totm may 2023 Elcano IV: Circumnavigate all the things!

[damerell]

Halfway home from the Panama crossing. The Pacific hasn't changed much; Hawaii has turned up on the zoom map, mostly because it is zoomed out a very long way, and what I think must be the Line Islands to the South.

 

[damerell]

Sunset, but there is nothing to collide with between me and home.

Back in the east half of the map, crossing the dateline.

I got a little confused here, forgetting both that my waypoint might not be absolutely spot on and that Omelek Island doesn't appear on the biome or altimetry maps (and barely on the visual map), but I spotted the VAB in the distance and headed for that.

And, finally, home again.

[damerell]

Returned home, Svetlana strolled into the KSC. "Anything much happen while I was away?"

"I think Jedcan ate the sandwiches you left in the fridge."

"No problem, they'd probably have gone off by now."

"Oh, and the astronomers have discovered three new gas giants with a bunch of moons, and another planet. Fancy another trip? Take your sandwiches this time."

I'm back, with the Outer Planets Mod installed. My first thought is to inventory the resources on the QA and the Hangarmoth. I plan to design a Hangarmoth II, but the QA's design is basically solid and any minor deficiencies can be made up by docking something to her existing stern. I did not mothball her completely (lucky!) and so I had a control channel to fire up one of the reactors and some radiators so I can do anything I want to before transferring kerbals up. My resupply situation is:

29,500 Fertiliser to full capacity. This does imply Fertiliser would have lasted for a mission circa 4x as long as Elcano IV (and I still don't understand how I got that so badly wrong) and that I don't need to dig deeper into the USI resource tree to keep the kerbals in Snacks, but already it means a considerable resupply mass. Hangarmoth II is to have only one Orion unit, which makes sense but does imply a strict limit on vessel mass (because it might be a huge amount of dV but it does have to be able to lift you off the ground) and so the Kerbin launch with extra mass will want considerable booster assistance.

I am less worried about the mass issue there than I might be. The Hangarmoth had huge Ore, MetallicOre, and Uraninite tanks - and little habitation capacity, so between these and my lack of understanding, the Hangarmoth was often expending huge amounts of dV to raise large amounts of raw materials into orbit to be processed into less dV. Hangarmoth II will have a larger habitation time limit and more processing capacity where necessary, and won't try to push unprocessed material into orbit.

The QA herself has no LFO storage. Currently I have 16,700 LF and the corresponding amount of O. I can save some weight on the Hangarmoth II launch by recovering this from the Hangarmoth; fortunately, the QA's stern docking port is the same type as the ports on the Hangarmoth, so I can dock to the Hangarmoth, suck it dry, and cast it off before docking to the QA.

There is no Machinery at all. It was jettisoned to save mass.

There is 39,300 monoprop, of which 6,700 fits in the tank on the QA. More scope for recovery there.

Supplies (the USI life support resource) are full.

146 atomic pulse units remain. Not a lot, but I can top off after the launch from Kerbin. I must also avoid the situation where the Hangarmoth is burning pulse units to land a huge reserve of pulse units just to shove them into orbit again, but without risking being stranded.

The QA's reactor is at 156/450 enriched uranium. There is more in the Hangarmoth's reactor, but while these USI reactors can be refuelled by kerbals on EVA, I don't know if I can steal fuel out of one for another's benefit.

Edited September 12, 2023 by damerell

[damerell]

At some point I shall review the thread and look for every time I wrote "if I were doing this again...", but I can start with the obvious stuff.

Each pulse unit (at maximum setting) provides a shove equivalent to 15,700 kN applied for one second. Hangarmoth II had better be able to pull about 1g (we might reduce this a bit, none of the OPM moons are as big as Tylo and the takeoff from Kerbin will be booster-assisted), implying a maximum mass of around 1.6 kilotonnes with each pulse unit providing 10 m/s dV. On the face of it this is an awkward number, since the Hangarmoth only got down under it (1.2 kilotonnes) when almost dry of everything; I have a couple more screenshots of it around 1.75 kilotonnes. However, only having one Orion unit does save 160 tonnes right off the bat. She also had capacity for circa 3,300 pulse units - 1.5 kilotonnes fully loaded. The biggest dV demand for OPM moon landings (not counting Tekto, where I expect to use an Eve-style approach) is Slate at 2,150 m/s - 430 pulse units for descent and return from the low orbit where I can leave the QA. A large magazine (240 pulse units) weighs 4 tonnes dry, so empty magazines are not a problem; Hangarmoth II should probably have a capacity around 1,200 pulse units for low-g worlds with good ISRU conditions, but should only be landing with a supply carefully tailored to the target world. Conversely, the QA has space for only 1440 pulse units; she should have another six-magazine unit docked to her to give me a similar overall capacity.

Hangarmoth's Hangar weighs 180 tonnes... but the endcap weighs 36 and the adapter to a more normal profile another 60, with neither part carrying anything useful like LFO. The Hangar now is an extremely awkward size, too, since the Mk VIII rover is just too big for two of it to fit, unlike the earlier rover marks. I don't expect the rover to get smaller (albeit this assumption is worth double-checking) and it seems very likely that a more conventional hangar (which unlike the LLL part the existing Hangar is made from can have its size adjusted in small increments) could transport one rover for much less mass. Probably to save part count I want a three-way symmetrical Hangarmoth II with two hangars holding standard rovers and one holding a drill-covered rover to deploy and dock externally. Then all my drills won't be part count in flight. LFO, monoprop, and pulse unit stores should all be in symmetry so a fuel balancer can always keep me balanced about the thrust axis.

