SSTO advice requested

[Skylar']

hi, can anyone give a bit of advice bilding efficient ssto ? i looked in youtube and othed stuff but thats only helps with the same ssto as it buildet in video. i tryed to build  a few by myself, and they get to orbit but they totaly non efficient as they can be. the best way i doing this, jus by putting a lot of powefull jet engines with trust/mass ratio over 2 at start and just raming myself into orbit by 45 degrees just like rocket  i know that it's way more efficientt ways to do this. whhat kinda engines do i have to use ?, degress at going to orbit ? trust/mass ratio ? something more to know ?

Edited January 26, 2016 by Skylar'

[T-Bouw]

There are a few tutorials on the forum about building and flying an SSTO.
But the gist of it is that you should "exploit" your jets for as much as you can.

Meaning, you should fly as high as your jets can (almost starving for air), at that point you go horizontal and build up your speed.
Once the speed doesn't climb as fast anymore, punch your craft through the atmosphere.
When the jets almost starve for air again, shut them down and kick in the rocket (mode).

Also, go easy on the controls high up. You can easily lose control of your plane and that'll ruin your attempt or at the very least make it less efficiënt.

[Evanitis]

Well, if you can get to orbit, you are trough the hardest part. From there it's only a matter of addig moar boosters for more payload, balance wet-dry CoM so the plane won't flip upon re-entry and finding the perfect ascent path for any given plane. That last part is the trickiest, as the ideal flight path depends on the power of the engines (most likely it's different in the jet and the rocket phase), the weight of the craft and it's drag profile.

Ideally, you want to climb to ~10km without exceeding ~320 m/s only on jets. Depending on your TWR it can be achieved by having full throttle with a 10-30° angle of attack. If you need more AoA than that to keep under the desired speed, it signifies that you probably have too much jet engines (needless weight).

Once you get to ~10km, you can start gaining speed by lowering the AoA to ~10°. Turboramjets or Rapiers with shock cone intakes should be able to take you to ~1200 m/s on about 18-20km. Ultimately you'll reach a point when you can't accelerate anymore. That's the time you can fire the rocket engines (or switch mode on Rapier). Once there, you can pull up - but do it slowly as a too fast pitch will bleed your precious speed. If your rocket 'stage' has high TWR, there's nothing wrong with a high AoA. 40° will get you out of the atmo fast and than you can circularize. But a lower TWR setup can also be good at this point, you just need a lower AoA. If you burn with nukes at this point, it can be as low as 10° - you'll get the escape velocity slower, but you won't overshoot your desired orbit height by raising your AP too fast.

Hope I could help a bit.

[AeroGav]

This is a bit of a cut n' paste from a tutorial i'm working on,  so sorry about the wall of text, needs breaking up with some pictures.  Hope it helps anyway..

 

Assuming you're not using aerodynamics mods like FAR,  performance doesn't come down to all that many factors actually.  Wing planform and placement don't matter at all,  four unswept, rectangular wing sections arranged like a biplane have the exact same lift and drag characteristics as a highly swept, supersonic delta of the same area. 

What counts - 

1.  Engine selection.     Rapier and NERV are the best, because NERV has the highest ISP of all non-airbreathers  and RAPIER works in jet mode to the highest speeds and atltudes.  And the "power play" method is not to use any oxidiser at all, and just let your NERVs boost from 25km up. More on that later.

2.  Lift to drag ratio.     At subsonic speeds, optimal lift to drag ratio occurs at 2 degrees angle of attack.  As you get faster, this increases, reaching 5 degrees by orbital velocity.    Peak lift:drag ratio is over 20:1,  a very nice exchange rate which means you can fly to orbit with NERVs alone. 

If the angle of attack needed to maintain level flight is below optimal,  you are going too fast (fix this by climbing more steeply, rather than throttling back),  or you have too much wing area , or are too low (again, climb steeper!).     More often however, i see people flying with excessive angle of attack, which generally means their wings are too small.

How much wing should I use?  
 

As your plane flies to orbit, it is steadily gaining speed, steadily getting lighter, and moving into thinner and thinner air.     With parameters constantly changing, what scenario should you design for?

In my opinion, the very high altitude regime, from 20-45km, is where the "rubber meets the road".   If your plane is efficient here, it can fly higher on airbreathing engines before being forced to switch on the rockets, and will be able to climb on the meagre thrust of a couple NERV motors, without resorting to higher thrust (but less fuel efficient) chemical rockets.

