My Jool 5 challenge attempt

[burn_at_zero]

Here goes...

I'm planning to do the Jool 5 challenge.

This will be on v1.1.3 in my current career save, which hasn't even seen a minmus flyby yet.
By posting my plan here hopefully I will actually complete it this time.

{Edit: I'm using FAR. Most of the details below have changed due to hardware constraints. I will leave all the tables and such for reference, but right now it looks like one SSTO, one light lander and one or two Tylo vehicles.}

This challenge attempt will be done in parallel with a permanent Laythe orbital base, which means I will be bringing crew and hardware above and beyond the basic requirements. That includes ISRU gear, but no mining will be performed during the attempt. I will likewise bring SCANSat gear and perform surveys to generate slope maps and such for landing, but will recover no science until after the challenge. I intend to stage operations from the Laythe orbital base; all exploration missions will start in and return to Laythe orbit.

Projected dV requirements: (all vehicles will include 40% margin)

Spoiler

LKO to Laythe: 4000m/s
Tylo: 11,186m/s
 - Laythe to Tylo: 1400m/s
 - land: 2600m/s
 - ascend: 2600m/s
 - to Laythe: 1390m/s
Vall: 5,138m/s
 - Laythe to Vall: 890m/s
 - land: 950m/s
 - ascend: 950m/s
 - to Laythe: 880m/s
Bop: 4886m/s
 - Laythe to Bop: 750m/s
 - land: 250m/s
 - hops: 1000m/s
 - ascend: 250m/s
 - to Laythe: 1240m/s
Pol: 4368m/s
 - Laythe to Pol: 900m/s
 - land: 170m/s
 - hops: 680m/s
 - ascend: 170m/s
 - to Laythe: 1200m/s

Approximate dV for return:
4,110 m/s + 40% margin = 5.8km/s

Mission vehicle roster

Spoiler

{All science vehicles must include a lab or minimum 3x crew parts for redundant sample storage. If this is not feasible for the Laythe jet then allow fuel for multiple trips.}
{To be updated post-design with actual masses, dV, etc.}

:: 1x mothership - 6km/s dV; serves as permanent Laythe base
:: 2x Laythe jet: unknown dV (needs testing), minimal O2 required; full science equipment. Consider seaplane.
:: 4x light shuttle: ~5.3km/s dV, minimum a=0.5g; full science equipment, rover capable, lab or 3x crew parts
:: 1x heavy lander: ~7.3km/s dV, minimum a=1.6g; multistage acceptable
:: 1x Tylo rover: ~3.7km/s dV, minimum a=0.8g; full science equipment
:: 2x heavy tug: ~3.9km/s dV fully loaded; klaw, rescue crew cabins, cargo capacity for tylo rover / heavy lander
:: 6x scansat: ~3.9km/s dV; full scanning instruments plus multiple transmitters
:: 3x Jool atmospheric probe: ~3.7km/s dV; full science equipment (disposable)
:: 1x return shuttle: ~5.8km/s dV, Kerbin landing capable; science lab for full data

Light shuttle and heavy tug are stackable; this might serve as the return shuttle and also doubles as a rescue craft for Tylo and Laythe.

Concept of Operations

Spoiler

Phase 1: Assembly
Components launched to LKO and assembled into Mothership

Phase 2: Transfer
Mothership burns for Jool
Mothership aerocaptures at Laythe (with reserve fuel for propulsive capture if necessary)

Phase 3: Mapping
3x comm relay satellites placed in 120° spaced Jool stationary orbits (15,010km)
6x mapping satellites placed in polar mapping orbits, 1 for each moon and 1 for Jool
3x atmospheric probes deployed to Jool

Phase 4: Exploration

 - Part 1: Tylo
Rationale: Tylo is the highest risk destination. Handling Tylo first allows the full mission resources to be committed to a rescue if necessary.

Heavy tug deploys heavy lander to low Tylo orbit
Heavy tug returns to Laythe and refuels
Heavy tug deploys Tylo rover + crew to low Tylo orbit
Tylo rover lands on Tylo
Tylo rover surface operations: science at all biomes then return to equator
Heavy lander lands near Tylo rover; rover completes rendezvous
Crew and science transferred to lander
Lander ascends, rendezvous with heavy tug
Heavy tug + lander + crew + science return to Laythe orbit
Lander + crew + science transferred to mothership
Heavy tugs placed on call for rescue duty
Tylo rover begins uncrewed extended exploration

 - Part 2: Laythe
Rationale: Second riskiest destination after Tylo. A rescue could cost hardware that would affect other destinations due to loss of redundancy.

Laythe jet + crew descend to Laythe
For each biome:
  : Collect all data
  : Atmospheric flight to next biome
Laythe jet ascends
Crew + science transferred to Mothership
Laythe jet refuels
 {If the jet does not carry 3x crew parts or a lab, repeat part 5 a total of three times to gain proper coverage of redundant samples.}

 - Part 3: Vall
Rationale: Vall is the second destination with surface roving requirements but otherwise uses the same hardware as Pol and Bop.

