A spaceplane question.

[AeroGav]

There's a difference between a spaceplane with droppable boosters, and TSTO where the lower is not intended to reach space and which should be recoverable.

I currently have a Ferram Aerospace / Advanced Jet Engine / Realfuels career mode.    AJE gets rid of the overpowered jet engines in stock game.   As such SSTO is harder, but here's a TSTO  that can put Jeb in orbit around the Mun/Minmus.    With a few more techs,  I should be able to land on it.

 

Here's a stock physics TSTO.  This was to see how well TSTO can do if,  like in RL*,  jet engines are only able to get 20% orbital velocity, so i restrict myself to wheesley jet engines.   The upper stage does well, but the lower separation altitude and long climb to orbit mean the lower stage is auto deleted when it goes out of physics range (below 25km altitude the game assumes any "on rails" craft to be destroyed)

*Even things like Skylon still have subsonic combustion, so the limit is mach 5 something , less than 20% orbital velocity. The only air breathing engines that might exceed that are scramjets - if we can ever get them working.

 On the other hand, this is space plane with disposable booster engines.    Doubt it would be possible to get such a payload to such an orbit with just 2 whiplash, 2 terrier and 2 nerv if you weren't staging.

 

Edited April 7, 2017 by AeroGav

[Vanguard319]

I've built my fair share of SSTOs. Some I've built could get to LKO on their own fuel, but had issues with carrying any viable payload, for cargo, or to get higher I came up with simple drop tanks made from 3 Mk.0 fuel tanks and a pair of small nose cones. they are pretty good for my aircraft too.

[KerikBalm]

Rl spacelanes: 

STS: SRB stage, drop tank (can be carried to orbit, cannot be recovered) (dont count 2 srbs as 2 stages, they operate simultaneously, they are the same stage)

X-15: B-52 air launch, would count as a stage. Doesnt reach orbit, so clearly not SSTO

Scaled Composites spaceplanes (ie space ship 1): similar to the X-15

Buran: booster stages, core stage

So, yea, nothing inherently SSTO about spaceplanes

[Hodo]

11 hours ago, AeroGav said:

There's a difference between a spaceplane with droppable boosters, and TSTO where the lower is not intended to reach space and which should be recoverable.

I currently have a Ferram Aerospace / Advanced Jet Engine / Realfuels career mode.    AJE gets rid of the overpowered jet engines in stock game.   As such SSTO is harder, but here's a TSTO  that can put Jeb in orbit around the Mun/Minmus.    With a few more techs,  I should be able to land on it.

 

 

I run a career mode with FAR and AJE, but not real fuels. And I found it is possible to get to orbit with jets... well close to orbital speeds to cut down on oxidizer needed.

I have used both the engines from the SR-71, and the RAMJET engines.  Both work pretty well.  The hardest part is getting them to 4 times the speed of sound.   You have to ride a very narrow line around 8km-11km ASL while accelerating to around mach 4.

Once you get to that speed you let the nose gradually pitch up to around 15-25deg ride the speed up till your engines lose power or start to overheat.   Which ever happens first.  Usually around 20-25km I can switch over to my rocket(s) engine.  And continue to climb to target AP.  

 

[AeroGav]

51 minutes ago, Hodo said:

I run a career mode with FAR and AJE, but not real fuels. And I found it is possible to get to orbit with jets... well close to orbital speeds to cut down on oxidizer needed.

I have used both the engines from the SR-71, and the RAMJET engines.  Both work pretty well.  The hardest part is getting them to 4 times the speed of sound.   You have to ride a very narrow line around 8km-11km ASL while accelerating to around mach 4.

Once you get to that speed you let the nose gradually pitch up to around 15-25deg ride the speed up till your engines lose power or start to overheat.   Which ever happens first.  Usually around 20-25km I can switch over to my rocket(s) engine.  And continue to climb to target AP.  

