WarSprite

I had a really quick play with it while I was designing my first probes and running into part count issues. It seemed like the ideal time to use EVA construction - lots of small light parts on a probe. With three Kerbals assisting Bill could manipulate 0.24 tons on the launchpad (Kerbin gravity). The Oscar B was my heaviest probe part at 0.225 tons, so that was manageable. The Hitchiker Storage Unit holds 1,500 liters per can *and* your four Kerbals, so even just one part (the Hitchiker can) was handling all the parts and the assembly team for building the full probe. The Hitchiker Storage Unit is a bit heavy for a caveman to include in the launch vehicle, but nothing to stop you building a crawler to carry the Hitchiker and assembly crew out to your rocket that's already on the pad. There were some issues. It worked fantastically for parts that were directly in the stack. However, I couldn't find a way in the UI to do symmetry in the assembly, so although I could individually place Micro Strut lander legs, the craft came out looking a bit deformed. The same symmetry issue affected placing fins (another great light small part to beat part count issues) at the bottom of the launcher. Bill has a limited range for assembly, so for probe assembly (top of the stack) so you need to get the can to "something like the right height" and have plenty of ladders on the can so the Kerbs can move around, which uses some part budget in your assembly vehicle that's carrying Kerbals and parts out to the pad. The benefit is that Bill has *some* range, so it is far less sensitive to being the exactly correct height like a docking port for traditional lawn assembly. The killer for me that stopped me playing with it was that I couldn't find any way to build inside an existing fairing (which seems reasonable) or to build a fairing up from a fairing adapter after I had constructed the probe. That may be me missing something in the EVA assembly UI, or may be a limitation. Due to all those draggy probe parts, and my flying ineptitude I really did need a fairing on the probe launchers to sort out CoM / CoP issues and get a flyable launcher. Overall it seemed like something with potential, and worth another play, but personally I just ended up stripping things down to fewer parts and (just) getting inside the normal part and mass limits. Oh good grief. Thanks for the pointer Blaarkies! Totally unaware of that. Yep, I'm a social media noob, and that includes good ways of sharing posts inside forums. Good pointer on the spoiler tag too. I did (around my last post) see another thread where someone suggested "Post Image" site https://postimages.org/ as a good way of getting images into the forum for those of us who are allergic to creating new accounts on services such as Imgur.

Thanks JAFO! /bow Ug Ug Ug! WarSprite.

Thanks Minimal I need to wait for confirmation from JAFO for my Caveman badge, but can't see a reason for a problem. Regarding NCD, you're a braver man than me. I may be wrong, as I've not even made an attempt, but NCD *looks* to be more about the grind, and less about individual rocket designs. There's always a couple of MMOs I can go back to if I want more "grind" I'm actually kind of disappointed that my run is over. I was loving the challenge of stretching those 18 tons as far as I could. It kind of makes a mockery out of my 150 ton first Mun lander in the regular game If anyone has thoughts on some of the other "Heritage Challenges" that keep you really focussed on craft design, I'd love some input folks!

