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

[Dave Kerbin]

Gamow 1 (Part 2)

In Kerbin orbit an injection burn is planned to reach the Mun. If you look closely you'll see that the burn happens to occur almost directly over the KSC, making it one complete orbit before leaving for the Mun. With 7 powerful engines the burn will only take 53 seconds despite the fuel being carried. Coasting out to the Mun is uneventful and upon arriving in high Mun space a crew report can be taken.

As the ship enters low space and prepares to make a capture burn some more science is done. Passing over the Midlands, Highlands and Highland Craters the 3 kerbals record Crew Reports and take gravity readings. There are 2 GravMax instruments mounted to the big transit stage. Each one is keyed to a different action group that also triggers a crew report. This way two different biomes can be captured in quick succession before having to go through the process of transfering data from the instrument into the command pod to make it ready for another reading. The capture burn provides about 600em from the engine's alternator, it's not very useful since I am running well within my safety margin and the batteries being charged will be discarded soon. Capture occurs just slightly north of the twin craters, the orbit missing them so I couldn't take readings.

The ship begins an orbit of the Mun, collecting information on all the biomes along the equator. In all 9 biomes are scanned as the ship circles around the dark side. and emerges back into the dawn.

Back on the light side a landing position is picked just short of the twin craters. I'm aiming for a flat area with no visible craters.

Before a deorbit burn can begin the battery systems are reviewed. An action group brings all the batteries on the lander stage online and then power is pulled from some of the transit batteries to top up the capsules own power supply. With all preparation complete the transit stage is used to brake from orbit. It was planned that the transit stage would provide at least 200-300 m/s for the descent (though the lander was designed with just enough dV to make the descent, ascent and return on its own) in order to ensure that its batteries would be attached up until that point (if any of the landers fuel was required for the Mun capture it would mean discarding the transit batteries at that point). With fuel saved up to this point the transit stage is able to completely brake from orbit with 50L of fuel left, so the lander only need to concern itself with a soft landing.

The Mk1-2 lacks landing radar (well there is an indicator in the cockpit I think) but I used to landing by sight anyway. Touchdown is at 5:58:20 at 3.1 m/s, 2 hours ahead of the first safety margin. Barrigh is the first down the ladder and is quickly joined by Kenby and Aldrick. While I have budgeted the electrical cost of a 10 minute EVA by the three kerbals I do want to keep their time on the surface short to conserve supplies. Barrigh plants the flag while Kenby gathers rocks.

After surfaces activites are down everyone gets back into the ship and things are stowed away to prepare for the last leg of the mission.

[Brucey]

Your extra weight is all the fuel you are using. You could get by with a smaller setup. I noticed you mentioned you haven't done any research so without knowing your stage deltaV or TWR it gets a lot trickier (coming down to luck and experience from what you've tried before).

Dave -- You should probably also ask folks if they use design tools like KER (or by hand) or just eyeball it. You are going to get radically different values for the two approaches.

I am using KER. (using it in the VAB only) I think its a bit unfair to say my design is poor. It merely has a large factor of safety built in and that's intentional, because had low confidence in my ability to efficiently rendezvous/dock. I could say a lot more here but I don't want to thread-jack Dave's excellent thread.

[Poddster]

Thanks for writing your guide on your ship construction method -- I bet it'll be useful to lots of people.

Previously, when trying to do similiar, I always encountered problems on the parts like your lowest section. I could never get the cloned engine stacks to align vertically, nor be rotated properly when doing the fake 16x symmetry. They'd always be poking out at a wrong angle, even when rotated using WASDQE (and even with shift). I never really had the patience!

ps: I really like the look of your lander. It's like a classic direct ascent Rocket Ship

[Dave Kerbin]

Gamow 1 (Part 3)

As soon as everything is stowed away the lander takes off. We don't need to wait for a docking window since the ship will return directly to Kerbin. It's not like there is anything in orbit anyway since the transit stage, split into 7 pieces, crashed into the Mun prior to the lander's touchdown and thus kept my universe debris free. But since the transit stage did so much of the work the lander has plenty of fuel and monopropellent and is only limited by a budget of 13 hours of power to reach home.

Orbit circularization is made into a fast 9.5km orbit to speed up how quickly we can reach a orbit breaking maneuver node (we need to orbit around to the opposite side of the Mun for this burn). With PreciseNode allowing me to discreetly set the maneuver node time and magnitude I wanted to try something I haven't done before, doing a Mun return with a single burn instead of two. Normally I'd perform two burns, the first one would be to exit Mun orbit and enter a Kerbin orbit with a relatively low PE (ideally one of several hundred km but before PreciseNode it might be in the 1-2 million km range). The second burn would be carried out after leaving the Mun's SOI to immediately lower the PE to the precise altitude I want for reentry. However in this case I plotted for a direct return with a single burn. I'm going to see if I can get home without any additional burns or RCS adjustments.