The air here is very, very thin.    In air breathing mode, bear in mind that your RAPIERs generate maximum thrust at mach 3.7.   You should probably fly slower than that below 20km to avoid wasting too much fuel fighting drag and to not blow up your plane with overheating, but above 20km, you want to accelerate to mach 3.7 then adjust your climb rate to maintain exactly that speed.      At such high altitudes, you need a lot of wing to generate sufficient lift while "only" doing mach 3.7, without having inefficient high angles of attack.

Once the air breathing engines are gone, feel free to fly faster, however your plane needs to gain altitude as the speed increases at a sufficient rate, or it is going to start overheating big time.  You could find yourself forced to pull up to angles of attack greater than 5 degrees to avoid blowing up.

Summary - you need as much wing area as possible.   

Assuming they're unlocked, the "power play" method is to construct your airplane from Big-S wing sections only, since these double up as fuel tanks for your NERVs and RAPIERs.

3.  Fuselage drag
 

The first rule here, is to avoid radially attached anything unless it's a wing or control surface !       Apart from landing gear, all accesories should be safely tucked away inside service bays or cargo bays.    Think reaction wheels instead of thruster blocks, radiators and solar panels can all go inside.

This goes with fuselage pieces.    Let's say you have nine cylindrical fuselage sections.   Attach them all in line, and the only drag you get is from the nose and tail.  Nine is basically the same drag, and frontal area ,  as one.   However, if you made the main fuselage 5 sections long and add a pair of nacelles each side, each two sections long, you are now presenting 3 times as much surface area to the wind.

I often see people putting sponsons on the side of their fuselage to make room for extra fuel tanks or intakes.     This is not a good reason to triple your drag !  The only reason to add nacelles is if you need more engine attach points.

Next, air intakes.   Insufficient air causes the engines to splutter, but intake spam won't make them operate any better or at higher altitudes.  The goal is to get enough air with a minimum of added drag.  The lowest drag way is to simply use engine pre-cooler, one per RAPIER, and put them inline with the rest of the fuselage pieces.  Nothing sticking out into the breeze - no drag.

Finally , when we've settled upon how many parallel strings of fuselage sections our design is going to have (eg.  one main fuselage, and an engine nacelle on each side) we have to consider what is going to go on the nose and tail of each stack, since this is where the drag is generated.       In terms of the tail , that's easy - an engine!  If we didn't need the engine , we wouldn't have created that parallel stack in the first place, would we?

But for the front , what should you use?   The tail cone connector, flipped 180 degrees so the pointy bit is forwards, appears to be the lowest drag selection, though it is somewhat heavy.

4.  Trim drag

One last design factor that influences performance, is Trim drag.   Namely, how much drag do your control surfaces generate while holding the nose up.    

Correcting a trim drag problem is tricky.

I am a great believer in playing things very safe with the centre of mass and centre of lift, placing the former well ahead fo the latter in a space plane.    It won't win any awards for agility, but space planes are subject to huge shifts in centre of gravity as fuel burns off and cargo gets unloaded.    So, this means a lot of force is needed to hold the nose up.

For starters,  we only want to be generating this pitch force with canards.    Passive tail fins that add stability are fine, assuming there is any room left at the rear of the plane not used for wings or engines.   However, keeping the nose up with control surfaces mounted behind the centre of gravity means generating downforce to lift the nose, and that means creating negative lift which the main wings have to overcome in addition to the vehicle's weight.

However,  wherever you place them, your pitch control surfaces will generate drag themselves as a result of the force they generate.  Just like the main wing, the drag is proportionate to the angle it meets the airflow.  If you only just have enough pitch authority to hold the nose up, chances are your canards/tailplanes/elevons/whatever are deflected at a large angle and making huge drag.

You could make your canards larger, so they don't need as much deflection angle, but this will also add lift ahead of your CG and make the plane less stable.  Also, by the time you've added enough control surface to have low trim drag, you 'll have added so much it is easy to snap the wings off with an inadvertent pull.

So, the best thing you can do is check the max deflection angle on the "right click for more info" screen  when you select a control surface  to use.  Lower, obviously, is better.  The standard canard and tail fin deflect to 30 degrees,  but some go to less, the Advanced Canard is especially interesting at only 10 degrees,  however in addition to having the small deflection angle it is also tiny, and you might need two or three pairs of these to be enough.

