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CoreI

Medium Tech Mk2/Mk1 SpacePlane

Question

So, in my career I have been searching for low cost ways to get crew/cargo into orbit. I do have a functional Falcon 9 replica (no barge), but that still costs money. So, in short I need an Mk2 or Mk1 SpacePlane that can SSTO and dock. However, I do not have the Whiplash, RAPIER, Goliath, Vector, or Aerospike engines.

Any tips/designs? Thank in advance!

Edited by CoreI

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A Panther will take you up to 800-900ish m/s and an altitude ~20 km.  Stick an appropriate rocket engine on there, and you ought to be able to get to orbit without too much trouble.

Though what "low cost" means depends on your definition of "cost" and on your play-style.  For example, in my own games, a staged rocket to orbit is cheaper than an SSTO.  Why?  Well, it may cost more funds... but not much more.  But it takes a lot less of my time.  And I measure cost not in funds, but in my time, since that's the really precious resource for me.  After a few launches, I can use the gameplaying time I've saved by not going SSTO, and spend it on dashing off a quickie contract that pays far more than the money I would have saved with a spaceplane SSTO.

That's just for me-- won't necessarily be relevant to someone who has a different play style or priorities.  Just something to bear in mind when you're determining which style works best for you.

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MK1 SSTOs are far easier to get to orbit than MK2. MK2 parts have perhaps 3 times as much drag as equivalent MK1. So for crew transports to orbit, generally MK1 is a better choice. The low drag of the parts makes them a little harder to reenter, though -- they have heating issues.

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I've tried panthers, but at my tech level the intakes are insufficiently powerful to get the panthers up to 20km without flameout. Although, I could put side tanks on and pop more intakes on them.

I see what you mean with in-game money and RL time. For me I tend to prioritize in-game funds. Although, I did manage to build an SSTO that launched vertically a few weeks ago (it could also come in really steep because it had tons of drag from the large amount of wings it had to life a dozen Mk1 fuel tanks), but the cost of the massive amounts of fuel involved made it more practical to stick with Falcon replicas.

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5 hours ago, CoreI said:

I've tried panthers, but at my tech level the intakes are insufficiently powerful to get the panthers up to 20km without flameout. Although, I could put side tanks on and pop more intakes on them.

That's probably not an intake problem.  All engines have built-in thrust curves based on both the engine's speed and altitude.  Once you get high enough, engines will flameout eventually regarding of how many intakes you have.  So you're probably getting all you can out of the Panther - it's just not great for high-altitude flight.

Note also that air requirements are a binary thing - either the engines have enough (in which case they supply thrust based on those speed and altitude curves) or they don't (in which case they stop working entirely). 

If you're running Kerbal Engineer Redux there is a readout on the "Vessel" tab that shows the percentage of intake air you're actually using.  MechJeb might have something similar; I'm not sure. As long as that number is less than 100%, you have enough intake air, and adding more intakes will not help (but will add drag).  

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I settled on a recipe for mid-tech spaceplanes that's a little cheaty but a lot of fun and very usable.  Mount two Terriers (or four if it's bigger with a bit of payload), attach Panthers to the back.  Disable the shrouds on the Terriers.  Clip the Panthers forward so the Terrier engine bells are hidden inside the Panthers.  Set Panthers to afterburner, launch on jets, stage Terriers when you start losing speed (anywhere above ~10km and they're good to go), the Panthers will flameout on the way to orbit.  

Terriers are a little light on thrust - it'll help to have plenty of wing and give it a little static incidence (5 degrees or so) and try hard not to get far off prograde.

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https://kerbalx.com/AeroGav/Firefox-II

 it uses nukes and a whiplash.   You could replace the whiplash with a panther and it should still work, looses a little delta v because airbreathing velocity will be about 770 not 1100 ish.   The biggest issue is that panther only weighs 1.2ton instead of 1.8 and it's already nose heavy, might need to offset nukes backwards v slightly to get a good balance.

.. actually I think it's got pre-coolers which you won't have either.   Any old intake will do for panther but replacing those might introduce other balance changes.  

MK2 low tech spaceplanes absolutely need angled wings to avoid the massive drag of mk2 fuselage, but that messes with the CoL indicators and makes adjusting handling very time consuming.