This goes well. I slow down time warp until I hit 1x as the ship is passing out of the Mun's SOI. This is to keep my reentry PE on track since passing between areas of influnce at high warp can through off orbits. This is because at high warp you are performing calculations for a longer time steps - if my velocity is x and position is y and acceleration due to gravity is z, where will I be in 10 minutes. If you are just about to cross into another SOI (where acceleration due to gravity will suddenly change) then some of that 10 minutes will have been calculated with the wrong value. As it is my PE stays within 78m of it's original value.

Approaching Kerbin's atmosphere with plenty of power and life support (and 680 m/s of delta-v in the tanks) the pods battery is filled up again from external batteries in preparation for seperation. The lander is oriented around to face tail first and at 60km the pod seperates and uses RCS to push away, first upward and then laterally to put the return pod on a different return vector to the lander stage. RCS and SAS are then used to keep the pod oriented (it should orient properly due to weight but using RCS prevents it from swaying which could expose parts to deadly reentry forces).

The pod safely splashes down at 12:49:56 off the coast of the westward continent, the crew and their cargo is quickly recovered. With the lander stage burned up the only thing left is the flag I left on the Mun. I'll be going to Minmus next, should I go manned or unmanned?

[Taleric]

Great mission

Makes me hungry for budget to encourage ambitious designs like this from other angles on top of science. Do a manned minmus and see if you can hit every biome in one mission at this stage

Edited May 22, 2014 by Taleric

[Dat_Spacewaffle]

I recommend going unmanned just to see if it is possible w/ the current technoligy you have, then if possible, do a manned mission

[Poddster]

I agree with the unmanned approach: If you're trying to keep as many Kerbals alive as possible, like you've stated, then sending an unmanned probe to do the science that isn't a simply EVA report reduces risk.

[Dat_Spacewaffle]

Just wondering, how much Delta-V does that craft have? It might be able to go there to Minimus without that many modifications

[Dave Kerbin]

Just wondering, how much Delta-V does that craft have? It might be able to go there to Minimus without that many modifications

I've actually already done the calculations I've just been too busy to boot up KSP.

Based on some screenshots from Poddster of his journey to Minmus it seems I can make a modified version of the rocket by unlocking the middle tier batteries (the first set of stackable batteries). His route involves performing an Kerbin escape velocity burn that intersects Minmus and then braking before you are flung out into deep space. That part adds about 400 m/s to my budget (yes he did it for less but I've never flown that path before and I'm using some other screenshots to determine a min/max requirement to reach and capture at Minmus using that approach). For that I need a 13 hour budget of power, plus a budget for orbit, landing and asscent/orbit (1-2 hours). Getting back Poddster is using a big burn (budget 600 m/s) that uses a radial push to encounter Kerbin's atmosphere on a direct line from the return instead of a more gentle pass around the back of Kerbin. Time budget of about 18-22 hours.

The transit stage would be stripped of the older batteries and replaced with a single 360 battery to top off each engine assembly (7 in total) just below the decoupler. The lander would require more extensive modifications. After stripping the old batteries the center fuel tank would be halfed - the center T400 tank would be replaced with a T200 tank and 4 '360' batteries. All 7 engine stacks would then receive 3 more batteries (7 total in the center now) and the outer 6 stacks would recieve one of the tiny 360 Core batteries. These modifications would ensure that the launch weight remains within a margin of error for the boosters and transit stage. The lander itself is heavier and carries less fuel, losing 20% of its delta-v, but the requirements are less.

Of course I would rerun all of those calculations before actually flying the mission, but it would have enough fuel to make at least one landing (a second hop should be possible if it was short, but the fuel requirements for the return dictate that it would be safer to do a single landing only).

[Dave Kerbin]

Gamow 2 (part 1)

Gamow has been modified for the run to Minmus I described. The principle changes are upgrading the battery technology and moving some of the battery capacity to the lander segment. The reason for this is the inverse for why it was on the transit portion in the first place. For the Mun I fully intended the transit stage to remain with the ship right up to descent. Fuel was budgeted to ensure this (resulting in most of Gamow 1's descent being powered by the transit engines) and the batteries placed on that segment where designed to cover all the power needed (including budgeted safety margins) up until descent.

Gamow 2 needs to work in the opposite manner. First I need every drop of power I can get, so throwing away any power with the transit stage is unacceptable. Second is that I'm not 100% sure about the delta-v requirements - I've been forced to consider the outcome of several scenarios where I am short on fuel and how to deal with them. The first scenario is if I get into Kerbin orbit and find out the injection burn maneuver exceeds the delta-v in the transit stage. In that event I can simply abort the mission without doing the burn, returning safely to Kerbin.

The second and third scenario are closely linked. After safely passing the first hurdle I should be on my way to a Minmus intercept with the transist stage attached. Executing the capture burn I might run out of fuel in the transit stage, forcing me to use the lander engines to capture (and avoid flying off into deep space or on a long orbit that exceeds the life support limit). This is the main reason the transit batteries are engineered to run out before actually reaching Minmus. If I'm forced to use the lander to capture I'll still have the power I need to return safely to Kerbin - I would simply skip the landing which should be enough to cancel out whatever delta-v was lost in the capture. The last scenario would be if I landed but didn't have enough fuel to return all the way to Kerbin (or couldn't return fast enough since getting there fast involves burning much more fuel). I want to avoid that scenario entirely by knowing the go/no go point. The lander alone slightly exceeds the delta-v requirements (including safety margins) to land, ascend and return. So if I can enter Minmus orbit with the transit stage still attached I am definitely a go. If I capture but have wasted more then a token amount of the landers fuel then I'm a no go and need to abort.