Here's the summary of my flights for the challenge - I find this gives an easy view of where science came from : # Area Experiment Recovery WKRS Total 1 Launch first vessel 5.4 3.0 2 10.4 2 Science flying high 14.0 0.5 1 15.5 3 Pressure scan flying low 5.0 0.1 0 5.1 4 Pressure scan flying high 6.5 0.0 0 6.5 5 Science in space low 22.8 4.8 3 30.6 6 Science in space high 34.2 0.8 1 36.0 7 Materials flying low 13.4 0.0 0 13.4 8 Materials flying high 17.2 0.0 0 17,2 9 Materials space low 19.2 0.1 0 19.3 10 Materials space high 28.7 0.0 1 29.7 11 Kerbin orbit 0 6.0 3 9.0 12 Minmus flyby 90.0 9.0 7 106.0 13 Minmus orbit 144.0 15.0 3 162.0 14 Minmus landing 180.0 22.5 2 204.5 15 Mun flyby 72.0 7.2 4 83.2 16 Mun orbit 108.0 9.6 2 119.6 17 Mun landing 48.0 18.0 3 69.0 18 Mun landing and science 132.0 3.0 0 135.0 19 Kerbol orbit 72.0 19.2 6 97.2 20 Duna flyby 180.0 3.2 4 187.2 Totals 1,192.4 122.0 42 1,356.4 Here's the screenshots of my science archives : https://drive.google.com/file/d/15Q-HFP4leApU32dZhKDQlnuw0H4tUoh5/view?usp=sharing https://drive.google.com/file/d/1BL-MaaPCg4RPS7xY0eQy7h7DBSCu04Ea/view?usp=sharing https://drive.google.com/file/d/14r85K7Unz7PPpCVywg9g6XkeuHyDgpSE/view?usp=sharing https://drive.google.com/file/d/11hlpsVL9qZAYsK_SWw-1AbkGQ3R-O50Z/view?usp=sharing https://drive.google.com/file/d/1zft02EJrPeR_IEBcUD2Eytb0tzP2GR2S/view?usp=sharing https://drive.google.com/file/d/1ytlK7oceZCsIentmPNaSxb5UEOMgdysj/view?usp=sharing Here's the screenshot of the pristine (primitive) KSC : https://drive.google.com/file/d/1yr4pogR7jA-JFgi6Vsy0C69loU_WsNMG/view?usp=sharing Here's the screenshot of the tech tree completed to level 5 : https://drive.google.com/file/d/11LYGBL8Gngq7OAI9G9MQbgc5pneGxXe_/view?usp=sharing That's the challenge complete with my three aspirational goals intact and achieved : No science at all from the KSC (area biomes or structure biomes). No science at all from Kerbin biomes, not even an accidental temperature scan flying low (which is biome specific). No contracts taken at all, so no science from contracts. Further, I never set foot in Mission Control (contracts) or Administration (strategies) and I mostly managed to stick with my thoughts on "visit new places, don't farm places you've already been". I did do two Mun landings (different probe designs) but I'm happy to think the surplus science from Duna makes up for that. I'd like to add that this has been great fun. Designing these "primitive" ships has been remarkably advanced to get the required performance, and flying them with limited propellant budgets has taught me more than I knew about orbital mechanics. Loads more still to learn though! A big thanks to Mr Peabody for his original work on the challenge and paul_c for his helpful feedback. Most of all, a big thankyou to JAFO for taking over the challenge administration, and for his encouragement to keep going. Cheers guys!

After some playing around, and JAFO confirming that launch window calculators are OK, I decided to go ahead with a quick excursion to Duna for the last 19 science that I need. Sure, Duna is going to be a little over-kill, but it's in keeping with my efforts to keep doing something new, rather than grinding science out of the same celestial body. Apologies to those who want pretty pictures of rockets - nearly all the screenshots are from the navigation screen, as it is there that the real work happens. Flight #20 - Duna Flyby This is the same variant of the launch vessel that I used for the Kerbol orbit. I'm getting a little better at flying it and after reaching LKO I had 2,195 m/s in the tank; I've done slightly better in some practice runs, but that's not bad, and far more than I need for the flyby. The launch window planner suggested year 1 day 229 for minimal propellant usage, so I left Jeb in orbit nomming some snacks while I timewarped. Despite notes to "be careful and take it easy" I nearly overshot the launch window, coming out of timewarp only 5 hours before burn time. After a few orbits I used the sundial to burn "about" 155 degrees from Kerbin's prograde direction. The first thing I do after the transfer burn is check how the exit looks compared to prograde, and burn radial in or out to visually make the exit parallel. In this case it was a bit of radial out. After that I adjusted apoapsis to 19.8 Gm which I've found reliable for a Duna encounter. https://drive.google.com/file/d/1NprDg2Errf6KYj6W1v72U_IJ0S-CkDK0/view?usp=sharing https://drive.google.com/file/d/1T9vtcXVMbrYQZbM2w67oPJozctnxJFT0/view?usp=sharing The actual Duna encounter was about the same as practice flights. The 12.81 Mm periapsis relative to Duna was well inside the sphere of influence, but not close enough to significantly affect my overall orbit around Kerbol. I switched to the ship screen and did all the science experiments, then let Jeb coast out of the Duna SoI and back to Kerbol orbit. https://drive.google.com/file/d/1Nd1nZQ70lYH7rHpM_xUKdY7t1B_XWPUt/view?usp=sharing https://drive.google.com/file/d/1VWTB-jWfulMqLolYP8BzveTUwIg2SVoX/view?usp=sharing After a lot of playing on low delta-v ways to get Jeb back to Kerbin, I settled on a method that works for me. I adjust periapsis to match Kerbin's orbit, then grab some numbers to do a calculation with. I note the time when Kerbin passes the ship's periapsis, and the time when the ship reaches it's periapsis. The difference tells me how far around its orbital path Kerbin is, so given Kerbin's orbital period, I know the duration I need to make the ship's orbit so that the ship and Kerbin both arrive at the ship's periapsis at the same time. A quick calculation and I burned to set my apoapsis to the calculated value of 18.7146 Gm to get the desired orbital period. I actually messed up this time, made an error, and used about twice as much propellant as needed; in practice runs this normally takes under 120 m/s delta-v whereas I used 217 m/s this flight. https://drive.google.com/file/d/1BtTb1OkFx2fWjuwMvZyZXAmt8faVKU2X/view?usp=sharing After that Jeb got to eat some more snacks while we waited for Kerbin to catch up. The encounter looked about what I've typically seen, and had a 12.4 Mm periapsis over Kerbin. Some radial-in at the edge of the SoI dropped that to 40km for re-entry. Surface speed is a little scary when you arrive at Kerbin's atmosphere, but the revised rocket keeps the Service Bay which does a great job of acting as a heat shield. Despite my error there was still 681 m/s worth of propellant in the tanks when I staged them away. https://drive.google.com/file/d/1SSWEe0kPWzY-1bEfnYp3woI-V4P0yg7l/view?usp=sharing https://drive.google.com/file/d/16Yrka6vChwDH3cW6knBMgVenJbWPbLhF/view?usp=sharing So that was that, Jeb home safe and sound with an experiment lunchbox full of Duna science. The flight got 180 science from experiments, 3.2 science for "Recovery of a vessel returned from orbit around The Sun" and 4 science from the WKRS, giving a total haul of 187 science. I don't understand why I was credited with recovery (second time) from around the Sun rather than the more valuable Duna flyby, but given that I only needed 19 science, the overall total was far in excess of requirements, so that's fairly immaterial. My next post will just be the pictures of Research and Development, Archives etc.