 

Flight Profile

How should one fly a space plane ? Each to their own of course, but this is generally how i do it, in an aircraft designed with the above principles -

1. Subsonic Initial climb

After takeoff, adjust rate of climb so that you're near the optimum 2 degrees angle of attack.  Angle of attack too low, climb steeper to slow down.  Angle of attack too high means we're stalling, nose over a bit.  Try to do this with pitch trim, if possible, it will save holding the same joystick angle for the next 20 minutes and getting cramp.

2.  Bust the sound barrier.

Generally at or above 10km,  i'm finding that @ 2 degrees angle of attack my air speed is starting to come up to 240 m/s.   There is a high drag region between 240 m/s and 440 m/s representing the sound barrier, you want to spend as little time here as you can.    So i often turn SAS on and set prograde assist to dive through the sound barrier ASAP.

3.  Supersonic climb 

After the sound barrier your Rapier engines gain thrust rapidly,  you find yourself pitching up hard to avoid getting too fast too low and overheating.   At the same time,  start nosing over at 15km so you don't find yourself in thin air at 20km without the power to accelerate.

4.  Milking the airbreathers

Above 18km,  there is little risk of overheat , so flatten out and increase speed to mach 3.7, where your RAPIER's power output is at its highest. Once you have attained this speed, climb at whatever rate stops the speed from increasing further.    When the climb rate is becoming negligible,  start up the NERV engines.    At 29.5km the RAPIERs will flame out completely, this phase of flight is over.

5. Hypersonic in the Mesosphere
Maintain around 5 degrees angle of attack with pitch trim , be ready to pull up more if things threaten to blow up.   Gradually you'll get higher and faster till you reach orbit.

Essential Mods

Tac Fuel Balancer.     Really hard to keep a space plane controllable once the rockets fire up.  Hit "Balance All" and be happy.

Kerbal Engineer Redux.    Gives a live display of Mach number,  Periapsis and Apoapsis (without having to switch to map screen)

Modular Fuels  .    Allows you to swap out the fuel tanks - eg. if you're building an oxidizer-free design like i suggest, you use this to make parts like the 2 into 1 adapter or the mk2 to mk1 fuselage adapter, carry only liquid fuel, and not waste tank capacity.

[fourfa]

Wow, thanks for that. Interesting advice.

I fear it might apply more to large craft than small ones though.  I'm playing with a tiny Mk2 crew shuttle - cockpit, crew cabin, one Rapierspike, and only a pair of Big-S Strakes for wings, ~16T fueled (was going for low part count to keep docked at my laggy space station).  It flies like crap with the above advice (subsonic climb, 10km speed run) and does not make orbit.  If I get to 450-500m/s at sea level however, the engine goes nuts through the whole ascent, and makes orbit with fuel left for rendezvous (took some iterations getting the fuel load just right).  This is similar to some other SSTO advice I've seen elsewhere - go fast low, then zoom climb.

Is this just because I'm light on wing compared to big cargo planes?  Therefore it needs the speed first to generate thrust, in order to develop enough lift? And maybe the high speed at sea level doesn't hurt me as much because of minimal size and drag...

Might be nice to put some numbers on flight regimes based on wing loading (total wing area divided by mass).  I know I've seen that in some scattered threads, but a nicely organized FAQ like yours could use it

Edited January 27, 2016 by fourfa

[AeroGav]

36 minutes ago, fourfa said:

Wow, thanks for that. Interesting advice.

I fear it might apply more to large craft than small ones though.  I'm playing with a tiny Mk2 crew shuttle - cockpit, crew cabin, one Rapierspike, and only a pair of Big-S Strakes for wings, ~16T fueled (was going for low part count to keep docked at my laggy space station).  It flies like crap with the above advice (subsonic climb, 10km speed run) and does not make orbit.  If I get to 450-500m/s at sea level however, the engine goes nuts through the whole ascent, and makes orbit with fuel left for rendezvous (took some iterations getting the fuel load just right).  This is similar to some other SSTO advice I've seen elsewhere - go fast low, then zoom climb.

Is this just because I'm light on wing compared to big cargo planes?  Therefore it needs the speed first to generate thrust, in order to develop enough lift? And maybe the high speed at sea level doesn't hurt me as much because of minimal size and drag...

