I solved the 'getting my spaceplane to far-away survey missions' problems: now a SRB question

[JoeSchmuckatelli]

I foolishly accepted a bunch of "test the temp above 19,000 on the far side of Kerbin" missions early on in my campaign.

Built a great mid-tech plane that can get to that altitude and is fun to fly - and anyone from Val to my most pencil-necked scientist or thick shouldered engineer can land... except trying to get to the far side of Kerbin at 300m/s bores me. 

Spent a couple of days blowing up stuff and failing to get any rocket to carry any plane that can fly (read: I can build a rocket, and I can build a plane, but I can't build a rocket that can carry a plane) - so those missions never got met.  Out of frustration, I just boot-strapped a quad of Kickbacks to my good plane via radial decouplers, girders and struts - which got me a good 1/4 of the way around Kerbin and allowed me to gobble up 3 of the survey missions.  Now I have to get fully 1/2 of the way around the planet (I really need money to upgrade R&D so I can keep climbing the tech tree).  The resulting 'rocket plane', while functional, offends my sense of 'what should work' aesthetics... but it worked.  So on to the question:

The Kickbacks offer somewhere near 500 max thrust at sea level, while the next engine up, the Pollux, offers over a thousand.  Does the 'thrust limiter' work linearly?  Saying, if I replace the Kickback's with Polluxes, and then limit the thrust - can I reasonably expect to get 1/2 way around Kerbin before dumping them and starting to fly?

[jimmymcgoochie]

I’d say it was better to research and unlock the Panther turbojet engine plus supersonic air intakes which can fly considerably faster and higher than the Wheesley and will require only minor tweaks to your plane, rather than trying to add 1.875m boosters in place of 1.25m ones which will cause a lot of mass and drag changes that could make your plane really hard to fly. A plane powered by Panthers should be capable of supercruising at 19km or even higher at speeds of 800m/s or more, and at that altitude the engines don’t use much fuel either so your range is much better than you might think.

Alternatively you could try an autopilot mod and fly at x4 speed; using a mod like Kerbinside that adds additional launch sites which might be closer to where you’re going; or building a small plane and sticking it inside a fairing on top of a rocket to get to your destination faster.

[JoeSchmuckatelli]

@jimmymcgoochie  I've got the panthers on the jet - they're how I can gobble up any suborbital missions (and land for the surface ones).. It's a great plane - but even if I get it up to 500m/s... Flying to the far side of the planet takes so long its not fun. 

 

Interesting to hear you say you can supercruise at 19k.  My plane (which is reminiscent of an F-15 = two closely spaced panthers) does not like to hang out at that altitude.  I'm (IIRC) getting up to the 500m/s zone at  10k, then 'punching it' to gain altitude just before entering the zone.  Usually end up topped out in the 25k altitude (although I have been higher) , drifting, engines flamed out and waiting to fall back into the atmosphere.  

What's your set up to cruise at 19 / 800?

 

Edit: I'm using the radial intakes... is that holding me back?  Also, when you say supersonic, are those available below the 500 cutoff (b/c that's my problem atm... not enough money to upgrade the R&D to get higher level tech).

Edited May 19, 2020 by JoeSchmuckatelli

[swjr-swis]

1 hour ago, JoeSchmuckatelli said:

What's your set up to cruise at 19 / 800?

Mk3-body plane using Whiplashes, cruises at 20-22km @ 1150m/s, can completely circumnavigate Kerbin with fuel to spare... and it has cargo room: https://kerbalx.com/swjr-swis/Transport-3a

Look specifically at the way the wings are placed and the CoM/CoL locations. You can replicate similar performance with Panthers and Mk2 or size 2/1 bodies, although it'll be a slightly lower cruising speed.

(This plane is an evolution from an original by @Hotel26, so definitely check out other designs from him).

 

A panther-based flying wing that can circumnavigate cruising at Mach 2.5 @ 22km: https://kerbalx.com/swjr-swis/Flying-Wing-Starboost88

Looks very different, but you'll notice the wing placement and CoM/CoL are very much alike. If'n it works...

 

 

[jimmymcgoochie]

@JoeSchmuckatelli Ramp intakes, either radial or stackable where circular intakes would go, will work well at higher speeds, and shock cones are better still but also much further along in the tech tree. I’m not sure where they sit in the stock tech tree as I’m using a modified tech tree right now- possibly one node up from the Panther itself? The Mk1 diverterless intake is a good replacement for engine nacelles to get a bit more speed too, and the XM-850 radial intakes aren’t recommended as they work poorly at high speeds; likewise circular intakes and engine nacelles don’t do nearly as well that high and that fast.

I’ve made plenty of Panther powered Mk2 bodied jets that can comfortably cruise at 800-900m/s and up to 20km altitude, but I suspect they were using engine pre-coolers and ramp or shock cone intakes which are more effective at supersonic speeds.

[JoeSchmuckatelli]

18 minutes ago, swjr-swis said:

Mk3-body plane using Whiplashes, cruises at 20-22km @ 1150m/s, can completely circumnavigate Kerbin with fuel to spare... and it has cargo room: https://kerbalx.com/swjr-swis/Transport-3a

Look specifically at the way the wings are placed and the CoM/CoL locations. You can replicate similar performance with Panthers and Mk2 or size 2/1 bodies, although it'll be a slightly lower cruising speed.