The existing arrangements to drill Uraninite and refine it were satisfactory, and unlike other raw/intermediate materials I am perfectly happy to take off with a full load of Enriched Uranium weighing a princely 3 tonnes (suppose I land somewhere with no MetallicOre, I can carry the uranium to the next world and make pulse units there).

Metal refining capacity should be doubled; a second refinery weighs 11 tonnes. On metal-rich worlds the existing drills could easily outpace one refinery, so there's not much need for more capacity there. The Machinery supply the refineries come with was adequate and if it turns out I'm using it all up by being much better at ISRU, great (and I am sure there will be at least one resupply mission).

Ore refining capacity should be at least doubled. A Convert-O-Tron 250 weighs only 4 tonnes.

Hangarmoth carried 114 tonnes of monoprop and 230 tonnes of LFO. Overall capacity was too low (hence the "mast" that was shipped out and stayed with the QA when tanks were full, came down when tanks were empty) but if we're cutting the mass of Hangarmoth II perhaps that will be about right, and it's not clear she needed anything like that capacity for even the worst landings. QA has capacity for 27 tonnes of monoprop and no LFO; something like the "mast" should be provided again to either leave excess fuel in orbit or bring down to fill up with ISRU.

Hangarmoth carried 104 days Supplies, but maximum habitation time with 4 kerbals was 31 days. This must be extended - I should be able to stay down a long time if ISRU conditions are good and the next transfer window isn't pressing - and she'd better be able to recover the Mulch the kerbals generate.

For a bit of a break I took a look at the Jool probes and the bus vehicle. To redesign the bus for a bit more dV is easy, but the scheme used for Jool where each probe carries a big enough antenna to phone home won't do. Each probe needs a default-on omni (so when they emerge from the hangar they're in control) and a directional antenna to reach the bus, which brings the one and only phone-home antenna. RA-2s will do for everything but Neidon's wildly eccentric-orbit moon Nissee. Commsat targetting can be adjusted in the Tracking Station to avoid the common problem discussed in https://remotetechnologiesgroup.github.io/RemoteTech/guide/overview/#targeting.

Edited September 14, 2023 by damerell

[damerell]

There's more low-hanging fruit to pick from the rover. The maximum habitation time is 242 days... generous, since even Tylo took only 8 days. Removing the 3-tonne habitat leaves 17 days habitation and supplies, and means more other parts can be fitted in without increasing the overall dimensions. This isn't altogether easy since that's where the airlocks are mounted, but the cunning designer can improvise. (However, for some reason even if the "habitat" was running on the cockpit when I saved, it was turned off when I loaded, reducing habitation limits. A boot-time kOS script should turn it on so I can't get stuck with all the kerbals sulking unable to turn on their own life support...)

Conversely, one of the oddities of the rover is the way electric charge drains so quickly if the reactor is off - at first I thought this was a bug in CAMREC, but it's simply that it's a 50 tonne electric vehicle with 1.2 tonnes of battery (512 MJ). A Nissan Leaf, say, weighs 1.6 tonnes of which 300kg is a battery (144 MJ). Furthermore, no-one tries to drive Nissan Leafs offroad up 10% slopes at 43 m/s in Eve's gravity. By and large the combination of the battery, reactor, and reserve fuel cells worked, but some of the removed space and mass could easily be used to increase battery storage and fuel cell output. The kOS script that runs the fuel cells should have been more aggressive about turning them on; I got home on Tylo with 85% of my LFO left.

The top-mounted engines are useless on medium-to-high gravity worlds, but weigh almost nothing; I don't want to have two different rover models. (Likewise, extra battery capacity will be useless on low-g worlds, but same argument.) The top-mounted solars are completely useless where I'm going and have been removed.

Tweakscaling the wheels up to 1.1x gives more ground clearance and a new top speed of 48 m/s, which will help on those long flat expanses. It does further increase maximum power but I'm going to try capping motor output at 50% with a kOS-controlled facility to restore it to 75% or 100%.

Finally added underbelly skids. Why did I not do that years ago? Note to self: the right-hand storage locker needs filled. All the action groups got cleared (why?)

Removing the crew bay means it can neatly be replaced with a Karibou storage part of the same dimensions filled with LFO. Another "why not years ago?" here - LFO is heavy, electric charge is not. Moving LFO down into the main body of the rover to replace the habitat and batteries moves the centre of mass down; adding the great big dorsal battery last seen on the Eve rover doesn't move it up all that much, and gives considerably more electric charge than the Mk VIII. (We still have an absurdly low proportion of our mass be batteries, but then, we do have a nuclear reactor and a bunch of fuel to burn; the last major change is adding a third fuel cell).

Compared to the Mk VIII this rover is three tonnes heavier, faster, more stable (I hope), and a very similar size. The main issue so far is that mod updates mean the fuel cells are now ODFC (OK) and do almost nothing - with all three running flat out, I get 96 EC/s and will burn through my LFO in 44 days. I guess the ODFC numbers I used for CAMREC have changed.

(Turns out OFDC picked a quadratic component for Tweakscaling fuel cells (what?) and since I'm actually managing fuel cell operation with kOS, I'm just removing ODFC for now.)

Edited September 14, 2023 by damerell

[damerell]

Slow progress, but I've tested the new probes and bus vehicle out to Urlum. I knew life support endurance was much more than expected, but a closer look means I think I have endurance for 162 Kerbal years. For these outer planets it is worth looking at all the launch window possibilities ("if I go to Sarnus first, I can then go to Urlum in x years, Neidon in y years, Plock in z years") and I hope I can have a plan to do them all inside that endurance limit.