In terms of construction I did underestimate the height of the upgraded batteries a bit. I had estimated that 4 batteries would be about the height of a T200 tank but with was more like 3. To keep the shape I wanted I moved one center battery from below the capsule on the lander stage to the top of the capture near the parachute. Otherwise the changes where stretching the ladder and adding some science instruments. I did perform a pad test to verify that I could move the camera around enough to select the center battery of the transit stage - this was combined with some calculations of how the batteries would drain since I wasn't using the deactivated battery method I used in the first flight. Instead I checked to ensure that enough power would have drained from the landers outer batteries that I could transfer the remainder from the transit stage up there when the time was right.

Because I need to stretch the life support consumables I can't carry 3 kerbals. With the mission risks involved I decide to carry just one, Barrigh. It should even out the number of missions everyone has done (1 solo, 1 group) and he's really the only one to trust to take a ship out alone so I put him in the pilot's chair with the other seats empty. The launch goes fairly well - I did have some minor issues with RCS attitude control that wasted a little fuel since I wasn't burn a bit up when I should have been burning purely sideways for orbital speed.

It's a 1050 m/s burn to Minmus. I'm not adjusting my inclination (6 degrees) as I hardly ever do that and it would cost about 250 m/s which I don't have budgeted. Making the burn some other routes present themselves.

With the basic burn done I do make a 30 m/s normal burn to bring my PE down to 30km. 10 hours into the flight and with Minmus still several hours away I go about moving all the electrical charge into the lander batteries. I start by shifting some power around in the lander to leave a single nearly empty battery. This way I only need to perform the camera gymnastics needed to reach the center transit battery once - I transfer all remaining charge from that center battery to the one I emptied out. The other 6 cells are then then drained into sequence, their charge distributed between the 3+1 batteries above them on the lander.

Arriving at Minmus some high orbit data is taken; in addition to the crew report I have a 2Hot to take readings with. I didn't bring along Goo containers since I didn't have the weight budget for them. However I do have an issue, the capture burn will cost just over 800 m/s, more then I had budgeted for. Now at this point I had extra fuel by burning under budget for the injection but I had some small unknowns from the launch. Without calculating my exact fuel cost the burn time and fuel left in the tank made it look close. It was good that this was one of the scenarios I had planned for so I was still confident I could bring Barrigh home safely even if the mission couldn't complete its objectives. I started the burn with a very close eye on my fuel supply. My estimate based on the burn time seemed to be panning out, fuel and delta-v markers where draining at about the same rate.

Ultimately it wasn't enough though - the transit stage was exhausted with 58 m/s left to burn. Since this was planned with the battery strategy it was safe to stage and use the lander engines to complete the burn. The lander safely made orbit with 95.6% of it's fuel reserves. The transit stage (well really 7 seperate engine assemblies) where now on an escape trajectory from Minmus. Since I was close to the end of the burn I have a feeling they where put into Kerbin orbit albeit a high one. Kerbin astronomers will need to track them down. This does end my streak of leaving no junk around Kerbin.

[Dave Kerbin]

Gamow 2 (Part 2)

Now in orbit (it's a bit inclined and it's retrograde since that's how we came in, but there is no docking so it's not a problem) we can take some readings, though I actually have to wait until the ship passes below 30km into "low orbit". The AP is just above that so I'll want to adjust that on the other side. During the pass around the dark side I collect crew reports on a number of places, in particular the Great Flats, Lesser Flats and thanks to the inclination the Flats are also found right beside the Lesser Flats. Getting good shots is another matter. A long while back I switched to XVID encoding to improve the capture quality of darker scenes over MJPEG. However it was really dark and apparently dark green doesn't compress very well. Even before I adjusted the contrast the images where filled with obvious compression artifacts. I did a 3 m/s burn on the far side to lower my orbit so I could take low orbit readings from any point.

Coming around I found the Highlands (Midlands, Lowlands and Slopes where all located quickly since they are everywhere) and began preparations to land in the one obvious flats area I couldn't scan because I was too high up (and also burning to capture at the time). The decision to land was based on the fact that I had only used ~60 m/s from the lander's supply which meant I should still be within my safety margin.

While I want to land in the flats area (Greater Flats as now detected by instruments and recorded) I am aiming to do it close to that out cropping. I might be able to grab a second biome.

It's a soft touchdown at 1.3 m/s, landing on the Minmus flats isn't especially difficult though I did try to save fuel by waiting until I could see ground scatter before really removing a lot of my vertical velocity. It's a longer climb down to the surface. Samples are taken and the ships instruments are also run. Satisifed that everything is in order Barrigh can return to the lander.

