Kerbodyne SSTO Division: Omnibus Thread

[Somtaaw]

The biggest problem with that idea is the difference in mass of the two engines. The RAPIER is a pretty heavy engine for what you get, the LV909 is not. This would shift your CoM towards the nose of the craft throwing off the handling and balance of the aircraft. On the otherhand you have Aerospikes available which are almost the same weight and wont change the CoM that much if at all and have better ISP then the 909s or the RAPIERs. The other downside is the loss of half of your air breathing engine power will have an affect of increased climbing time, longer runways for take off and a much slower acceleration to speed for orbital burn.

Most cases I usually design a new craft for exclusively that reason just to take stuff to and from my space station at 100km orbit. The same SSTO also takes satelites and places them in Geosync orbit, pretty sad that it flew all the way to 2868.5km x 2868.5km orbit and managed to launch 2 satelites then return back to the KSC over shoot by 400km turn around then fly back to land.

I can understand that, but what I meant is more for after I hit my station. I designed my SSTO to primarily actually fill the role very much like the US shuttles. It lifts cargo and crew to my station, performs general operations, and then brings crew back to the ground. Emphasis on my shuttle is the general workhorse in space.

My Space Station

in the bottom right hand, is where my shuttle would dock, refuel, potentially pick up probes or satellites for it to move around. So if I use two of those docking rings to park say:

docking clamp

Remote control ring small

small rcs fuel block with a ring of rcs thrusters

LV-N engine

Then attach 2 of my RAPIER engines through docking clamps, so after I hit orbit/dock, I just eject the rapiers, swap in the LV-Ns and now it's a space workhorse, until such time as I need to land. Park the nukes back on the station, and land purely using 2 RAPIER engines. at that point I recover the plane, and if I relaunch it, it goes up with 4 RAPIER again. Or am I thinking like an idiot, and need to roll up a newspaper to hit myself for being bad?

[Wanderfound]

Now the only tricky part is figuring out how to adjust my recently completed space station mark 2, code named Hephaestus, to include a good docking section for this beauty of a plane.

Now would you say I over muscled the base design, by going with 4 RAPIERs for the core weight?

Also, would you say that swapping out 2 of the RAPIER engines for say LV-909's or another variant of interplanetary engine would be easily done? Or would that require considerably redesign?

I'm a big fan of modular, so perhaps slide 2 docking clamps in likely onto the wings, for interchangable engine assemblies? I think in the end it might be very similar to your latest Impatienze design, just with twin expanded engines over the one.

Well, from the POV of "minimum thrust required to go to space", then yeah; it's got about four times as much engine as it needs. But there's nothing wrong with that; why fly a truck when you can fly a sportscar?

This is a large part of the appeal of spaceplanes. Because of the 100% recovery thing, the easy refuelling and the efficiency of jets and wings, there's no need to scrimp and save and economise mass like you do with rockets. You can afford to overpower it, you can afford to load up on "luxuries" like science gear and mod parts (TAC-LS, Scansat, etc), you can afford to build omnicapable multipurpose things instead of having to specialise.

If I was going for extreme long range, I'd either swap the lateral engines for LV-N's or change the tail bicoupler and engines for a single Mk2->1.25m adaptor and a single LV-N. Do that, and you could fly it direct from KSC to Laythe.

But it wouldn't be nearly as much fun to fly.

For a longer-ranged but still high-speed design, I'd be inclined to swap the lateral engines for Aerospikes. Any of the engine swaps is going to require a bit of adjustment to maintain the weight balance, but that's mostly just a matter of shifting the lateral tanks a bit forwards or back on the main fuselage.

The lack of rigidity in docking ports makes modular engines tricky unless they're low-thrust. LV-N/909s are okay, but if you then swap out to a high-thrust option it'll probably wobble all over the place.

This is why the modular bits on the Impatienze are just unpowered trailers: the only thrust on that ship (the lateral RAPIERs) acts to pull the docked sections straight rather than pushing them crooked.

