A spaceplane question.

[FletcherDragon]

I have a simple little question about space plane design that I think might inspire some discussion around here today, it may be obvious for some but for people like me it really isn't, which is why i'm asking.

Because I'm one of those weirdos who doesn't enjoy building rockets as big as they can be! I prefer more compact -pocket sized rocket- spacecraft. In order to do this many of my spaceplanes incorporate drop pods in their construction to assist with accent. Basically just a fuel tank on a decoupler bolted to the belly of the aircraft which is jettisoned when empty, usually while still in the upper atmopsphere 

My question is to ask you out there weather or not drop pods affect the inherent SSTO nature of a spaceplane or not. Given that hitting the stage function would eject the pods giving the vehicle more than one stage, it does not really change much about the spaceplane's configuration. Drop pods are actually used by fighter jets IRL when traveling long distances, its pretty far fetched to think about a fighter jet with drop pod fuel tanks as a two stage vehicle. don't you think?

I want to know if you think that drop pods would make a spaceplane multi-stage?

[Hodari]

If you're dropping ANYTHING before reaching orbit, it's not an SSTO.

[Hotaru]

22 minutes ago, FletcherDragon said:

the inherent SSTO nature of a spaceplane

There isn't really any "inherent SSTO nature of a spaceplane" at all; they're two completely unrelated categories of vehicle which happen to frequently intersect. You can have a multi-stage spaceplane or an SSTO rocket.

So no, an orbital spaceplane with drop tanks isn't an SSTO. It's an orbital spaceplane with drop tanks, which is a perfectly reasonable thing for a spacecraft to be. Drop tanks can be a good way of increasing the vehicle's payload fraction at relatively low cost, since you're only jettisoning cheap tankage, not expensive engines.

Also, using the "stage" function in KSP doesn't necessarily have anything to do with how many actual stages the vehicle has; you could, for instance, be using it to ignite two separate sets of engines (jets and rockets) or to deploy a drag chute on the runway and the vehicle would still classify as "single-stage."

[Foxster]

Its your game, an SSTO can be anything you like. 

However, as the others have said, if you share the craft with this community then what you will have is a space plane, not an SSTO. 

[regex]

49 minutes ago, FletcherDragon said:

I want to know if you think that drop pods would make a spaceplane multi-stage?

Yes, of course they would. Spaceplane =/= SSTO (and vice versa!). The STS Orbiter was a spaceplane and it was pretty far from an SSTO. I've also built a few lifters in my time that were SSTOs from the launch pad and had no wings.

Edited March 30, 2017 by regex

[FletcherDragon]

19 minutes ago, Hotaru said:

There isn't really any "inherent SSTO nature of a spaceplane" at all; they're two completely unrelated categories of vehicle which happen to frequently intersect.

Also, using the "stage" function in KSP doesn't necessarily have anything to do with how many actual stages the vehicle has.

Yeh~ you're absolutely right. I still have yet to learn how to think before opening my big fat mouth. But I still had to ask anyway because it wasn't really obvious to me. I always sorta thought that the stage fiction was the determining factor of the craft stage number.

[fourfa]

We can probably construct a spaceplane using drop tanks (and the inexpensive small hardpoints) that is cheaper per ton to orbit than a fully recoverable SSTO. By shedding mass and drag after the long climb to altitude, you can optimize the orbiter for the hypersonic phase. So there is good reason to look into it. 

But yeah the kerbal community definition of SSTO has been well covered here

[something]

Well if you do drop parts before reaching orbit, then you do have a space plane, but not an SSTO. Would you, however, get rid of the tanks after you finished orbital insertion, you would have a SSTO space plane and the drop tanks would be payload from a technically point of view (although some challenges around here require to detach payload as full as it had been on take off).

If your drop tanks have an engine attached, you technically built a shuttle, according to the shuttle challenge....