Reviewing consumables it seems I'm good for power (at least a days worth) and fuel wise I have 1089 m/s. That's close to my safety margin, if I go over on the return burn I could really use that fuel to get home safely. I look around to get an idea of how far away those slopes are (the darker portion near the bottom, the little object is the lander). If I had jets for my space suits it might be just within range for an EVA to run over there and take a sample. Walking it's too far to risk. I could fly the lander over there but I can't reasonably land on the slope so it would be a matter of landing close and hoping I could reach the part that registers as 'slope' biome by foot. Ultimately I decide it's not worth the risk - I haven't used this return path before so I'm very iffy on the fuel use. This mission was planned for a single landing (I've already exceeded my science objectives by cover 2 more biomes from low orbit then scheduled) so I'll stick with that even if it loses 150 science. The science I have in the lander is already past the amount estimated as the requirement to do the next mission. So we launch back into orbit.

Back in orbit (this time a normal equatorial one thanks to a lander close to the equator and a easterly launch) the return burn is calculated. To get one that appears right I need to apply a lot of prograde thrust, 500 m/s, combined with radial and normal adjustments to place me on a return to Kerbin. The final result is a 527 m/s burn that will return me to Kerbin in 18.5 hours on a retro-grade approach (I'll fine tune the PE enroute). This will leave me with a healthy supply of fuel - in hind sight I could have flown to another biome but I had no way of knowing for sure I'd have that fuel so I stuck with the safety margin. In future I'll have a better idea of the fuel requirements for this kind of run. The return burn will take me close to the surface, 7 km over a large ridge. However the burn time is low, estimate is 46 seconds, so I'm not worried about a collision. Because the center fuel tank has less fuel I need to factor that into the burn time though it's not very hard - a 1/7th loss of thrust midway through a 46 second burn will throw off the burn time by an amount almost too small to correct for. I start the burn 3 seconds early (T-26s) to account for it.

The burn is successful and the lander safely passes well above the ridge and back toward Kerbin.

The return brings the ship on a retrograde encounter with Kerbin's atmosphere. I've tweaked the arrival to 27km and as the PE is neared the ship rapidly picks up speed since without the atmosphere to slow it down it is on an escape trajectory once it slingshots around the planet. The return pod seperates and uses RCS to push away and then move a little laterally.

However orbital mechanics can be fickle when approached too casually and the pod, now on a faster orbital path, nearly hits the lander as it quickly moves past it.

At more then 3 km/s the reentry speed has me a little concerned for the safety of the crew. The heatshield reaches a temperature of 1308 C before cooling down. After the worst of the reentry is over everything else fell into place. With good daylight the pod splashes down and is recovered, returning Barrigh and his science.

[Dave Kerbin]

I've located the transit boosters discarded by Gamow 2. They are currently in a high orbit around Kerbin though the kerbals at the observatory claim they are on an escape trajectory - from the orbit it looks like they could be nudged out into deep space by Minmus in a couple of weeks. At least at the moment they don't pose any danger, even if they where pushed into a lower orbit they would more likely impact Kerbin then enter a path that would endanger ships holding in LKO.

[Dave Kerbin]

Hall 1

While I could gain some more science around Kerbin I want to get out and explore. My final destination is an (unmanned) landing and sample return from Laythe so Eve is a good stop where I might get some experience in precision landing. From the tech tree I'm unlocking several parts but banking the rest of my science. I'm getting the basic solar panels, the first item to cost 360 science. I'm unlocking Precision Engineering (which also gives me the radial RCS tank) in order to reach both Miniaturization (interplanetary antenna) and Unmanned Tech (2em probe with built in SAS). And finally High Altitude Flight is unlocked to get the Sensor Nose Cone.

I'm not interested in developing a seperate launch platform for this mission. The blueprints for Gamow 1 are brought up and everything above the heatshield is removed (pod, RCS tank, parachute) and then the landing legs and old batteries are taken off as well. Assuming I keep the same launch weight this platform should provide all the delta-v needed to reach and brake at Eve. Including the heatshield and any other addons I make I have a healthy budget of 20 tons. The probe is mostly batteries. With Eve's thick atmosphere I won't need many parachutes (my previous Eve lander had many parachutes because it was a design intended to land on Duna too). The old 'lander' portion is now a second orbital stage. I examined several solar panel arrangements but I was never happy with the look, it's hard to arrange the big panels in a way that looks aerodynamically credible, it would be nice if they came in a package that could be unpacked a single time and didn't have sun tracking. With a lot of spare weight I ended up just coating the ship with solar cells. I'm still under the weight budget by several tons and it means I have little to worry about when it comes to correct alignment.

After waiting for a window launch is pretty standard. I did make a mistake, I had intended to collect sensor nose cone readings for Kerbin and that lost me 80 science. Fortunately the expected science return for this mission is big enough that I should be able to unlock everything I want even without that experiment.

With PreciseNode it's almost too easy to setup a course to Eve. I dropped the node in by hand, typed in 2 numbers and I had a transfer already setup. I made a tiny change to the time in order to lower the PE and then I was ready for the burn.

Out in deep space temperature readings can be taken and beamed back to Kerbin. Solar alignment isn't really an issue as long as I don't point the nose or the tail at the sun. As I approach Eve I setup a course correction to set my PE to low orbit, make sure it will be a prograde orbit and to put it roughly around the equator. This is helped a lot by the conics model that I seemed to have stumbled into which lets me easily see my approach.

It will take 1600 m/s to capture at Eve without aerobraking. The 1st orbital stage runs out of fuel after the first 1000 m/s so the 2nd stage is started up to complete the rest. Orbital readings of Eve are taken and then the batteries are given a chance to recharge (solar power provided some assist to the transmission).

In addition to the science my goal here was to try a precise landing. I spotted a prominent dimple above a darker area and decided I would try to land there. However I ran into a few problems. One was that I was already very close to it in my orbit and so I really started burn far too late. I also didn't really have enough fuel to completely stop over the target, I misjudged my orbital velocity (going much faster over Eve compared to the Mun or Minmus) and really should have been aiming for a longer approach. Realizing this I stopped my burn before my descent path came too close to one of Eve's smaller seas. You can see the dimple to the left of the sea and my descent which is going to be to the right of it. I realized I didn't have the fuel or the TWR to avoid falling into the water if I kept burning.

I did get a bit distracted as I entered the upper atmosphere. I was trying to keep my solar panels as long as possible while I started taking some readings so I only realized I was taking too long when the 2nd transit stage starting smoking. I immediately cut the link to the transit stage as it was consumed by the atmosphere. I relied on the navball to stay on track as the probe was frequently obscured by the explosions and it wasn't until the transit stage had been completely consumed that I could verify if the probe had come through all right. Fortunately there is no shrapnel in KSP.

After things cool down work can resume and lower atmosphere readings are also taken. The probe has some tiny legs that extend just below the bottom of the heatshield. They are all set to be rigid so that they don't retract inward when touching down. In theory Eve's atmosphere provides enough drag that a soft landing is possible on the heatshield, at least at lower altitudes but I wasn't taking any chances. I also transfered power from the large bottom battery into the upper batteries. In the event that the heatshield and large battery where damage by impact there is enough power in the remaining batteries to perform surface operations.

Safely on the surface after a 5 m/s touchdown the Double-C and other instruments can report their findings. I now have 4335 science to spend toward my next and final mission in this playthrough, going to Laythe.

[Dave Kerbin]

I'm still in the early concept stage for a Goo return mission to Laythe. I've unlocked the technology I think I'll need. I've unlocked all the normal engines now including LV-909s, LV-45s and Mainsails (LV-N and ion are still locked) and all the fuel tanks including the large diameter ones. I've unlocked the decoupling and docking parts in all sizes. I've unlocked radial decouplers and the very large heatshield. Finally I've unlocked the most important part, the NUK-NUK reactor. There are some parts which I don't have unlocked however: in addition to the ion engines I don't have fuel lines, advanced batteries or inflatable heatshield. I also don't have the final set of probe cores, the retractable solar panels or cubic struts for mounting things in odd places.

Since my best probe core consumes 2 em/min I'll need to carry 2 reactors with me to Laythe orbit and back to Kerbin. No fuel lines means that staging will need to be simple. Design a lander/return craft that can reach Laythe orbit is also challenging due to the parts - the extra large heatshield is still not as big as the inflatable heatshield and that greatly limits how wide a ship I can land. I may need to try an orbital drop test to see if small diameter parts can be radially mounted to other small parts and still be considered inside the shield. Visually it looks like they are a bit over the edge but I've found the heatshield mechanics might not be based on that. That width also poses problems for engines, I need a certain amount of thrust to take off in Laythe's near Kerbin gravity.

[Pipcard]

I really love the solar panels on the Hall-1 transfer stage. The probe that lands looks really cool, too.

[Dave Kerbin]

Still working on things when I have spare time. I found the main design restrictions where thrust for lift off from Laythe, low center of gravity for a safe landing and finally fitting it all inside the heatshield.

One option which could still be viable is simply using a large 16X fuel tank (720L) in a single stage lifter. It would need to use the Poodle engine to provide enough thrust (I also looked at radial rockomax engines but the ISP was too low).

Another option is using an adapter so I can link together multiple engines - but that doesn't seem to work well for center of mass.

Finally one option I've brought all the way to the prototype stage is using the tiny booster rocket. Two provide enough thrust for lift off from Laythe and 6 (3 stages) combined with a small liquid tank and engine for final orbit. The design certainly looks nice but I think it might simply be heavier then just throwing on a big fuel tank.

[Death Engineering]

I mean.. I hate to mention it if you've already ruled it out, but is an air-breathing ascent from Laythe possible with your tech level?

[Dave Kerbin]

I mean.. I hate to mention it if you've already ruled it out, but is an air-breathing ascent from Laythe possible with your tech level?

I'd really have to test out the engines, I rarely if ever use the jets so my ability to estimate the correct amount of fuel, thrust and intake (and avoid intake spam) wouldn't be easy. I think I only have the basic engine and intake part wise. I have thought of doing some kind of plane since that would make it much easier to make a precise landing, but like I said I have very little experience with them, I don't think I have the small control surface part, and I'm completely in the dark as to what kind of heatshield I might need to allow it to enter the atmosphere for a landing without breaking up.