As it is, it can easily reach orbit with tanks better than half full, and the demonstration science probes and Fine Print satellites that I stuck in the cargo bay each have a few thousand m/s of ÃŽâ€V of their own. It can launch those satellites from LKO into pretty much any position in the Kerbin system (i.e. Kerbin/Mun/Minmus) without even visiting your space station. If you do go for an orbital top-up, the mothership could take itself interplanetary as well.

Edited November 28, 2014 by Wanderfound

[Somtaaw]

Might give it a try then, and call it the OOPS Mk 4. Turn the lateral RAPIERs into ready to nuke propulsion. I especially like that you helped keep my design very streamlined and tight, because if you look at my space station, which is still being produced and docked together, the location of my docking ring is eventually going to be fairly cluttered. I needed a plane that could slide in, dock, pick up what it needed, and then either back out or rotate and slide through like a stiletto.

I'll post a screenie after I get the mildly redesigned Mk 3K up.

[Wanderfound]

Might give it a try then, and call it the OOPS Mk 4. Turn the lateral RAPIERs into ready to nuke propulsion. I especially like that you helped keep my design very streamlined and tight, because if you look at my space station, which is still being produced and docked together, the location of my docking ring is eventually going to be fairly cluttered. I needed a plane that could slide in, dock, pick up what it needed, and then either back out or rotate and slide through like a stiletto.

I'll post a screenie after I get the mildly redesigned Mk 3K up.

Careful you don't bump the wings; snapping one off while in space can make reentry a bit awkward.

My stations often have a specialised spaceplane port, stuck out on an extension to provide docking room:

[Somtaaw]

Posted a link to mine. Currently the only docking ring is sticking out on its own, so easier to dock to. But eventually I'll be building out beyond each docking ring, and/or sticking more spacedocks to build upto 4 additional rockets or planes directly in orbit. Then I'll have to start really worrying, but better to design the base design now, and only have to fine tune later.

Currently each piece of my station is somewhere between the mark 3 and mark 5, depending on the refit cycle.

[Rakaydos]

So I've been testing the Manticore V5, based on the craft entered in the contest. Having used flaps to move my "neutral pitch" to a high lift area, I'm starting to have problems with reentry stalling.

https://www.dropbox.com/s/vv6fa6vlf47qucr/Manticore%20v5.craft?dl=0

1: Toggle raipier settings

2: Toggle raipiers

3:Toggle turbojets

9: toggle belly Vtol RCS (double click on physics load to turn off)

0: Toggle cargo/docking bay

Since the flaps positioning is most of what changed between the Mk3 and the Mk 5 (mk4 was a different apprach to Vtol that had it's own issues), is there a way to change "flap settings" for reentry?

Edited November 29, 2014 by Rakaydos

[Wanderfound]

Cool; I like the ring-hangar.

What's the blue thing on top?

[Wanderfound]

So I've been testing the Manticore V5, based on the craft entered in the contest. Having used flaps to move my "neutral pitch" to a high lift area, I'm starting to have problems with reentry stalling.

https://www.dropbox.com/s/vv6fa6vlf47qucr/Manticore%20v5.craft?dl=0

Since the flaps positioning is most of what changed between the Mk3 and the Mk 5 (mk4 was a different apprach to Vtol that had it's own issues), is there a way to change "flap settings" for reentry?

Got a screenshot?

Although this isn't how the terms are defined in the real world, in FAR the only difference between "spoiler" and "flap" is that spoilers toggle to full deflection and back with a single action, while flaps shift in three stages (requiring two action groups, one to increase, one to decrease). Either way, you can set the deflection to whichever way you choose.

If the flaps are causing trouble, just deactivate them during reentry. Or consider setting up opposing surfaces to act as neutral-pitch airbrakes:

[Somtaaw]

the blue thing on top is part of ExtraPlanetary Launchpads (I think), and it's a recycle bin. Turn it on, and anything that comes close to the bin vanishes. Technically I should have another piece of EPL attached to the recycle bin so it helps manufacture rocket parts, but :effort:. I'll get to it when I get to it.