Might be nice to put some numbers on flight regimes based on wing loading (total wing area divided by mass).  I know I've seen that in some scattered threads, but a nicely organized FAQ like yours could use it

There's a conflict here.      The RAPIERs develop 5 times the thrust at mach 3+ as they do below mach 1, so your RAPIER engines want you to go through the sound barrier ASAP, which works best with a really small wing so you can do that at sea level.  You'll  have huge AoA and huge drag at altitude, but before long you'll switch closed cycle and be thrust borne and orbital velocity borne rather than wing borne.

A large winged design works best if you're flying to orbit wing borne with the low thrust to weight of nuke engines only, but the initial climb at subsonic rates will be sluggish.

Yes, don't try to apply my flight profile to a high wing loading design.    When attempting to mimic my profile you'd surely have noticed you were flying a much higher angle of attack than i was recommending,  due to your small wing not liking low speed.   Small wing design gets the rapier into the sweet spot faster and has better TWR  in the climb, particularly the first part.  Large wing design works better up high.  I prefer the large wing because re-entry is easier -stay higher longer and avoid the worst heat - and off-airport landings safer.

 

My preferred wing for a small spaceplane is  a big S delta with big S strakes attached to both the leading and trailing edges.   Then another one used as an actual strake.   Then a swept wing section added to the wing tips and tilted up 15 degrees for a bit of "gull wing" dihedral stability.    I've used that config on a mark 1 single engine 20 ton design,  and it's about the minimum i'd fit to a mark 2 aircraft.

 

As for my mark 3 monstrosities...

 

 

I did upload a Youtube video of one of my flights to orbit in a large wing , 30 Ton mark 2 plane with 2 NERVs and only one RAPIER.    It did take ages to climb to 10km  because the single RAPIER was only making 90kn of thrust subsonic,  which is enough for only 5 degree climb angle.   What I saved from having a really high lift drag ratio i lost by having so little thrust, that most of it was being swallowed up just to stay airborne for the 15 minutes it took to reach 10km.   Used as much fuel getting to 10km as i did going from 10km to orbit...

Conclusion, if you're going with a large wing design 2 nuke and 2 rapiers is the way to go , or at least give the single rapier a boost in the shape of a pair of juno or panthers in the sluggish subsonic part of the flight envelope.

 

https://www.youtube.com/watch?v=0O5dXyvhRw0

[Nothalogh]

7 hours ago, AeroGav said:

This is a bit of a cut n' paste from a tutorial i'm working on,  so sorry about the wall of text, needs breaking up with some pictures.  Hope it helps anyway..

 

Assuming you're not using aerodynamics mods like FAR,  performance doesn't come down to all that many factors actually.  Wing planform and placement don't matter at all,  four unswept, rectangular wing sections arranged like a biplane have the exact same lift and drag characteristics as a highly swept, supersonic delta of the same area. 

What counts - 

1.  Engine selection.     Rapier and NERV are the best, because NERV has the highest ISP of all non-airbreathers  and RAPIER works in jet mode to the highest speeds and atltudes.  And the "power play" method is not to use any oxidiser at all, and just let your NERVs boost from 25km up. More on that later.

2.  Lift to drag ratio.     At subsonic speeds, optimal lift to drag ratio occurs at 2 degrees angle of attack.  As you get faster, this increases, reaching 5 degrees by orbital velocity.    Peak lift:drag ratio is over 20:1,  a very nice exchange rate which means you can fly to orbit with NERVs alone. 

If the angle of attack needed to maintain level flight is below optimal,  you are going too fast (fix this by climbing more steeply, rather than throttling back),  or you have too much wing area , or are too low (again, climb steeper!).     More often however, i see people flying with excessive angle of attack, which generally means their wings are too small.

How much wing should I use?  
 

As your plane flies to orbit, it is steadily gaining speed, steadily getting lighter, and moving into thinner and thinner air.     With parameters constantly changing, what scenario should you design for?

In my opinion, the very high altitude regime, from 20-45km, is where the "rubber meets the road".   If your plane is efficient here, it can fly higher on airbreathing engines before being forced to switch on the rockets, and will be able to climb on the meagre thrust of a couple NERV motors, without resorting to higher thrust (but less fuel efficient) chemical rockets.