Light shuttle + crew transfer to Vall orbit
Light shuttle lands
Light shuttle rover surface operations: science at all biomes then return to equator
Light shuttle ascends
Light shuttle + crew + science return to Laythe orbit
Crew + science transferred to Mothership
Light shuttle refueled

 - Part 4: Bop
Rationale: All hardware should be well-validated by this point. Bop is next outward from Vall.

Light shuttle + crew transfer to Bop orbit
Light shuttle lands
For each biome:
  : Collect all data
  : Suborbital hop or surface drive to next biome
Light shuttle ascends
Light shuttle + crew + science return to Laythe orbit
Crew + science transferred to Mothership
Light shuttle refueled

 - Part 5: Pol
Rationale: All hardware should be well-validated by this point. Pol is next outward from Bop.

Light shuttle + crew transfer to Pol orbit
Light shuttle lands
For each biome:
  : Collect all data
  : Suborbital hop or surface drive to next biome
Light shuttle ascends
Light shuttle + crew + science return to Laythe orbit
Crew + science transferred to Mothership
Light shuttle refueled

Phase 5: Return
All science data transferred to storage lab
Expedition crew transfer to return shuttle
Return shuttle burns for Kerbin
Return shuttle makes Kerbin orbit {aerobrake preferred, propulsive allowed}
Return shuttle lands at KSC

Contingencies

Spoiler

 - Phase 1
Risk: component failure
Strategy: fly replacement parts from Kerbin

 - Phase 2
Risk: Insertion failure
Strategy: Dump hardware, return to Kerbin orbit
Risk: Aerocapture failure
Strategy: Powered capture either at Laythe or Jool
Risk: Excessive propellant used
Strategy: Refuel flight at next window
Risk: Loss of hardware
Strategy 1: Balance all redundant hardware; perform aerocapture on one side only
Strategy 2: Enclose all separable craft in cargo bays or aeroshells

 - Phase 3
Risk: comm sat failure
Strategy: switch to 180° spacing
Risk: sat out of propellant
Strategy: rescue sat with heavy tug
Risk: mapping sat failure
Strategy: refuel and retask another mapsat after mission primary endpoints reached

 - Phase 4

 :: Part 1, Tylo
Risk: loss of heavy tug
Strategy: two tugs provided; operate one at a time
Risk: lander failure
Strategy: assemble heavy tug and shuttle as rescue stack; heavy tug will be discarded during ascent

 :: Part 2, Laythe
Risk: loss of jet
Strategy: two jets provided; operate one at a time
Risk: failure during surface operations
Strategy: rescue with the other jet or a shuttle + heavy tug stack; heavy tug will be discarded during ascent

 :: Part 3, Vall
Risk: loss of shuttle
Strategy: four shuttles provided; operate one at a time
Risk: failure during rover operations
Strategy: rescue with the other shuttle or either heavy tug

 :: Part 4, Bop
Risk: loss of shuttle
Strategy: four shuttles provided; operate one at a time
Risk: failure during surface operations
Strategy: rescue with the other shuttle or either heavy tug

 :: Part 5, Pol
Risk: loss of shuttle
Strategy: four shuttles provided; operate one at a time
Risk: failure during surface operations
Strategy: rescue with the other shuttle or either heavy tug

 - Phase 5
Risk: Loss of return craft
Strategy: Return with shuttle + heavy tug stack
Risk: Injection failure
Strategy: interplanetary rescue mission; voids challenge
Risk: Aerocapture failure
Strategy: propulsive capture
Risk: Insufficient propellant or damage that prevents landing
Strategy: LKO rendezvous and crew return

Science checklist

Spoiler

in space high	surface sample	EVA report	crew report	mystery goo	materials study	temp scan	pressure scan	gravity scan	seismic scan	atmo scan
global		x	x	x	x	x	x
biome								x
in space low	surface sample	EVA report	crew report	mystery goo	materials study	temp scan	pressure scan	gravity scan	seismic scan	atmo scan
global			x	x	x	x	x
biome		x						x
flying high	surface sample	EVA report	crew report	mystery goo	materials study	temp scan	pressure scan	gravity scan	seismic scan	atmo scan
global		x	x	x	x	x	x
biome										x
flying low	surface sample	EVA report	crew report	mystery goo	materials study	temp scan	pressure scan	gravity scan	seismic scan	atmo scan
global				x	x		x
biome		x	x			x				x
surface landed	surface sample	EVA report	crew report	mystery goo	materials study	temp scan	pressure scan	gravity scan	seismic scan	atmo scan
global
biome	x	x	x	x	x	x	x	x	x	x
surface splashed	surface sample	EVA report	crew report	mystery goo	materials study	temp scan	pressure scan	gravity scan	seismic scan	atmo scan
global
biome	x	x	x	x	x	x	x	x

Biome list

Spoiler

Jool (atmosphere)

Laythe (atmosphere)
 - poles
 - shores
 - dunes
 - the sagen sea

Vall
 - poles
 - highlands
 - midlands
 - lowlands

tylo
 - highlands
 - midlands
 - lowlands
 - mara
 - minor craters
 - major craters

bop
 - poles
 - slopes
 - peaks
 - valley
 - ridges

pol
 - poles
 - lowlands
 - midlands
 - highlands

Edited October 10, 2016 by burn_at_zero

[burn_at_zero]

The two main challenges I see are the Laythe atmospheric craft (with which I have too little experience to predict) and the Tylo lander (which I would like to be SSTO / reusable if possible).