[Dave Kerbin]

Innes 1 (Part 1)

There is a new version of BTSM so I really wanted to get this wrapped up. I felt I had a design for the landing/rendezvous but only had a set of estimated delta-v numbers for the rest. I don't have fuel lines so my normal method of making an efficient ship for this kind of journey was out. Instead I just tossed together something very fast - it's very ugly and overweight (launch efficiency is 11%) but surprisingly the system that nearly lost the mission was the module I had spent the most time on. I had also been considering layouts that would add more science instruments but ultimately dropped them. The goal is to get a sample and return. You can see the launcher is big - this kind of ship won't fly after I update to the latest version based on the launchpad restrictions I've read so far. It was also built even faster then the transit stage without checks or revision which is only possible in .23.5. As the fuel is almost empty on the first stage it starts to bend wildly, things stabilize after that.

There is a lot of mass to be pushed with 6 poodle engines so I spent the remaining fuel in the 2nd booster stage to raise my orbit to 250 km. This way I'll avoid entering the atmosphere during the burn. After I finished the circularization I ditched the booster with a little remaining fuel so that I could fire the main transit engines for a brief second and calibrate the manuever node's burn time indicator. At this stage changing orientation is a slow process, I've burnt about 80L of monopropellent. It's a 1924 m/s burn to make the Jool intercept that will take 12 minutes to complete and consume seven and half orange tanks worth of fuel. I've shed almost half the ships weight.

66 days into the trip a pair of course corrections are made. The first one tightens up the approach to Jool, burning 74 m/s to bring the PE from far beyond Bop and Pol to below Tylo's orbit. This burn is immediately followed by a smaller (4.1 m/s) but much more precise burn to setup an encounter with Laythe. This is all thanks to PreciseNode which lets me plan and execute this burn from over 200 days out.

Enter Jool's SOI a final course correction is plotted (16 m/s) to fine tune how I'll enter orbit around Laythe. Jool is still a small dot but it's gravity extends far enough to be felt almost 2 weeks before arrival at Laythe.

Another 4 orange tanks worth of fuel are burned to capture around Laythe into a 69 km orbit. It's not quite equatorial (later figures suggest I'm inclined around 2.5 degrees) but it's close enough to support a landing and return. I'm ahead in fuel for the transit section and should be good for the return trip as long as I can actually make the landing and return.

[Dave Kerbin]

Innes 1 (Part 2)

Now in low orbit around Laythe I need a place to land. There is a continent on the right but it passed into the night side as I entered orbit. The current day side is almost entirely ocean with no land mass near the equator. Fortunately as I approached Laythe I noted that it had a quick rotational period so I should have to wait too long. Five and half hours later the planet has turned, first revealing a single island at the equator before also revealing the large continent I observed earlier. However with daylight to help study it from orbit the continent seems extremely mountainous near the equator and is not much thicker there compared to the island either.

With the landing site picked the probe detaches on the dark side of the planet. It has a 6 hour battery supply to make the landing and return. For the descent I have about 600 m/s though thrust is low. The descent engine, fuel tank and some monopropellent (to avoid wasting any of the ascent supply on the way down) are mounted outside the heatshield where they will be destroyed. I have learned that this doesn't affect the functioning of the heatshield so there is no seperator for them. On the dark side I lower my PE to just above the atmosphere on the light side and plot a manuever to hopefully land me somewhere on land. The burn needs to start very early so my target isn't even on the horizon as I burn for almost 2 minutes.

About 70% of the way into the burn I pause while the projected path is still off the coast of the island. I'm not entirely sure about drag and I don't want to undershoot. As soon as it is clear I won't undershoot the island I burn to close up the path to the coast so that I can't overshoot.

It takes a while to reach any significant atmosphere. Reentry effects don't start until about 23km when the monopropellent tanks on the descent stage explode and they don't last very long. Both the engine and fuel tank don't heat up enough to suffer damage so once it has slowed down enough they are ejected with the heatshield. The landing legs are deployed to get them out of the way of the parachutes just before they are deployed.

During the soft portion of the descent the one spare Goo container is used to sample the atmosphere. I'm coming down in the center of the island toward a relatively smooth desert.

After soft touchdown the main Goo container is used and a Double-C reading taken. The next phase will be ascent back to the transit stage in orbit.

[Dave Kerbin]

Innes 1 (Part 3)

To ascend I need to wait until the transit section has orbited back around. There is a small issue of it being in a retrograde orbit so I need to launch in the opposite direction. All of the landing equipment is dropped as soon as the probe takes off. I had considered several engine configurations for the probe but using the large tank I found only two real options, the Poodle or the 8 radial rockomax engines. Both had similar delta-v values so I took the lighter and shorter version that used the little radial engines.