In my last post I shared that I was 19 science short of completing the challenge. Having looked at the delta-v maps on the net, Duna looked like a tempting target to get that last bit of science. I'm relatively new to the game, and have never left the Kerbin system and gone interplanetary before, so visiting somewhere new was also an appealing target. It also turned out to be a bit of a learning experience My thoughts were that according to the delta-v map, my manned rocket has the range for Duna, and that Duna has a nice low inclination (unlike Eve) simplifying the journey. At interplanetary distances an unmanned probe seems unlikely to work (range attenuation of the control signal), confirming my thoughts of sending Jeb in my current iteration of crewed rocket on a fly-by to pick up my last science points in space high over Duna. I have a memory that I've previously read that launch window calculators are considered "allowable" in the challenge since you're not changing anything in game, just using the information from your Caveman game to get some decisions, but still making the flight in your primitive game. So I started practicing in a Sandbox game using the excellent Launch Window Planner. I quickly got to the point I could reliably get an encounter with Duna and perform the fly-by. That's around about when I found out that space is big, and planets (even in the compressed KSP system) are small. Getting Jeb back from Duna turned out to be a lot harder than getting him to Duna in the first place. My problem is self administered by using a single 18 ton caveman launch, which limits how much performance is "in the tank". It has plenty of delta-v to reach Duna and do a fly-by, but not enough to enter orbit around Duna and then later burn for a return to Kerbin. If it did, then those same launch window planners would make getting Jeb home a lot easier. Even worse, having boosted to an elliptical orbit to reach Duna there isn't quite the delta-v left to drop apoapsis back down to Kerbin's orbit and "just let Kerbin catch me" at some point. I tried a lot of sundial navigation, and even got Jeb home a couple of times, but nothing that I could make work reliably. Time to do some reading on orbital mechanics. After a couple of false starts I now have a little spreadsheet that takes a couple of numbers from my orbit and Kerbin's orbit, and gives me a suggestion on how to get the two to intersect at the same space and time to recover Jeb. After a few test flights this seems to work quite reliably in my Sandbox development game. So yay! Ready to send Jeb on a fly-by past Duna to pick up the last of the science @JAFO - can you confirm that external launch window calculators and spreadsheets are considered "allowed" in the Caveman Challenge? Not mods to the game, but external tools where you transcribe information you read from the game in to the tool, and then use the information the tool provides to make your in-game flight decisions and manoeuvres. Specifically I have been using the Alex Moon Launch Window Planner : https://alexmoon.github.io/ksp/

