SSTO - what am I doing wrong?

[angeldust]

Hello everybody,

I'm trying to get my first SSTO to orbit, but it just won't work!

I've attached the craft file. Can anybody tell me if he/she is able to take this thing to orbit and

- if yes, tell me the flight-profile

- if no, why not and what did I do wrong?

- give general tips on how to fly a SSTO to LKO and how much rocket-deltaV is required?

Here is the craft file: https://www.dropbox.com/s/imynxmxtrqhgeu2/Fly-er%202.craft

Thank you ever so much!

Edited December 7, 2013 by angeldust

[Hodo]

It would be nice to have pictures first and a list of the mods you use.

I just downloaded your craft and couldnt load it because I didn't know what mods you use.

[Rhomphaia]

You should probably have removed the mechjeb part before uploading.

The main problem I can see is that, due to the way you have stacked the intakes, there is no way to get the oxidizer to the rocket engine.

Apart from that, I don't have a huge amount of experience with high intake SSTOs but it looks to me like you are carrying a huge amount of jet liquid fuel.

If you were to lower the intake ratio, then you should replace some of that with fuel/Oxidizer and use a more powerful rocket. otherwise just ditch it altogether.

Edited December 7, 2013 by Rhomphaia

[angeldust]

Ok so I fixed it and deleted Mechjeb, updated .craft file is here

Here is what I do:

I fly the plane to 10000 m in a 40-40 degree angle, then I shallow down to 20 degrees, build speed until i reach 0.10 IntakeAir, this is where I pitch up again and start the rocket, disable the jets and try to put my apo at 75000 meters. But it never works!

PS: And here is a pic

PPS:in this picture the plane has an aerospike instead of the m LV-909 but alas to no avail: I run out of fuel before I can circulize the orbit!

Edited December 7, 2013 by angeldust

[Deathsoul097]

Remove the jet fuel on the aerospike and replace it with the rocket-fuel tank of the same size. It will lower your TWR slightly, but if you wanted TWR you wouldn't use an aerospike. Other than that you should be good to go. Except for the intakes on the wings. Get rid of those. After 15Km their benefit is massively outweighed by the drag and mass they have.

[Murph]

If you've not already tried it, you might want to look at the Aeris 4A tutorial on the wiki:

http://wiki.kerbalspaceprogram.com/wiki/Tutorial:Aeris_4A_mission

For sanity's sake, please do replace the LV-T30 on the supplied stock Aeris 4A with the Toroidal Aerospike. It can be flown successfully with the LV-T30, but it's a PITA to avoid leaving the absurd looking (on a small spaceplane) engine on the runway during takeoff.

If you follow the step-by-step on the wiki, it should get you to a 100km circular orbit pretty easily. The ascent profile given there is pretty simple, not necessarily optimal in terms of fuel efficiency, just easy to fly. Once you've mastered that, it should make it easier for you to figure out what's going on with your own plane.

[angeldust]

Ok, I changed that and replaced the Aerospike with a normal (gimballed) thruster. Ad ditched the air intakes on the wing

Now how to fly this thing optimally? I reached a 7500 x 7500 orbit (YAY!!) but now I have 283 m/s delta V left... barely enough to get it back down to Kerbin, but not enough to reach my space station at 200 000 x 200 000 m!

Am I flying it wrong?

How would you do it?

EDIT: I've seen the Aeris tutorial and based my craft design kinda on this one... the profile is copied too =)

Edited December 7, 2013 by angeldust

[pokeman]

Managed to get a slightly modified version of this into orbit. Swapped the middle jet fuel out for some more rocket fuel (also removing the need for fuel lines) and only 2 ram intakes per engine, still felt cheaty stacking them once but whatever. Actually it went pretty smoothly maybe a little RCS or a reaction wheel for more control on the pitch up stage but it did fine otherwise.

I did notice without that 30% more fuel it wouldn't have made it but I did also recenter the SoL and SoM so i'd try that and see if it helps.

Edited December 7, 2013 by pokeman

[Rhomphaia]

Ok so I fixed it and deleted Mechjeb, updated .craft file is here

Here is what I do:

I fly the plane to 10000 m in a 40-40 degree angle, then I shallow down to 20 degrees, build speed until i reach 0.10 IntakeAir, this is where I pitch up again and start the rocket, disable the jets and try to put my apo at 75000 meters. But it never works!