I still have plenty of electrical power but ascending I start to get really worried about fuel. It's draining really fast. I'm basing my ascent profile on how I launch from Kerbin but referencing the atmosphere scale instead of the altitude reading since the atmosphere on Laythe is lower. As I reach the start of the gravity turn the fuel tank is almost half empty which is not good. I thought I had a good idea for the delta-v requirements - 2800 m/s min and 3200 m/s for safety. While the atmosphere makes it hard to determine my average ISP during the ascent I was expecting about 3000 m/s (worst case burning at the surface the ship would have over 2750 m/s unless Laythe ISP is even lower then Kerbin). Maybe it was my ascent profile (it didn't look good at the circulization point where I had to spend 782 m/s) and maybe it was because I was going into a retrograde orbit where I was losing out on the free velocity from the moon's rotation but I barely made it into orbit. I entered a 55 x 71km orbit and when I looked I had 0.67 L of fuel left in the tank.

There are only two things going for me. The first is that for the moment I have plenty of power which means I have some time (about 5 hours in the current configuration). And second I made it into orbit with very little RCS used, I relied on the excessive amount of thrust vectoring I had at my disposal for everything but lining up the circulization burn. You see the original flight plan was to enter orbit and rendezvous with the transit section. That section would be dead in space since it doesn't have a probe core which means that any little bump will send it into an uncontrolled spin. To dock when in RCS range the little top part of the probe would detach and move in. It's light weight would make docking easy and it carries it's own 40 minute power supply in addition to all the RCS gear, science instruments and probe core.

With the probe almost out of fuel the plan changes. I'll need to seperate much earlier so I can use the RCS thrusters as my primary engine. With just the docking segment I'll have almost 300 m/s of delta-v to work with which I'll need in order to cover the inclination difference. KSP .23.5 introduced a feature with manuever nodes that lets you place them one or more orbits into the future. I used that to peek ahead and find that if I waited 2 orbits I would have an opportunity to setup a close encounter of about 8 km right at the point where the 2 orbits crossed each other (descending node). It's a cheap maneuver at just 4.6 m/s so it's ideal for my purposes. Prior to executing it I charged up the batteries on the docking segment so that I could seperate - at this point I was assuming that I'd need RCS to complete some of the burn.

Fortunately I got really lucky. The fuel was enough to complete the course change with 0.08 L now remaining in the tank, about 0.5 m/s based on the previous performance. At this point the liquid engine is useless but by completing the entire burn with it I still have the battery (in hind sight I should have really planned to complete the entire burn with the full probe attached even if it would have wasted RCS, as battery power was the more essential resource at that specific point). Approaching the closest encounter point I charged the docking batteries again, this time locking down both of them so that only the probes battery was being drained. This way I could keep that battery charged right up until the moment of seperation. The docking section seperates leaving the ascent body behind and executing a 129 m/s burn with RCS thrusters to zero out the relative velocity (roughly matching orbit and inclination) and bringing me down to 30 L of monopropellent.

From here I start a series of burns to try and quickly bring the docking section to the transit section. I don't want to burn too hard as any speed I add (change of orbit) will have to be undone to dock. Instead each small burn puts me about 2-3 minutes away from my next close encounter where I roughly half the distance each time. 15 minutes after seperating I am within 150m of the transit section. I'm approaching from behind (in relation to its docking port) so I'm going to need to pass it and turn around to dock - the transit stage is inert so it can't turn to face the probe. I have 14.68 L of monopropellent left having burned half my supply to rapidly reach this distance and match orbits.

At this point final docking is easy since the probe is so light, ensuring that the magnetic docking port can easily pull it in and dock without disturbing the transit stage. As soon as it docks the probe recieves power and begins recharging its batteries. With plenty of fuel, mono propellent and an unlimited power supply now attached the probe should be able to make it home after the close call during ascent, which again ironically was the stage I had planned and checked the most before launch.

[Dave Kerbin]

Innes 1 (Part 4)

I was originally planning on trying to burn back to Kerbin directly from Laythe orbit to take advantage of the added velocity. However I'm not sure it would work and from my low orbit I was concerned I could hit the atmosphere so I made a simple burn to exit Laythe's orbit and make the return to Kerbin from around Jool. With so much weight shed the ship can now turn easily on RCS, speaking of which I transfered the remaining RCS from the 6 tanks hidden in the center (visible in part 1 in the rear shots) to the probe's own tank to refill it.

Out in Jool orbit I found that I couldn't burn directly to Kerbin either, as my orbit was going to reencounter Laythe around the time I needed to burn. I played around with some minor adjustment to my orbit and got a path that would boost me past Laythe using its gravity to pass Vall and get another assist from Tylo to steady my orbit up there.

It will take a 1638 m/s burn to reach home but I know I'll have enough since the outer transit stage is still left and the inner stage has around that much by itself. With 500 m/s burned from the outer stage it is finally shed and the return stage is used to complete the burn. This also reveals the pair of NUK NUK reactors that have been providing the power for this trip.

On the way home a minor correction is made to bring my PE within a few hundred km of Kerbin. After entering Kerbin's SOI and passing the Mun one last burn is setup, an intentionally inefficient burn to lower the PE to 26 km that will also slow the ship down by almost 400 m/s. I simply consider this a good use of the remaining fuel that will hopefully ensure a safe reentry. With the batteries held at a full charge the entire trip the return stage is discarded to burn up.

