Advantages of TSTO piggyback spaceplanes

[MedwedianPresident]

While most KSP players build SSTO spaceplanes, I prefer launching spaceplanes using suborbital carrier vehicles (Classic piggyback TSTO), launching them from standard airplanes or launching them on top of a rocket.

 

Who else prefers TSTO or approaches with even more stages over SSTO's? Post and discuss your designs here!

 

My list of advantages of TSTO's:

 

- More realistic (many spaceplane designs of the present and past are actually TSTO concepts)

- Allow a spaceplane to not carry jet engines (unless they are needed for landing, but most realistic spaceplanes land in unpowered flight anyway)

- Allow for lighter, simpler and smaller spaceplanes that carry only their payload instead of engines only used for takeoff

- Carrier vehicle (e.g. the hypersonic bomber from which the spaceplane is launched) is reusable and can be used to do a variety of in-atmosphere tasks while the spaceplane is in orbit. 

- More modularity - if you have developed a good carrier vehicle, you can launch a big variety of rockets or spaceplanes from it

- Is safer - usually, no SRB's or only short-burning ones are involved in the launch profile, guaranteeing a safe suborbital abort without explosions and crying kerbals and a maniacally laughing Jeb.

- Carrier vehicle usually holds enough fuel to be used to transport the spaceplane for long distances in-atmosphere while SSTO's usually only have enough jet fuel to safely fly from the Eastern Kafrican Alps (known as "the Oops Too Short Trajectory Crash Mountains" to many) to the KSC and for a short jet-powered acceleration to supersonic speeds. I think that landing somewhere on the other side of Kerbin and knowing that an airplane will come which will transport the whole spaceplane to the KSC is better than crashing in the mountains west of KSC regularly after struggling to use the last bits of leftover fuel to keep up the trajectory.

 

 

It should also be noted that "carrier vehicles" (e.g. large planes on which the spaceplane is mounted and which accelerate it to a hypersonic speed) can also be rocket-powered - I have successfully performed experiments with such designs in the past and am working on one now.

 

Here are the KS-44 spaceplane (an upscaled Dyna-Soar designed for small and medium missions such as deploying minor sattelite or space station service) and the KS-98 rocket-propelled unmanned reusable hypersonic carrier vehicle on the runway.

 

Edited August 11, 2016 by MedwedianPresident

[ZooNamedGames]

What is TSTO???

ok I figured it out already BUT I'm asking so Someone else doesn't have to.

Edited August 11, 2016 by ZooNamedGames

[GoSlash27]

Spaceplanes are strictly a means to an end for me; Get supplies to a station in orbit (and perhaps back to KSC) as cheaply, easily, and safely as possible. Furthermore, spaceplanes represent a large investment of R&D time and effort, so I only design them for "routine" missions; ones that must be flown regularly and do not require any redesigns to fit the payload so that they will recoup that cost. That basically means crews and fuel.

Since I run 100% vanilla, anything that drops off during a staging event is lost.

 Putting all of this together, I don't use TSTO spaceplanes. SSTO spaceplanes are simply better at doing the job I use spaceplanes for.

Best,
-Slashy

Edited August 11, 2016 by GoSlash27

[XB-70A]

I use both, with a preference for the fat TSTO during a long time... then I discovered that smaller and lighter can also be funnier. I past my time with the tiny SSTO now instead.

I got some shots in stock by the way.

The Raven was possible to use as a complete SSTO by keeping the SRB when the load was low or if it was a crew transfert, I jetisson them if it was a freight/heavy payload.

The Vulture just was bigger Raven but purely single stage :

 

The Kolibri Mk I was dedicated to simple crew relay and datas transferts :

 

The Kolibri Mk II is just a bigger one for crew rotations :

 

I got many others in hangars now being totaly "stockalized" to not be anymore annoyed with parts missing during mods updating.

Edited August 11, 2016 by XB-70A

[foamyesque]

1 hour ago, GoSlash27 said:

Spaceplanes are strictly a means to an end for me; Get supplies to a station in orbit (and perhaps back to KSC) as cheaply, easily, and safely as possible. Furthermore, spaceplanes represent a large investment of R&D time and effort, so I only design them for "routine" missions; ones that must be flown regularly and do not require any redesigns to fit the payload so that they will recoup that cost. That basically means crews and fuel.

Since I run 100% vanilla, anything that drops off during a staging event is lost.