PPS:in this picture the plane has an aerospike instead of the m LV-909 but alas to no avail: I run out of fuel before I can circulize the orbit!

Add an action group to close all the intakes. use this as you switch to rocket power. with this and the aerospike I got into orbit using your ascent profile though ran out of fuel ~10m/s before circulization burn was finished. Still a lot of jet fuel, I replaced the two outboard tanks with radial engine bodies, made it to orbit with a couple hundred Delta V to spare.

[Murph]

You shouldn't really need a gimballed engine, TBH  reaction wheel torque ought to be sufficient to keep you pointing in the right direction under the Aerospike's thrust.

The trick to getting the most out of a plane like that is to figure out how to get the largest orbital velocity out of the turbojets alone, before transitioning to rockets. This basically means getting high (20,000m+) and fast. Levelling out a little somewhere around 20,000, keeping prograde on or just above the horizon, building speed until it's more or less maxed for your plane/engine combo, then raising the nose to somewhere in the 15–45º range and switching to rockets. Don't try to build your speed too low, you'll just end up in chronic flaming drag. You don't need the speed until you're within maybe 10–20% of the max altitude you can comfortably fly at on jets.

Every plane is different, and it's really a case of trial and error to find what works best for you and your plane. An example profile might be:

30º after takeoff

20º at 12,500m

15º at 20,000m

30º and switch to rocket at 22,000m

If your prograde vector drops below the horizon line on the navball at any point, that's probably a mistake. You really want to maintain a positive rate of climb from runway to orbit, although it's ok for that rate of climb to drop to around 0 when you level out for speed before shooting for the stars again.

Vary the angles and altitudes, pay attention to the fuel used/remaining, keep playing around and seeing what works better. It's time consuming, but can be very satisfying when you find the sweet spot of max efficiency.

[angeldust]

soooo... I just ditched everything and built a new one! Mz Fly-er 3 can make it to a 200 x 200 orbit, rondevouz and deorbit as it is and still has a little bit of jet fuil left to land at KSP! AWESOME! Thank you everyone for your help! With your help the second design was a huge success!

And thank you Murph especially, I will see how the best ascent-profile is!

Now on to bigger things: Spaceplanes with payload! YAY!

PS: Here the new (successful) design:

[Taki117]

Is it bad that I kinda want that craft file?

[angeldust]

I'd be flattered!

Here it is: https://www.dropbox.com/s/h98cudaat726381/Fly-er%203.craft

EDIT> does anyone know why it is that when I try to dock with the inline docking port and use "Control from here" and "Set as Target" the target on the navball is all wrong and I have to visually eyeball it, so that it will connect or control from the space station and move that big thing around, instead of the small plane?

Edited December 7, 2013 by angeldust

[ripvanlemon]

does anyone know why it is that when I try to dock with the inline docking port and use "Control from here" and "Set as Target" the target on the navball is all wrong and I have to visually eyeball it, so that it will connect or control from the space station and move that big thing around, instead of the small plane?

When you set "control from here," the navball orients to the part you're controlling from. In this case, since the docking port is facing up, the navball reflects that.

[Taki117]

If you have your inline clamp-o-tron open, it will show the navball from the clamp-o-tron (And reorient controls appropriately) if you are not adverse to using mods NavyFish's Docking port Alignment Indicatorprovides a pop up that appears whenever you set your target as a docking port that is very intuitive and easy to use, regardless of vessel orientation.

[Col_Jessep]

I was bored so I Youtubed you how I got the Flyer 2 into orbit. The only changes were that I traded 2 of the liquid fuel tanks for LOF:

Probably not the best ascend but I hadn't flown this bird before.

· Beginn with gaining altitude fast.

· Build up as much speed as possible.

· One Turbo Jet needs ~ 0.08 air, so throttle back if you fall below 0.16 on this SSTO.

· You can drop lower again to gain even more speed! Sometimes that's advisable.

· Once you are not getting any faster you want to start climbing again.

· Switch to rocket engines and pull the nose up if possible, to 30-45° if you can.

· Get your AP to 75-85km. Burn the rocket engines again if you are dropping below 75km.

· Circularize.

· Be nice to cats! =3

Maybe it helps somebody. I had fun but I would probably switch the large control surfaces for several small ones and add some larger wings for more lift.