(This plane is an evolution from an original by @Hotel26, so definitely check out other designs from him).

 

A panther-based flying wing that can circumnavigate cruising at Mach 2.5 @ 22km: https://kerbalx.com/swjr-swis/Flying-Wing-Starboost88

Looks very different, but you'll notice the wing placement and CoM/CoL are very much alike. If'n it works...

 

 

If that 'FatBoi' can supercruise, then I'm excited to unlock those parts; been wanting a way to carry a rover around!  Also; now I'm inspired to try a flying wing design as well!  

 

EDIT:  after reading the links -- are people playing KSP with joysticks?  I've got an old Sidewinder (which may have been used on a Win 98 machine)… I wonder if that would work.

Edited May 19, 2020 by JoeSchmuckatelli

[swjr-swis]

10 minutes ago, JoeSchmuckatelli said:

are people playing KSP with joysticks?  I've got an old Sidewinder (which may have been used on a Win 98 machine)… I wonder if that would work.

Some people are, but note that it's not straightforward to get them working on KSP. From what I've read here in the forum, it's recommended to use certain mods to get best results. Me myself, I use keyboard and mouse, and no mods, so I design my planes to work with those.

[bewing]

If your plane can't go supersonic with panthers on it, then it's either got way too much drag, or you are not using the afterburners.

Too much drag probably means that you are using MK2 parts, because they tend to be very draggy. A streamlined plane can easily supercruise at 800 m/s at 20km altitude, and circumnavigate the planet.

 

[JoeSchmuckatelli]

5 minutes ago, bewing said:

If your plane can't go supersonic with panthers on it, then it's either got way too much drag, or you are not using the afterburners.

Too much drag probably means that you are using MK2 parts, because they tend to be very draggy. A streamlined plane can easily supercruise at 800 m/s at 20km altitude, and circumnavigate the planet.

 

I've just learned that it can.  Pilot error was holding me back.

Apparently, the correct way to fly is to level out at 9 (where the plane 'likes' to be) and punch up the speed with only a little elevation added; it will then climb to 15-18 and cruise along in the 750+ range for as long as I like.  

My old method used too steep of an angle of attack.  -- Oh, and I am using Mk 2 stuff; its the best I've got.

Learning has occurred.

Edited May 19, 2020 by JoeSchmuckatelli

[bewing]

2 hours ago, JoeSchmuckatelli said:

Oh, and I am using Mk 2 stuff; its the best I've got.

MK2 stuff is pretty, but MK1 is far superior for building planes with.

[JoeSchmuckatelli]

Filing that away for future reference! 

[swjr-swis]

9 hours ago, bewing said:

Too much drag probably means that you are using MK2 parts, because they tend to be very draggy. A streamlined plane can easily supercruise at 800 m/s at 20km altitude, and circumnavigate the planet.

While I would usually recommend taking @bewing's advice, this is one area where I feel people keep holding on to 'well-known' design wisdom that has been proven wrong. Yes Mk2 can be draggier than other crosssections, if one ignores other much more important design details. In particular, when the plane is built with proper angle of incidence on the wings, allowing its body to stay pointed close to prograde on cruise, drag is minimized and an Mk2 body has hardly any influence anymore.

Proof of concept, a science explorer aircraft using an Mk2 body and Panther engines that can circumnavigate with fuel to spare even on less than full tanks. Cruise: Mach 2.77 (825 m/s) at 19-20km.

Provide enough wing surface, some angle of incidence, keep CoM stable and CoL close, and you have most potential performance issues solved before even tweaking your design. Note that I even included some notorious drag-inducing features in this plane (radially attached intakes and a ladder), and huge wings, but the plane still has no problem going supersonic.

Spoiler

Mach 2.77 at 19km (20km with tanks emptying)

Get anywhere on Kerbin in under 45 mins, full circle in 1h25.

 

9 hours ago, JoeSchmuckatelli said:

Apparently, the correct way to fly is to level out at 9 (where the plane 'likes' to be) and punch up the speed with only a little elevation added; it will then climb to 15-18 and cruise along in the 750+ range for as long as I like.

All depends on the build. The above plane can climb at a 45 degree angle with afterburners on and you can wait until reaching cruising altitude to level out, by which time you're already going supersonic. Or you can let it take off and climb to cruise altitude all by itself without ever touching the controls. I'm not even really fine-tuning with this, everything is placed and angled in (fine) snap mode, which makes it easier to replicate in your own designs.

[TheFlyingKerman]

The trick for long, efficient flight is the prograde lock autopilot. You just need to tune the wing incidence so that the plane holds the desired altitude. Give this a try

https://kerbalx.com/TheFlyingKerman/LKA-1CIII

920m/s at 12000m and hands off flying.

[AHHans]

10 hours ago, bewing said:

MK2 stuff is pretty, 

Yes.

10 hours ago, bewing said:

but MK1 is far superior for building planes with.

No!
It might be lighter and faster, easier to get into orbit with less fuel used, and all that. But it doesn't look as good, so there!
Oh, yes, and MK1 cockpits are in more danger of overheating.

[Klapaucius]

I don't know if this is helpful or not, but a bunch of us manged to push solid rockets pretty far. These are all SSTOs, but you can probably adapt some of the designs.  I'm not sure what you have on the tech tree or not, but perhaps this will be helpful: