Mod Virgin - Career playing with "Better Than Starting Manned"

[Dave Kerbin]

Clarke 1 and Clarke 2

With mastery of the rockets steering we can now turn to the most important matter, safely sending up kerbals. While we have learned a lot about the conditions up there we still haven't sent anything living so we need to be cautious.

Clarke 1 won't travel all the way up to the place with no air, instead this trip will be a short one to evaluate how well the pilot respondsas well as testing some biological samples. Navigation on this flight won't be difficult but it will be dangerous so a special candidate, Wilmon Kerman, is selected. The first stage carries the ship up beyond 10km and things seem to be going fine. At this point the second stage takes over and begins to turn into a more horizontal flight - we don't want to go too high. When the second stage separates it also arms the parachutes - this way if something goes wrong like Wilmon losing consciousness or maybe going insane from seeing whatever is up there he will still be returned safely to the ground.

It is rather scary looking down from up here, so it's a good thing that no pilot input is required from this point on. As the ship nears the surface at a terrifying speed the parachute opens for a soft touchdown.

Clarke 1 earns 85 science and unlocks Space Exploration

For the second mission a braver, smarter kerbal will be needed. Sidwell Kerman is up to the task and boards Clarke 2 which has an added stage and a new capsule designed after examining the goo samples and reading Wilmon's crew reports. This capsule should work even in a vacuum. With the added stage the first stage only reaches 7 km, but the third stage adds plenty of additional power. Like Bester 2 the ship is able to reach above the atmosphere and from there it can burn to enter orbit.

Entering an orbit like Bester 2 Sidwell can make observations about many places on Kerbin as he quickly passes over them. On the far side he reaches an altitude of over 250km and reports his findings. After making observations of all the various places he can see and completing an orbit Sidwell turns the ship around and uses the engine to brake. Based on the information from Bester 1 and 2 the new capsule has a device to counter the effects of reentry and is able to safely return to the surface.

Clarke 2 earns 280 science and unlocks Advanced Flight Control, Aerodynamics and Heavy Rocketry

[Dave Kerbin]

Delany 1

With space flight now possible for kerbals it's now time to make a dry run at reaching the Mun to confirm how far it is away and discover if there are any unexpected conditions between here and there. Delany 1 will complete this mission, carrying several pods with biological samples to test conditions along the route and some instruments to scan with when we get near to the Mun. It's a night launch but that doesn't seem to pose any extra challenges.

A 100 km orbit is achieved and circularized by burning the last of the fuel in the second stage. The third stage is ready to go to the Mun with about 10.5 hours of battery life.

I had planned on a pure free return but I couldn't really get the timing to work out - with a set amount of battery power I didn't want to risk getting to the Mun and not being able to collect readings. Instead I opted for a fast trip and use a course correction once in Mun orbit. As it travels to the Mun Goo samples are exposed in low and high Kerbin orbit to get an idea of the conditions along the route.

Swinging through high and then low Mun orbit more Goo samples are exposed and the temperature and pressure are recorded. Passing close to the Mun a gravity reading is taken to help prepare for a future landing. With that done a course correction is made to bring the probe back for reentry on a skip trajectory - the probe will decend to 33 km for aerobraking, enough to lower the AP into the atmosphere but not enough to break orbit entirely, rise back up to around 50 km and then descend back into the thicker atmosphere but now going much slower then the Mun return velocity. With the power running out a few hours before return the capsule is already seperated and the parachute armed. A soft landing is made in the desert.

Delany 1 earns 269 science and unlocks Landing and Advanced Landing.

[Dave Kerbin]

Effinger 1 (Part 1)

After 7 missions we finally have the technology to send kerbals to the Mun. The crew will consist of the two experienced kerbals, Sidwell and Wilmon, who launch into orbit in the early morning. Their ship is close to the pad weight limit, 124.987 tons. Some monopropellent was drained from the tanks to bring it under the limit, so it launches with 48L in total.

The second stage takes the ship into orbit but has only 1L of fuel left for the 78 m/s circularization burn. The third stage being required to make orbit was planned and I'm still ahead on fuel. I'm pleased with the inclination - 0.5 degrees which is small enough that I'm not going to correct it before making the Mun burn. That's good because it also cuts down on the time spent in LKO since I can immediately plan my injection burn instead of waiting for the right point to change my inclination (and then circle around again to where I can make for the Mun). I need to get to the Mun fast, so my burn is 930 m/s for a 3.5 hour trip. I do end up correcting the inclination as a 10 m/s burn midway to the Mun, something I'll need to keep in mind for future use.