After the Mun landings with probes, it's time for a nice easy crewed flight to pick up some more science. After my learning with probes, I've made some small changes to the manned ship, switching to a single Reliant booster for lift off and a hence a low TWR design. This leaves a little more mass / parts budget for fuel tanks, so a little better delta-v. I don't need it for this flight, but I can't resist tinkering with designs. Jeb likes having a bit more propellant to play around with though Flight #19 - Kerbol Orbit I sent Jeb off on a quick trip out of Kerbin's sphere of influence. Dropping outside the SoI made sense as an easy situation to reach to get some more science. It wasn't my best launch on this design, but 2,060 m/s in then tanks after I reached LKO was still far more than needed, so good enough. In test flights I've tried leaving Kerbin by pushing escape velocity to the listed 3,431 m/s but this uses more propellant than basing it on just getting out of range of the 84.16 Mm Kerbin sphere of influence. So at about 8 o'clock on the sundial I boosted apoapsis to a target of 84.5 Mm. I was a little late on the burn, and overshot on the thrust a little, but no big deal on either count. The trajectory still put me in the prograde direction ahead of Kerbin in its orbital path, which is what I wanted. https://drive.google.com/file/d/15h8FJE6h5torbTlmrZ9gZfCnyDO40FgO/view?usp=sharing A long coast along the orbit, and Jeb found himself outside Kerbin's sphere of influence, so it was time to do the science thing. That just left a retrograde burn to slow orbit around Kerbol down to 9,280 m/s and then I just let Kerbin catch up to Jeb. Given the large apoapsis of the flight I bottled out of my normal 41 km periapsis for Kerbin re-entry and thrust for 41.5 km and a shallower re-entry. In practice this didn't make much difference to my surface speed at Kerbin, but did mean that I skipped out of the atmosphere for a (thankfully) quick orbit before finally coming down. Lesson learned, trust your numbers from your test flights. https://drive.google.com/file/d/1g8n9aUlEnnkSjoXlVFC11_SiDIa6JOse/view?usp=sharing https://drive.google.com/file/d/1wuez9tK9IL8jguQ8gibWomtsfbYISdOQ/view?usp=sharing Whilst it's not as big a deal for me as when Jeb did his orbit of Kerbin and reached pilot level 1, having done Minmus landing, Mun orbit, and now Kerbol orbit, he has levelled up and can now push all the SAS buttons Of course, having target hold marker available would be nice for docking manoeuvres, if I went down the orbital docking route. https://drive.google.com/file/d/125hGXALSUZAwy4LIRpNSLCvay7TMW9GV/view?usp=sharing This flight netted 72 science from experiments, 19 from recovery and 6 from the WKRS bringing me to 476 science in the bank. I've had Kerbol planned from the outset, but only known for the last flight or so what was now confirmed. It is not quite enough! That's a tantalising 19 science short of completing the challenge. I'm now not quite sure what to aim for. I can of course farm somewhere I've already been for the remaining science, or even break my personal targets and just do a few Kerbin biome spots. Easiest would be two flights to pick up the points for recovery from Minmus orbit, and recovery from Mun sub-orbital flights. However, given that I've kept trying to visit new places on this run, those are slightly less appealing when I look at the delta-v map and see how close Duna is. I think some test flights in Sandbox may be called for...

Thanks for the encouragement JAFO ! Sounded awesome! So I looked and couldn't see any such option in my game. So I googled. Dammit, "Advanced Tweakables" option in settings. That's fantastic. Not just for the lander, but for many of my regular Caveman rockets, draining the bottom tanks to move CoM up and improve stability before reaching Max-Q is a fantastic thing! How did I not know about this?!? Thanks for the pointer JAFO

