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Possible to perform a flyby with only the first 2 tech nodes unlocked?


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Hi there,

Brief

Is it possible to perform a  Mun or Minmus flyby with only the first two nodes of the tech tree unlocked (Engineering 101, Basic Rocketry)? Also, all buildings and launch sites haven't received any upgraded yet either.

According to my maths it’s impossible to get enough delta v and thrust to get to the mun with only 30 parts and a 18 tonnes weight limit. But I’ve seen people do things on this forum/and KSP that blew my mind, so I’m hoping some creative out of the box thinker can help me out here. :)

Background

I just started a career game with the reward sliders (rep, science and reward/earnings) set to 10%. I finished an “all sliders on 20%” career game recently and that was really doable. The sliders on 10% however, changes everything!

With these settings, the game is really difficult. The science rewards from biomes on kerbin are really low and it's really challenging to find a way to make profit on contracts. I found a way to make some profit with sub orbital tourist flights, but my current income rate is too darn low and it gets rather boring after a while. After two evenings playing (~ 6 hours) I earned 60k worth of kredits. I’m planning to upgrade the launch site first, since it’s fairly cheap and I could really use a higher weight limit. It would be better if I had more science so I could build more efficient rockets though, but the science reward of a biome on kerbin only yields ~1 science ( with  1 thermometer, 1 crew report and an eva report). So it would be great if I could get to the moons of kerbin somehow to increase my science output.

Hope you guys can help. Any tip would be welcome! :)

 

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Tip: you can always get two eva reports over every Kerbin biome that does not involve touching a building -- by jumping, and timing your click properly. So it sounds like you are missing out on one EVA report over many/all of the KSC biomes.

I believe this video from @Cunjo Carl shows that you can, in fact, get landed on minmus, and scoot around a bit to take up to 3 biome readings, within the 18/30 launch limit.

IIRC, his launch to minmus is about an hour into this 7 hour video. The biomes have changed on minmus, though, so you need to know the new secret spot to land.

Edited by bewing
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Yes, there is a solution. But it's a tight one - you'll have to fly it well or your Kerbal will be stranded in a Mun-intersecting orbit, which might eventually eject him from Kerbin's SOI entirely if you don't rescue him.

mk1 command pod         0.800   (remove monoprop)
mk16 parachute          0.100
thermometer             0.005
-----------------------------
stage 3	total           0.905
part count              3


stage 3                 0.905
tr-18a decoupler        0.050
fl-t100 fuel tank x8    4.500
lv-t45 engine           1.500
-----------------------------
stage 2 wet             6.955
stage 2 dry             2.455
stage 2 vacuum dV       3268 m/s
part count              13


stage 2                 6.955
tr-18a decoupler        0.050
hammer srb x3          10.680
-----------------------------
stage 1 wet            17.685
stage 1 dry             9.255
stage 1 mixed atmo dV   1111 m/s (estimated)
part count              17

Total vessel dV         4379 m/s (estimated)
Mun free return	cost   -1000 m/s (estimated)
Kerbin ascent has       3379 m/s (estimated)

A Kerbin ascent into a 75x75 km orbit is usually estimated at 3400 m/s for a reasonable rocket. You have a solid first stage with tons of TWR, so you easily should be able to beat that with an aggressive trajectory.

Tune your SRBs so that the center one burns out a good bit before the two others, that smoothes out the acceleration curve. It will still be a difficult to fly ascent, because the SRBs don't have thrust vectoring. You'll probably have to revert several times to get the aggressive turn exactly right.

If you don't know what a free return trajectory is and how to pull it off, this might be the time to look it up... :P

Once you're on the way to the Mun, only have SAS active when you absolutely need it. The alternator on your LV-T45 is your only power source, and it'll pretty much stop giving you anything after your transfer burn.

On your return to Kerbin, you probably want to aerobrake for one pass before going for EDL, just to be safe (you don't have a heatshield). Set your atmospheric periapsis accordingly, with a correction burn at your flyby periapsis.

