My First (Sandbox ) SSTO

[NewtSoup]

Hey guys,

Bit of advice needed.

I've been following Matt Lowne's video on making a basic SSTO
 

 

So I made the craft he builds ( pretty accurately, same fuel tanks engines and a good COM / COL position ) but I'm having real trouble getting it into orbit.

Now I'm very aware this video was made in 1.05 and I'm playing 1.3.1 - Are there big differences between the two versions that render the craft non viable or do I just need a lot more practice?

Matt doesn't seem overly precise in his wander into LKO and onwards.  I've yet to hit LKO.  

Here's my craft file:

https://drive.google.com/open?id=18JGd3Mkp-Qc8Q8UCJ2lWNccSpZ_BLX2C

On the runway I set the winglets on the end of the wings to have authority of 10% or it gets a little roll happy.

[Guest]

There are differences but they're not that drastic.

What trouble are you having, specifically?

[Hotel26]

I just did a fast build and I did not make it either on first try.  But I forgot to engage my NERV and only did so when the OX ran out.

I think the OP may be having trouble with technique rather than the aircraft.

I'm gonna take another run at it, because it feels like it can do it...

UPDATE: great fun!

1. Use all the runway at KSC to build speed.  (Why not?)
2. Climb at about 50 deg (once you've got the speed to do it and keep accelerating) to get above 8km fast.  Speed built to around 260 m/s
3. Lower the nose to about 30 deg  then and watch for that magic number, 343 m/s, and the giant boot in your tail.
4. Get to about 18-20km quickly but still allowing the speed to build.
5. Start to level out to only a mild climb and let the speed continue building.  Stay under 22km, say.  You want to spend as much time in this zone as you can until the speed reaches around 1500 m/s and the red heat bars come out to play.
6. Then set a 20-30 deg attitude for space, switch to LF/OX ("closed cycle") and ignite the NERV as well when the climb is nicely established.
7. Aim for an apoapsis of 80-85 km to give yourself time to circularize.  You'll use the last of your OX on this orbit insertion burn and then you'll need to wait until the NERV finishes the job.

I came out of all that with 0 OX and 1583/3700 LF.  My orbit is 98x75.

Plane is fine and not at all boring.

(I just don't know what you can do with it at Minmus except have the pax EVA and hope there's an orbital gas station there with a Tesla claw for a recharge...)

Good luck!

Edited February 6, 2018 by Hotel26

[NewtSoup]

Very Cool, thanks guys.

Yes, I wanted to make sure it was just me that was struggling and not the plane itself.  Now I know it will still fly I shall keep trying until I can say "I can do Space Plane Science"

 

[Guest]

I looked at the craft a bit, and this is not a "basic SSTO." It's a special-purpose craft: a SSTO that can also do long-range missions. That's a tough combination because the requirements are diametrically opposed. For SSTO you need enough lift, low aerodynamic resistance, and a lot of thrust, but can easily afford to pile on a few more engines and a few more lifting surfaces if it gets you into a better attitude and faster acceleration. For long-range missions, you'll want the exact opposite: the most efficient engine you can get, and as little non-propellant mass as you can manage. 

So if you want to make a craft that's able to do both, the "sweet spot" will necessarily be at the exact point where it's pretty bad at both things. Which means that especially the SSTO part will be tricky: you'll have to finesse the launch like @Hotel26 just did, and then sit through really slow burns as it gets where it's going. It can be fun pushing the limits in this way, but IMO it's not a good way if you're only just starting with spaceplanes as it's hard enough to make one that even makes orbit if you've never done it before -- planes are a lot more complicated than rockets which basically just have a pointy bit at one end and fire at the other end.

A basic SSTO is a good deal simpler beast than this. 