I should get around to building a better docking ring, but at its core.... uhh, Docking Ring in VAB. Simplicity at its best, although I'd tweaked it slightly to halve the available lighting on the ring itself. So for it's mark 3 iteration, I'm likely going to add at least one or two more brackets to extend how far out they reach. Hopefully enough so it won't interfere with the neat Assembly Ring mod I found. As an avid Trekkie fan, I just had to have it, and it comes in 1.5m, 2.5m and 3.5m assembly. That's only the medium, because I don't need to build 3.5m rockets in space.

[Rakaydos]

Got a screenshot?

This one does what I want on the way up:

This one does what I want on the way down:

The changes to the foward canard may be a little difficult to replicate, but is there any way to "re-set neutral" on the trailer flaps?

[Wanderfound]

This one does what I want on the way up:

http://i.imgur.com/tneSzDs.png

This one does what I want on the way down:

http://i.imgur.com/xVc9lF6.png

The changes to the foward canard may be a little difficult to replicate, but is there any way to "re-set neutral" on the trailer flaps?

It looks like you're doing that by just angling a non-flap control surface rather than actually setting them up as flaps.

Start with the non-angled version. Right click to access the control surface tweakables, then set it as a spoiler. By default, the spoiler will be triggered along with the brakes; go into the action groups and remove the spoiler controls from the brakes, and add them to a custom action group (i.e. 0-9). Now you can toggle them on and off whenever you like.

If you want finer control of the deflection, set them as flaps instead of spoilers, but with a negative deflection (flaps default to deflecting down, spoilers default to deflecting up). Now set two action groups: one to increase deflection, one to reduce it.

The animations on flap/spoiler deflection are slow; they require ten seconds or so to shift.

[Rakaydos]

And I still have control athority on top of flap deflection?

[Somtaaw]

Do have one question Wanderfound, for the OOPS Mk 3K, is it supposed to be kind of sluggish in a vertical manner? While doing takeoff, and trying to climb to 15km it was all I could do to get her to nose up to ~40 degrees. And it kept trying to nose down to stay on a flat trajectory.

Or is that only because I'm trying to have docking ports on the laterals, in preparation for the orbital nukes.

[Wanderfound]

And I still have control athority on top of flap deflection?

Yup.

(stupid 10 char limit blah blah)

[Somtaaw]

nevermind my previous post, found out about FAR's flight assistance toggles, and thats made it much easier to get an acceptable climb without mashing the S button, and then praying I don't tip so far upwards I flip the jet.

I do, now have the question as to how you got a HUD for mach speed, stall, etc, that you used on your tutorial pictures for the Kerbodyned shuttle of mine. The data along the very bottom on either side of the navball.

[Wanderfound]

Do have one question Wanderfound, for the OOPS Mk 3K, is it supposed to be kind of sluggish in a vertical manner? While doing takeoff, and trying to climb to 15km it was all I could do to get her to nose up to ~40 degrees. And it kept trying to nose down to stay on a flat trajectory.

Or is that only because I'm trying to have docking ports on the laterals, in preparation for the orbital nukes.

The four engine version should be capable of a near vertical climb, if you pull the nose up gradually. The extra stability built into it will make it resist extreme AoAs, though. If you've cut it down to two engines, then yes, you will lose the vertical climb ability. Keep in mind that only a tiny handful of real world fighters can climb vertically; a 40° climb is actually very steep in real world terms. This is one of the reasons why overpowered planes are more fun to fly; you can get them up into the low-drag 25,000m+ zone much more quickly.

Other possible problems:

* Are you using some sort of PID tuner or other SAS damper? The pitch oscillation typically induced by the oversensitive stock SAS tends to cause a gradual nosedive.

* Pardon the obvious, but are you certain that it was at full throttle and didn't have flaps or spoilers deployed?

* If you've added docking ports in front of the lateral engines while keeping them in place, this would have shifted the engines back a bit, substantially altering the CoM/CoL relationship. Ditto if you've removed the lateral engines (but shifting CoM forwards in that case). Engines be heavy.