Here are my thoughts on the Tylo lander before I get into the VAB. We will see how it looks once I actually build it. I intend to post the .craft file once it is built and tested.

Spoiler

Tylo lander: go nuclear?
 - lv-n TWR allows for a vehicle with A of 0.8g to be 1 part engine (39.24%) 1.548 parts everything else
 - Isp is 800s, at 7.3km/s fuel is 60.55% by mass (not achievable)
 Redesign for A = 1 at landing and hope we don't lose too much dV to gravity drag
 - 49.05% engines at that point
 - return requires 3650m/s dV = 37.19% fuel, therefore 13.758% payload and dry mass
 - landing requires a further 0.2711 * landed mass in fuel
 - tankage is 0.125 for standard tanks therefore total fuel of 0.643 = tanks of 0.080375
 - remaining mass = 5.72% of landed mass

Lander is crew-only, but requires three crew parts minimum or a lab to store all samples. Preliminary parts list:

0.2t    large reaction wheel
0.2t    4x RCS
0.2t    4x fuel duct
0.2t    4x TCS small
0.4t    4x LT-2 landing gear
0.16t    2x PB-NUC RTG
0.4t    2x large docking port
4t    2x MK2 crew cabin or 4x MK1 crew cabin?
2.1t    MK2 inline cockpit?
2t    adapters, struts, etc.
total: 9.86t payload = 172.378t landed mass = 104.375t initial fuel = 219.11t initial mass
28 engines=7x4 engine packs = 84t of engines (alternative 6x4 engines plus 6x radial allowing center stage landing gear). Note that 7x0.2t for quad adapters fits within the 2t budget.
roughly 7x rockomax x200-32 tanks as LF only allows 112t fuel (7.3% margin)

This is 22.22 tons of initial mass for each ton of surface payload (excluding engines and fuel tanks). If I can reduce the mass per crewmember or find a better way to store science with mod parts then that will greatly reduce the mass of the lander.

 

[sdj64]

Very thorough planning and ambitious goal to gather science from every biome. This is great!

In my experience, a single stage Tylo lander is about equal mass with nukes or chemical engines (Terriers, an Aerospike, or a Poodle all are competitive depending on payload weight).  It might be simpler to go with a 2 stage lander or ISRU especially if you're dropping off a rover and spending time on the surface.

[burn_at_zero]

Tylo lander mk1 results:

Not good. I made an error in my first calculation, so the lander ended up being just under 300 tons fueled even after mass savings available through mod parts.

Spoiler

{60.55% fuel}
37.19% fuel for descent
 - 62.81% mass remains
 - 49.05% of this is engine
30.81% engines (0.628g start, 1.0g surface)
23.36% fuel for ascent
07.57% tank mass
01.07% remaining

Actual dV = 7130m/s
Pre-margin dV = 5200m/s
Margin: 37.12% {Acceptable}
Fueled mass: 294.81 tons
Liquid fuel: 176 tons
Dry mass + RCS: 118.81 tons
 - engines: 90t
 - tanks: 22t
 - crew hab: 2.5t
 - adapters: 0.9t
 - guidance unit: 0.5t
 - RCS fuel: 0.48t
 - docking ports: 0.4t
 - EVA ports: 0.4t
 - batteries: 0.2t
 - RCS thrusters: 0.2t
 - reaction wheel: 0.2t
 - RTGs: 0.16t
 - RCS tanks: 0.15t
 - ladders: 0.01t

maximum thrust: 1,800 kN
minimum fuel burned to land: 83.14t
maximum landed mass: 211.67t
minimum landing TWR: 0.8669 {>0.8 safe}
{the low TWR most likely means a lot of gravity loss}

Actual Tylo test result: 52% of total dV used in landing (extreme gravity losses; expected value was 31.5% used). Craft is grossly deficient in rotational control and fell over on landing at a mild slope. Conclusion: reusable nuclear is not reasonable for a Tylo lander. A six-minute landing burn is just too much gravity loss.

 

Mark 2 will be a staged vehicle, chemical, hopefully not too huge.

[burn_at_zero]

@sdj64 Thanks! I did a lot of the planning during free moments at work, when the client is unavailable and the math is all by hand.

Haven't had much free time at home (prioritizing the family over games), but I hope to make some progress tonight. I'm also doing this in my current career save, so I have to work up enough cash and science to build the thing in the first place. Self-imposed limitation, but it feels less meaningful to do it in sandbox. Maybe a better way to put it is, once I do all this exploration I'm not likely to come back to Jool for a while so I may as well benefit from it. (I am doing limited flight tests in sandbox, but no hyperedit.)

In retrospect I'm a little bit proud that my nuclear lander worked on the first design and third landing attempt. By 'worked' I mean reached zero velocity at the surface of Tylo intact. Maybe some of the LETech landing legs would make it stable. Still, I would like to make the vehicles as modular as possible; if I can stack the two tug designs and use them for Tylo crew recovery then all the better. If I have to dip below 40% margins I'll do so, but I like having outrageous reserves.

This challenge certainly takes both patience and perseverance.