 

The J-58 is 500 tech cost, ATM I just got the Pratt & Whitney F-100 and the Russian Lyulka.  Only gets to about Mach 1.7 airbreathing. I'm sure it'd go to 2.5 if you stripped all the rocket fuel out of it.   Wave drag area's only like 0.23m3, ungainly as it looks it's actually a low drag ship,  but it does suffer a rather vicious "mach tuck" which makes flying it on keyboard difficult.   Wants to pitch up to 10 degrees AoA when you hit 0.8 mach,  then starts pitching down hard at mach 1.

[Gargamel]

On 4/6/2017 at 8:53 PM, Alshain said:

@FletcherDragon I feel like pointing out that there is absolutely nothing wrong with it not being an SSTO.  SSTO is just a label.  There are perfectly good TSTO designs.  The only reason for SSTO is to reduce cost (in theory), but in some cases cost may not matter to you.  I've built planes that would otherwise be SSTO's but then to reduce drag I put nose cones on the back of the rocket engines (non-RAPIER designs) with decouplers.  No, it's technically not an SSTO, but who cares?  Nose cones are cheap.

I'm kind of a nit when it comes to the SSTO definition, as anything that uses one stage to get to orbit qualifies, not just spaceplanes.    But in your example, I'd think it still falls into a SSTO, as your are not dropping expended tanks or engines, just a cowling for aero.  If there was a mechanic in game to shield the engines, and then open those shields, it's the same thing as your design. 

[Hodo]

13 hours ago, AeroGav said:

The J-58 is 500 tech cost, ATM I just got the Pratt & Whitney F-100 and the Russian Lyulka.  Only gets to about Mach 1.7 airbreathing. I'm sure it'd go to 2.5 if you stripped all the rocket fuel out of it.   Wave drag area's only like 0.23m3, ungainly as it looks it's actually a low drag ship,  but it does suffer a rather vicious "mach tuck" which makes flying it on keyboard difficult.   Wants to pitch up to 10 degrees AoA when you hit 0.8 mach,  then starts pitching down hard at mach 1.

 

You have to much wing for those speeds.   This is part of the reason for your "tuck" issues.

Remember as you reach supersonic speeds the point of lift moves back on the lifting surface.  The faster you go the further it ends up moving.   This is why I prefer the cranked arrow delta wing design.  It gives me the lower speed stability I want for landing at a speed slower than 130kn, but still gives me the supersonic speed control that I want around mach 1.5-3.0.   

 

I have recently fallen in love with the reverse swept wings, those have so many advantages for light weight aircraft.

Edited April 8, 2017 by Hodo

[AeroGav]

26 minutes ago, Hodo said:

 

You have to much wing for those speeds.   This is part of the reason for your "tuck" issues.

Remember as you reach supersonic speeds the point of lift moves back on the lifting surface.  The faster you go the further it ends up moving.   This is why I prefer the cranked arrow delta wing design.  It gives me the lower speed stability I want for landing at a speed slower than 130kn, but still gives me the supersonic speed control that I want around mach 1.5-3.0.   

 

I have recently fallen in love with the reverse swept wings, those have so many advantages for light weight aircraft.

Yeah I just like large wing area and low landing speeds.  If you look at the end of the video i touch down at 62m/s which is quite slow for FAR.  I missed the runway completely and have also ended up putting down on the hills near KSC so Val owes her life to the airplane's low speed performance.

This other one i made (not using Advanced Jet engine) did not have such issues with "tuck"

It does have too much wing area for best speed in level flight, you can see from the ridiculously low AoA - and if we climb any higher that engine will lose power.    However when it's got a pair of nukes hanging off the wings,  the higher altitudes and greater mass make the extra lift more useful 

This one also lands nice and slow.

[Hodo]

2 minutes ago, AeroGav said:

Yeah I just like large wing area and low landing speeds.  If you look at the end of the video i touch down at 62m/s which is quite slow for FAR.  I missed the runway completely and have also ended up putting down on the hills near KSC so Val owes her life to the airplane's low speed performance.