Edited March 30, 2017 by something

[Toastie_Buns]

Technically, aren't all our designs TSTOs?

https://en.wikipedia.org/wiki/Two-stage-to-orbit#Airplane-like_first_stage

[regex]

1 hour ago, fourfa said:

But yeah the kerbal community definition of SSTO has been well covered here

Well, no, not really. The "Kerbal community" definition tends to prefer "SSTO == Spaceplane" and it's a very common, and egregious mistake around here considering the two are anything but the same.

Unless I'm reading you wrong and you meant exactly that...

4 minutes ago, something said:

If your drop tanks have an engine attached, you technically built a shuttle, according to the shuttle challenge....

The STS Orbiter was a spaceplane. That is, it's a craft that acts like an aircraft in an atmosphere and a spacecraft in space. its drop-tank did not have an engine attached. Buran was a little different so that begs the question: "Which one was a shuttle?"

Answer: They were both spaceplanes, "Shuttle" is a colloquialism of the U.S. STS program.

3 minutes ago, Toastie_Buns said:

Technically, aren't all our designs TSTOs?

https://en.wikipedia.org/wiki/Two-stage-to-orbit#Airplane-like_first_stage

No, because the aircraft stage is "dropped" after the rocket stage is deployed.

[FletcherDragon]

Funnily enough most of my planes don't actually have any payloads besides heaps of kerbals. So I guess that does mean drop tanks are extra stages. ehh.. I thought it'd just be cool to say that I'm good at making SSTO's but guess not cos I need drop tanks and stuff.  

[something]

1 minute ago, regex said:

The STS Orbiter was a spaceplane. That is, it's a craft that acts like an aircraft in an atmosphere and a spacecraft in space. its drop-tank did not have an engine attached. Buran was a little different so that begs the question: "Which one was a shuttle?"

Answer: They were both spaceplanes, "Shuttle" is a colloquialism of the U.S. STS program.

 

The STS used a drop tank and two SRBs to propel the Orbiter into Orbit. As both boosters and a tank were dropped on its way to LEO, this was a 3 stage rocket.

The Buran programme used a several LOX engines to get the Orbiter into Orbit. As the 4 boosters and the central stage were dropped, this was a 3 stage rocket.

So yeah, all real world "shuttle" or space plane examples did drop engines on its way to orbit...

[regex]

Quote

So yeah, all real world "shuttle" or space plane examples did drop engines on its way to orbit...

Ah, so that definition considers an SRB to be a "two-part component". vOv

E: The trip-up for me being that a "drop-tank" doesn't imply an engine being attached. So I wouldn't call the SRB a "drop-tank with an SRM", it's an SRB. The same for Buran, those are liquid-fueled boosters, not drop-tanks.

Edited March 30, 2017 by regex

[juanml82]

If you're dropping stuff and you're mixing rapiers and nervs, you can get a lot more of dV in space by dropping the rapiers as well. Landing back on Kerbin would require gliding and using the nervs, which aren't that useful in the lower atmosphere though. Or a vertical landing using parachutes.

[Red Iron Crown]

7 hours ago, fourfa said:

We can probably construct a spaceplane using drop tanks (and the inexpensive small hardpoints) that is cheaper per ton to orbit than a fully recoverable SSTO. By shedding mass and drag after the long climb to altitude, you can optimize the orbiter for the hypersonic phase. So there is good reason to look into it.

I am really skeptical that this would work out cheaper, I've played around with it a bit and found that the additional parts required balance out any fuel savings, at best.

[obi_juan]

I made SSTO/SSTA with a 169tn empty and 980tn full*, with more than 5400-deltaV.

Also I made Spaceplanes with drop-tanks o have more delta-V in the space and rescue more stranded kerbals.

It is your game and you can make the ships as you want, by my self I think that your way is a good way to play. Could you show us the spaceplanes that you make?

[jros83]

12 hours ago, Hotaru said:

 

Also, using the "stage" function in KSP doesn't necessarily have anything to do with how many actual stages the vehicle has; you could, for instance, be using it to ignite two separate sets of engines (jets and rockets) or to deploy a drag chute on the runway and the vehicle would still classify as "single-stage."