[NewtSoup]

6 minutes ago, Brikoleur said:

I looked at the craft a bit, and this is not a "basic SSTO." It's a special-purpose craft: a SSTO that can also do long-range missions. That's a tough combination because the requirements are diametrically opposed. For SSTO you need enough lift, low aerodynamic resistance, and a lot of thrust, but can easily afford to pile on a few more engines and a few more lifting surfaces if it gets you into a better attitude and faster acceleration. For long-range missions, you'll want the exact opposite: the most efficient engine you can get, and as little non-propellant mass as you can manage. 

So if you want to make a craft that's able to do both, the "sweet spot" will necessarily be at the exact point where it's pretty bad at both things. Which means that especially the SSTO part will be tricky: you'll have to finesse the launch like @Hotel26 just did, and then sit through really slow burns as it gets where it's going. It can be fun pushing the limits in this way, but IMO it's not a good way if you're only just starting with spaceplanes as it's hard enough to make one that even makes orbit if you've never done it before -- planes are a lot more complicated than rockets which basically just have a pointy bit at one end and fire at the other end.

A basic SSTO is a good deal simpler beast than this. 

That sounds fair.  The bulk of the SSTO / Spaceplane videos on youtube ARE quite specialised then I think and I thought Matt's example here was fairly "normal".  I suppose it is normal in a way.  However,  I am further encouraged as I now feel that if I can fly this to Minmus and home again and by that I mean simply land on Kerbin without exploding, I think I will have really achieved something as a space plane newbie.

[Hotel26]

Well, I wrote that in LKO, too, before the following transpired.

Coming down was a b!!!!.  I got overeager to handle the controls again passing 30km, impatient I suppose.  It tumbled and then converted to an ever-quickening, flat spin which took me  the thick air of below 5km (over a dark sea, flying at night again!) to pull out of.  Not fun!!

The controls are quite soggy, except for roll.  Yaw is the worst.  Under power, the RAPIER vectoring helps, which is basically how I got it pulled out.  But there's no doubt that the machine is quite treacherous.

And I broke the outer wing and an engine off, weaving over the runway, but that was my own bad approach, actually, that fouled all that up.

I'm glad I did the build though.  Building other people's planes is a good way to learn!

Here's a basic space plane to practice with (shameless plug): Aquila Peregrine.  [I have to acknowledge @swjr-swis for a LOT of help with this one!]

Edited February 6, 2018 by Hotel26

[NewtSoup]

2 minutes ago, Hotel26 said:

Coming down was a b!!!!.  I got overeager to handle the controls again passing 30km, impatient I suppose.  It tumbled and then converted to an ever-quickening, flat spin which took me  the thick air of below 5km (over a dark sea, flying at night again!) to pull out of.  Not fun!!

Well, Matt does admit he kind of threw this together from "feeling" and experience rather than taking time and care of it.

Yes, I noticed the roll was super sensitive too, which Is why I've now turned it down to just 10% on the outer winglets.

[NewtSoup]

ORBIT ACHIEVED - it was messy and I used more fuel than I should have but I still have over 2400 m/s of dV left and I'm in a 108 km orbit above Kerbin!.   I ended up dipping back into the atmosphere with Periapsis at 65km before getting a circular orbit.  I know I have plenty of DV to hit Minmus so I think I'm going to go for broke!

[Guest]

Good luck. With 2400 m/s you can go anywhere. Won't necessarily be able to come back though. Jool is about 2000...

[NewtSoup]

Just now, Brikoleur said:

Good luck. With 2400 m/s you can go anywhere. Won't necessarily be able to come back though. Jool is about 2000...

Hah yes  I don't think will go to Jool though.  Not today at any rate.  Today is for Minmus and then back to Kerbin alive. Landing anywhere near the KSC will be icing
 

[Guest]

Just now, NewtSoup said:

Hah yes  I don't think will go to Jool though.  Not today at any rate.  Today is for Minmus and then back to Kerbin alive. Landing anywhere near the KSC will be icing

Yeah re-entering from Minmus orbit with a plane can get a bit intense. So good luck with that.