After the effects of reentry are over (velocity was over 4 km/s but the shield still had ablative material left over when it was done) the heatshield is detached and the parachute armed for automatic deployment. The probe comes in for a smooth landing and the science is recovered, completing the mission.

This completes this playthrough of BTSM.

[Dave Kerbin]

BTSM Career #3 - Mun on a Dime

This will be my third playthrough of BTSM and I've got an even shorter goal this time (I do like the early game with limited technology much more then the later game). BTSM has been updated with weight limits, so now there are real, fixed goal posts for me to meet. My objective with this playthrough is to send a manned mission to the Mun, collect a soil sample and return everyone safely. The catch is I want to do it with as few techs as possible (I did a low tech landing on the last playthrough but I'm going to try and beat it) and in particular I want to see if it's possible to do this mission without unlocking Advanced Construction. Advanced Construction is an important tier 5 tech (tier 6 is where space suits and other Mun equipment are) and contains 3 key items: docking ports, struts and finally it unlocks a 250 ton pad limit. Until you get Advanced Construction the largest ship you can launch is 125 tons with the latest version of BTSM.

I had thought of trying to restrict my playthrough up to the Mun landing as well but I couldn't think of a good set of restrictions that wouldn't be too easy or completely impossible. So instead I've partially role played it, with an emphasis on missions that are advancing my space program from a role playing perspective and not just randomly collecting science.

[Dave Kerbin]

Asimov 1 and 2

The goal of the Asimov missions is to explore the basics of going up and figuring out what it is like 'up there', since that is where the Mun appears to be.

The first mission reaches an altitude of 23 km and transmits back that it gets rather cold up there. We'll definitely need to learn more about the conditions between here and the Mun so we can be prepared for the trip, we might need to bring winter coats.

Asimov 1 earns 4 science and unlocks Basic Rocketry

The second mission adds more boosters so we can go higher and a barometer is added on the back with some batteries to get air pressure readings too. By firing the boosters in groups we don't run out of fuel until we are already at 27 km, higher then our last mission. The pressure readings up here are very low, and both the pressure and temperature continue to drop as the probe coasts higher. It's really too bad we couldn't steer in case we might reach the Mun. Finally it reachs a maximum altitude of 76 km and makes a shocking discovery - not only is it colder then the coldest winter up here, there is no air!

Asimov 2 earns 44 science and unlocks Basic Flight Control and General Rocketry

[Dave Kerbin]

Bester 1 and 2

With going up figured out we need to figure out how to navigate. We need fins to steer and an engine that can be used more then once so that we can change our course. Something that we've been scratching our heads on is the realization that going up also means coming back down - but since the planet isn't flat how exactly does 'down' work? We've put together an instrument that can measure this downward tug called gravity. As we pass over the curvature of Kerbin we can study it closely and figure out how to find our way when down keeps changing.

Bester 1 takes off on its new liquid engines and is able to fly straight with the use of its fins. Once it reaches an acceptable height ground control commands it to start turning toward the mountains but the turn stalls part way through, it's still climbing but not turning. It seems the fins only work when there is enough air around and as Bester 1 climbed the air became too thin. Since we don't have control over its direction anymore the engines are throttled down and the probe is left to coast. As it travels westward information about gravity is recorded as it passes over the grasslands and into the highlands, then the mountains. Here it reaches the highest point yet reached by a probe and checks the temperature to see if it keeps getting colder the higher you go. After that the probe begins descending down toward and past the western shore. As the air thickens it seems to heat up and the probe begins to crack at the strain, breaking up over the water before it can make any determinations about it.

Bester 1 earns 108 science and unlocks Survivability, Flight Control and General Construction

Bester 2 attempts to correct the issues of Bester 1. First a new tiny engine using a fuel that can be ignited in small bursts is added in a set of clusters called a reaction control system that will allow the ship to turn or rotate even without air. The second improvement is an inovation to counter the ballooning mass of the probes (Bester 1 is fifteen times the mass of Asimov 1) - rather then send the whole probe up an explosive charge can seperate a small part of it. After lifting off the RCS system assists in turning the ship even when the fins become useless and when fuel runs out on the first stage the second stage seperates into its own ship to carry on the journey on a course that traces the curve of Kerbin's surface.

A second burn in space to keep following the terrain has the effect of putting the ship into 'orbit'. It is always falling but never losing altitude. This will be very useful and the ship can now coast without any additional thrust, passing over the north pole's ice caps and surrounding tundra before coming out above the ocean on the other side of the planet and continuing down toward the south pole. The planet is also rotating beneath the ship, so by the time Bester 2 gets back to the point where it launched it is now above a desert on the western continent instead. With lots of interesting data collected the probe is commanded to try and stop. By burning in the opposite direction it is able to return, though the same heat and pressure consumes Bester 2 as it did Bester 1.

Bester 2 earns 100 science and unlocks Science Tech and Advanced Rocketry