[burn_at_zero]

Turns out I'm terrible at spaceplane design. I have one fairly easy to fly airplane under my belt in FAR, but apparently I lack the secret sauce for stability above mach 2.5 or so.

(Spoiler: me complaining about realistic aircraft physics being hard)

Spoiler

Three solid hours of trial and error (not counting all my reading up on the subject over the last few days) left my most successful design spinning out and breaking up consistently at mach 3 / 20-24km. Roughly 90% of attempts didn't make it off the runway (about evenly split between tail strikes and hitting the last marker light, with two ocean crashes). Some of those variations had rear gear so close to CoM that the front gear would come off the ground when the plane loaded on the runway, yet even with full flaps at 110m/s I couldn't get the nose up. Engines were in plane with the wings and body, so CoT passed directly through CoM. I think I might have too much power and not enough control authority (even with multiple SAS and controls on every trailing edge) as I consistently broke mach 1 under 3km altitude while holding S the entire flight (even at half throttle) and had trouble exceeding 15° pitch. That's with the CoL indicator fully inside the CoM indicator, on a long SR-71 clone with canards; should have been plenty of torque. Two variations were able to hit 45° pretty easily but they spun out just over mach 2 every time.

If I come back to this I'll try something more like a dart or a flying wing. I really like the look of the mk2 parts, but to fit everything I need I have to use a long cargo bay, a crew bay and the cockpit. Throw in a LF fuselage, two-node tail section and two nukes and the result is super long. I had to move the wings and engine stacks pretty far back to prevent tailstrike while keeping CoM/CoL stable and allowing the rear landing gear to sit just behind CoM. Looked a lot like a blackbird but it was just too hard to fly. Maybe something with a wider wingspan and shorter body will handle a little better.

 

Rather than spend more time learning how to design semi-stable supersonic aircraft I'm going to stick with what I know. I'll build a VTOL rocket with jet assist takeoff and parachute assist landing. That means I'll need an amphibious science rover or something clever to collect data from the Sagen Sea. I will try to build something that can cruise in atmosphere on jet power alone.

 Hoping to have at least one of these two problem children solved tonight.

[burn_at_zero]

First, some progress. I will provide screenshots of the prototypes that are close to ready. I expect a few minor adjustments but these are essentially complete.

Here's two screenshots of the heavy tug, one unloaded and one loaded with 126 tons cargo:

Spoiler

goal:  heavy tug: ~3.9km/s dV fully loaded; klaw, rescue crew cabins, cargo capacity for tylo rover / heavy lander

achieved: 3.9km/s dV, 126t cargo, 4 crew, loaded TWR 0.3.
not achieved: klaw. Just no good place to put it.
bonus: engine pods are connected by docking port and could be swapped out if desired. I may create chemical pods and use them to make a backup Tylo lander if necessary.

Next up, the heavy rover. This one will land itself at Tylo and remain on the surface. Not visible is the 2.5m docking port on the underside (at CoM) for the heavy tug to position it in low orbit. The propellant tanks on the sides are jettisoned partway through the descent. Also, don't believe the stats on those giant wheels; I've had this thing over 80m/s on Kerbin.

Spoiler

goal:  Tylo rover: ~3.7km/s dV, minimum a=0.8g; full science equipment

achieved: 4.2km/s dV, min a=0.61 at first stage, 1.05 at second stage (during descent). Yes it flies straight, even in atmosphere and even with FAR.

Here is the light rover, intended for Vall, Bop, Pol or any other airless world besides Tylo. It's roomy, with space for 13 kerbals.

Spoiler

(The struts insist on glitching. They are not structurally necessary with KJR but the offset plates I used for the wheel mounts just looked wrong.)

The light tug docks with the upper port on the light rover. No good screenshot at the moment. Each craft has its own set of landing gear at the same level. After landing the rover retracts gear and undocks, dropping a few cm and allowing it to drive away. The tug remains in place until the rover returns, driving under it and redocking easily. Alternatively, the tug can hop closer to the lander to save some drive time on the lighter worlds.

Lastly, the mothership core. This section is propulsion, probe bays and the habitat with 3.75m docking ports at each end. I've had to commit some minor part clipping to make a wheel, but I think using crew tubes in some places for appearance (costing mass and parts with no benefit) should offset that.

Spoiler

(numbers won't be accurate for final dV and TWR as another 1000+ tons of gear still needs to be attached.)

 

Now for the bad news. I did a test assembly in space and everything fits, but my machine simply can't handle the load. The lower core, two heavy tugs, one light tug and one light rover have brought me into seconds per frame territory with frequent crashes. The craft are completely uncontrollable without mechjeb. The last docking I performed took 2.5 hours and there are three more large craft plus a fuel section and another six probes to go.

I've removed all mods I'm not actively using but I'm stuck at 8gb ram max. Looks like it's back to the drawing board. I will have to reconsider some of my original goals, cut back on redundancy, reduce the propellant margins and eliminate extras like the crew ring. I may also need to split up the docking locations across two mothership sections so the individual craft don't take so long. If the final sections take two hours to dock it's not so bad; I can let mechjeb do it over dinner or something. Topping off fuel before departure is going to be quite a job.