Entering high orbit around the Mun I begin planning my next major manuever, an intercept. I have 3 hours of life support at this time so I can't spend a lot of time orbiting around the Mun. A pair of manuevers should setup my initial intercept within a single orbit or about 2 hours, leaving me with enough time to complete the rest with a safety margin.

But before I go any further I should rewind to what was was going on 12 hours prior to Effinger 1 entering the Mun's SOI...

[Dave Kerbin]

Fearn 1 and Effinger 2 (Part 1)

12 hours before Effinger 1 reached the Mun (over 9 hours before it was even launched) a different ship was on the pad. Fearn 1 was launched unmanned, controlled by a QBE probe core. Like Effinger 1 it is close to the weight limit at 124.995 tons and also drains some monopropellent to stay under, though it still has a very large reserve at 200L in total.

Fearn 1 has a larger 2nd stage so it not only makes orbit but has enough fuel for most of the Munar injection burn. Again this is by design, though due to some last minute design changes relating to monopropellent it reaches orbit with slightly less liquid fuel delta-v then desired. Still within the safety limits but some delta-v expected for padding is not there. There is a chance I might have to use that large monopropellent reserve to make up some delta-v late in the flight. Inclination is 0.7 degrees and I correct it while still in Kerbin orbit. Because of later time constraints it's important that Fearn 1 be a on a nice equatorial orbit to speed up intercept later on.

It's a straight forward burn out to the Mun and Fearn 1 arrives at a 15 km PE 4 hours and 5 minutes after launch where it captures into a circular orbit. As soon as capture is completed and a smooth 15 km orbit is confirmed the battery level (2631em) is checked and delta-v is calculated (1685 m/s). Delta-v is close to the cut off, but I do have that monopropellent reserve (154L) to fall back on. With everything checked out Fearn 1 is given a final command to align itself to point 'north' and then all systems, including the probe core itself, are shutdown. The ship is now drifting in stable orbit and could stay there for weeks if necessary (this was part of the plan, as it means I don't need to juggle time restraints or get multiple launches perfect - each launch can be aborted and a replacement prepared without ruining the rest of the sequence).

After Fearn 1 is inserted into orbit there is a second unmanned ship to be launched. Basically a copy of Effinger 1 but launched several hours in advance and under probe control instead of being manned. Effinger 2 uses nearly an identical ascent path to the one that will be used shortly by Effinger 1, but is slightly less accurate. Orbital inclination is 1.1 degrees and a maneuver is used to correct it before burning to setup a 4 hour trip to the Mun.

Capturing into a 30 km orbit the fuel and power are checked. There is a lot of extra delta-v though power is close to the limit at 5053 em. That was somewhat expected and a good deal of planning for Effinger 2 went into how to deal with the power situation. Like Fearn 1 the ship is aligned to face north and then shutdown. One small things was noted during the flight of Effinger 2, is that the RCS thrusters where not very effective for certain attitude changes. 2 thrusters where attached just before the launch of Effinger 1 to fix this as those attitude adjustments would be required for that mission (I've recently discovered that RCS thrusters are massless so no monopropellent adjustments had to be made)

[Dave Kerbin]

Effinger 1 (Part 2)

After the planned burns and a few smaller ones at the intercept point to match orbit the ship is able to meet up with the drifting Fearn 1 on the day side of the Mun. Along the way a few crew reports are taken of the Mun's surface. RCS thrusters are used to approach to within a few meters and the ship is turned to face north like Fearn 1. Effinger 1's probe core is activated for the first time and takes over the job of station keeping.