The air here is very, very thin.    In air breathing mode, bear in mind that your RAPIERs generate maximum thrust at mach 3.7.   You should probably fly slower than that below 20km to avoid wasting too much fuel fighting drag and to not blow up your plane with overheating, but above 20km, you want to accelerate to mach 3.7 then adjust your climb rate to maintain exactly that speed.      At such high altitudes, you need a lot of wing to generate sufficient lift while "only" doing mach 3.7, without having inefficient high angles of attack.

Once the air breathing engines are gone, feel free to fly faster, however your plane needs to gain altitude as the speed increases at a sufficient rate, or it is going to start overheating big time.  You could find yourself forced to pull up to angles of attack greater than 5 degrees to avoid blowing up.

Summary - you need as much wing area as possible.   

Assuming they're unlocked, the "power play" method is to construct your airplane from Big-S wing sections only, since these double up as fuel tanks for your NERVs and RAPIERs.

3.  Fuselage drag
 

The first rule here, is to avoid radially attached anything unless it's a wing or control surface !       Apart from landing gear, all accesories should be safely tucked away inside service bays or cargo bays.    Think reaction wheels instead of thruster blocks, radiators and solar panels can all go inside.

This goes with fuselage pieces.    Let's say you have nine cylindrical fuselage sections.   Attach them all in line, and the only drag you get is from the nose and tail.  Nine is basically the same drag, and frontal area ,  as one.   However, if you made the main fuselage 5 sections long and add a pair of nacelles each side, each two sections long, you are now presenting 3 times as much surface area to the wind.

I often see people putting sponsons on the side of their fuselage to make room for extra fuel tanks or intakes.     This is not a good reason to triple your drag !  The only reason to add nacelles is if you need more engine attach points.

Next, air intakes.   Insufficient air causes the engines to splutter, but intake spam won't make them operate any better or at higher altitudes.  The goal is to get enough air with a minimum of added drag.  The lowest drag way is to simply use engine pre-cooler, one per RAPIER, and put them inline with the rest of the fuselage pieces.  Nothing sticking out into the breeze - no drag.

Finally , when we've settled upon how many parallel strings of fuselage sections our design is going to have (eg.  one main fuselage, and an engine nacelle on each side) we have to consider what is going to go on the nose and tail of each stack, since this is where the drag is generated.       In terms of the tail , that's easy - an engine!  If we didn't need the engine , we wouldn't have created that parallel stack in the first place, would we?

But for the front , what should you use?   The tail cone connector, flipped 180 degrees so the pointy bit is forwards, appears to be the lowest drag selection, though it is somewhat heavy.

4.  Trim drag

One last design factor that influences performance, is Trim drag.   Namely, how much drag do your control surfaces generate while holding the nose up.    

Correcting a trim drag problem is tricky.

I am a great believer in playing things very safe with the centre of mass and centre of lift, placing the former well ahead fo the latter in a space plane.    It won't win any awards for agility, but space planes are subject to huge shifts in centre of gravity as fuel burns off and cargo gets unloaded.    So, this means a lot of force is needed to hold the nose up.

For starters,  we only want to be generating this pitch force with canards.    Passive tail fins that add stability are fine, assuming there is any room left at the rear of the plane not used for wings or engines.   However, keeping the nose up with control surfaces mounted behind the centre of gravity means generating downforce to lift the nose, and that means creating negative lift which the main wings have to overcome in addition to the vehicle's weight.

However,  wherever you place them, your pitch control surfaces will generate drag themselves as a result of the force they generate.  Just like the main wing, the drag is proportionate to the angle it meets the airflow.  If you only just have enough pitch authority to hold the nose up, chances are your canards/tailplanes/elevons/whatever are deflected at a large angle and making huge drag.

You could make your canards larger, so they don't need as much deflection angle, but this will also add lift ahead of your CG and make the plane less stable.  Also, by the time you've added enough control surface to have low trim drag, you 'll have added so much it is easy to snap the wings off with an inadvertent pull.

So, the best thing you can do is check the max deflection angle on the "right click for more info" screen  when you select a control surface  to use.  Lower, obviously, is better.  The standard canard and tail fin deflect to 30 degrees,  but some go to less, the Advanced Canard is especially interesting at only 10 degrees,  however in addition to having the small deflection angle it is also tiny, and you might need two or three pairs of these to be enough.