 

Alternatively look on my KERbalX profile for "Coopie". This is a panther/terrier mk2, but it's much larger ship to lift same cargo, with less dv

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14 hours ago, CoreI said:

So, in my career I have been searching for low cost ways to get crew/cargo into orbit. I do have a functional Falcon 9 replica (no barge), but that still costs money. So, in short I need an Mk2 SpacePlane that can SSTO and dock. However, I do not have the Whiplash, RAPIER, Goliath, Vector, or Aerospike engines.

Any tips/designs? Thank in advance!

When in doubt, @Matt Lowne

Edited by Lo Var Lachland

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12 hours ago, AeroGav said:

 

https://kerbalx.com/AeroGav/Firefox-II

 it uses nukes and a whiplash.   You could replace the whiplash with a panther and it should still work, looses a little delta v because airbreathing velocity will be about 770 not 1100 ish.   The biggest issue is that panther only weighs 1.2ton instead of 1.8 and it's already nose heavy, might need to offset nukes backwards v slightly to get a good balance.

.. actually I think it's got pre-coolers which you won't have either.   Any old intake will do for panther but replacing those might introduce other balance changes.  

MK2 low tech spaceplanes absolutely need angled wings to avoid the massive drag of mk2 fuselage, but that messes with the CoL indicators and makes adjusting handling very time consuming.

 

Alternatively look on my KERbalX profile for "Coopie". This is a panther/terrier mk2, but it's much larger ship to lift same cargo, with less dv

https://kerbalx.com/AeroGav/Firefox-I

OK real quick and dirty mod to make this whiplash nerv ship into a panther nerv.

used one panther and two junos (?!) since they weigh about the same as a whiplash.   Changed the pre-coolers for diverterless ramp intakes.

20170112221726_1_zpsyqkvt4pm.jpg

Abort action group toggles nukes, or just activate via staging sequence.  

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Since when is NERV-A medium tech? Isn't it a 550 node?

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2 hours ago, fourfa said:

Since when is NERV-A medium tech? Isn't it a 550 node?

The OP didn't mention it as an engine he did not have.    I haven't built any panther/nervs before, since in my career games i acquire whiplash first.   They are both 500 tech cost parts, but if you've gone after spaceplane tech from the very start like i do, it's one node away from something you'll have already,   whereas getting the NERV requires unlocking several rocket and fuel tank techs i otherwise wouldn't bother with.

But , it seems a lot of people develop their rockets first, and may have 2.5m engines and nervs before they even unlock aviation.   This is something for these guys...

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3 hours ago, fourfa said:

Since when is NERV-A medium tech? Isn't it a 550 node?

Terriers and Swivels both seem like viable, lower-tech options.  I've generally used LFO engines for planes that only go to LKO, and NERVs for planes that go further.  Obviously there's a set of tradeoffs with LFO engines vs nukes: lower weight, more thrust (for the Swivel), cheaper(if that matters), but higher fuel consumption.  And you need to deal with balancing two resources instead of just LF, of course.  

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On 12 January 2017 at 8:20 AM, CoreI said:

So, in my career I have been searching for low cost ways to get crew/cargo into orbit. I do have a functional Falcon 9 replica (no barge), but that still costs money. So, in short I need an Mk2 SpacePlane that can SSTO and dock. However, I do not have the Whiplash, RAPIER, Goliath, Vector, or Aerospike engines.

Any tips/designs? Thank in advance!

Built for FAR, and a bit old now, but the basic ideas should be obvious:

https://kerbalx.com/Wanderfound/Kerbodyne-Panther

https://kerbalx.com/Wanderfound/Kerbodyne-Panther-Twin

Panther based SSTOs are very doable, but they're limited in range and capacity. Light cargo and low orbit only.

Basically: low weight, low drag, get as high and fast as you can before adding the rockets. Carry a bit more oxidiser than you would on a higher tech SSTO; the rockets will be burning for longer. Thuds, Terriers and Swivels are good for the oxidising phase.

Low tech parts have low heat tolerance; use a gentle reentry and keep your nose high until you level off.

Edited by Wanderfound

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I found pics of my mid-tech career SSTO:

ERObjVZ.jpg

4OyyQ4o.jpg

Two panthers, four Terriers.  Extra fuel, RCS thrusters, solar, and science cans in the cargo bay.

