Minimum equipment need for SSTO spaceplane?

[JeramyM]

With the recent release of B9 for 1.0.5 (thank you B9 team, love your stuff) I have been attempting to build a SSTO spaceplane.  But I am not sure I have the equipment to do so.  I just unlocked supersonic flight in the tech tree.  Can I do it with that or do I need to wait until I unlock hypersonic flight?

Edited December 17, 2015 by JeramyM

[Snark]

Pretty sure it's doable at low tech levels.

Relevant:

http://forum.kerbalspaceprogram.com/index.php?/topic/124883-the-sixx-kerbins-first-tech-level-6-ssto-spaceplane/#comment-2268363

[Pecan]

Tech 6: 

Tech 4:

 

 

[JeramyM]

Okay, cool.  Thank you.  So it's doable, I just need to tinker with it.

I just didn't want to waste time trying to do something impossible when I could use it getting science to getting the tech to do the thing I wanted to do.

[AeroGav]

I managed a very early spaceplane using 12 Junos and a Swivel.     It had fixed gear , which were blown off with radial decouplers on takeoff,  the Junos were able to get us to mach 1.3 and 13km or so,  then i'd light up the rocket.   At 17km I'd use decouplers again to blow the cluster of Junos off the wing when they flamed out.      Given that you're very likely to receive a contract to test a Swivel after unlocking basic rocketry, you can build this aircraft as soon as you unlock flight, beelining directly to flight and spending points on nothing else.

I'm currently playing a self imposed "no rockets" challenge in career mode, it's been quite a grind.  The Juno spaceplanes aren't good for much more than your first orbit and EVA reports over the Kerbin biomes, after that it's grind , grind and grind some more till you have Panther engines.    These have the advantage that you can build a vehicle that doesn't need to discard its jets every launch, which helps you save up for building upgrades.    After sending about 3 or 4 other spaceplanes up to orbit to refuel it, one of these Panther/Terrier craft finally made it to Minmus, which finally unlocked enough Science for the Whiplash.  Imagine things are going to kick up a notch from this point..

[Geschosskopf]

6 hours ago, JeramyM said:

With the recent release of B9 for 1.0.5 (thank you B9 team, love your stuff) I have been attempting to build a SSTO spaceplane.  But I am not sure I have the equipment to do so.  I just unlocked supersonic flight in the tech tree.  Can I do it with that or do I need to wait until I unlock hypersonic flight?

All spaceplanes are required to have a docking port and enough RCS fuel to dock.  If they don't have this, there's no point in building them at all because they can't do anything useful once they're in space.

Otherwise, you of course need the basic stuff of jets, rockets, intakes, fuel, wings, cockpit, and landing gear.  It IS, as @Snark pointed out (via @GoSlash27) possible to build low-tech spaceplanes, but without docking ports and RCS, they have about zero usefulness.

[Starhawk]

I use early career space planes for lucrative rescue contracts.  None of them have RCS or docking ports.

Happy landings!

[fourfa]

2/3 of my career staff are kerbals rescued by close rendezvous and EVA transfer.  Doesn't *require* RCS or ports, though certainly RCS makes the rendezvous simpler

[Snark]

5 hours ago, fourfa said:

2/3 of my career staff are kerbals rescued by close rendezvous and EVA transfer.  Doesn't *require* RCS or ports, though certainly RCS makes the rendezvous simpler

I populate my career exclusively with rescued kerbals.  Doesn't need RCS or ports at all-- I never bother with RCS unless I'm actually docking to something.  Matching velocity at rendezvous is trivially easy even without RCS, just point your nose target-relative-velocity-retrograde and blip the thrust until relative velocity is zero.

RCS is terrible-- it adds mass, it adds drag, it has a crappy Isp.  Its only saving grace is that it's really good when you need to be able to thrust in arbitrary directions without rotating your ship, and there's not any other good solution.  So it's perfect for docking, and bad for everything else.  (Well, okay, it can be useful in supplying torque for very large craft.  I just happen not to use it for that, myself.)

[ForScience6686]

Heck, for rescues I don't even match velocities.  Just get close enough to switch to the stranded astronaut and switch.  They have plenty of dv in their pack to catch up with the rescue craft, and I can usually leave my rescue craft in its elliptical orbit to catch the next rescue on the next pass.