 

Alternatively: if you can manage to upgrade the launchpad, you have plenty of part count left to add MOAR BOOSTERS to the first stage and thus end up with more dV for in-space maneuvers. :wink:

 

Edited by Streetwind
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1 hour ago, bewing said:

I believe this video from @Cunjo Carl shows that you can, in fact, get landed on minmus, and scoot around a bit to take up to 3 biome readings, within the 18/30 launch limit.

That is actually using the tier 2 launchpad, with a 140 ton mass limit. No other way to get that massive amount of SRBs fitted otherwise. You can see him upgrade the pad at around 21:30.

He's also using technology not available to @xendelaar. He says he only has the first two nodes, so no thumpers can be used.

Edited by Streetwind
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I tried your rocket -- I couldn't gravity turn it properly. I modified it with an extra stage -- tossed 1 hammer, added another decoupler (and an extra thermometer). That worked very nicely. Plenty of dV left in LKO.

 

 

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@Streetwind:

No, 1 hammer, decoupler, 1 hammer, decoupler, liquid stage + 1 thermometer. (14.19t on the pad)

(Just for fun, I also tried with 3 hammers in a row and explosive decoupling, but that didn't work so good :D )

Edited by bewing
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Huh, that actually works out TWR-wise. Neat.

However, it has about 70-75 m/s less dV overall. And the free return is more expensive than a normal transfer... You said it still had enough? Well, maybe I overestimated the extra cost a bit, who knows :P Good call on the second thermometer too, I forgot he cannot EVA yet.

Incidentally, there is also enough mass allowance left to add the third SRB again, for extra margin. Using the offset tool, you can have the lower stage be two side-by-side Hammers, above which the rest of the rocket is centered. Thrust limiting brings the TWR to a similar level as that of the single Hammer.

mk1 command pod         0.80   (remove monoprop)
mk16 parachute          0.10
thermometer x2          0.01
----------------------------
stage 4	total           0.91
part count              4


stage 4                 0.91
tr-18a decoupler        0.05
fl-t100 fuel tank x8    4.50
lv-t45 engine           1.50
----------------------------
stage 3 wet             6.96
stage 3 dry             2.46
stage 3 vacuum dV       3264 m/s
part count              14


stage 3                 6.96
tr-18a decoupler        0.05
hammer srb              3.56
----------------------------
stage 2 wet            10.57
stage 2 dry             7.76
stage 2 mixed atmo dV   560 m/s (estimated)
part count              16


stage 2                10.57
tr-18a decoupler        0.05
hammer srb x2           7.12
----------------------------
stage 1 wet            17.74
stage 1 dry            12.12
stage 1 mixed atmo dV   654 m/s (estimated)
part count              19


Total vessel dV        4478 m/s (estimated)

 

100 m/s more than my first draft! That easily ought to be enough for a no-risk Mun flyby. :)

Say, can you do a free return around Minmus? I've never tried, but this rocket should theoretically have the dV. Unless Minmus is so weak that it won't lower your periapsis enough.

 

Edited by Streetwind
Fixed stage numbers
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40 minutes ago, Streetwind said:

I forgot he cannot EVA yet.

And like you said, not enough EC to transmit with an antenna either.

But no, I can't quite seem to get my Ap high enough -- I get really close, but no cigar. A reliant engine instead of the swivel would certainly do it. So all you need is to get a part test contract for a reliant and it'd all work.

I don't think you need a full free-return trajectory, though -- you just need to get your Ap to 9Mm a bit before the Mun arrives. At that altitude, the Mun won't affect your trajectory hardly at all. And making your transfer burn at 60km altitude actually helps, too.

 

 

Edited by bewing
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3 hours ago, xendelaar said:

I just started a career game with the reward sliders (rep, science and reward/earnings) set to 10%. I finished an “all sliders on 20%” career game recently and that was really doable. The sliders on 10% however, changes everything!

 I’m planning to upgrade the launch site first, since it’s fairly cheap...