Edited August 1, 2016 by burn_at_zero
fixing image links

[Geschosskopf]

13 hours ago, burn_at_zero said:

I've removed all mods I'm not actively using but I'm stuck at 8gb ram max. Looks like it's back to the drawing board. I will have to reconsider some of my original goals, cut back on redundancy, reduce the propellant margins and eliminate extras like the crew ring. I may also need to split up the docking locations across two mothership sections so the individual craft don't take so long. If the final sections take two hours to dock it's not so bad; I can let mechjeb do it over dinner or something. Topping off fuel before departure is going to be quite a job.

This is why I do flotillas and have never even considered participating in the Jool-5 challenge.  I just don't want to deal with such lag monsters.

On the subject of trimming things down, do you use either Kerbal Planetary Bases?  Both those have jumbo KAS pipes that you can make crew tubes out of.  So you put something at the end of each spoke, then connect their ends with tubes on EVA once in space.   You end up with a polygon instead of a ring but it does drastically reduce part count.  

Bop and Pol have like no gravity so roving there is a problem (besides collider issues with Pol).  Some folks use an up-pointing ion engine to provide downforce.

 

 

[Mister Dilsby]

This is good stuff, @burn_at_zero! I love to see such detailed planning, tests and contingencies. I have a Jool-5 in progress myself built around a basically stock mothership (the only mods are for life support, and for power generation to support life support) At a total count of about 800 parts the mothership is flyable in 1.1.3, but there is indeed some lag--not in the "seconds per frame" range, but maybe a 1/2 to 1/3 speed kind of thing. 

As to the craft, I went with a single stage Tylo lander/rover that will refuel on the surface. It has four drills, an ISRU and fuel cells. I had originally tested a design with LV-N engines but ended up going with aerospikes; it just wasn't going to work without the thrust of a chemical rocket engine. This craft will also handle Vall. For Laythe I have an SSTO floatplane, pretty basic design with twin RAPIERs. RCS-fueled landers will handle the small moons. The ship also carries scansats and a pair of expendable atmospheric probes for Jool itself. 

Good luck! Jool-5 is no joke, especially doing it with a single craft. I started my mission last November and I've only gotten to one moon so far!

[burn_at_zero]

Thanks for the support, I appreciate it.

ISRU just feels like cheating  That's my usual approach but for this challenge I want to minimize overall mission time and get into the spirit of 'bring it all from home'. That's also why I don't want to reuse one mapping probe for all five moons, though I might have to cut back to just two or three.

The rover/lander has more than enough dV to hop to every biome on each of Bop and Pol (five 180° suborbital hops) without refueling or driving around. I should be able to do the same on Vall, though landing near a biome boundary and doing a little driving would save fuel. I should just make it a pure lander to save on parts (60+ eliminated) and mass.

I did successfully build a LF-only SSTO spaceplane. It takes a (very) long time to make orbit, but it should work on Laythe with some refinement.

The crew ring looks nice from a distance but I don't like the way the parts split. 96 seats is a little excessive; I should be able to cut back quite a bit here. I wish there was a parts pack with wedge pieces to make a nice ring, but that would be hard to do without requiring specific spoke pieces.

Unfortunately the probes are as simple as I can make them. They could be lighter but not with fewer parts. The survey scanner's sheer size is hard to manage and the narrow-band scanner sticks out too far for 1.25m aeroshells, which means I'm pretty much stuck with a 6t cargo bay for each one unless I get creative.

The most practical thing to do would be to install KIS/KAS and take all the sensors and smaller bits inside containers. I would have to assemble the probes from parts in orbit. For performance reasons that probably means making a dockable workshop module on the mothership that separates; the probe assembly would be done with the rest of the ship off-grid.

Since I have fuel tanks plus and Space-Y I should just go with a 5m or 7.5m mothership core. I'll spend some time tonight and see what I come up with. This is taking a lot longer than I thought it would, but it's nice to have real challenges for a change.

[burn_at_zero]

The long silence is a sign of intractable problems. This means some screenshots of progress and also some ranting towards the end which is safe to skip. On the plus side my career save now has the tech tree maxed and 10 million funds banked, all without going more than a few km outside Kerbin's SOI. On the minus side I've gone another month without even assembling the stack in orbit; worse, it's beginning to look like my computer can't handle the load and I will need to redesign the mission. Time will tell.

I've found a solution to the probes, but it looks ugly. I used radial-attached engines for propulsion which allows for a docking port on one end and the survey scanner on the other end. I offset it with the high-resolution ore scanner, so both instruments are canted away from the end of the probe at a crazy angle. It fits inside a 1.25m aeroshell which mounts neatly to the mothership. It's possible to undock/redock after popping the shell, so the probes can move themselves to different docking ports if needed (including hitching a ride on a tug to reach the target SOI).

Spoiler

I also put together two ballistic Jool atmosphere probes with enough batteries for two sets of transmissions each. (There's not enough time during the descent to power the data feed with RTGs unless you get crazy; easier and cheaper to take enough battery power along for the ride.) These have to be released on the interplanetary approach unless you want to circularize pretty low over jool proper and use RCS to deorbit. Tests in sandbox were acceptable.

Spoiler

The mothership core is indeed a 5m propellant tank, with 2.5m tank 'arms' and a forest of docking ports. Probes are attached to the mothership core on the ground and launched as a unit. It looks awkward but it flies just fine with FAR. The probes are a *very* tight fit with the heavy tugs. I don't understand why this craft flies but my planes don't.