So while flying practice flights, I had a bit of a "D'oh" moment on the next design. I had been using a X200-16 tank, Rockomax adapter and Skipper engine to keep the parts count down. I realised that I can get the same tank capacity in the same two parts using FL-T800 tanks unlocked in the same node as the X200-16. I don't know why I overlooked that previously, but hey-ho. The tweak to using FL-T800 tanks and a Reliant left me with a little more mass allowance for more delta-v. Some of the extra delta-v is taken up by the longer ascent of the low TWR design; the Skipper excels in a quick fast ascent on an 18 ton rocket, but if you fly a sensible profile the Reliant is a net win over my previous thoughts. The other benefits of the revised low TWR design are that you can use the tiny reaction wheel (the Skipper needed the small reaction wheel for more control authority) so I no longer needed the Advanced Flight Control node and of course, without the Skipper, I don't need the Heavy Rocketry node. So I had to unlock Fuel Systems node for the large tanks, and the Miniaturisation node for the TS-06 Stack Separator, leaving me 244 science in the bank. The new low TWR design flies much like the previous probe, so after a couple of launches I was ready for a flight in my Caveman game. Flight #18 - Mun Landing and Science This one has 7,586 m/s delta-v in the stack. That's not quite as useful as it sounds, since 1,380 m/s is in the ascent stage; you have to land and complete the science before using that, but it's still a healthy margin. The gentle take off went well and left 4,026 m/s in the tanks for the mission after reaching LKO. https://drive.google.com/file/d/1dUpr2Y0I1PMb5mZwFpTv91Td_ECpOwQr/view?usp=sharing https://drive.google.com/file/d/1IDYdExdzYstkIaJIwAiHmXPg0hOisoAs/view?usp=sharing The normal sundial navigation for Munar transfer, and I had a nice retrograde encounter with -126 km periapsis. Having managed to score the Northwest Crater on the previous flight, any landing spot was a good one - I didn't need to worry about avoiding the "common" Lowlands biome. The landing used 730 m/s worth of propellant, leaving 745 m/s delta-v in the landing stage in addition to the ascent stage. Given that the Mun landing was the phase of the flight that could prove tight, this was an excessive safety margin, but I'd rather that way than running out of propellant. https://drive.google.com/file/d/1LifNuCw4D01u40ZZj5hQPbKju1i21eTF/view?usp=sharing https://drive.google.com/file/d/1sSgP9YyMPedlUVIz4ReL0CL33CPxHYiu/view?usp=sharing On practice flights I've been staging on the surface and just using the ascent stage, to ensure it had the legs for return to Kerbin. It does, but since there was fuel left in the lander, no need to waste it in the real run, so I took off using the lander, and staged in orbit before my escape burn. The weaker TS-06 separator only drops periapsis by about 10 km, so back in Kerbin's sphere of influence I set a 40 km periapsis before staging the engine away. This dropped me to a 31 km periapsis as hoped. A cruise home, point retrograde, turn off stability assist, and re-entry went as expected. https://drive.google.com/file/d/1eI-MXWs8VskL1OAiDGQMmhw9rK3iCbsQ/view?usp=sharing https://drive.google.com/file/d/1X9VgP7NpqVw3vwGvrsHtzNrIVxDFcDLN/view?usp=sharing When I got rid of the last engine I still had 1,088 m/s in the tank which is a really large safety margin on the flight. I suspect you could forget the TS-06 Stack Separator, and build this with the TD-12 Decoupler to save unlocking the Miniaturisation node. The full science package on this probe netted 132 points from experiments, however since I've previously landed on the Mun, only 3 points for recovery and none from the WKRS. That brought my total to 379 science in the bank. So that's Minmus and the Mun "completed" in that they have both seen fly-by, orbit and landing. The total science haul is getting close, but it's not there yet. So for the next flight I'm sending Jeb off for a Kerbol orbit, to stick with the idea of visiting new places rather than farming biomes on objects that I've already been to.