20% completed? Without science lab transmissions i hope? Thats really impressive, well done it. I tried 10% once, EVERY launch is nerve wrecking (no reverts....so click on "Hard", then custom down only the rewards, and also disable contract science rewards via the "Contract reward modifier" mod).
I tweaked it up to 30%, there was definitely a steep wall between LKO and Mun SOI but you know better than me at this point it's possible to cross.

Don't upgrade the launch pad. Use the Runway instead, just tilt your rockets right side up before launch. This way, you only upgrade one building that gives you the ability to build planes as well...unless of course you dont plan on building anything with wheels.

Also, what are the "Hard" difficulty settings for network comms? They really become a pain in the *** if you don't keep an eye on their range

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47 minutes ago, Blaarkies said:

Don't upgrade the launch pad. Use the Runway instead, just tilt your rockets right side up before launch. This way, you only upgrade one building that gives you the ability to build planes as well...unless of course you dont plan on building anything with wheels.

Also, what are the "Hard" difficulty settings for network comms? They really become a pain in the *** if you don't keep an eye on their range

I go the other direction. I build my medium-sized planes in the VAB and launch them to the pad -- then drive them onto the grass to take off. It's less convenient, but upgrading the VAB gives you another biome, and upgrading to a T2 SPH doesn't.

The network comms "hard" settings aren't really a problem at the early stage, where every flight needs a pilot anyway. They only start to hurt when you are trying to fly with probe cores.

 

 

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1 hour ago, bewing said:

But no, I can't quite seem to get my Ap high enough -- I get really close, but no cigar. A reliant engine instead of the swivel would certainly do it. So all you need is to get a part test contract for a reliant and it'd all work.

I don't think you need a full free-return trajectory, though -- you just need to get your Ap to 9Mm a bit before the Mun arrives. At that altitude, the Mun won't affect your trajectory hardly at all. And making your transfer burn at 60km altitude actually helps, too.

The free return is useful because it could allow a pass through low Mun orbit, so the second thermometer actually has a use. Together with the fact that the crew report will also be worth more, that will be quite a boon at 10% science returns. Of course, maybe an SOI-grazing would be enough to unlock General Rocketry, and then he could mount the Reliant and do more demanding missions with a bigger margin...

Pretty surprised though that nearly 4500 m/s isn't enough. It should be. I'm going to try this out when I get home.

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Thanks for the mention, @bewing! @Streetwind is right though, it uses some things that won't be available for @xendelaar. There's also been dramatic physics changes since then that render that lovely old craft unusable. Science marches on! Along these lines, I've restarted the speedrun for v.1.2, and have remapped the story missions and World's Firsts cash bonuses which you might find useful, @xendelaar.

Link

I like the setup you made, @Streetwind, and I think serious improvement can only be made with a bit of shenanigan. That said, if the mission is to stretch the possible by running career with 10% returns, it doesn't seem unreasonable to stretch KSP mechanics a bit with our launcher. This rocket uses the offset glitch to attain a Mun/Minmus flyby (they're pretty close dv-wise for a vertical launcher) with about 360-400m/s to spare. That should be plenty to flyby/orbit/return either or flyby both if you handle your burns and gravity assists carefully. It might also  be a decent choice to use the monetary spoils during the mission to upgrade the astronaut complex, because EVA science from polar orbits is lovely, and you can always return to Kerbin for free using a trick I'll edit in later today. Also, if you happen to be planning to really min/maxing this for funds, I'd probably go Kerbin orbit/return followed by Mun flyby/orbit/return and would be happy to share how to force the story mission system to give you the missions you want when you want them.

If you decide to use it, remember, tap the spacebar while physics is kicking in at launch, head straight vertical and let it wobble a little-, but not more than 10 degrees off course before decoupling. Also, don't forget to enable crossfeed on that decoupler!