Spoiler

So far I have the core, habitat module, two heavy tugs and the Tylo rover docked at 150km LKO. I'm already seeing kraken warning signs like harmonic oscillations and 'floppy' engines, which is not a good sign considering I need to dock at least five more craft in the 50 to 90 part range. If my machine can't handle the load I will have to revise my whole mission profile and start over.

Spoiler

kraken sign: (note the dramatically non-parallel engines, as if a pernicious influence beyond the reach of Euclidean geometry were preparing to pull the craft into the abyss)

CPU stress tester:

I have a working SSTO spaceplane. It needs oxidizer. I've spent over 24 hours of game time trying to build an LF-only version and I simply can't do it. The current 'good enough' model will parachute-land on Laythe and do short horizontal takeoff; there is enough crew space to bring an engineer. I can see why some people like flying planes to orbit in KSP but I find the experience awkward, tedious and excessively dangerous. The design process with FAR I've found to be masochistic in the extreme, perhaps because I'm not a practicing aerospace engineer for my day job. Nevertheless, it flies and sometimes it survives to orbit. (For the record, I do enjoy flying planes in atmosphere with FAR up to around mach 3; hypersonic velocities and rarefied atmospheres at 20+km are nightmarish.)

Spoiler

As the name implies, this is the fifth major structural plan and the only one that was remotely stable above 18km and ~700m/s. I've spent hours poring over how-to guides, explainers and youtube videos and even more hours making adjustments, tweaks and full-scale rebuilds then test flying. Every single part you see was essential. Every design parameter is in the green at the appropriate speed and altitude settings. The massive vertical tail structures help keep yaw under control at max altitude. The canards were critical to maintaining control over pitch. The ridiculously overpowered set of four RAPIERs is needed to have any kind of control on the edge of flameout and to have enough thrust to punch through the upper atmosphere without needing to run nukes for ten minutes. (The only other design that made orbit was all LF, but I had to run nukes for more than ten minutes to do it and the double-dip trajectory was very difficult to survive on the rare occasions that it actually reached 1+km/s and 25+km.) The wide offset of the engines further controls both yaw and roll through a large lever arm. Any fewer than six radiators and I lose either the cockpit or the engines about 90% of the time. Five chutes are the minimum to survive a landing on Kerbin undamaged with minimal fuel burned. The balance and landing gear alignment are exquisitely tuned for takeoff at any point between 70-120m/s with a little input, and you can pull back all the way while still on the ground without tailstrike. The thrust is such overkill that I usually have well over half the runway left at takeoff and I sometimes forget to retract gear until I'm in orbit. It handles rough terrain like a breeze, even the nasty hilly stuff behind KSC; taxi to a hilltop, pick up speed on the downslope and use the next upslope as a ski lift.

Yet somehow it spins wildly out of control with no warning and at varying altitudes and velocities, exploding if below about 20km. If it is high enough I can usually just cut thrust, allow it to stabilize (usually upside down) and power through. It's fun to fly at low altitudes and reasonable speeds, but very frustrating when hypersonic. I gather the sharply varying profile has something to do with that but every tweak I make ends up making the behavior worse.

Re-entry is usually just a long, slow, risky fireworks show at high AoA. Not too much worry for the heat (surprisingly, since it likes to try to cook the occupants on ascent) but it likes to flatspin and break up at the slightest hint of roll or yaw. Still, it will make a reasonable contingency crew return vehicle.

[Nefrums]

The problem with your plane is that it is that all the engines are to far back.

In the SPH check your CoL and CoM.  I guess you know the basics of that CoL should be behind CoM.   

Now in the SPH simulate what happens when you spend your fuel by decreasing the LF in all your fuel tanks, and look how that affects CoM vs CoL.

I suspect that your CoM moves behind CoL as your fuel drains. And that this is what is causing you plane to suddenly become unstable.

Don't use radiators on your plane they add alot of drag, if you overheat try using a steeper acsent profile.  

Have you tried using the Smart A.S.S  from MechJeb?  It makes flying space planes much easier. 

 

In regards to your computer not being able to handle the ship.  This is due to to large part count.   Try using fewer and bigger parts.   Mods help alot.   Try the quad nuke, it is identical in mass/performance with 4 regular nukes but each saves you 4 parts (one engine instead of 4 + 1 adapter).

 

Edited September 8, 2016 by Nefrums

[burn_at_zero]

Thanks for the input. I will try moving some things around to get my CoT closer to CoM and get a better CoM/CoL balance.

I'll post screenshots later tonight, but CoM remains ahead of CoL even at zero fuel. The canards and long delta wing section are good for that. At high altitude the plane tends to drift back and forth, corkscrew and then flip over so it feels like a loss of yaw control (or like losing yaw control first while all the control surfaces lose effectiveness). It doesn't happen on every ascent but it does happen more often on flights that needed a lot of corrections at lower altitudes. I can usually pull out of it below about 18km and try the ascent again.