Well, after a bit of a learning experience, and many design iterations and tweaks, I now have not one, but two probe designs. I've spent a couple of days running practice flights on the first design, and today was happy enough to load the craft to my Caveman game and finally progress a little further. This first probe has a couple of advantages; it uses fewer tier 5 science nodes, so can be used earlier in the challenge, and it has huge reserves of delta-v. The penalty for this is that it only carries the thermometer and barometer; I'll need to fly my second design for a full science package. Unusually for me, this first design is a low TWR launcher; no big deal, and I'm not sure why most of my designs end up as high TWR launchers, I just need to take the ascent a little more gently with this. I had a good think about Paul's comments on communication relays. It seems that range attenuation isn't a problem for the Mun (at least on Hard difficulty), it's just the blackout when you're behind the Mun. I flew a good few practice flights in Sandbox arranging manoeuvres so that I never needed to do anything behind the Mun. This does not give you full flexibility for every trajectory and landing site, but for a simple "put down anywhere on the Mun" it seems to work just fine, and saves designing and launching communication relays. One thing I needed to keep reminding myself is that it's "just a probe". If I splash the flight I'm just wasting 11K funds, it's not like I'm losing Jeb. That's not to say "be complacent", but when I keep reminding myself of that it takes some of the pressure of the flight. Before the flight I had to unlock more nodes for the first time in a while. This design needed me to add Electrics and Flight Control for the probe, General Construction and Advanced Construction for the fairing, and Propulsion Systems for the Spark engine. Spending on these nodes left me with 355 science in the bank before the flight. Flight #17 - Mun Landing I'll start with an image taken in the VAB of the design in case anyone is interested; 7,618 m/s of vacuum delta-v on the total stack. Launch was nominal leaving me in a nice 71 km LKO with 4,133 m/s in the tank for the Mun mission. https://drive.google.com/file/d/1lEn-b1zdRjtQgYY8M-U4G3UpVaKg2Ron/view?usp=sharing https://drive.google.com/file/d/10Ny2loDW7JuDntFwGQ6Lf0lFjc1vrZIc/view?usp=sharing The Mun transfer burn went well, and gave me a nice encounter just after Kerbin apoapsis, with a 85 km Mun periapsis. A touch of radial in at the edge of the system brought the periapsis down, and then I circularised at periapsis. The orbit was near equatorial, and just missed the Northwest Crater; a minor correction allowed me to pick that for a landing site. https://drive.google.com/file/d/1edFdsul4WYT9E22Rfp4F6MdSJk2McrQ4/view?usp=sharing While practicing this flight I found that Minmus has left me with bad habits. When reaction wheels can pick the ship up you're less careful about the landing. The Mun is not so forgiving; use landing legs, set down somewhere level, and keep the ship pointy-end up while you land One thing that I've been doing with this design is turning off the fuel feed on the FL-T200 on the lander. This causes it to drain the FL-T100 first, which in turn lowers the centre of mass when it comes to a Mun landing. It's just a minor benefit, but anything that helps keep the ship upright is a good thing for me. Murphy's law means that the little tank empties during the descent / landing stage, but it turns out to not be a huge deal to then enable the propellant flow back on the large tank. I took the descent carefully, and burned more fuel than an optimum landing using 885 m/s to land, but the design has a large margin, so that didn't worry me. Once down, I did the science (yep, all TWO experiments), sucked the data into the lunchbox, and got ready for lift off. https://drive.google.com/file/d/1rcGv_S6NBHmrUWmfPU1yzsp_vg4H3Mws/view?usp=sharing https://drive.google.com/file/d/15vUJp1l0ylRHg2BQLS58r8hrV3Ky-FPx/view?usp=sharing Back in orbit I hit an escape burn at about 02:30 on the clock to 810 m/s orbital speed. This gave a lovely trajectory out from the Mun, dropping me back into Kerbin's influence with a periapsis of 400km. During testing I've been staging the engines away at the Mun end of the encounter, and have noticed that due to the light weight of the probe, the impulse from the decoupler makes a significant change in velocity and hence periapsis. In this design it drops the periapsis about 20 km, so I burned for a 45 km periapsis, then staged the engine away. There was 996 m/s propellant left in the tank at this point - the design really is overkill. That left the probe core recovery package with a 25 km periapsis, which is just fine. I timewarped close to Kerbin, came out of hibernation, pointed the package retrograde, and turned off SAS altogether. As remarked in my development notes, the stable design just tucks in behind the heatshield and naturally follows retrograde direction all the way down with no thermal problems at all. https://drive.google.com/file/d/1wg-NggGALjGG5zyLTNJk4wPuvLjbJUss/view?usp=sharing https://drive.google.com/file/d/1RCdbwT0GRQ3fqVbiZZeMKJJjfHvOi4L7/view?usp=sharing The science haul on this flight was unsurprisingly small given that it only carried two experiments. Recovery awarded 48 for the experiments, 18 for the recovery, and 3 from the WRKS. Those 69 points brought me to 424 science in the bank. That's more than enough for the extra nodes that I want for the more advanced probe, so it's all good. The main thing for me was proving a probe land / return within Caveman limitations. My next flight will be another Mun landing, with the next probe for a full science package. It may be another couple of days before I make that one - I still need to practice flying the advanced design, and it has considerably less delta-v available, so will be a touch more challenging.

