I am very pleased to announce my first mun/return mission without the use of a m

[hubbazoot]

YUSSSSS! This mission was a roaring success, and a pleasant surprise to boot. With some help from the orbital mechanic tool (the app, no mods), I was able to successfully navigate to Mun, land, and return without glancing at the map once.

General mission overview:

Liftoff took me a couple of tries to get down properly, lots of pilot errors. Jettisoned first stage at 10km. It took me several attempts to actually get a stable orbit I felt I could deal with, and my actual trip to the Mun was a 'Well, this isn\'t quite what I\'d like, but hell, why not?' Second stage jettisoned at 80km, still re-entered atmosphere.

I WAY overshot my target orbit of 75km and ended up settling into a rather round orbit at ~147km. From there, I waited until the Mun cleared the horizon of Kerbin, and started my hohmann transfer. Hohman transfer completed with about 50% of the fuel left in my third stage, things are looking good.

I get into a direct descent pattern over the Mun, I have no idea which part of Mun I\'m over, from eyeballing it, it looks like I\'m on the side Kerbin-up. I\'m at about 1000m/s at 1000km, I start braking at 100km, following my speed=altitude/1000 rule.

From what I can see, it looks like I\'m descending directly over a rather steep valley, I nudge it over onto some nicer looking terrain. 4km up, I still have about 30% fuel left in my third stage. I do one last braking burn, then jettison the third stage.

Landing SUCCESS!

Kerbin is almost directly overhead, still trying to decide what to do, decide to do a one orbit \'round and then return back to Kerbin the same way I got here: wait for earth to clear the horizon, and accelerate to \'escape velocity.\' I plug in the numbers and accelerate just enough to clear Mun\'s gravity well.

Back in orbit around Kerbin, doing about 700m/s and am 10000km up, not quite sure what the orbit looks like. I decide to wait for the Pe to roll around. I\'m about 5000km up, and doing about 950m/s. Set the hohmann transfer in for a 30km Pe, we\'re gonna do another direct descent. I\'ve got slivers of fuel left in the tank, and my craft needs to do a powered descend. Whoo boy.

I come back into Kerbin HOT, screaming through the upper layer of the atmosphere at about 3000m/s, finally slow down to 2km/s when I hit the middle layer and finally start slowing down, parachute deploys.

I\'m coming in nice and easy over the middle of the giant ocean, 300m up, the parachute finally decides to open. I come in on a nice powered descent, braking last minute and hitting the water a little hard. Craft is destroyed, crew is alive.

MET: ~7h

What I\'ve learned: I could save a lot of fuel by waiting until a little later to do my Mun escape orbit, I think it\'d save me fuel doing the descent into Kerbin. I need to tweak the fuel a little bit; not so much fuel in the third stage, more fuel in the lander.

I\'m probably overly proud of this mission, but I\'m very impressed with both the craft and myself. Here\'s the proud vessel that led me there, the Opul 1.

[Kosmo-not]

I think you have every reason to be proud of this accomplishment.

I was thinking not long ago about doing the same sort of mission. I haven\'t gotten around to trying, yet.

[Joshua21B]

Congrats Getting that first successful moon mission is a challenge. Once you\'ve got it down though it gets much easier. I can do a moon intercept no problem without mechjeb. You\'ll just get a feel for it after a while.

[Zephram Kerman]

Without using the map? Yes, be proud. If I had a spaceship, I\'d hire you.

[hubbazoot]

Congrats Getting that first successful moon mission is a challenge. Once you\'ve got it down though it gets much easier. I can do a moon intercept no problem without mechjeb. You\'ll just get a feel for it after a while.

Not just without the mechjeb I\'ve never used, without the map.

Thanks, guys, I\'ve been bristling about this all night. That ship I built is so absurdly stable and easy to turn it kinda spooks me out. It\'s pretty strong, too, almost no physics wobble in 2x and none in 1x.

[LambdaCactus]

This is awesome.

I can guess at how most of it can be done, but how did you accomplish orbital insertion? (Or did you skip it?) What I mean is, how can you tell if you\'re coming in for a low perigee or an impact, and how do you know which way to correct for that?

[maltesh]

Well, he said he did use an orbital calculator program. The game provides your altitude, your velocity, and your flight path angle on the instrument panel

Along with the mass of the object you\'re orbiting, you can determine the exact shape of your spacecraft\'s orbit, and its position in that orbit from that information. With the object\'s radius, you can work out whether or not you\'re on course for impact. I wrote an orbital calculator that did that about nine months ago.