Well said. It's a catch-all extrapolation; it can mean stages in the classic sense AND be a means to control different, circumstantial functions, frequently in the same craft.

[AeroGav]

On 30/03/2017 at 4:38 PM, Hotaru said:

There isn't really any "inherent SSTO nature of a spaceplane" at all; they're two completely unrelated categories of vehicle which happen to frequently intersect. You can have a multi-stage spaceplane or an SSTO rocket.

So no, an orbital spaceplane with drop tanks isn't an SSTO. It's an orbital spaceplane with drop tanks, which is a perfectly reasonable thing for a spacecraft to be. Drop tanks can be a good way of increasing the vehicle's payload fraction at relatively low cost, since you're only jettisoning cheap tankage, not expensive engines

I have made quite a few staged spaceplanes.   The thing is, mk1 and especially 2.5m fuel tanks have a very good capacity to drag ratio, you don't save very much by offloading them.  Most of the drag is from you mk2 and mk3 fuselage parts.   Also,  the limiting factor is how much mass you can get supersonic.  If you have enough engine power to get those fuel tanks supersonic, might as well carry them to orbit.   Finally,  there's a bit of a discrepancy in cost of parts, if we're going to talk economics.      Liquid fuel tanks have little value when empty, over 80% of the cost is in the fuel itself.    But oxidizer costs almost nothing, yet the empty tank is worth 60% of a full one.   The oxidizer container must have to be lined with platinum or something.   

What does work, is dropping Whiplash engines.   They only cost 1/3 of a RAPIER or 1/6th of a NERV.

Since your gross mass is limited by what you can boost through mach 1, these things are here to help.    Sling a pair on underwing pods with a small hardpoint, circular intake and mk1 LF fuselage (crossfeed enabled) and boost to mach 1.  Once you're going at mach 3+ , the RAPIER produces 8 times it's static thrust,  which means you only need one RAPIER per 50/60 tons of vessel.    At that ratio, you don't mind dragging their 2 ton mass to orbit and back.

[Hodo]

On 3/30/2017 at 11:12 AM, FletcherDragon said:

I have a simple little question about space plane design that I think might inspire some discussion around here today, it may be obvious for some but for people like me it really isn't, which is why i'm asking.

Because I'm one of those weirdos who doesn't enjoy building rockets as big as they can be! I prefer more compact -pocket sized rocket- spacecraft. In order to do this many of my spaceplanes incorporate drop pods in their construction to assist with accent. Basically just a fuel tank on a decoupler bolted to the belly of the aircraft which is jettisoned when empty, usually while still in the upper atmopsphere 

My question is to ask you out there weather or not drop pods affect the inherent SSTO nature of a spaceplane or not. Given that hitting the stage function would eject the pods giving the vehicle more than one stage, it does not really change much about the spaceplane's configuration. Drop pods are actually used by fighter jets IRL when traveling long distances, its pretty far fetched to think about a fighter jet with drop pod fuel tanks as a two stage vehicle. don't you think?

I want to know if you think that drop pods would make a spaceplane multi-stage?

 

Not going to cover the obvious that others have beat into the ground about SSTOs.  

But the idea of drop tanks on a space plane is one option, often not the most practical option if cost is a factor.  But it depends on the way you play the game.  If you are playing a full RO version of KSP then you may have to use a more conventional Space Shuttle program style of launch.   But if you are running a FAR version but otherwise stock, you may not need to go through the hassle of drop tanks.  But if you run AJE with FAR then you may want to re-think your designs completely as jets lose their OP nature.  

 

I love SSTO space planes, been doing them for the past few years.   My only major issue with drop tanks is they change the CoM of the craft and can upset the balance of the craft for re-entry or during space flight.   But it is a challenge, and it ultimately comes down to how you want to play.

[Gargamel]

On 3/30/2017 at 11:12 AM, FletcherDragon said:

... -pocket sized rocket- ...

