Clipperride]

I had a similar problem when starting out with the hanger. I'd suggest putting your current design on hold and experiment with something smaller to practice with.

The larger you build the more drag you have to contend with. If you right click on a runnign engine, you can see the amount of thrust its producing. Unti you're moving at ~250/300m/s your air breathing engines aren't working at anything like their full potential. A smaller plane means accelerating less mass past this thresholds. Experimenting with something easier to master will help when you return to larger craft.

Another way to go is with rocket assisted take offs. A pylon carrying a solid rocket booster at the back or on the wings can sometimes get your plane upto a speed where it will continue to accelerate on its own. As you can drop the spent boosters, you aren't adding weight for the entire flight.

Happy experimenting

[Warzouz]

This is a big plane to put only 4 kerbals to LKO !

You don't need that many wings. You don't need that many engines. Structural and radial intakes aren't suited for space planes (use shock cones).

FYI, my passenger space plane can carry 10 kerbals to LKO (with 600m/s left for space operations) weights 36 tons and carry 2 rapier and 1 turbojet.

[Val]

Try this ascent profile:

1. After take-off, accelerate to 400 m/s at sealevel (below 300 m altitude)
   
2. Pitch up slowly, while still accelerating, to 15^o above the horizon.
   
3. At 8 km start pitching down so you're flying level with the horizon between 9 and 10 km altitude.
   
4. Accelerate to 1000 m/s.
   
5. Again slowly pitch up to 15^o without losing speed.
   
6. At 22 km switch RAPIERs to rocket mode. (You'll lose too much speed if you wait until they switch automatically)
   
7. At 27 km pitch down to 10^o and hold that.
   
8. When AP reaches 60 km, point the craft prograde.
   
9. When AP is 80 km or more, throttle down and coast to space.
   

---

Off-topic

My passenger spaceplane SSTO takes 160 kerbals to space. But it also weighs 280 t and is power by 6 RAPIERs and 4 Turbo Ramjets.

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Edited September 25, 2015 by Val
Clarification

[Spacetraindriver]

4 things you need

-Center of mass near center of lift

-Enough Thrust

-Enough Fuel

-Call them kerbals

Most times your SSTO is perfect, but you don't know HOW to fly it.

I just point up a lot and hope for the best. I more of an airliner guy.

Although I have tried making a ssto with a Boeing 747...

Edited September 25, 2015 by Spacetraindriver

[Smalish]

Ho wow, so much answers ! I didn't even think !

Thanks a LOT to all of you people, I'll try everything, and tell you if it works. For the news, it does because I added more POWER... But then again you said it yourself, it's a ludicrous amount of engines to send 4 (only 2, actually, for my next mission) in LKO where they sould meet with the rest of my space station crew.

I'm going to see if I can try to clean the thing and make it smaller or faster but keep the design.

I'll let you know next tile I have a good result

Otherwise.. I might just try to do something new again. But I want to know how to fly them spaceplanes !

[Clipperride]

Hope you keep at it as it is rewarding when you get from the runway to orbit. It just takes longer to design aa working space plane as an apparently minor change may have you moving the wings to keep CoL behind the CoM. Then you find your landing grear is now in the wrong place...... and so it goes on

Once you get the hang of an ascent its much easier to spot where you're having problems.. Have fun

[Cairol]

Some good tips here.

Guess I'll also give those space planes another try.

My ratio of successful SPs/SSTOs to successful rocket designs is like 1:50.

And I don't even speak about efficiency.

[Smalish]

I tried it, it worked fine. I just decide to remain in low altitude a bit longer, and even though it took more fuel, I definitely gained more speed. So much, in fact, that I achieve a low orbit stabilisation and a meeting to a space station followed by a successful docking to it in one go ! I was amazed (it's the first time I even dock that fine). Thank you guys !

Btw, for those with the same problem : I also used loads of RCS gaz to correct my orbit and trajectories. I have this very cool MkII expansion mod that adds -among all sorts of things- an "RCS reactor", it's powerful enough in space to achieve a lot of things pretty smoothly !

Anyways, thanks again, you've got a "hi" from my Jeb, Bill, Bob and Valentina that arrived safely at the station and will now get ready for a munar journey. C:

[Guest]

And here I was about to tell you, "you're probably climbing too fast."

The biggest problem people face with Space-Planes and SSTO's, is not building them, it's flying them properly.

[Clipperride]

While learning the ways of the space plane, keep it small. This little Mk2 can get to Munar orbit and back (just!)

Returning to your original design, as you can see, I quite like getting planes up to speed (where the engines become much more effective) using SRBs. Even a couple of "Hammer" solid rockets attached via some radial decouplers can really help get bigger vechiles up and running.

Edited October 3, 2015 by Clipperride

[ForScience6686]

Like others are saying, start small to learn the basics then scale up to larger craft. You begin to destroy designs by continuing to add parts, keep only what is needed for the mission and scrap everything else. Only use radial intakes for early jets, they cause a lot of drag.

[Van Disaster]

Pretty sure I've seen this done in stock, you might have to dig a while though...

The problem there was the shuttle doesn't have any rocket engines, just RCS - so no doing what I did other times & just sticking extra tanks & boost stage to whatever winged thing I was trying to lift. Having a reusable lifter stage isn't the worst idea anyway if you combined approaches - suborbital reusable first stage - could be just a plane, could be a plane with some rocket boost to get a bit higher, disposable orbital boost second stage - maybe solid rockets for that for ease of use - and extra tanks to get it to it's final destination.