There are a few options to ensure that you\'re going to hit the Mun.

1. Slow down. If you slow down enough inside the Munar SOI, you\'ll hit the Mun.

2. Burn in the R- direction. It\'s halfway between your orbital prograde and orbital retrograde directions, on the Navball, and on the arc that passes through the 90-degree pitch dot in the center of the brown hemisphere. Doing so will steepen your descent angle, resulting in being on course for impact.

[LambdaCactus]

Well, he said he did use an orbital calculator program. The game provides your altitude, your velocity, and your flight path angle on the instrument panel

Yes, this makes sense... it can be worked out with some trial and error and approximate numbers too.

2250m/s to orbit Kerbin; 3000m/s to shoot for the moon; 600m/s to orbit the moon. (Just off the top of my head, might be off a little bit.)

Along with the mass of the object you\'re orbiting, you can determine the exact shape of your spacecraft\'s orbit, and its position in that orbit from that information.

Mmm, yes a little bit, but not really. For orbital insertion, you will know your speed, but not your true vector. Given the same speed, it\'s either a collision into the moon, or a flyby. Small difference in angle, big difference in results.

There are a few options to ensure that you\'re going to hit the Mun.

But I wouldn\'t want to hit the moon. :-(

Ok, I just thought of something. If you watch the prograde marker as you reach the moon\'s gravity, it will either be near 90° straight down, or off by some degrees. (Straight down is bad.) A burn to the side should move it off to an angle, but I have no idea how much, how far out. A good approach means the marker will slowly move away from -90° as you come around, eventually crossing the horizon at perigee... (retro-burn here). So if you watch your approach rate towards the moon along with the movement of the marker, you might be able to kind of estimate which one will happen sooner: impact, or marker on the horizon. Very rough idea, but it might be doable.

[maltesh]

Mmm, yes a little bit, but not really. For orbital insertion, you will know your speed, but not your true vector. Given the same speed, it\'s either a collision into the moon, or a flyby. Small difference in angle, big difference in results.

You can get quite accurate results on your flight path angle by looking at the angle your velocity indicator is above the horizontal direction. That\'s what my program initially did.

You can get extremely accurate results by taking two altitude and velocity measurements ten seconds apart, assuming that the spacecraft moved in a straight line between them, and retroactively working out the flight path angle from that. That\'s what my program eventually did.

If you know your altitude and velocity at any two points, and the time it took you to travel between them, it\'s possible to work out the exact shape of your orbit from that, though the math gets hairy when you remove the 'I traveled in a straight line' assumption. I\'d intended to eventually rewrite my program to do that, but by then, we had a map view.

But I wouldn\'t want to hit the moon. :-(

Of course you want to hit the Mun. You just want to do it slowly enough that the spacecraft survives.

Coming to a stop inside the Munar SOI will ensure that the former happens. Burning at the right time before impact to allow the latter is the tricky part.

[hubbazoot]

This is awesome.

I can guess at how most of it can be done, but how did you accomplish orbital insertion? (Or did you skip it?) What I mean is, how can you tell if you\'re coming in for a low perigee or an impact, and how do you know which way to correct for that?

The orbital tool was this one here:

http://kerbalspaceprogram.com/forum/index.php?topic=562.0

Orbital insertion went something like this:

Once I was at about 40km, I started looking for my 'goal' speed and altitude. Since I need a speed of 2286 m/s to orbit at 75km, I started accelerating to 2286 m/s as soon as I could. You know you\'ve reached your Ap when the vertical ascent meter starts to come back down to zero you\'re at your Ap. I\'d plugin that altitude into the round orbit calculator. If I wasn\'t going fast enough to maintain a round orbit at that altitude, I accelerated to the speed I needed for a round altitude.

Granted, this led to a pretty severe overshoot and I ended up settling into an orbit twice as high as my goal. For the munar insertion, I followed the hohmann transfer for going from my current altitude at ~150km to the mun\'s orbital altitude of 11400km. Once I reached the goal speed, I time accelerated until my altitude snapped from Kerbin-relative to Mun-relative.

As for the how-did-I know-I-would-hit-the-mun-part, I didn\'t. I just killed off all my horizontal speed till I was falling straight down.

The trickiest part was figuring out when to escape the mun\'s orbit and when to decelerate for kerbin. And honestly, I made an educated guess.