*insert Beavis chuckles*

 

C'mon.... I can't be the only one? 

 

[FletcherDragon]

On 4/3/2017 at 8:12 AM, gargamel said:

C'mon.... I can't be the only one? 

 

So far.. Yes you are but that wasn't really the intention. I was making fun of the 'bigger is better' kerbal mentality. 

On 4/1/2017 at 6:45 AM, Hodo said:

My only major issue with drop tanks is they change the CoM of the craft and can upset the balance of the craft for re-entry or during space flight.   But it is a challenge, and it ultimately comes down to how you want to play.

Oh. I find that adding drop tanks as the very last components after the plane itself has already been constructed doesn't really change the aerodynamics. because drop tanks are only carrying the fuel for accent which is used up first. Then again the small mass of my planes also have small drop tanks and the COM doesn't really change position that much at all.

 

Here is an example of what I make. This one is my most recent, it can get itself from the surface of Kerbin to the surface of Minmus and back without refuel, The two short cargo bays hold a Dart rocket motor each giving it VTOL capabilities on smaller bodies. And in addition to all that its designed to tow a planetary base or station module on interplanetary missions and return by itself if its first refueled in Kerbin orbit.

http://steamcommunity.com/sharedfiles/filedetails/?id=899240618

Lots of functionality crammed into a soberly proportioned package.

Edited April 6, 2017 by FletcherDragon
Added content.

[Hodo]

20 hours ago, FletcherDragon said:

So far.. Yes you are but that wasn't really the intention. I was making fun of the 'bigger is better' kerbal mentality. 

Oh. I find that adding drop tanks as the very last components after the plane itself has already been constructed doesn't really change the aerodynamics. because drop tanks are only carrying the fuel for accent which is used up first. Then again the small mass of my planes also have small drop tanks and the COM doesn't really change position that much at all.

 

Here is an example of what I make. This one is my most recent, it can get itself from the surface of Kerbin to the surface of Minmus and back without refuel, The two short cargo bays hold a Dart rocket motor each giving it VTOL capabilities on smaller bodies. And in addition to all that its designed to tow a planetary base or station module on interplanetary missions and return by itself if its first refueled in Kerbin orbit.

http://steamcommunity.com/sharedfiles/filedetails/?id=899240618

Lots of functionality crammed into a soberly proportioned package.

That is a good looking craft, but as far as drag is concerned running a clean config, without drop tanks will be more efficient than running drop tanks.   I have built combat aircraft that are not SSTOs that run drop tanks to extend their range.  But for the most part I found DTs, are just more of a hassle then they are worth. 

 

Every one of my SSTO space planes and SSTOs in general have to be able to achieve a circular orbit at 100km x 100km.   If they can not achieve this they are useless to me.

No drop tanks, and it is a completely mission capable single seat craft.  Granted not my best, I have several others that are already well past this design.  I had gotten rusty in the year I took off.

[FletcherDragon]

2 hours ago, Hodo said:

as far as drag is concerned running a clean config, without drop tanks will be more efficient than running drop tanks.   I have built combat aircraft that are not SSTOs that run drop tanks to extend their range.  But for the most part I found DTs, are just more of a hassle then they are worth.

I've never had much trouble with drop tanks at all. I've popped a couple on the runway during takeoff before but unlike staging large pieces of a vertical rocket which more often than not end up turning my ships inside out. Drop tanks on planes I build always seem to function pretty well. They usually only carry enough fuel to get to get me up to 10k and about 600 to 700m/s which really helps reduce the overall size of the plane without sacrificing its ability to make it to and from any of the kerbin moons.

[Alshain]

@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.

Edited April 7, 2017 by Alshain

[FletcherDragon]

1 hour ago, Alshain said:

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've never actually ever considered doing that before! sounds like some really good plans.

And also I wasn't really bothered . I just though bird'dd be fun to have bragging rights.

Spaceplanes are cool either way weather they have one or more stages IDC~