If you have removed the lateral engines, then as well as halving your thrust you will have also probably increased the the CoM/CoL offset. A pitch-down tendency is exactly what you'd expect in that case; the shift gives the tail drag more leverage, encouraging the plane to straighten out its position relative to the airflow. But because planes always require some AoA even for level flight, a plane that is perfectly aligned with the airflow is a plane that is in a dive.

(as always, screenshots be good when diagnosing aero issues; it would remove the ambiguity about whether the lateral engines are still there)

Run a 0-25° AoA sweep in the FAR analysis tools at the speed and altitude you're having trouble, then experiment by shifting the CoM forwards and back and see what it does to the analysis (you may need to shift the wings to keep the CoL constant while doing this). You don't want the yellow line to inflect up, but so long as it stays angling down even a tiny bit you're okay. The closer it is to flat the more manoeuvrable (but less stable) the plane will be.

Edited November 29, 2014 by Wanderfound

[Wanderfound]

nevermind my previous post, found out about FAR's flight assistance toggles, and thats made it much easier to get an acceptable climb without mashing the S button, and then praying I don't tip so far upwards I flip the jet.

I do, now have the question as to how you got a HUD for mach speed, stall, etc, that you used on your tutorial pictures for the Kerbodyned shuttle of mine. The data along the very bottom on either side of the navball.

http://forum.kerbalspaceprogram.com/threads/80842-Plugin-0-25-Kerbal-Flight-Data-%28Release-13-21-11-2014%29

Extremely worthwhile, should be stock. Kerbal Flight Indicators ​by the same author is also very useful.

[Somtaaw]

The four engine version should be capable of a near vertical climb, if you pull the nose up gradually. The extra stability built into it will make it resist extreme AoAs, though. If you've cut it down to two engines, then yes, you will lose the vertical climb ability. Keep in mind that only a tiny handful of real world fighters can climb vertically; a 40° climb is actually very steep in real world terms. This is one of the reasons why overpowered planes are more fun to fly; you can get them up into the low-drag 25,000m+ zone much more quickly.

Other possible problems:

* Are you using some sort of PID tuner or other SAS damper? The pitch oscillation typically induced by the oversensitive stock SAS tends to cause a gradual nosedive.

* Pardon the obvious, but are you certain that it was at full throttle and didn't have flaps or spoilers deployed?

* If you've added docking ports in front of the lateral engines while keeping them in place, this would have shifted the engines back a bit, substantially altering the CoM/CoL relationship. Ditto if you've removed the lateral engines (but shifting CoM forwards in that case). Engines be heavy.

If you have removed the lateral engines, then as well as halving your thrust you will have also probably increased the the CoM/CoL offset. A pitch-down tendency is exactly what you'd expect in that case; the shift gives the tail drag more leverage, encouraging the plane to straighten out its position relative to the airflow. But because planes always require some AoA even for level flight, a plane that is perfectly aligned with the airflow is a plane that is in a dive.

(as always, screenshots be good when diagnosing aero issues; it would remove the ambiguity about whether the lateral engines are still there)

Run a 0-25° AoA sweep in the FAR analysis tools at the speed and altitude you're having trouble, then experiment by shifting the CoM forwards and back and see what it does to the analysis (you may need to shift the wings to keep the CoL constant while doing this). You don't want the yellow line to inflect up, but so long as it stays angling down even a tiny bit you're okay. The closer it is to flat the more manoeuvrable (but less stable) the plane will be.

Thinking it might be the differences in FAR. you're running a newer version, perhaps there was a tweak, because even the stock OOPS Mk.3K chart with the Cd/Cl/Cm lines goes absolutely berserk. Uploading a picture shortly

[Wanderfound]

Thinking it might be the differences in FAR. you're running a newer version, perhaps there was a tweak, because even the stock OOPS Mk.3K chart with the Cd/Cl/Cm lines goes absolutely berserk. Uploading a picture shortly

You always want to be using the latest version of FAR; the first couple of post-.25 releases had some serious aero bugs, and the pre-.25 FAR did not have the wing weight/strength tweakable. If you're flying with a pre-.25 version of FAR, your wings are about 1/3rd the weight of the ones on my design. This will substantially mess up the balance.