With the ships 5m apart some minor adjustment is done (H and N keyd) to try and match their velocity along the north/south axis as closely as possible. We need to be less then 0.1 m/s along that axis to make the next part work. The outer thrusters are given a quick tap to start the ship spinning around the north axis and then Wilmon opens the hatch. Climbing down the ladder he tries to position himself at the same level as the hatch on Fearn 1. As the ship spins he fidgets a bit up and down the ladder to try and be sure he is right. This was why it was so important to eliminate velocity on the up/down axis, so that he could line himself up strictly by eye without having to calculate vertical drift as well. When the time comes he lets go of the ladder and begins to drift. Without his grip on the ladder the centripetal force has been transformed into a linear one propelling him toward Fearn 1. Smiling at the feeling of being free in space he travels for a few seconds before he gets within reach of the ladder right of Fearn 1's hatch. He grabs on and once he is happy he climbs the ladder around to the hatch and enters the ship (when at a junction between ladders going in different directions use the A and D key to make your kerbal turn 90 degrees).

The next part of the operation is time sensitive. Fearn 1 is still not operational (the probe core is disabled and it takes 2 kerbals to run the system - we can assume Wilmon is still using his space suit until environmental controls are brought online) but due to Wilmon it has been imparted a small amount of rotational velocity. If we wait too long it will be out of alignment and impossibly difficult to safely reach as it tumbles uncontrolled. The station keeping system on Effinger 1 makes a small adjustment on the north/south axis again to align the two the best it can and cancel out velocity on that axis. Then Sidwell gets out and prepares for his own transfer as Effinger 1's hatch lines up for a second time with the sling path. Sidwell makes a perfect trip, grabbing on just above the hatch. Upon entering and powering up Fearn 1 with Wilmon the ship immediately starts blowing RCS thrusters, as the SAS system had been previously left in the on position by the probe system.

Everything seems to have gone correctly except for one thing. Neither Sidwell or Wilmon remembered to bring the crew reports with them, they are still in the cabin of Effinger 1. Time, power and risk won't be spared to try and retrieve them at this time, in fact a plan has already formed on how they can probably be recovered without adding any burden to the rest of the mission.

[Dave Kerbin]

Fearn 1 (Part 2)

Being on the Mun's light side there isn't much point in staying in orbit for long since that only burns life support. After passing over the canyon (and taking a crew report) a deorbit burn is made that seperates Fearn 1 from Effinger 1 (without a crew Effinger's power reserves are now enough for about 2 orbits operated by the still active probe core). Once the burn is complete the landing legs are extended as the descent begins toward a nice and flat area free of any large craters.

For landing the ship is rotated to align east/west (the same as launch, with the orange north marker at the bottom). This is so that the two fuel tanks are aligned to match any residual horizontal velocity when we land - a velocity line drawn through the tanks would also pass through the center of the ship, so that the extra mass there doesn't gain any leverage over the ship and twist, flip or otherwise imbalance it on landing. That's important since the landing gear is set to be rigid in order to prevent the engines from touching the ground (granted the leg setup was designed while the ship still had a single engine, the double engine/large fuel reserve design came later after an interesting pad weight test).

The landing is mostly smooth, the lander is not quite aligned with the terrain (last minute breaking) and it teeters a bit to the other side though RCS thrusters and SAS keep it firmly planted. The lander actually carries several instruments including a Double-C, 2Hot and PresMat which are all used to gather readings on the surface to make sure it is safe to go outside (this data is all transfered to the capsule). To save on supplies Sidwell is the only one to get out. He collects a soil sample and records his observations before planting a flag and then returning to the capsule. There is still 958 m/s of delta-v for ascent so we are good there. There is also enough power to meet all requirements and 100 minutes of life support which is our current limiting factor.

Launch from the Mun won't be for 40 minutes to give time for the orbiting Effinger 2 to line up. During this window Effinger 1 (still fresh on power) makes some final maneuvers which will be covered later on since they don't affect the rest of the mission. When it is time Fearn 1 launches to intercept Effinger 2 which has been orbiting at 30 km for hours.

The initial intercept is on the dark side, but since it will take one or more orbital corrections to actually get into range I decide against trying to fast track it. With adequate power and life support and the relative position of a light side meeting point it makes more sense to get to that point using supplies on Fearn 1, delaying the time when Effinger 2 is powered back up and begins depleting its own reserves. Finally meeting near the same point where the Effinger 1/Fearn 1 transfer occured the same procedure is used to send over the crew. This time Sidwell remembers to take the data with him before going over. After that Fearn 1 needs some SAS stabilization and is brought back into alignment with Effinger 2 for the 2nd transfer. Wilmon isn't as excited by the transfer but things go ok and he boards Effinger 2 and powers it up with Sidwell. There was one other important thing that was carried over and that was power - in developing the return profile it became clear that there wasn't enough mass to carry a complete safety margin, it was very close but not enough. The solution was that since some of the batteries would be empty from the probe core, I could rely on bringing 400em across from Fearn 1 in the space suits. Once on board the suit could be hooked up and that power dumped into the ships batteries, providing another 30 minutes of power (completing the safety margin needed for a complete orbit around the Mun to reach the departure point).