[NewtSoup]

1 minute ago, Brikoleur said:

Yeah re-entering from Minmus orbit with a plane can get a bit intense. So good luck with that.

I've done it with an Ore Barge carrying 3050 units of ore from Minmus that had to LAND on Kerbin but that used parachutes.  I'm going to use most of my excess fuel / aero braking to circularise in LKO before attempting to de-orbit.

Here's a gratuitous screenshot of my ore barge in orbit with it's huge number of parachutes.

[Guest]

2 minutes ago, NewtSoup said:

I've done it with an Ore Barge carrying 3050 units of ore from Minmus that had to LAND on Kerbin but that used parachutes.  I'm going to use most of my excess fuel / aero braking to circularise in LKO before attempting to de-orbit.

Oh, you'll have plenty for propulsive braking back to LKO from Minmus. Only potential difficulty is that the burn will take a very long time so you might need to split or finesse it.

[NewtSoup]

I will see what happens at the time.  My only real issue right now is that I can't get a Minmus encounter as the Mun prevents it.  The closest enounter I can get right now is a 1000km retrograde polar orbit.  I think I'll warp forward a day or two 

Edited February 6, 2018 by NewtSoup

[NewtSoup]

Always learning in this game

I came up with an idea, I'm sure I'm not the first.  Rather than change inclination in LKO and then do a second burn for Minmus injection what I did was create a node for the inclination, then create a second node to find out where to burn to get an encounter with Minmus.  Once this node was set and I knew the dV needed I then deleted the node that would alter the inclination and JUST did the main burn.  Once that was done I did not have a Minmus encounter.  But I figured that was no problem as I'd done the main burn at the right place and all that was off was inclination.  So I then created a midpoint node for a correction burn on inclination and got a really nice Minmus encounter for just 24m/s of dV rather than the 350ish it would have taken to correct the inclination in LKO.

Edited February 6, 2018 by NewtSoup

[NewtSoup]

Made it to Minmus.  Landed Backwards of course with just enough translation so that when the NERV clipped the Minman suface it rotated the ship onto it's landing gear.  This was done VERY carefully at <2m/s surface speed.

[NewtSoup]

And we're on our way home.



This looks like a fun return plan.  A cheeky gravity assist off the Mun with a close 10km flyby on the light side!  Bonus.  I'll correct inclination in a high kerbin orbit and then circularise and de-orbit.

Actually that flyby may be on the dark side.  No matter though. It's all good fun!

Here's the Mun Flyby  Not Light, Not Dark, But a Grey Kerbal!

Edited February 6, 2018 by NewtSoup

[NewtSoup]

Mission Ends.  Aero Breaking Maneuvers in the Upper Atmosphere as I had only 88 m/s left of dV ( I'm such an inefficient pilot )  Got the AP down to around 2500 km this way before using 40 of the remaining dV to dip the PE into the atmosphere proper.  I completely missed the KSC by a continent but I'm just happy I made a safe landing.  I had no flat spins the craft behaved very well for me all the way down.  I did burn off the air-brakes, but it turned out they weren't really necessary anyway.  I touched down in the desert and only knocked of a single rapier.  I could reload the save and do it without the damage I'm positive but I think I call call this first mission an unqualified Success!


AeroBraking


Landed

Edited February 6, 2018 by NewtSoup

[suicidejunkie]

For Minmus transfers, that's my typical strategy.

Pull out a rough burn to get AP up in approximately the right place, then put a tiny normal burn halfway to Minmus which pulls the orbit up to meet Minmus' orbit.

Then fine-tweak the timing on the main burn to get an intercept.

 

For training purposes, it is handy to go from Minmus to the edge of Kerbin's SoI, then drop back in a retrograde orbit which will easily catch a thin flyby of Mun.  Minor RCS puffs can turn that into a bit of a gravity assist braking, and then you land on Kerbin with 3-stars for everyone.