 Putting all of this together, I don't use TSTO spaceplanes. SSTO spaceplanes are simply better at doing the job I use spaceplanes for.

Best,
-Slashy

 

That's more or less the position I'm in, as well. A piggyback -- or, more amusingly, bomb-bay drop -- approach is really cool, but it doesn't actually help in stock since the carrier vehicle can't be recovered. 'bout as far as I might go in stock is with drop tanks or a pair of small solids for a TWR kick between Panther top speed and <0.5TWR orbit insertion velocities.

[Van Disaster]

I tried piggyback last career run & decided multistage vertical launch was a much better idea at low tech levels. After that I just use a boost stage - usually on the wingtips - from 20km to 45km-ish if the craft needed it, like say, if it had nuclear space engines. SSTO all the way for high tech level craft though, albeit with B9 fuselage parts.

[Blaarkies]

Falcon 9's all the way! ...well, using the Twin-Boar engine, and a heatshield up front, also some parachutes. Ok, ok, but it looks like a Falcon 9 after the landing is done

[ZentroCatson]

I use both, but I for now have only used space-shuttle style TSTOs with a non-reusable external tank. Both are quite difficult to fly, but I find a space-shuttle style TSTO easier to fly. Using a carrier plane for lifting a spaceplane is a cool idea, @MedwedianPresident. I'll definitely try that out!

On the topic of SSTOs, I find them difficult to design, especially ones that are meant to carry a payload. That's why most of my SSTOs are for crew transfer.

Edited August 11, 2016 by ZentroCatson

[DunaRocketeer]

I'm sure there are ways of creating heavy-lift SSTO's that don't look like an ugly mess of tanks, engines and wings, but I haven't been able to make one yet, so I make do with TSTO. Most of my payloads are launched on TSTO's that reuse at least the boost stage via a runway landing. As the OP mentions, it offers flexibility for upper stage designs, and adds an element of complexity to otherwise routine launches. Variations on the vehicles shown below are the basis of my entire space program for all of 2016.

 

Edited August 11, 2016 by DunaRocketeer

[Firemetal]

Do you mean like the space shuttle? Yeah I do use them occasionally but in a career save, SSTOS are more fund efficient. Find my Taurus Shuttle in the showcase thread in my sig.

[KerikBalm]

10 hours ago, MedwedianPresident said:

- Carrier vehicle (e.g. the hypersonic bomber from which the spaceplane is launched) is reusable and can be used to do a variety of in-atmosphere tasks while the spaceplane is in orbit. 

- More modularity - if you have developed a good carrier vehicle, you can launch a big variety of rockets or spaceplanes from it

- Is safer - usually, no SRB's or only short-burning ones are involved in the launch profile, guaranteeing a safe suborbital abort without explosions and crying kerbals and a maniacally laughing Jeb.

- Carrier vehicle usually holds enough fuel to be used to transport the spaceplane for long distances in-atmosphere while SSTO's usually only have enough jet fuel to safely fly from the Eastern Kafrican Alps (known as "the Oops Too Short Trajectory Crash Mountains" to many) to the KSC and for a short jet-powered acceleration to supersonic speeds. I think that landing somewhere on the other side of Kerbin and knowing that an airplane will come which will transport the whole spaceplane to the KSC is better than crashing in the mountains west of KSC regularly after struggling to use the last bits of leftover fuel to keep up the trajectory.

-It should also be noted that "carrier vehicles" (e.g. large planes on which the spaceplane is mounted and which accelerate it to a hypersonic speed) can also be rocket-powered -

#1 - In vanilla KSP, it is very very difficult to reuse a carrier vehicle

#2 - I don't see how its any more modular. I've even developed module "strap-on SSTOs" that are just mini radially attaching SSTOs, that I can attach to basically anything around the CG to increase the payload capacity.

example:

Spoiler

^that main plane is not meant as a kerbin SSTO, its a Duna cargotransporter, hence the VTOL engines:

#3 - the separation event makes them more dangerous... as does trying to balance the thrust and shifting mass in piggyback designs

#4 - thats all in the design, and many many SSTOs have plenty of fuel. After all, SSTOs can get better than a 50% payload fraction

#5 - there are pleny of rocket only SSTOs

 

9 hours ago, GoSlash27 said:

 

Since I run 100% vanilla, anything that drops off during a staging event is lost.