This other one i made (not using Advanced Jet engine) did not have such issues with "tuck"

It does have too much wing area for best speed in level flight, you can see from the ridiculously low AoA - and if we climb any higher that engine will lose power.    However when it's got a pair of nukes hanging off the wings,  the higher altitudes and greater mass make the extra lift more useful 

This one also lands nice and slow.

 

The other problem I see with that design is the control surfaces angles.  If you have them set for pitch authority the angles on those wings near the end will not give you the best authority.  They are not going to give you much use.  Same for the leading canard.   The leading edge "slats" or controls are to close to the CoM to be much use for pitch.

It does look cool, but sometimes looks dont function well.

[FletcherDragon]

Wait wait wait wait.. OK OK, how about we switch the thought process a little bit here for a moment. Originally I was debating weather a spaceplane was or was not an SSTO because it dropped some small auxiliary fuel tanks on the way up. it was then brought up that engine shrouds or fairings of some kind being detached does not count as multi-staging because they did not contain fuel or equipment at any time. 

If we all agree that this hypothetical plane that used drop tanks made its way into orbit is not an SSTO, Then lets send it on a hypothetical mission. This vessel makes an inter-planetary journey to Duna lets say and makes a safe landing, utilities onboard facilities or base facilities to refuel, Do science! Get funds! Etc Etc, and makes a return trip to the orbit of Duna and back to Kerbin. The ship has ample power to return to orbit of Duna without the use of droptanks... all hail the NERV rite?

Is this hypothetical space plane still a TSTO now that it has returned to Duna's orbit in a single stage AFTER having climbed out of kerbin's gravity well leaving tanks behind..?

Am I thinking too hard? I think I am... Its far too late to be thinking~~

[AeroGav]

53 minutes ago, Hodo said:

 

The other problem I see with that design is the control surfaces angles.  If you have them set for pitch authority the angles on those wings near the end will not give you the best authority.  They are not going to give you much use.  Same for the leading canard.   The leading edge "slats" or controls are to close to the CoM to be much use for pitch.

It does look cool, but sometimes looks dont function well.

Can you expand on this?   The pitch authority is all from the canards, the trailing edge of the wing is roll control and flaps only.  The leading edge devices are high lift devices.       I assume you mean that highly swept surfaces  are ineffective as pitch controls in FAR, or are you saying they are too close to CoM be effective ? It is true that pitch authority is limited on both vessels, they pitch easily to 7 or 8 degrees of alpha then hit a brick wall, but i assume that's the canard stalling before the main wing which is kind of a safety feature,   though i'd probably like a few more degrees authority.  Prevents stalls and tail strikes, it's not a fighter.

[Hodo]

43 minutes ago, AeroGav said:

Can you expand on this?   The pitch authority is all from the canards, the trailing edge of the wing is roll control and flaps only.  The leading edge devices are high lift devices.       I assume you mean that highly swept surfaces  are ineffective as pitch controls in FAR, or are you saying they are too close to CoM be effective ? It is true that pitch authority is limited on both vessels, they pitch easily to 7 or 8 degrees of alpha then hit a brick wall, but i assume that's the canard stalling before the main wing which is kind of a safety feature,   though i'd probably like a few more degrees authority.  Prevents stalls and tail strikes, it's not a fighter.

Both the canards which are at a very high sweep so when they actually move they dont move even with the craft, they move kind of like air brakes, out from the airflow.   

Which should lead them to stall way before they actually should, unless you have the inner canards as your actual moving surfaces.   Unfortunately I am not at home so I cant take your crafts pics and highlight exactly what I am talking about.   

I am a huge fan of canards on 90% of my craft, they are a great "safety" feature.  But you can often achieve the same goals with a better wing design.   I have learned over the years, less is more with SSTO wing designs.