Well probe design for the Caveman Challenge was a new experience I'm so used to the Command Pod (just point it at a sensible periapsis) that the odd little challenge in probes was a surprise. So I thought I'd share my "lessons learned", firstly in case anyone can suggest better ways of doing things, and secondly in case anyone new to the challenge is reviewing the thread and wants some random inspiration. Science Box Recovery : Having discovered the hard way that the low temperature limits on probe cores make recovery "interesting", my first thought was avoid recovering the core at all, and just return the science. This is remarkably easy to get working; if anyone isn't familiar, just point your ship to a reasonable periapsis, activate a parachute on the science lunchbox, and stage it off your probe. The game will class it as debris, but as long as you use the Tracking Station and switch to your science box, you can "ride it down" through the atmosphere; it won't be deleted, and you're credited with the science when it touches down. It works a treat, and those things are fantastically resilient. The only issue is that they are "debris" not a "vessel" so you don't get science credit for "Recovery of a vessel from X" or WKRS records (or any contracts). If the experiment science is all you want, then in my opinion this is definitely the way to go with probes. I wanted those recovery points too, so filed this as "useful" and moved on. Parachutes : A Mk12-R radial drogue is more than enough for a bare science box, and is just enough to recover a science box and Stayputnik, but for anything larger the impact velocity is a bit high, so I use a Mk16 or a MK2-R radial parachute. I'm used to manually staging my parachutes when I'm happy with the altitude and surface speed, so it took a little while for me to be comfortable with staging in space and letting the automatic parameters pop the laundry out. If you're only recovering the science box you have to do this, as the lunchbox can't activate the chute; if you're recovering a probe core it's a good idea to do this anyway, just in case you run out of electric charge and the probe dies before you manually activate the chute (don't ask me how I know that). I've taken to setting the pressure to 0.32 as this deploys at just under 7 km (on Kerbin) inside the "troposphere". If the vessel is still travelling too quickly for the parachute at that altitude, you've set your periapsis too low, and it's going to be a "shovel and trash bag" recovery regardless. Electrical Power : Probes and reaction wheels need electrical power. You don't actually need solar cells at all; with careful use of "hibernation mode" on the probe core outside of your manoeuvre windows, a small battery is adequate for exploring the Kerbin system. Given the part count limits on the Caveman Challenge, eliminating two to four solar panels is a real help. Be aware that it's hard to find somewhere to put the Z-100 Battery Pack that doesn't stick into the plasma stream on re-entry, and if it does, it will burn off. If that happens, the core's built in electrical charge doesn't last long. One solution is the Z-200 Battery Bank that is stack mounted so not in the air stream, and benefits from a higher temperature tolerance. Another solution is designing the probe for aerodynamic stability so that you don't need the probe core to be functional during re-entry and hence don't need electrical charge. Probe Design for Re-Entry : The probe cores all have low temperature thresholds. I can't bring them in on their own, and need to use a heat shield. It turns out that, contrary to some forum advice, a 0.625 meter heat shield can shield the probe cores, but only just. The probe cores are only just shielded, so are very sensitive to not pointing exactly retrograde; when they're not exactly retrograde, the edges of the probe core stick out past the heat shield and into the plasma stream. When you're arriving with a surface speed of 3,000 m/s or more, putting any part of the probe core into the hot plasma, even just an edge , will mean that it will overheat and explode in a matter of moments . If I'm manually driving a probe down, I find the OKTO's built in reaction wheel a bit weak for pinpoint aiming, so like to have an external reaction wheel for better control authority. This helps my bad driving keep the probe very close to exactly retrograde, and hence the probe core behind the heatshield. However, an even better solution is to make the probe aerodynamically stable. If the probe is stable, you just get it roughly retrograde at the top of the atmosphere, turn off SAS altogether, and it just tucks in and sits behind the heatshield all the way down with no risk of overheating. Slashy wrote a lovely post pointing out sectional density and drag considerations when choosing the stack order in your probe. I actually still had issues despite following his suggestions, and suspect his probe design was relying on the drag of the OX-STAT solar panels to stabilise the probe. I don't have solar panels to apply drag to the back of the probe. My eventual solution was to turn the science lunchbox sideways and radial mount it on the top of the stack; the drag from this acts wonderfully as "tail feathers" at the back of the probe, and the side of the box is the perfect size for a Mk2-R radial chute. Heat Shield : As discussed, I find a small science return probe can be perfectly shielded by the 0.625 meter heat shield. I started with the engine still on the front, but found that the extra mass and lower drag from the engine shape meant that even on a gentle re-entry, the probe did not shed enough speed to safely pop the laundry. Hence now I set up the periapsis and stage the engine and tanks away. With the heat shield, probe core, science box and parachute, I have found the recovery to be very insensitive to periapsis. Anything under 41 km will come in in one pass, and (so far) anything over 20 km survives the re-entry. I need to test lowering the periapsis further to find the lower limit that the probe survives. My experience on heat shield ablator has been counter-intuitive for me. The steeper your re-entry the less ablator you seem to use. Even though part temperatures are lower on a high periapsis gentle re-entry, you are spending more time at high relative velocity to the atmosphere, and hence at high apparent kinetic energy / temperature, so you use more ablator. For my probe anything under 40 km recovery periapsis is using less than 10 units of ablator, so you can skim the heat shield down for lower mass, and better upper stage delta-v. Launcher : Having a working probe and space vehicle, you need to get it off Kerbin. I found I really needed the Airstream Protective Shell. Most of my designs are high TWR launchers, and the fragile probe parts really don't like the temperature on ascent. Even when I redesigned the launcher for lower TWR and a gentle ascent, all those probe parts are quite draggy, and launcher stability was a real problem without a fairing. Part count has been a bigger problem than weight limit, so I ended up using just one fairing adapter, fairing anything fragile or draggy in one large shield, and damn the extra mass. So that's been my experience so far. I'm sure this is all old-hat for the regulars, but hopefully there is something useful somewhere for anybody new to the challenge. I really can't stress enough the benefits of an aerodynamically stable probe re-entry. You don't have to drive it, it's really resistant to overheating, you don't need electrical power, you don't need (or want) an engine - stable re-entry simplifies everything. Feedback and suggestions for improvement are always welcome!