 

Flight Profile

How should one fly a space plane ? Each to their own of course, but this is generally how i do it, in an aircraft designed with the above principles -

1. Subsonic Initial climb

After takeoff, adjust rate of climb so that you're near the optimum 2 degrees angle of attack.  Angle of attack too low, climb steeper to slow down.  Angle of attack too high means we're stalling, nose over a bit.  Try to do this with pitch trim, if possible, it will save holding the same joystick angle for the next 20 minutes and getting cramp.

2.  Bust the sound barrier.

Generally at or above 10km,  i'm finding that @ 2 degrees angle of attack my air speed is starting to come up to 240 m/s.   There is a high drag region between 240 m/s and 440 m/s representing the sound barrier, you want to spend as little time here as you can.    So i often turn SAS on and set prograde assist to dive through the sound barrier ASAP.

3.  Supersonic climb 

After the sound barrier your Rapier engines gain thrust rapidly,  you find yourself pitching up hard to avoid getting too fast too low and overheating.   At the same time,  start nosing over at 15km so you don't find yourself in thin air at 20km without the power to accelerate.

4.  Milking the airbreathers

Above 18km,  there is little risk of overheat , so flatten out and increase speed to mach 3.7, where your RAPIER's power output is at its highest. Once you have attained this speed, climb at whatever rate stops the speed from increasing further.    When the climb rate is becoming negligible,  start up the NERV engines.    At 29.5km the RAPIERs will flame out completely, this phase of flight is over.

5. Hypersonic in the Mesosphere
Maintain around 5 degrees angle of attack with pitch trim , be ready to pull up more if things threaten to blow up.   Gradually you'll get higher and faster till you reach orbit.

Essential Mods

Tac Fuel Balancer.     Really hard to keep a space plane controllable once the rockets fire up.  Hit "Balance All" and be happy.

Kerbal Engineer Redux.    Gives a live display of Mach number,  Periapsis and Apoapsis (without having to switch to map screen)

Modular Fuels  .    Allows you to swap out the fuel tanks - eg. if you're building an oxidizer-free design like i suggest, you use this to make parts like the 2 into 1 adapter or the mk2 to mk1 fuselage adapter, carry only liquid fuel, and not waste tank capacity.

One more thing to add, push your apoapsis to just above 50km and do a burn up there to push your periapsis out the other side to become your apoapsis at your desired orbit, and then circularize at new apoapsis for under 50m/s dv

Edited January 28, 2016 by Nothalogh

[Warzouz]

18 hours ago, AeroGav said:

My preferred wing for a small spaceplane is  a big S delta with big S strakes attached to both the leading and trailing edges.   Then another one used as an actual strake.   Then a swept wing section added to the wing tips and tilted up 15 degrees for a bit of "gull wing" dihedral stability.    I've used that config on a mark 1 single engine 20 ton design,  and it's about the minimum i'd fit to a mark 2 aircraft.

...

I did upload a Youtube video of one of my flights to orbit in a large wing , 30 Ton mark 2 plane with 2 NERVs and only one RAPIER.    It did take ages to climb to 10km  because the single RAPIER was only making 90kn of thrust subsonic,  which is enough for only 5 degree climb angle.   What I saved from having a really high lift drag ratio i lost by having so little thrust, that most of it was being swallowed up just to stay airborne for the 15 minutes it took to reach 10km.   Used as much fuel getting to 10km as i did going from 10km to orbit...

Conclusion, if you're going with a large wing design 2 nuke and 2 rapiers is the way to go , or at least give the single rapier a boost in the shape of a pair of juno or panthers in the sluggish subsonic part of the flight envelope.

I've not much experience in SSTO space plane (I've only build one used for passenger and Kerbal recovery). My design is more about small wings and bigger engine. It's a 36T plane with 2 rapiers and 1 ramjet. It has quite a punch from 0 to 10km and can cross sound barrier while climbing (even I use the prograde SAS to reduce drag). It goes to space with around 500m/s left (which allow comfortable docking or double kerbal rescue)

Atmoshperic return is quite delicate because I don't have much drag to slow down and I must reignite the engine (only the ramjet, not the 2 rapiers) to land. I usually recover control on the plane quite low in atmoshpere (before, it falls like a rock, maybe the advanced canards are not enough).

Anyway, It flies carries it's 10 passengers to LKO without taking forever to reach.

PS : I'm more of a SSTO rocket fan