Mostly true, but not 100% true.

Ever since the update to what... a 22.5 km physics bubble? early decoupling boosters have been viable.

Those were RATO packs that burn just enough to get a "modular" spaceplane into horizontal flight from a vertical launch from the runway... only a few seconds of burn before decouple, but after achieving orbit, I switched back, and there they were. I particularly like the launch escape system for awesome thrust for what... 1.5 seconds?

The other option is to decouple while on a suborbital trajectory, high enough in the atmosphere that it oesnt despawn and you can switch back in time after acheiving orbit.

Spoiler

This is my best attempt at a 2-stage 100% recoverable spaceplane:

Its a PITA to use

Recovered booster:

Orbiter going orbital, Booster marked in yellow, still in space

Booster doing its boostback thing at apoapsis

Trajectories:

Basically: get Apoapsis over 70km, stage. Burn orbiter engine to get apoapsis even higher and farther away in time and to get closer to orbital velocity. Once in space, switch back to booster, point retrograde, burn retrograde to reverse orbit (its got airbreathers and spacre LF to carry it back if there's not enough reserved for a proper reversal at apoapsis). Switch to orbiter and circularize/raise PE out of atmosphere. Switch back to booster and fly it back to the runway before it drops too low

This isn't 2 stage, but:

The External tank does get recovered... but across the ocean east of KSC, around the shores of the other continent.

7 hours ago, foamyesque said:

 

That's more or less the position I'm in, as well. A piggyback -- or, more amusingly, bomb-bay drop -- approach is really cool, but it doesn't actually help in stock since the carrier vehicle can't be recovered. 'bout as far as I might go in stock is with drop tanks or a pair of small solids for a TWR kick between Panther top speed and <0.5TWR orbit insertion velocities.

As above.... you can recover a carrier vehicle, but that vehicle needs to be designed to get on a suborbital trajectory that gets it into space. That means you then have the choice between a boost-back, or a boost-forward to take it to orbit... or having it land quite far away from KSC for a bad recovery %.

Especially if you use airbreathers, that boost-back is going to be way more expensive than the boost-forward to get it into orbit. Rapiers in airbreathing can get you to >1,400m/s surface or >1,600m/s orbital considering orbital velocity in low orbit is ~2,300 m/s, the boost-back is clearly inferior to the boost forward... particularly as you need an additional "boost-forward" to get your Ap above 70km for the requisite switching.

Even discounting the recovery %'s, the airbreathers get you so close to orbital velocity, and the wing mass isn't soo high... and the rapiers aren't such dead-mass because they're also rockets that can supply the thrust you need, at least during the initial transition to rocket power and climbing out of the atmosphere... that you really aren't taking much useless mass very "far" (in the sense of the ~700-800 m/s extra you need to achieve orbit), and the complexity of a two stage design (and presumably added drag because piggy back designs are draggier)... that it doesn't really help much. In payload fraction challenges the multistage airbreathing designs barely manage better fractions than the single stage designs.

In my TSTO mainly rocket design posted above, I found that I could forgo the separation, and take the whole stack to orbit, with a little more fuel left over... ie it performed better as a SSTO than a TSTO... at least operating within the confines of KSPs mechanics

 

1 hour ago, ZentroCatson said:

On the topic of SSTOs, I find them difficult to design, especially ones that are meant to carry a payload. That's why most of my SSTOs are for crew transfer.

Yea, I spend a lot of time developing a particular heavy lift SSTO, but once I had it... well, the payload flexibility is great.

Spoiler

(thats the result of docking the payload from the picture 2 up with the ssto from 1 above)

Eve lander? it can do it

 

Mk3 bay payloads?

 

 

47 minutes ago, DunaRocketeer said:

I'm sure there are ways of creating heavy-lift SSTO's that don't look like an ugly mess of tanks, engines and wings, but I haven't been able to make one yet,

I think this one should count:

I'm less sure about this one (a continued modification of the previouslty pictured huge SSTO):

Mk laythe cargo SSTOs aren't so bad either... I hope

 

(the one in the background is not an SSTO... except with a rapier rover that can load in the cargo, and fire engines with the rear bay open

[Empress Neptune]

I experimented with this and came up with a pretty reliable way of recovering the carrier plane. It's not the simplest mission though. You would basically launch the plane out of the atmosphere and carry a payload with a very high TWR. The rocket payload would get to a high Apoapsis before getting out of active ship range thanks to its speed and that would give you enough time to fly the carrier back to KSC. Naturally it's better to turn around on takeoff and head west before turning again so that you will be heading east toward KSC when staging, but this makes it take even longer.