[GoSlash27]

JeramyM,

 I would say that tech level 6 is the minimum for a practical SSTO spaceplane*, and it's marginal. There's no room for error or inefficiency at this tech level. If you don't feel confident in your ability to make efficient spaceplanes and fly them precisely, I'd recommend holding off until tech level 8.

They can be built at lower tech levels, but they won't have enough payload capacity to make it worth the effort. You can start making really good spaceplanes at tech level 8.

* "Practical" = crew capacity at least 4 kerbals, docking port, RCS, and at least 100 m/sec DV in orbit.

Best,

-Slashy

Edited December 18, 2015 by GoSlash27

[Geschosskopf]

20 hours ago, Starhawk said:

I use early career space planes for lucrative rescue contracts.  None of them have RCS or docking ports.

Happy landings!

 

16 hours ago, fourfa said:

2/3 of my career staff are kerbals rescued by close rendezvous and EVA transfer.  Doesn't *require* RCS or ports, though certainly RCS makes the rendezvous simpler

 

10 hours ago, Snark said:

I populate my career exclusively with rescued kerbals.  Doesn't need RCS or ports at all-- I never bother with RCS unless I'm actually docking to something.  Matching velocity at rendezvous is trivially easy even without RCS, just point your nose target-relative-velocity-retrograde and blip the thrust until relative velocity is zero.

RCS is terrible-- it adds mass, it adds drag, it has a crappy Isp.  Its only saving grace is that it's really good when you need to be able to thrust in arbitrary directions without rotating your ship, and there's not any other good solution.  So it's perfect for docking, and bad for everything else.  (Well, okay, it can be useful in supplying torque for very large craft.  I just happen not to use it for that, myself.)

I only rarely get more than 1 rescue contract offered per game year.  And when I do, it's so early in the game that I don't have anything more than a Juno, if even that.  So I do them with rockets when I do them at all,. and still make a hefty profit.  Rockets are cheap enough for me and far less trouble to make work.  Of course, the rockets don't need RCS or docking ports, either.  But it mystifies me how people get so many rescue contracts.  To fill out my roster, therefore, I must buy Kerbals.  And being as they're totally untrained noobs, I refuse to pay more than a token amount for them.  Yay for Custom Barn Kit :).  If I COULD just pick Kerbals as needed from the tree (and even turn a profit doing it), I most certailnly would.  But the opportunities I get for this occur only once every 5 or 6 games it seems.

So, the niche market of rescue missions aside, what good is an SSTO spaceplane based on Kerbin?  At the bottom line, it's just another way of getting something, usually something rather small or a handful of Kerbals, to and/or from orbit.  By the time I have the airplane parts to make even a marginal spaceplane, I already have the rocket parts to carry much bigger, more useful payloads to other planets, and they make so much money on contracts and milestones that they turn huge profits even if no part of them every returns.  This remains the case at every higher tech level from there on.  So I've never found an economic justification for Kerbin-based SSTOs.  Sure, they might save you some money, but it's an insignificant amount when taken in the context of your contract income by that point in the game, especially when factored against the player time involved to make the spaceplane work compared to making the rocket work.

Now all that said, I do enjoy making SSTO spaceplanes.  I think they're cool.  But I also consider them toys for the idle rich.  With stock parts, they just don't carry enough of a load to be worth the trouble to make or use on a regular basis.

[GoSlash27]

36 minutes ago, Geschosskopf said:

So, the niche market of rescue missions aside, what good is an SSTO spaceplane based on Kerbin?  At the bottom line, it's just another way of getting something, usually something rather small or a handful of Kerbals, to and/or from orbit.  By the time I have the airplane parts to make even a marginal spaceplane, I already have the rocket parts to carry much bigger, more useful payloads to other planets, and they make so much money on contracts and milestones that they turn huge profits even if no part of them every returns.  This remains the case at every higher tech level from there on.  So I've never found an economic justification for Kerbin-based SSTOs.  Sure, they might save you some money, but it's an insignificant amount when taken in the context of your contract income by that point in the game, especially when factored against the player time involved to make the spaceplane work compared to making the rocket work.

 

Geschosskopf,

 Spaceplanes are excellent for logistics duty; ferrying Kerbals and supplies to orbit (and kerbals back home).