This page here helped quite a bit: http://kerbalspaceprogram.com/~kerbalsp/wiki/index.php?title=Mun

Since I know the mun\'s SOI is 2430km, I did a hohmann transfer from my orbital altitude of 75km (like I said, I overshot quite a bit) up to 2430km. As soon as I saw my altitude snap over to Kerbin-relative, I knew I made it.

At that point, I was descending, but still going pretty fast. At this point, I made probably the most fuel-expensive part of the mission: I decided to wait and see where my perogee was. As soon as I reached the perogee, I then plugged in the numbers to do a hohmann transfer from 5000km down to 30km, and made that my target speed.

Should I make a how-to video?

[Max Grant]

Oh, darn! I thought I was going to read about your Un/return ission.

Or, that you\'d acquired a replacement sponsor, the letter \'j.\'

Nice ship, btw.

[LambdaCactus]

As for the how-did-I know-I-would-hit-the-mun-part, I didn\'t. I just killed off all my horizontal speed till I was falling straight down.

Ah, that\'s what I was wondering... so you basically skipped trying to orbit the mun. (Not criticizing, I\'m just trying to understand the parameters of your challenge.)

The trickiest part was figuring out when to escape the mun\'s orbit and when to decelerate for kerbin. And honestly, I made an educated guess.

Well, since the mun\'s orbital speed around kerbin is about 540 m/s, you want to burn away from the mun so you basically follow its orbital trail backwards and effectively cancel out that orbital speed and fall into kerbin... (If kerbin is straight overhead in the sky at your landing spot, that means burn east.)

You also need to launch with more speed so you get 500m/s at the edge of the SOI (2400km) altitude. A hofmann transfer to just pop out of the mun\'s SOI sounds like it\'s a bit too soft... I expect you\'d end up in an elliptical orbit, and like you said, burn a lot of fuel to slow down at the bottom.

Should I make a how-to video?

Sure, I would watch it! I\'m off to try this myself...

[Zephram Kerman]

I\'m very impressed! Out of the whole flight, I can only think of one change to suggest. On the way back to Kerbin, it is much more efficient to decelerate at apoapsis instead of periapsis. So once you pop out of Mun SOI, just 'stop and drop', the same way you did to land at the Mun. (Or, figure out your PE, and then Hohman transfer from AP directly to 30km aerobraking altitude.)

Yes, a video of this flight would be very interesting and useful! 8)

[hubbazoot]

I\'m very impressed! Out of the whole flight, I can only think of one change to suggest. On the way back to Kerbin, it is much more efficient to decelerate at apoapsis instead of periapsis. So once you pop out of Mun SOI, just 'stop and drop', the same way you did to land at the Mun. (Or, figure out your PE, and then Hohman transfer from AP directly to 30km aerobraking altitude.)

Yes, a video of this flight would be very interesting and useful! 8)

The choice to wait until I got to my periapsis was actually a gamble to save fuel in case I was going slow enough and at the right angle to be able to descend back into Kerbin without it. I REALLY didn\'t want to do a direct descent into Kerbin as I\'m pretty sure I wouldn\'t survive that.

I\'ll make a video today.

[LambdaCactus]

I did it!

My mission parameters:

• 
  [li]Stock parts[/li]
  [li]No calculator or other nav add-ons: totally kowboy[/li]
  [li]Circular(ish) orbit at Kerbin before transfer burn[/li]
  [li]Orbital insertion at Mun (i.e. controlled speed/low perigee landing)[/li]
  [li]Nice atmospheric re-entry[/li]
  

I was just able to complete this after a few tries. It\'s actually quite thrilling to fly totally seat of the pants. I had a rough idea of the kind of numbers I would need, so I did the whole run by feel. 3 attempts total:

The first attempt looked good until I skimmed into lunar terrain... that little lander engine was too little too late once I noticed my orbit insertion was going to be sub-surface.

Second attempt, I had a good efficient launch with a bit of a low orbit. I was mostly circular around 75k, but then misjudged the velocity I\'d need for lunar transfer. I was aiming for 3000m/s which might be fine from 120-150k altitude, but a lot of that speed bleeds off coming up from a low orbit... I ended up in a long elliptical orbit to about 6000km. I was a bit surprised at first when I noticed I was no longer climbing, so I peeked at the map to see how far off I was (it was a failed pass anyway). Ok, maybe just get these guys home then: I made a short burn to drop my periapsis down from 75k into the atmosphere, thinking I would just come back for a landing. However, once I was in the atmosphere I could see my speed was still too high and I would skim off. At 45km my descent levelled out and my speed dropped to 2300-ish. This is too perfect! I still had plenty of fuel, and I could circularize this and make another run! I managed to get the aerobraking pass circularized around 100k, waited for the mun to come around again, and then screwed up the burn again: still too slow! I left the crew in elliptical orbit as a souvenir of a failed but really fun double-attempt.