[Somtaaw]

I also went and re-grabbed the mk3K just in case I'd accidentally moved wings or something.

This is the result of the FAR analysis. And what I did, for what I'm designating the n variant, lateral RAPIERs pulled away. Docking clamp 1.5m attached, RAPIER attached directly to the clamp, and re-did the action group to ensure both engines toggle off when told to.

edit: so the lateral engines move back by only a few inches, whatever the distance of a docking clamp is.

And for flight, I've been managing to get to the 20-24km height before my velocity starts to drop like a stone with only 2 RAPIERs running in jet mode. if I toggle them over early and restart the lateral engines I start gaining velocity again but I couldn't get into even a suborbital flight before running out of fuel.

Edited November 29, 2014 by Somtaaw

[Wanderfound]

I also went and re-grabbed the mk3K just in case I'd accidentally moved wings or something.

This is the result of the FAR analysis. And what I did, for what I'm designating the n variant, lateral RAPIERs pulled away. Docking clamp 1.5m attached, RAPIER attached directly to the clamp, and re-did the action group to ensure both engines toggle off when told to.

You need to adjust the speed on the analysis; that's set for only about 60m/s. Try it at Mach 3.

[Wanderfound]

And for flight, I've been managing to get to the 20-24km height before my velocity starts to drop like a stone with only 2 RAPIERs running in jet mode. if I toggle them over early and restart the lateral engines I start gaining velocity again but I couldn't get into even a suborbital flight before running out of fuel.

As for this...the speed required to maintain level flight increases as the air thins. Climb quickly to 15,000m or so, but then pull the nose down to just above the horizon and crank it up to Mach 5 as you ascend to 30,000m. More AoA = more drag = less speed. Have a peek at the test flight screenshots on my revision of your design.

[Rakaydos]

It looks like you're doing that by just angling a non-flap control surface rather than actually setting them up as flaps.

Start with the non-angled version. Right click to access the control surface tweakables, then set it as a spoiler. By default, the spoiler will be triggered along with the brakes; go into the action groups and remove the spoiler controls from the brakes, and add them to a custom action group (i.e. 0-9). Now you can toggle them on and off whenever you like.

If you want finer control of the deflection, set them as flaps instead of spoilers, but with a negative deflection (flaps default to deflecting down, spoilers default to deflecting up). Now set two action groups: one to increase deflection, one to reduce it.

The animations on flap/spoiler deflection are slow; they require ten seconds or so to shift.

Since I want the control surfaces to angle up for launch, but down for landing, would I set the control surfaces to a negative spoiler, and turn on the brakes in orbit to shift "modes"?

IE: not have the brakes on for takeoff, and leave the brakes on for landing.

[Wanderfound]

Since I want the control surfaces to angle up for launch, but down for landing, would I set the control surfaces to a negative spoiler, and turn on the brakes in orbit to shift "modes"?

IE: not have the brakes on for takeoff, and leave the brakes on for landing.

You can't set a control surface to flap/spoiler deflect both up and down. However, you can give it a static pitch in one direction, then use a flap setting to adjust it from down to level to up.

However, you'd probably find it easier to set one pair of surfaces to deflect up, and another pair to deflect down. That way, you can trigger the up-deflecting one on one control group, the down-deflecting one on another control group, and both at once for airbrakes.

And, as I know has been mentioned to you a few times, the easiest way to improve the Manticore's performance would be to convert it from a biplane to a monoplane. Sopwith Camels are cool, but there are good reasons why we don't use them any more.

Edited November 29, 2014 by Wanderfound

[Rakaydos]

...I asked if I could use a single flap setting to deflect downward, so I can activate it for landing. until I include a NERVA, I'm not goting to be worried about landing on Laythe, so I really dont care about airbreaks yet.

It didnt sound like you answered my question.