 As you point out, most missions are not ideal for spaceplanes and they will not show adequate reward for the time and effort. But there are a few missions that *will* pay off big in career mode. Specifically missions that must be conducted constantly in career and only go from KSC to a station in orbit.

 If you can take advantage of this, you can spend a lot more time conducting science in your career and a lot less time fulfilling contracts for funding.

 Finally... don't assume that spaceplanes can't handle large cargo. They can... but they might not be the best solution for most situations. Except rocket fuel. If you can orbit and transfer "mass quantities" of rocket fuel with a spaceplane, you can pwn Kerbal Space Program.

 There's no point to any of this in sandbox mode. Career is where spaceplanes really shine.

Best,

-Slashy

 

[AeroGav]

I agree with Slashy , whilst lower tech Spaceplanes are very much a labour of love, at levels 8 and up they start becoming worthwhile on pure mass fraction/delta v considerations alone,  though some cargo loads have a shape that might fit easier on a rocket - though the converse is also true.

I've found spaceplanes particularly good at IRSU refineries - being SSTO, you'll arrive at the mining site with lots of empty fuel tanks that you might have discarded on a staged rocket, and your landing gear can be used to taxy around the surface looking for the best mining spot.

Also remember that people conflate SSTO, Re-usable  and Space Plane, but they are not necessarily the same thing.   SSTO rockets exist, some are re-usable.   Staged rockets can have re-usable stages.    And Space planes may use the atmosphere for jet engines and wing lift, but don't have to be single stage or re-usable. 

Here's a two stage vehicle from one of my career games.   Both come back to Kerbin intact, the airplane lower stage releases the rocket upper stage on a sub-orbital trajectory.     The rocket stage goes to Mun  , Minmus or Duna, re-enters on it's little stub wings then lands under parachute.   It's a wierd second stage because i was attempting to fulfill a few contracts at once - needed to explore Minmus, and rescue someone from Minmus orbit. I hadn't invented lander cans, and the mark 1 passenger cabin wasn't in game yet (version 1.04).

 

 

This is an example of a Space plane that's not an SSTO.    It's going to be my new reusable interplanetary crewed vehicle,  taking Kerbals from orbit to planetary bodies several times over.   At the front is a docking port so the service bay can be swapped out for ones with a different sensor kit as they get invented,  I've used modular fuel tanks to make the type 2 to type 1 adapters liquid fuel only.   At the rear, a docking port separates the propulsion section, some tanks that hold oxidiser only and an aerospike.    This can be upgraded to liquid fuel only tanks and an LV-N at a later point.

During ascent, it jettisons the jet engines, and eventually the nose cone, wings, tail, canards, everything it will not use as a spacecraft.   Wasteful, but as an interplanetary vehicle it should see several missions.   TBH, it would be a fairly awkward load for a rocket to launch in one stage as well. Especially given that i'd beelined aircraft techs and only had the smallest size rocket engines available - Thuds, Swivels, Aerospikes, Terriers.   I've never actually built a rocket that did more than put a Gemini capsule on the Mun, I'm just not that good at rocket building.

 

Here it is after discarding the aeroplane bits,  traversing Minmus.    Only takes about 600dv to taxy across the biomes, easier than landing a rover IMHO.

 

edit - the above vehicle is tech 8?  1 Aerospike and 2 Whiplash.     Once you unlock RAPIER and LV-N, your space planes can fly to minmus single stage, taxy over the surface and get all the biomes, then land back at KSC with all the science.

Edited December 19, 2015 by AeroGav

[Wanderfound]

A low-tech FAR option:

 

 

Craft file at https://www.dropbox.com/s/32tqilijw0igw7n/Kerbodyne%20Panther.craft?dl=0

 

As you can see, Panther-based SSTOs are possible, but the payload is minimal and the fuel margins are very thin. SSTO spaceplanes don't become easily practical until the Whiplash engines are available.

Once you do have your Whiplashes, however, the game is yours. SSTO tankers can lift fuel to orbit at minimal cost; nuke/RAPIER spaceplanes can easily explore the entire system if refuelled in orbit and/or given small ISRU rigs.