With the transfer complete I don't really have any further use of Fearn 1. It will simply remain in Mun orbit as junk.

[Dave Kerbin]

Effinger 2 (Part 2)

With the move to the return capsule things are going well. Effinger 2 has enough power to run the life support system for 5.5 hours, right on the mark. Thanks to a better then expected Kerbin launch (planning on paper can never really capture the exact efficiency of an air ascent so my designs tend to always come up with extra delta-v from that portion) there is over 700 m/s available though only 400 m/s will be used since the return burn was calculated far in advance based on a known altitude and return path (depositing Effinger 2 into a 30 km holding orbit was very deliberate). It won't take too long to reach the return point though in the mean time some more crew reports can be taken (some are redundent with the ones already collected, including a high orbit one I'll take later, but I want them in case the others are lost). Fearn 1 is still drifting nearby up until the burn for home. (that other ship on a return course will be explained shortly)

Approaching initial reentry the service module is ejected after transfering electricity and life support to the command pod and some monopropellent to the service module (only a small amount is needed and any excess is extra weight for the parachute for which the landing velocity is expected to be close). The reentry is designed to limit the air pressure the capsule is exposed to on the first pass to keep temperatures under 1400 degrees. The capsule then skips back up to 42 km where it makes a much slower second and final descent. Landing over water is ideal and at the last moment the remaining monopropellent is used to brake a little more to make a safe water landing at 7.5 m/s.

Oh, those Golden Grahams. Crispy, crunchy, graham cereal, brand new breakfast treat...

[Dave Kerbin]

Effinger 1 (Part 3)

Rewinding a few hours Fearn 1 has landed and surface operations have been completed. While the crew waits for Effinger 2 to circle around ground control takes advantage of the remaining power on Effinger 1 to line it up for a return to Kerbin. It made sense for the ship that carried the crew out to simply be a copy of the ship that would bring them back, and a consequence of that is that Effinger 1 has the same landing capabilities (this was also an important safety feature so that if something went wrong during the launch, or if the orbit inclination or fuel level was unacceptable, then the crew could abort and return to Kerbin). Without the preparation that went into Effinger 2's atmospheric skip return it's not smart to try the same return from a lower Mun orbit. Instead Effinger 1 is sent on a course that will take it to within 45 km of Kerbin's surface - low enough to induce drag but high enough to generate little heat. Since the battery won't last much beyond Mun orbit (and indeed the capsule will be seperated from the rest of the ship before it does) it doesn't really matter how long it takes for it to finally make it to Kerbin's surface. Indeed it takes many passes.

After finally making a gentle reentry the unmanned capsule is deposited in some grasslands. It's a bit heavier then Effinger 2 (more monopropellent), doesn't have the benefit of RCS thrust slowing it down and is landing at a higher altitude. All this means that a feature meant for the manned capsule is put to use, the destructable landing cushion.

While some of the crew reports are redundent the capsule does bring back valuable information, completing the manned mun mission program. Mun landing preparation included 7 launches gathering 890 science over a period of 13 hours and 10 minutes (enough science to unlock all of tier 5 except for Advanced Construction, though in this case 2 items where ignored to grab a tier 6 item). The Mun landing itself needed 3 launches (for a total of 10) and took 20 hours to complete the main objective, with another 39 hours required to bring back the last crew report ending the program on Year 1, Day 4, 0:00:15.

[FlowerChild]

Hehe...nice job on pulling it off a Mun landing at that low a tech level Dave. Looks like I was wrong in thinking it would be impossible with a 125 ton mass limit

Didn't expect the low-tech crew transfers in order to be able to use multiple ships to do something like that, but certainly makes sense and I don't really view it as a balance issue on my end given the difficulty involved in doing it.