Smart A.S.S. helps once aerodynamics are not much of a factor and I can rely on gyros or RCS. So long as the control surfaces are effective MJ seems to have trouble with the delay between input and result. Usually it leads to positive feedback oscillations (much like stock SAS) and the plane eventually flips or spins out. I control the thing using trim inputs through most of the flight. If I had a joystick or some other analog control this would be simple, but the keyboard is a binary input and causes drastic reactions under 15km even to taps on the keys. Cutting back on control surfaces or their max deflection makes it easier to control at low altitude but impossible to control when suborbital.

I can hit 400+ m/s at 2km altitude just off the runway pretty easily. I can also easily climb above useful oxygen levels and flame out if I'm not paying attention or if something else has gone wrong and I'm trying to correct. Staying at a useful altitude (22-24km with rapier, 20-21km with ramjet) to pick up speed can be challenging. My heat problems tend to come when I can't keep that altitude envelope and the plane dives below 20km at 1+ km/s. That's usually the point where I give up trying to build more speed in atmosphere and head up as fast as I can, kicking on nukes then switching mode once I run out of air. Even then it takes a couple minutes of nukes at 100% to get all the way out of the atmosphere.

Sounds like I should pack more oxidizer, ditch most of the radiators and try to get better control of the craft at high altitude. Maybe moving parts around to smooth out the edges will help since there are a lot of sharp transitions in the current design.

Also sounds like I should revisit the mission architecture and get rid of a lot of redundancy. I don't particularly care how long the mission takes in-game so I could just as well use a single mapping satellite that can return and refuel, maybe with a spare (~10t, ~80 parts). I could rebuild the mothership's propulsion section to be an independent tug, which would eliminate both of the heavy tugs (~400t, 140 parts). The Laythe plane would do fine for Pol and Bop landings, probably Vall as well, so no light landers (~160t, ~200 parts). I might go the other way and use a single light lander instead of a plane, though that will mean taking quite a bit more LFO. A redesign of the Tylo vehicles might allow me to combine the two, though I'd have to pull a Tylo Elcano. May as well.

[burn_at_zero]

I quit.

There's zero point in continuing this ridiculous obsession.

I've put in about another 16 hours of game time with absolutely nothing to show for it. I can't get a craft that is stable above mach 3 and can't get an all-LF SSTO no matter what I do. I considered sending a subsonic cruiser aircraft and just using a massive rocket to return to orbit, so I built a couple of moderately successful designs. Then I asked myself if I'm really ready to spend several consecutive hours fending off children and family obligations while flying across Laythe to reach every biome without being able to save. No. I choose sanity.

A few additional SSTO attempts followed, including my final design which has all-green stability derivatives at all relevant conditions (including the inevitable yaw and breakup around mach 3.3 and 16-18km). I've eliminated anything not essential for flight and science, no radiators or other eternal protrusions, confirmed basic alignments like CoM to CoL, experimented with a range of small adjustments of every single part on the plane. Whether or not I use FAR's assistance, whether or not I use SAS, whether or not I switch between them, same end result. SAS sends me into unrecoverable spins, while FAR tends to overcorrect and throw me into unrecoverable rolls. On two occasions I managed to break 35km, and on one of those I reached 64km before falling back to fiery doom. Oddly enough the craft is more stable with the landing gear extended than retracted; I'd forgotten to retract on my first successful mode switch, but retracting gear threw me into an unrecoverable spin and disintegration.

At this point I can either uninstall FAR or KSP. Either way, I won't be completing this challenge as intended. Maybe next year, maybe without FAR. If there's a spaceplane involved it almost certainly won't be something I designed. As it is I'll be updating once the next version is released, starting a new campaign and forgetting that spaceplanes exist.

Thanks everyone that offered advice. I learned a bit about supersonic aerodynamics in the process, so I suppose it was worth it. Hopefully anyone else attempting this has better luck than I did.

[Nefrums]

Don't give up!

Spaceplanes are easy when you figure out how to do them.

Here are some general tips:

1. Never add a radial mounted part except: wings or stacks of tanks with engines at the back and nosecones at the front.
2. Don't have to much lift.  0,25/t is enough. 
3. Don't have to much control surfaces. Less is always better so long as you are able to have some control. Gimbaling engins are often bad.
4. Use the right amount of engines.  1 rapier per 15-20t
5. Keep CoL/CoM balansed with full and empty tanks.
6. Have the right noce cone at the front.  Have one that can handle the heat or add a Communotron 16 on front of it to handle the heat.
7. Find a good ascent profile.  Keeping a steady climb from 10-20 km is better than trying to turn up from level flight at 20 km.

Trouble shouting guide:

• I can't get to mach 5 in airbreathing mode.  => see point 1,4 and 7
• SAS make my plane wobble back and forth = > see point 3
• My ship overheats:  => se point 6

 

[burn_at_zero]

Is it normal to yaw out of control at high altitude? I've tried less control, more control and super-oversized tails with no effect. I've tried keeping thrust along the centerline and I've tried putting engines on wingtips, but there seemed to be no difference. I could try TCA (thrust-controlled avionics mod) to see if that gives me enough yaw authority.  

I'll spend some time this weekend and see what I can do. First though, I really need to post pictures of the designs I've tried so hopefully you can tell me what I'm doing wrong.