 

I find SSTO's to be much better in general. I don't have any problem landing on KSC from orbit and the spaceplanes I use tend to have plenty of return fuel left over, so there isn't really a risk of crashing.

[wumpus]

3 hours ago, Firemetal said:

Do you mean like the space shuttle? Yeah I do use them occasionally but in a career save, SSTOS are more fund efficient. Find my Taurus Shuttle in the showcase thread in my sig.

Looks more like some of the preliminary shuttle designs.  They were a lot more like the Falcon 9, but with manned first stages that landed horizontally.

It certainly looks like a cool experiment, but nothing you would want in a career path.  I'm pretty sure you would start out using the flight manager mod (to land both stages) and eventually use the "stage recovery" mod to blow off landing the first stage.  Compared to "spacex style":

• Allows mortals to hit the runway for "100%" recovery (which might feel overpowered)
• Is *slow* up and fairly slow down (or not: note that OP didn't use jet engines.  These might be fast spaceplanes).
• Does not require parachute for landings not within a few km of KSC, more realistic.
• Since OP didn't use jets, this might work in Realism Overhaul, and always useful for pining for the "space shuttle you really wanted" (since the mechjeb needed for spacex to work hadn't been invented when the shuttle first flew, much less when it was designed).

[Archgeek]

SSTOs, so dull.  Weary of the acronym, really.  For lulz, how about a silly Buran-style shuttle on a Falcon-ish recoverable booster that goes and lands itself while the shuttle coasts to apoapse?  That sounds amusing.

[Firemetal]

2 hours ago, wumpus said:

Looks more like some of the preliminary shuttle designs.  They were a lot more like the Falcon 9, but with manned first stages that landed horizontally.

It certainly looks like a cool experiment, but nothing you would want in a career path.  I'm pretty sure you would start out using the flight manager mod (to land both stages) and eventually use the "stage recovery" mod to blow off landing the first stage.  Compared to "spacex style":

• Allows mortals to hit the runway for "100%" recovery (which might feel overpowered)
• Is *slow* up and fairly slow down (or not: note that OP didn't use jet engines.  These might be fast spaceplanes).
• Does not require parachute for landings not within a few km of KSC, more realistic.
• Since OP didn't use jets, this might work in Realism Overhaul, and always useful for pining for the "space shuttle you really wanted" (since the mechjeb needed for spacex to work hadn't been invented when the shuttle first flew, much less when it was designed).

TSTOs or my shuttle? SSTOS can carry things up to a size limit and for almost no cost. Then it is time to use rockets and if you can, recover the stages. At this rate, TSTOs are impractical.

[wumpus]

24 minutes ago, Firemetal said:

TSTOs or my shuttle? SSTOS can carry things up to a size limit and for almost no cost. Then it is time to use rockets and if you can, recover the stages. At this rate, TSTOs are impractical.

Thus my comment "nothing you would want in career mode".  Load in Realism Overhaul and it might make sense, but TSTO *rockets* are pretty much the standard.  The real catch is that parachutes really don't work all that well IRL* (they are good for capsules and salvaging cylinders of thick steel that hit the sea at over 100mph) so using horizontal landing is an option for those stages.

* not sure what happens in RO.  I have enough trouble relearning the aero model of 1.0+.

[Van Disaster]

You can make parachutes huge, they just get heavy ( and fairly bulky ) - KSP parachutes are OP, I agree.

This is fun if sometimes tricky to detach:

Spoiler

but these are rather more practical ideas.

Spoiler

I don't care for stock & I've used FAR since... probably 10 mins after discovering it in some teens version of KSP, but stock is close enough that ideas cross over ok. The ... let's call it suborbital kick booster idea is one I favour, lugging a boost stage up on jets is no big deal because of jet efficiency & it doesn't really limit jet top speed/alt much. Sure you're still carrying jets around in space but the whole system is less complex, and you may need some jets for recovery anyway.

My spaceplanes - particularily early ones with Junos for recovery flight - usually have enough jet fuel to fly half an atmospheric orbit *at least*; although I do generally try and glide recover them anyway, because it's fun. Sometimes, particularily with early flights where you haven't calibrated the recovery procedure, you miss by a long way...