[Dave Kerbin]

Some background on various parts of the mission. I used my original BTSM save to play around with some of the ideas before committing to the final mission (I also wanted to know exactly what techs I would need so I could ensure the missions I was planning returned enough science - while the ships where not complete I had all the numbers balanced before the end of the Clarke missions so I knew which items needed to be unlocked). My goal of course was getting to the Mun without using Advanced Construction and generally as low tech as possible. I originally started with most of the tier 6 items but worked down from there.

FlowerChild was correct in his original assessment that a manned mission to the surface of the Mun might be possible (in fact Effinger 1 had about the right amount of remaining power and delta-v to land though without legs it might not have been pretty) but that was as far as you could go on 125 tons. My own math agreed with him but I was sure there was a way around it. I considered one profile where the crew would land in one ship and take off in another one, but the weight savings from only needing life support for half a journey where just not enough to even suggest it was possible. My next idea was a crew transfer. I didn't have docking ports so they couldn't do it internally and I didn't have jetpacks so they couldn't do it under their own power but many times in the past I've used the mechanics of centrifugal force to toss previously connected ships apart by releasing the docking port after starting a spin. My first trip to the Mun used it to accurately get the used lander safely out of the way.

But throwing something away and accurately throwing a kerbal at a target are two things so I sent up a test mission to LKO. Of course with most of the tech tree unlocked I would have a safety net. Infinite power, lots of monopropellent, both ships under probe control and SAS, and most importantly the crew would have jetpacks so they could simply grab the controls and fly back for another try if they missed. Merdun and Jorster piloted the ship which carried the docking target with it before it was detached and positioned about 10m away for testing.

Initially things don't go very well. Merdun misses the target half a dozen times and needs to use his jetpack to flyback.

Eventually I bring the ships closer, to 5m and try again. Here I learn more about the factors that control success or failure and finally make a successful transfer. With some more practice I understand what needs to be done to make it work without the safety net on a real mission.

The 3 factors I identified where:

1. The release angle doesn't matter. Now in reality the angle that the kerbal is released (if you draw a line from him to the center of the ship he is holding onto and to the target ship) is the key factor in what direction he will fly off in. Release too early and he'll go too wide, release too late and he'll cross over and miss the target on the other side. But once you are controlling a kerbal the camera is moving in such a way that it's just not very practical to try and precisely judge that angle. From my animated gif earlier you can see how I'm constantly moving the camera to get the correct angle, because the rotating ship keeps moving the kerbal and the camera attached to him away. Of course this leads directly into the second factor.

2. You must be close. This seems really obvious but because of the camera issue you need to get really, really close to the target. Close enough that you significantly reduce the impact that the angle of release has on success. You want it to be like shooting the side of a barn. With Effinger 1/Fearn I was holding my breath not because of the risk of losing the kerbals, but because the radial fuel tank on Effinger was coming within inches of Fearn on each rotation. If they collided it would have thrown the unpowered Fearn off course and trashed the transfer.

3. The vertical element matters a lot. It wasn't until I got closer that I found out how frequently a correctly timed fling would still fail because the kerbal would go above or below the target. Because of orbital mechanics the ships are never 100% stationary in relation to each other. There is a small and growing amount of relative movement. On the other two axis this small movement isn't important because it is easily out matched by the sling velocity of the kerbal. But on the up/down axis this small difference means that even though the ships are correctly aligned when we start spinning in the 10 seconds or so it takes to align, release and float across the distance they can easily have moved 1m vertically, enough to miss the hatch entirely. I realized that for the final ship I would need two things, one was careful attention paid to try to align and cancel out vertical velocity, and the other was a tall ladder so that I could either adjust my vertical position up until the last second, or so that I had an extra tall target to aim for (aim for the center and I could drift up or down and still hit it).

[Dave Kerbin]

(Further R&D background)

The sling method wasn't my only idea for crew transfer but it was the most viable. Another involved having an extended ladder sticking out of both ships but that would have required switching between the ship and the kerbal rapidly to keep them perfectly aligned. A variant on the sling idea was to actually send the ship on a collision course using RCS, have the kerbal (who is holding onto a ladder right in position to be squashed between the two) let go, then reverse course at the last second so only the kerbal drifts forward. Again this would have required some timely switching and I wasn't confident it could work 100% of the time.

Once I had figured out a viable design (mostly with tier 6 tech) I assembled it in the VAB to see what it would look like. Without Advanced Construction there would be no struts, and without fuel lines I could end up dictating overly tall fuel tanks to match what was designed on paper (pure numbers).