[Geschosskopf]

58 minutes ago, GoSlash27 said:

 As you point out, most missions are not ideal for spaceplanes and they will not show adequate reward for the time and effort. But there are a few missions that *will* pay off big in career mode. Specifically missions that must be conducted constantly in career and only go from KSC to a station in orbit.

Yes, spaceplanes do a good job of supply runs to stations in Kerbin orbit, but that begs the question----what career mode purpose is served by having a station anywhere in Kerbin's SOI?  Other than getting a big contract payout for launching the starter kit, and that only when it doesn't require something stupid like 5000 units of ore, I can't think of any.  Refueling systems within Kerbin's SOI cannot be justified either economically or playtime-wise, and the Mobile Processing Lab doesn't farm anywhere near enough science anywhere near fast enough to compete with a single trip to Minmus in a biome-hopper.  So why do you need a station at Kerbin?

[AeroGav]

45 minutes ago, Geschosskopf said:

Yes, spaceplanes do a good job of supply runs to stations in Kerbin orbit, but that begs the question----what career mode purpose is served by having a station anywhere in Kerbin's SOI?  Other than getting a big contract payout for launching the starter kit, and that only when it doesn't require something stupid like 5000 units of ore, I can't think of any.  Refueling systems within Kerbin's SOI cannot be justified either economically or playtime-wise, and the Mobile Processing Lab doesn't farm anywhere near enough science anywhere near fast enough to compete with a single trip to Minmus in a biome-hopper.  So why do you need a station at Kerbin?

This might sound daft, but surely if you're going to do IRSU at all, Kerbin SOI/ Minmus is the best place?   Since every interplanetary mission first has to make Kerbin orbit, and that requires more delta V than the interplanetary phase of the journey,  Minmus IRSU is very useful.  Though without the interstellar mod, you're pretty much done by the time you;ve got IRSU researched anyway.

[GoSlash27]

7 hours ago, Geschosskopf said:

Yes, spaceplanes do a good job of supply runs to stations in Kerbin orbit, but that begs the question----what career mode purpose is served by having a station anywhere in Kerbin's SOI?  Other than getting a big contract payout for launching the starter kit, and that only when it doesn't require something stupid like 5000 units of ore, I can't think of any.  Refueling systems within Kerbin's SOI cannot be justified either economically or playtime-wise, and the Mobile Processing Lab doesn't farm anywhere near enough science anywhere near fast enough to compete with a single trip to Minmus in a biome-hopper.  So why do you need a station at Kerbin?

 Primarily for construction of interplanetary missions. It's much easier to assemble large ships in orbit with empty tanks than it is to launch them all at once with a full load of fuel. And of course it makes more sense financially to refuel and reconfigure existing ships after their missions than simply jettisoning them and allowing them to burn up.

Best,

-Slashy

[Geschosskopf]

11 hours ago, AeroGav said:

This might sound daft, but surely if you're going to do IRSU at all, Kerbin SOI/ Minmus is the best place?   Since every interplanetary mission first has to make Kerbin orbit, and that requires more delta V than the interplanetary phase of the journey,  Minmus IRSU is very useful.  Though without the interstellar mod, you're pretty much done by the time you;ve got IRSU researched anyway.

No, actually a refueling system within Kerbin's SOI never pays off because 1) you have to invest a lot of money to set it up, and 2) you invest a huge amount of time setting it up and then using it.  The value you put on your personal time creates a hard cap on the number of times you'll use the system, which most people find is far less than the number of uses needed to pay off the initial money investment.

But even if that doesn't bother you, it's highly unlikely that you'll use the system enough to pay it off anyway, simply because you don't NEED to.  By the time you have the parts needed to create such a system, you should be rich enough that savings on launch fuel have an insignificant effect on your bottom line.  Furthermore, by this point, about the only place to save on launch costs is not having to lift the fuel for the transfer stage because your payloads will be making up the bulk of your mass and price.  If the payload is too big to fit in a spaceplane (which is likely), then you've got to use a rocket irreducibly big enough for the job.  And because you'll be using nuke transfer stages, they don't need much fuel anyway so don't have a huge effect on lifter cost.  Besides, the whole point of being rich is to just do what you want when you want.  If you want to go to Jool, you want to go now and can afford to go nonstop from the ground up

It has always been this way with all the mining systems the game has ever had.  None of them have ever been worth the time and money except at other planets.  This is largely a result of the toy size of the KSP universe, which keeps down the demand for, and therefore the price of, fuel.  The realworld planets to set up Lunar fuel systems simply are so unnecessary in KSP as to be economically unviable.  Now, if your thing is to model such systems for fun/coolness, knock yourself out.  But there is no way to justify doing them in economic or practical terms in KSP.