Hey Paul, thanks for the input! I've been heading down the route of probe launcher development, rather than crewed docking. In Sandbox I haven't seen any problems with comms needing a network. Do you have any feedback on what difficulty level you start to need to launch relays? I'm going to be happy with a single biome land / return for this, so the probe development is looking hopeful. But yep, definitely finding out the part limit hurts for probe development. Spent a couple of hours last night wanting "just one more part" before I had an epiphany. Mind, those moments when you crack an irritating problem are rather nice

It's a good call on the Lander Can JAFO, definitely. I haven't used it on my "standard" rocket, since I didn't have the nodes when I needed that rocket... and it's just kept going ever since. I'd actually love to do a crewed landing on the Mun. Having said that, I'm "nearly there" with a probe core, and given how tight that is, I suspect the rocket equation is just way to punishing on the extra mass on the final stage. Well, at least for my design skills! So, back to the drawing board, a few refinements, a couple of practice runs in Sandbox, and I'm hopeful I shall have something that works!

And the last easy one... Flight #16 - Mun Orbit I used the same rocket as previously of course. Launch was OK, but I could tell the profile was a little high - I didn't drag the kick into the gravity turn quite far enough. Still, the 1,656 m/s in the tank was more than good enough to continue. I used the full 11.4 Mm apoapsis for a solid encounter. I was a bit surprised at how much before apoapsis it happened, but that's sundial navigation for you. It was a nice one with a -3km periapsis. A touch of radial out to get that out of the ground, and I was soon in a 55 km orbit. https://drive.google.com/file/d/1O0iaCAFlEmmg_3lvQQno9SAwc-Jqf86c/view?usp=sharing https://drive.google.com/file/d/1lwFpYFDJxSiV1rqTyUj6bsMC57uIRRfq/view?usp=sharing A quick trip through the science instruments, and it was time to head home. A 1:30 clock burn to 780 m/s orbital speed took me away from the Mun, and dropped me back into Kerbin's SoI with a -211 km periapsis. A touch low from previous notes, but easy enough to raise up to 41 km for re-entry. The surface speed looked good, so another safe landing for Jeb. https://drive.google.com/file/d/1AMYv0-aG7UtIa-XkVbWzi7o9PtE3leJC/view?usp=sharing https://drive.google.com/file/d/1uMdB89K6rgTHzp_XOK-UV8fCGOwOO-sY/view?usp=sharing That orbital flight netted 119 additional science, bringing the balance to 715 spare in the bank. Together with the 153 science that I've already spent, I'm most of the way there However, I now feel that I'm a little stuck. I could just farm Minmus, but I'd rather avoid that, and stick to new flights. In particular I'd love to do a Mun landing, since that would finish the Kerbin storyline. The problem is that I've never developed a Caveman rocket for Mun land and return; the gravity well makes that non-trivial for cavemen The 715 science in the bank can unlock seven Tier 5 nodes, so I have a fair choice of toys to play with, but a definite lack of experience on how to squeeze *that* much extra performance out of the ship. I've some ideas with a final stage using a Spark, and of course an OKTO would be lighter than the Command Pod, but my gut reaction is that part count starts to look daunting. It may be a while until my next flight report while I spend a *lot* of time finger-painting ideas on the cave wall.

Captains log, stardate *bzz* *crackle* Flight #15 - Mun Flyby After a Minmus landing, the first couple of flights to the Mun (flyby and orbit) are going to be easy. I'm back to the safe variant of the rocket with the Swivel, to reduce the chance or problems on launch. I still find the ascent to orbit the worst part of the whole flight. Launch and ascent were nominal, leaving me with 1,677 m/s in the tank at my 71 km LKO. To avoid a big gravity turn sending me off into the stars, I push apoapsis to 9.5 Mm for a fly by. Timing on the transfer burn was another good one, with an encounter *just* before Kerbin apoapsis, giving me a nice wide fly by without too much gravitational acceleration from the Mun. https://drive.google.com/file/d/1Xu0kzy5thiXnMbG5d7IFF0bJtujAw4N2/view?usp=sharing https://drive.google.com/file/d/1LltZJAJBzDAoMpbRFGfEIMnFcryQ1Cmr/view?usp=sharing The science run was fine, and return to Kerbin had a 13km periapsis, taking a massive 4 m/s of propellant to raise to 41.0 km for re-entry. Here's my obligatory two shots of grabbing the science, and of the start of re-entry. A lower surface speed and more remaining propellant than the Minmus flights https://drive.google.com/file/d/153_SXxhNEwOT2bTyT_aD0UAG7oGiu5e3/view?usp=sharing https://drive.google.com/file/d/1O0zavZCfQ7R0uy2iqNMMfcTlaXuFvXly/view?usp=sharing That quick little run added 83 science, giving me a spare 595 science in the bank. Next flight will be a Mun orbit.