I originally started out with the Apollo style pod to shuttle the crew to the Mun and back, using the tier 6 batteries and the tier 6 probe core. The batteries where the first to go when I figured out that I could do both trips in under 5 hours. The rest stayed for a while as I tried to find ways to save weight on the return trip - getting to the Mun and landing seemed be a solved problem if I could get the return to work. I had 4 combinations - Apollo or Can, tier 6 probe core (2.5em/min) or tier 5 (5em/min) that I would plug each set of new numbers into to see how low I could go. Using the more primitive probe core meant carrying an extra 750em in power while the Can required an extra 257em/hour to operate, offsetting most of the weight savings.

My fear that I could end up with an unworkable design was correct when I reached a workable tier 5 + can set of numbers. To save weight both lander and transit designs originally used a single engine (I alluded to that when I talked about the lander originally having an engine in the middle that needed to be protected by the landing legs). This meant that the numbers dictated a lot of fuel in one long tank. Here you can see two revisions of the transfer ship (the second one has the final pod design, only the engine/fuel tank layout was revised) and a pre-final version of the lander. Despite trying to design it to keep the weight balanced for landing it really didn't look right.

With that in mind I tried putting it on the launchpad.

This is how joints work in .23.5. Nothing on that ship is broken yet - it slowly leaned over and eventually the center of weight had moved far enough that the part right side started to tip off the launchpad (you can see it starting to tip) which caused the bent over top to come in contact with the ground and explode.

I reworked it, combining the transit and landing into one stage and moving some fuel to the 2nd stage booster so that I could use two engines. The transit ship got the same modification though initially there was an issue with fuel tank placement, it would prevent the top of the capsule from ejecting. That was solved by rotating the 2nd stage booster 90 degrees so that the 3rd stage engines could be lowered.

[Dave Kerbin]

BTSM 1.62 is out and there was a question about how to return Goo using just the tier 4 techs and the heat shield from tier 5. This is how Goo can be returned from Mun orbit using the heatshield for proper reentry rather then any tricks.

The first stage requires some more attention throttle control to balance everything since TWR changes by a good margin when the solid boosters cut out and overheating must be managed too.

As the gravity turn starts the first stage is released and it slides out from between the side engines which still retain 2 of the control surfaces so that they can still be used to aid in the turn (though I really needed those engines because of the limited fuel tank selection, it was the best way I could find to save weight and add more fuel without breaking my TWR). RCS is activated at this time as well so that we can remain stable on the other axis as well.

With orbital speed at 1.4km/s the 2nd stage is released and the third stage takes over. TWR is low at this stage, barely over 1 until some fuel is burned off and even then it's not going to reach 2 during this burn. That means the first burn will need to go on for a while, shooting for a long flat trajectory to put all the thrust into increasing orbital speed. When the AP reaches 74km the PE has already appeared on the other side at 38km. It's a further 6 minutes of coasting before a 31m/s burn to circulize.

The ship carries 7 of the type 2 batteries along with a special 100em, 0.5t model in addition to the probe core for a total of 3000em or 5 hours of operation. My estimated requirements where for 1200 m/s of delta-v to complete the orbital portion of the mission and I appear to have 1210 m/s so things are going as planned. An 890 m/s (budgeted 900 m/s) course is plotted to swing close to the Mun with about 10 minutes of battery power to spare. Since it is already on a free return I should need less then the budgeted 300 m/s to correct it into a suitable/survivable return trajectory.

Flying to the Mun both Goo containers are exposed in high Mun orbit and low Mun orbit respectively.

At the lowest point over the Mun a planned 73 m/s burn is made to alter my return trajectory so I don't slam straight into Kerbin. After the burn is made I have 6 minutes of battery life though I won't be using it, instead the return capsule is released and the probe left to die.

The return capsule comes in to 35 km and passes over a familiar location but it wasn't actually enough to stop it (22 units of shielding are depleted). The Orbit has lowered to 437 km and the second time around the capsule makes a successful stop and splashdown in the ocean south of the desert 501 km from KSC.

We have successfully return Goo from Mun orbit using tier 4 plus the heatshield (about 2000 funds are refunded for recovery of the craft, mostly the cost of the two goo containers).