 

[Hodo]

1 hour ago, FletcherDragon said:

Wait wait wait wait.. OK OK, how about we switch the thought process a little bit here for a moment. Originally I was debating weather a spaceplane was or was not an SSTO because it dropped some small auxiliary fuel tanks on the way up. it was then brought up that engine shrouds or fairings of some kind being detached does not count as multi-staging because they did not contain fuel or equipment at any time. 

If we all agree that this hypothetical plane that used drop tanks made its way into orbit is not an SSTO, Then lets send it on a hypothetical mission. This vessel makes an inter-planetary journey to Duna lets say and makes a safe landing, utilities onboard facilities or base facilities to refuel, Do science! Get funds! Etc Etc, and makes a return trip to the orbit of Duna and back to Kerbin. The ship has ample power to return to orbit of Duna without the use of droptanks... all hail the NERV rite?

Is this hypothetical space plane still a TSTO now that it has returned to Duna's orbit in a single stage AFTER having climbed out of kerbin's gravity well leaving tanks behind..?

Am I thinking too hard? I think I am... Its far too late to be thinking~~

 

I am of the school of thought if it drops ANYTHING that is power, or fuel or a lifting surface of the craft, it is no longer a SSTO.  

If it drops landing gear or shrouds around something that is fine.   

[AeroGav]

1 hour ago, Hodo said:

Both the canards which are at a very high sweep so when they actually move they dont move even with the craft, they move kind of like air brakes, out from the airflow.   

Which should lead them to stall way before they actually should, unless you have the inner canards as your actual moving surfaces.   Unfortunately I am not at home so I cant take your crafts pics and highlight exactly what I am talking about.   

I am a huge fan of canards on 90% of my craft, they are a great "safety" feature.  But you can often achieve the same goals with a better wing design.   I have learned over the years, less is more with SSTO wing designs.

 

I appreciate you taking the time to help me with this, but should we take this to a more appropriate thread ? 

I kind of see what you're saying about highly swept canards.   I am now using B9 procedural wings so I can make a canard highly swept while still having it move correctly.   I also appreciate that in FAR, you don't need large wings because supersonic lift is much greater than stock, and supersonic l/d ratio peaks at higher AoAs.  Unfortunately, like real life, lift at low speeds is much less so Cessna landing speeds are a thing of the past.

A small winged f-104 style design would be much easier to design for low wave drag.    However at the moment i am wanting to make large winged supersonic aircraft just for the hell of it.  My current project is a science plane for career mode.   The requirements are

• Sufficient Range to fly to the North Pole and back
• Supercruise - at least mach 1.3 non afterburning
• Lowest possible landing speed at half internal fuel given the above.

 

This is my current best effort -

According to FAR static analysis,  supersonic L/D peaks around 1.25mach at about 2.5 AoA.  Stalling AoA is between 40-45 subsonic.

Without the mid-span ailerons drooping, we can get 25 AoA before the canards give up. Flying level at 42m/s, about 85 knots - with near full fuel.

Drooping the ailerons lowers Alpha max to 15.9.  This raises our minimum speed to 49-50 m/s , but is more usable.  I still think we'd bust the tail off landing like that and i've only got the smallest gears unlocked in tech tree, so can't give her any more ground clearance.  Notice we're making more lift, but still only flying level.  I guess the downward component of our thrust isn't adding to lift so much at the reduced AoA.

At altitude,  you can see the airframe/engine matching issue.    

 

Flying at best supersonic L/D AoA at best supersonic L/D mach number , we make too much lift and rise to an altitude that's beyond the engine's comfort zone.  Above 15km the power really drops off and i'm having to use full A/B to maintain speed.     There's 3 jet engines in this tech node and it's currently using the lightest - the AL31.  I chose it because it sounded high tech (variable bypass) but i might try one of the others. 

 

Edited April 8, 2017 by AeroGav

[Hodo]

That is a much better looking and functioning aircraft.  Now you have broken one barrier, the stars are your limit!  

I love B9 P-wings.  But still mess with stock wing parts quite a bit because I find it a bit of a challenge to come up with decent wing designs with them.