Successful mission spoilers below.

Final attempt: good on launch but I was too slow to accelerate into orbit: I missed the apogee and dropped back into the atmosphere a bit. Still, I saved it and set up a slow climb up from 63km. At moonrise I was nearly level around 75km, and accelerated to 3150m/s. I reached the lunar gravity going a bit fast so I made a bit of retro-burn so I wouldn\'t just pass by. I watched my altitude drop until about 720km where it levelled out. I took a wild guess: retrograde burn, 160m/s sounds good. Honestly this was such a lucky guess that I couldn\'t believe it... I just checked the numbers in Orbit Mechanic and I was dead on! This would bring me in to a low perigee at 3 km above the surface: perfect! I still had my second stage with some fuel for slowing down, and when I burned it up, I was sitting 3km up, in level flight, going 65m/s. Couldn\'t have done it any better.

Here\'s how I actually checked if that approach from 720km was sane as I was coming in: when you\'re in an elliptical orbit, the prograde/retrograde markers oscillate up and down in a sine wave: at apogee/perigee they are on the horizon, and at the ascending/descending nodes (half way between apogee/perigee at the steepest descent or climb), the markers reach the furthest away from the horizon. Let\'s say it oscillates between 40 degrees above the horizon and 40 degrees below the horizon... like a sine wave, it slows down as it reaches the highest and lowest points, and it passes through the horizon quickest. I knew I had to get from my horizon at 720km altitude to my low horizon somewhere near the surface. This means the prograde marker would dive down to some angle, pause there, and start returning to the horizon as I approach perigee. I watched that marker as it dipped. I could see it pause at -40 degrees, and I checked my altitude once I confirmed that it slowly started returning: the altitude was 350km, so I knew I was close since this is half-way between 720km and zero. This is harder to do when the approach is not so steep since the movements are smaller... If you want precision instead of seat-of-the-pants flying, use a calculator!

My lander had full fuel at touchdown because of that perfect approach... Return trip: I knew Kerbin was just over the horizon from my landing spot and I was near the equator, so the direction I needed to go was straight up (perpendicular from the Mun-Kerbin line, aka the horizon). With 2 full tanks of fuel, I could just burn straight up instead of doing the more efficient method of orbiting before transferring off. I accelerated to 900m/s, which left me about 60m/s Kerbin-relative speed after leaving mun gravity (actually it was too much the other way, I was coming back retrograde). This set me up for a really steep descent, Ideally I would\'ve liked to decelerate in the high atmosphere rather than coming straight down... oh well, still landed by parachute.

Fun! The map feels like cheating now.

[maltesh]

Well done. Minor point:

, and at the ascending/descending nodes (half way between apogee/perigee at the steepest descent or climb), the markers reach the furthest away from the horizon.

Halfway between the apoapsis and the periapsis on the boundary of an elliptical orbit are the ends of the minor axis, not the ascending and descending nodes.

[hubbazoot]

Fun! The map feels like cheating now.

It certainly does, doesn\'t it? ;D

I\'m still working on the video, I\'m making sure the narrative is actually good and explains all the things relative to making the ship a success. I should have it done later tonight.

[samstarman5]

I imagine once you get a feel for the velocities needed for Kerbin orbit, TMI, and coming down from Munar orbit, then the map becomes just window dressing. It\'s still pretty window dressing, though.

It won\'t be useless, though. Come when the other planets show their ugly faces, then it is a whole new ballgame.

[LambdaCactus]

Well done. Minor point:

Halfway between the apoapsis and the periapsis on the boundary of an elliptical orbit are the ends of the minor axis, not the ascending and descending nodes.

Thanks for the correction, yes that\'s what I meant. I hope that part made sense anyway.

[hubbazoot]

I imagine once you get a feel for the velocities needed for Kerbin orbit, TMI, and coming down from Munar orbit, then the map becomes just window dressing. It\'s still pretty window dressing, though.

It won\'t be useless, though. Come when the other planets show their ugly faces, then it is a whole new ballgame.

I still find it incredibly useful for establishing more precise orbits, and anything more 'advanced' than getting to the Mun, yes I 100% agree.

[hubbazoot]

Alright, I finally got the video finished and am now going through the painful process of uploading it, but then the file got corrupted, so I\'m trying again.