Edited by fourfa

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I can throw it up on kerbalx later.  not much to reveal that you can't see - wings at 5 degrees incidence, tailplanes flat.  Center of mass is nearly stationary, just under those RCS thrusters.  Oscar-B fuel tanks in the center of the Round-8 tank stack, about half the Round-8s have no oxidizer. Lift center a couple notches behind CoM.  Oh, and a heat-protecting Comm-16 on the nose.

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 My curiosity was about design performance specifications.  Probably not the best choice of words,  my bad. 

 

Anyway,  a craft file to test it myself would be very nice.  I'm starting to play with spaceplane and something better than my own designs may be of great help to practice. 

 

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On 1/12/2017 at 11:30 PM, AeroGav said:

The OP didn't mention it as an engine he did not have.

 I do have The NERV. 

 

On 1/11/2017 at 6:39 PM, bewing said:

MK1 SSTOs are far easier to get to orbit than MK2. MK2 parts have perhaps 3 times as much drag as equivalent MK1. So for crew transports to orbit, generally MK1 is a better choice. The low drag of the parts makes them a little harder to reenter, though -- they have heating issues.

Hmmm. I have never tried doing it with Mk1. Would reentering shallower help with heating? Or perhaps more wing surface area could help slowing down.

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1 hour ago, CoreI said:

 I do have The NERV. 

 

Hmmm. I have never tried doing it with Mk1. Would reentering shallower help with heating? Or perhaps more wing surface area could help slowing down.

 

Just keep the nose up as you reenter:

PSFTwBa.jpg

 

As for a basic design idea:

puIEtwP.jpg

Two Panthers, one Twitch (for circularisation and orbital manoeuvres), two Thuds (for apoapsis lifting).

Edited by Wanderfound

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16 hours ago, CoreI said:

 I do have The NERV. 

 

Hmmm. I have never tried doing it with Mk1. Would reentering shallower help with heating? Or perhaps more wing surface area could help slowing down.

It is tricky to re-enter safely on a mk1 pointy cockpit and also a panther/nerv spaceplane is likely to overheat on launch.   The inline cockpit gets much less incoming heat from being further back in the ship - if you can put a couple of items ahead of it in the stack  - eg. diverterless supersonic intake, then an ncs adapter and a small nose cone right at the tip, you should be good.  Plenty of wing area will help on re-entry too,  and on launch if you are using the nerv.  Not so much use with a chemical rocket.

The only reason to go mk2 is if there is no alternative to mk2 cargo bay.

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Alright guys,  i've had some time to properly tune the Panther/NERV version of my mk2 ssto .  

 

https://kerbalx.com/AeroGav/Firefox-I   (updated craft)

20170115201301_1_zpszqmzcd5x.jpg

Got rid of the silly Junos, added a bit of extra fuel.  Removed some wings with the idea of having it level off at 14km for the speedrun (Whiplash speedruns take place at 17km so need more lift).  It runs a bit hotter on the nuke powered ascent as a result, and gets a slightly lower l/d ratio, but it's easier to hold the nose down in airbreathing mode so reduces the porpoising. 

2500dv in low kerbin orbit, which isn't bad.    My panther/terrier ship has the same cargo bay, but looks like this

20161121175806_1_zpsx5gxkbqt.jpg

It is 9 tons heavier than the "firefox" but has less delta V in orbit, and gets much closer to melting its nose cone off on ascent.

Incidentally, i did try a single panther two nuke version of Firefox 1.   It maxed out at 260m/s at 6km alt,  so i just pressed space bar with SAS set on prograde to see what happens.    It did actually get to orbit , but only had 1800dv so the quad motor seems superior, though you could improve on that with a more intelligent flight profile i'm sure.

Edited by AeroGav

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6 minutes ago, AeroGav said:

only managed 2k delta v to LKO

 

1 hour ago, AeroGav said:

It did actually get to orbit , but only had 1800dv

Do you mean it has this amount left over once it's in orbit?

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39 minutes ago, CoreI said:

 

Do you mean it has this amount left over once it's in orbit?

yes

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10 minutes ago, AeroGav said:

 

50 minutes ago, CoreI said:

 

Do you mean it has this amount left over once it's in orbit?

yes

 

Whoa. I had a working Mk2 SSTO (thanks to Scott Manley for the design) a few versions ago in an old save before the whiplash was moved further in the tech tree. It could just orbit and revondouz.

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