The 1 exception is to put your rockets on the pad less fuel, then launch an IRSU rover from the runway to fill them up on the pad.  Then recover the rover.  This effectively has zero start-up investment (due to recovering the rover) and isn't much of a timesink, so immediately turns a profit.   But it's pretty cheesy.

4 hours ago, GoSlash27 said:

 Primarily for construction of interplanetary missions. It's much easier to assemble large ships in orbit with empty tanks than it is to launch them all at once with a full load of fuel. And of course it makes more sense financially to refuel and reconfigure existing ships after their missions than simply jettisoning them and allowing them to burn up.

OTOH, it's way easier to send a scad of small ships and assemble those that need it at the destination :).

[JeramyM]

Thank you all for the excellent information.  Still tinkering away, made a suborbital plane last night, needs more fuel.

 

As for why I want spaceplanes.  They are pretty.  They may not be the most efficient/easiest way to do things.  I just like them.  Same reason I want an unreasonably large kerbin station.  It makes me happy to do so.

[AeroGav]

4 hours ago, Geschosskopf said:

No, actually a refueling system within Kerbin's SOI never pays off because 1) you have to invest a lot of money to set it up, and 2) you invest a huge amount of time setting it up and then using it. 

My bee-line tech order usually goes thus -

1.  Whiplash

2. NERV

3. RAPIER

4. IRSU

All of which can be obtained by farming Kerbin,  Minmus, and to a lesser extent, the Mun.   With these techs under my belt, i'd strongly dispute the "huge amount of money and time"  argument.

 

    Put a drill bit, IRSU convertor, gigantor solar array and small ore tank on one of your larger space planes, fly it to Minmus, land horizontally on the greater flats, brake to slow down, taxy to the NE corner, park it and leave it mining.     Done.     Subsequent space planes can fly to Minmus with a science payload, land, taxy up to the IRSU ship, connect with KAS and fill their tanks.   Now you're at Minmus with 6k delta V, a full suite of instruments, kerbals, in a vehicle with wings and wheels - you can go anywhere from here.

To get full tanks with low kerbin orbit refuelling instead (no IRSU), given that i'm generally down to 30% fuel by the time i make orbit , means another 3 flights and orbital rendezvous of clunky craft that weren't built with docking in mind.    Or a hell of a lot of in-orbit assembly (would rather gouge my eyes out).   Or a truly humungous single launch return rocket... beyond my skill to construct, or fly.

 

The problem with IRSU is that once you're at that point, I tend to loose interest in the career game, it is effectively "won".    Why leave Kerbin SOI for more science, when there are no techs worth discovering.    Electronics for better unmanned probes?  Why, I can go everywhere fully Kerballed.    Ion drive?  Why, I have tons of fuel and NERV, delta V is not a problem.      Type 3 rockets?  Ok, to launch what exactly?  All  the hardware i need to go anywhere is already in orbit.

You see, when you get down to it, flying aroud Eeloo is not actually that fun.   The fun is in designing new vehicles, making it to a new planetary body is great because it validates your design and piloting skills and means you're about to unlock the science for more components.   When you no longer need to design new vehicles, and there's nothing left in the tech tree that excites you,  it gets a bit meh.    Well, hopefully Interstallar can fix that.

 

 

Edited December 19, 2015 by AeroGav
PHOTOBUCKET links not working

[AeroGav]

I'd also say that credit to the developers, the game is agnostic to the spaceplane vs rocket debate.     You can complete the game building exclusively one or the other, it doesn't matter.     You can IRSU or not.    You can meticulously fly everything up in aircraft then back down to the runway again, getting 100% recovery on every flight.    But,  in the time it took you to do that, you could have launched half a dozen disposable rockets,  and spammed contracts to make up the money.  In any case, upgrading your buildings costs far more than launch hardware.