I have my science payload down to a single MK2 cargo bay, which includes all science parts, two passengers and enough RTGs to run it all. The plane designs are in the 25 to 30 ton range (50-65 parts); I've tried one or two ramjets or rapiers with one or two nukes, and a heavier craft had two nukes and four ramjets, Take-off TWR has been anywhere from 0.3 to about 1.2. Rapiers seem to have better high-altitude thrust than the ramjets. My choice of MK2 cross-section means the nukes are way out from CoM and prone to tailstrike if I put one on the centerline. I don't know how much lift I have (not sure where to see that in the editor) but it is probably too much; I get level flight at low altitudes with only a degree or two AoA and landings take a lot of distance. (The ramjets help with that actually since you can reverse thrust.)

Mostly I wish I had a joystick.

Edited October 7, 2016 by burn_at_zero

[burn_at_zero]

Let's see if this album embed works.

I grabbed top, front and side shots of most of the major forms I've tried. I didn't include shots of all the minor variations.

Side A is a shot with full fuel, gear down, CoM/CoL displayed. Side B is a shot with no fuel, gear up, CoM/CoL and trans-sonic curves displayed.

{edit} This isn't embedding properly. Here's a link for now, until I figure this out.

{many edits later} Imgur albums apparently can't be embedded here. Photobucket is a dumpster fire, so I'm just leaving this as a link for now.

Laythe planes

Edited October 8, 2016 by burn_at_zero

[TwinKerbal]

it doesn't work

could you provide a craft file?

ill get FAR and fly it up, tweak it, or maybe make a new one based off of the design.

also, how far does the ssto have to fly? like a 100x100 orbit around laythe, or to vall?

personally, i feel like it would be more efficient to fly the ssto to vall, and dock there.

good luck

[burn_at_zero]

Laythe orbit would be adequate. I'd prefer it to be able to SSTO at Kerbin for testing, but if that is much more difficult than Laythe I can get it to orbit by rocket. I'll have a depot orbiting Laythe at minimum, so even if it does end up needing to fly elsewhere it can refuel along the way.

Craft files:

dropbox link

Mods:

If you have trouble with any of it let me know; I can replace the payload with an empty MK2 long bay and repost. Everything outside that part is stock, but there are airlocks inside from NF Construction (I think). Thanks in advance for looking.

Edited October 8, 2016 by burn_at_zero

[TwinKerbal]

Ok, so i've been doing some testing (writing speeches gets boring real fast), and the primary thing i've realized is that FAR and SSTO crafts are HARD! LIKE REALLY HARD!

But in all seriousness, I have gotten ONE SSTO up. It was pre-downloaded from another guy, search up S5 Arrow SSTO KSP on google. You can take out the mk2 passenger bay and replace with a cargo hold with all the science minus the science processing lab. It works, i got it into orbit and another time I made it into a suborbital trajectory, then had phantom forces take over. The only issue is that it tends to rip apart a lot.

Here are some links to help you out:

 

Hmmm....

I tried downloading your planes

They didn't load, I used this mod:

http://spacedock.info/mod/563/Near Future Construction

Missing:

crewtube-airlock-125

TPtank1mL05625

Edited October 8, 2016 by TwinKerbal
added some links :)

[TwinKerbal]

Ok, so I slapped together a rocket. It works on Kerbin for a 250x250 orbit with some dV to spare.

Craft file here:

https://kerbalx.com/TwinKerbal/Laythe-Ascender

It has all the science available in a 2.5m service bay.

Personally, you should just send a flotilla of ships. It is too much work for a poor PC to handle a massive mothership.

I'll keep working on the SSTO crafts.

[DerekL1963]

19 minutes ago, TwinKerbal said:

Personally, you should just send a flotilla of ships. It is too much work for a poor PC to handle a massive mothership.

That depends on your PC...  and makes the journey ineligible for the Jool-5 challenge.

Personally, I think the basic problem here is the whole scheme is too ambitious.

[burn_at_zero]

Thanks for the input, and for the craft.

The part crewtube-airlock-125 is from Station Parts Expansion, it's a one-person airlock. I have two of them in the bay so I can store multiple science reports like soil samples and gravity measurements without having to carry a full science lab or three full-size crew parts.  TPtank1mL05625 is from FuelTanksPlus, it's a 1.25m 1200-unit tank. I think the designs that use that one probably aren't worth pursuing.

It seems like an SSTO with a payload of less than 2 tons should be possible.

Yes, the original plan turned out to be too ambitious. Rather, too overbuilt. I just need to be more kerbal about things and not bother with redundancy. The low-gravity lander is easy; the Tylo lander is a little tricky but it's done. Only this SSTO stands between me and gigantic piles of science.

[TwinKerbal]

ok.

I'm back after a lot of testing.

Got two crafts to show for it.

They both have SCIENCE!

https://kerbalx.com/TwinKerbal/E43

https://kerbalx.com/TwinKerbal/S5-Arrow-FAR

 

[DerekL1963]

2 hours ago, burn_at_zero said:

The part crewtube-airlock-125 is from Station Parts Expansion, it's a one-person airlock. I have two of them in the bay so I can store multiple science reports like soil samples and gravity measurements without having to carry a full science lab or three full-size crew parts.

Hm....  Maybe you want to wait for 1.2 and the new science container?