Edited August 11, 2016 by Van Disaster

[GoSlash27]

8 hours ago, KerikBalm said:

Those were RATO packs that burn just enough to get a "modular" spaceplane into horizontal flight from a vertical launch from the runway... only a few seconds of burn before decouple, but after achieving orbit, I switched back, and there they were. I particularly like the launch escape system for awesome thrust for what... 1.5 seconds?

The other option is to decouple while on a suborbital trajectory, high enough in the atmosphere that it oesnt despawn and you can switch back in time after acheiving orbit.

KerikBalm,

 True, but I would never do that. My objective is to make a cheap reliable "space truck" that's easy to use. I'm not about to compromise that just to make it possible to recover a spent stage that I didn't need in the first place.
 TSTOs are fun to play around with in sandbox, but I have no use for them in career.
 

YMMV

-Slashy

[Firemetal]

7 hours ago, Archgeek said:

SSTOs, so dull.  Weary of the acronym, really.  For lulz, how about a silly Buran-style shuttle on a Falcon-ish recoverable booster that goes and lands itself while the shuttle coasts to apoapse?  That sounds amusing.

Coming from someone who doesn't know how to build SSTOs or Falcon 9 replicas.  

[Corona688]

Realistically speaking, you don't get the carrier back.  Theoretically you could, but with no one to fly it, it disappears once you're xx km away.

I've built spaceplanes that used droptanks.  That's less painful than dropping an engine.  I've never built a big spaceplane, though.  At some point in my designs they stop being elegant and just become the same application of overwhelming force, sideways.

[KerikBalm]

9 hours ago, GoSlash27 said:

True, but I would never do that. My objective is to make a cheap reliable "space truck" that's easy to use. I'm not about to compromise that just to make it possible to recover a spent stage that I didn't need in the first place.
 TSTOs are fun to play around with in sandbox, but I have no use for them in career.

I never claimed they were practical or fund efficient, I was just pointing out that *technically* you can stage before achieving orbit, and recover the spend stage.

FWIW, I have used RATO packs in career which I then recovered right there on the runway. I didn't make it like that for "efficiency" gains of a 2 stage, but to allow something to get into horizontal flight that was problematic to design for a horizontal takeoff (because the "payload" was a tail sitter Duna VTOL)... and I didn't want to give it enough airbreather thrust to do a vertical takeoff, so I gave it the detachable RATO packs.

In that case, it did allow for a cheap way to orbit. A Horizontal takeoff design would have been more complicated, sticking it on top of a SSTO rocket (or any rocket) would have been more expensive and complicated by the fact that the payload had lots of wing area that would make it unstable.

This was the payload in question:

Launched with modular "S"STOs

Although recovery of them was annoying, it was fun doing the experiment in career rather than sandbox

Playing KSP should be fun eh? if doing things in KSP is work not fun, then take a break. I'm not doing 4 recoveries for every payload I launch, but for that specialized payload, as a 1 off thing, I was willing to do the RATO staging and multiple recoveries.

 

That is the only time I used the RATO packs in my career save. I did experiment with putting them on large SSTOs that had trouble lifting off by the end of the runway as well... but it was just better to design them to not need the RATO packs.

[GoSlash27]

3 hours ago, KerikBalm said:

I never claimed they were practical or fund efficient, I was just pointing out that *technically* you can stage before achieving orbit, and recover the spend stage.

KerikBalm,
 True... but since the entire point of my spaceplanes is to be practical and fund efficient, these avenues are not open to me.

Best,
-Slashy

[TimePeriod]

I only use rockets and never find a need nor a use for any other design.

[Xyphos]

it depends on the payload and purpose.
if transporting a kerbal or three, to anywhere (except Eve or Tylo) Mk1 SSTO. (maybe even an SSTA)
if I'm launching a simple probe or comsat, Mk2 SSTO.
if I'm launching modules for a space station, Mk3 SSTO, unless it's too heavy, then I'll do a Mk3 TSTO.
Rarely will I ever launch a Rocket, that's too inefficient for my tastes.

Edited August 12, 2016 by Xyphos

[GoSlash27]

10 hours ago, TimePeriod said:

I only use rockets and never find a need nor a use for any other design.

^ Good point. There should be an option in the poll for "I don't use either".

Best,
-Slashy