[thereaverofdarkness]

My best SSTO jet plane yet actually uses 8x Rockomax 24-77 engines. It has just one jet fuel fuselage and some 800+ liquid fuel in the fuel/oxidizer tanks. I used 6-8 radial intakes, two RAM intakes, 3 jet engines, and a wide wing setup making the ship look much like a triangle. I tried several designs with LV-909s but had much more success with this one because of the low TMR (thrust to mass ratio) with the 24-77s. This means the engines aren't adding much weight to the plane. This allows the jet engines to take me closer to orbit. The faster they can go, the more air that comes in the intakes, and the longer the engines can run, the higher the jet can go, and the higher it can go the faster it can go. Small changes make a big difference here.

I get the plane up to about 25km altitude and flying nearly 1km/s, and then I shut off the two side engines (hotkey to shut both off at the same time so the plane doesn't spin out of control), then run on a single engine until around 27-28km and about 1200m/s when I can't get it to go any faster and I've used almost as much liquid fuel as is in the jet fuel fuselage (the "fuelselage", if you will). Then I turn on the rocket engines and leave the jet on to assist. After about 1500m/s I tilt upward and let the jet turn off if it needs to.

It would probably be possible to extend this further with the 48-7S engine, though I am unwilling to use this engine any time I can make do with others because its TMR is far too high for its Isp. It seems like a cheat engine to me. Also I'm trying to figure a way to get the plane into orbit with engines of a higher Isp value. Give me a moment to try to fly your craft and I'll see what I can do with it, then I'll upload mine. Maybe what I learn from yours or what you learn from mine will improve both of ours.

Edited December 8, 2013 by thereaverofdarkness

[thereaverofdarkness]

Here's my spaceplane: https://www.dropbox.com/s/wyg1njf3dp5q96r/SSTO%203%20Triangle%202.craft

Pics:

I'm a sucker for beautiful sunrises! ^__^

I don't think Kenwell trusts my flying capabilities. I don't blame him...

I flew the old craft file you made, and I noticed it didn't have a docking port or thruster packs. There was too much RCS fuel on it, too. You might already be aware of these things. I haven't flown your latest version yet but I did notice that your craft controls really well. I'm on the fence as to whether or not I find your AV-8 winglets visually appealing but they do seem to get the job done. I'll have to try something like that. As for making docking easier, I'd suggest taking the unnecessary cockpit off the front and putting a docking port right on the nose, like I did with mine. Makes docking super easy. I only have 100 RCS fuel but it's more than enough for docking. Also, it doesn't need the batteries. I put 4 flat panels on mine, just to make sure it can pick up sun from any angle. I didn't bother with fold-up panels because they're unnecessarily large just to power a cockpit, and they don't work in atmosphere.

[angeldust]

Thank you all for your wonderful craft designs!

The Fly-er 2 is just too small for a 200 x 200 Orbit, at least with my flying skills. But I'm glad that, with some improvements, it can still make it to a decent orbit!

The Fly-er 3 is my favourite, and it follows some of the same styles as the Fly-er 3, so I'm not mad!

@thereaverofdarknes: Thank you for your criticism, I think I will notch down the RCS and consider packing less Batteries and Solar Panles... that will ensure a little bit more delta V, whitch is good because it always helps to have a little reserve. By the AV8 Winglets do you mean the double T- empennage ? Because I simply LOVE the style, it gives the craft much needed lift at the tail and huge control if you stick a control surface at the tail fin. It kinda is like the T-empennages on real airplanes, just a little overkillier

The

[Sirine]

I have depressed a moderator...perhaps you should take a look?

http://forum.kerbalspaceprogram.com/threads/59870-Help-with-spaceplane-%28?p=809349&viewfull=1#post809349

[RoboRay]

Thank you all for your wonderful craft designs!

The Fly-er 2 is just too small for a 200 x 200 Orbit

Actually, you can often improve performance by going smaller, not larger.

My two-seat ground-to-orbit taxi is just 13 tons fully-fueled and can reach orbit with nearly 700m/sec of delta-v remaining.

Javascript is disabled. View full album

This is an older album, but the design hasn't needed any major changes.

Edited December 8, 2013 by RoboRay

[Vanamonde]

I have depressed a moderator...perhaps you should take a look?

Thank you Sirine, but I got tired of failing at that project and am busy failing at another one right now.