Kerbal_Space_Program_2017_03_08_08_14_05

 

Lastly, I totally salute you for trying this @xendelaar! That's a heck of an undertaking you've put yourself on. Shoot me a PM if you wind up putting anything in the missions reports about it. I'm super curious to hear more.

Edited by Cunjo Carl
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3 minutes ago, Cunjo Carl said:

you can always return to Kerbin for free using a trick I'll edit in later today. Also, if you happen to be planning to really min/maxing this, I'd probably go for Mun flyby/orbit/return and would be happy to share how to force the story mission system to give you the missions you want when you want them.

OK, I'm extrememly interested to read about these things in your upcoming post. :D

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40 minutes ago, Kryxal said:

Math says 4500 should do the trick ... I remember FRT being around 860

Depends on your origin orbit. From 75x75km, 860m/s is a barebones Hohmann transfer. I'm estimating ~1000m/s from that orbit for free return (though I may be wrong).

 

48 minutes ago, Cunjo Carl said:

it doesn't seem unreasonable to stretch KSP mechanics a bit with our launcher.

Yes it does! :P I will never, ever advise people to glitch and exploit their way to success, unless they specifically ask for it. I mean... if you're willing to admit that you need to cheat, might as well avoid jumping through hoops, and just turn on infinite fuel for the last leg of the journey when your regular fuel does run out. Same result with less effort.

(I realize that people's mileage varies on this.)

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7 hours ago, bewing said:

But no, I can't quite seem to get my Ap high enough -- I get really close, but no cigar. A reliant engine instead of the swivel would certainly do it. So all you need is to get a part test contract for a reliant and it'd all work.

Okay, I tested this. Turns out, I suck at math :P

I don't know when during my various revisions exactly the mistake got introduced, but the dry mass of the upper stage is not 2.46 tons, it's 2.96 tons. That means it has 2683 m/s worth of dV, not 3264 m/s. A difference of 581 m/s, which is all the difference in the world. I got the rocket into orbit with 630 m/s left; if I had 580 more, I'd have 1210 m/s to play with. It would have been easily enough for any flyby tomfoolery with either Mun or Minmus.

Sorry @xendelaar for getting your hopes up, this doesn't work :(

You know, I still greatly enjoyed this exercise. I really do wonder if there's a solution to this.

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A-HAAAAA! SUCCESS IS MINE! :D

I managed to get this thing into a 72x72km orbit with 1030 m/s left. (Hammers are 70% thrust and attached to a decoupler under the engine.) And then I figured, might as well go for it and see how far I can get...

...turns out my estimate of 1000 m/s for a free return was way overestimated. I achieved a 23km retrograde Mun periapsis with 880 m/s, which necessitated a 21 m/s correction burn at that periapsis to lift my Kerbin periapsis out of the ground and up to 41km. Not sure if that is exactly the best altitude, but finetuning it is not a matter of dV anymore, so as a proof concept this stands.

There you go: low space Mun flyby with all tier 1 buildings and only 10 science points is technically possible! Now you just need to pull it off without patched conics and without maneuver nodes... <___<;; Well, at least you have about 130 m/s spare to play with.

 

Edited by Streetwind
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1 hour ago, Streetwind said:

Depends on your origin orbit. From 75x75km, 860m/s is a barebones Hohmann transfer. I'm estimating ~1000m/s from that orbit for free return (though I may be wrong).

 

Yes it does! :P I will never, ever advise people to glitch and exploit their way to success, unless they specifically ask for it. I mean... if you're willing to admit that you need to cheat, might as well avoid jumping through hoops, and just turn on infinite fuel for the last leg of the journey when your regular fuel does run out. Same result with less effort.

(I realize that people's mileage varies on this.)

Wow, maybe try not being so scathing next time? There's a slider bar for whether people are playing against the physics or playing against the game, and it's different for each person and each circumstance. I'd never use tricks like these in a challenge, but the prompt 'is it possible' leads to them being valid suggestions. Maybe they'll fit the desired playstyle, maybe not. But ouch!

I think Mun flyby will be just possible without shenanigan, but I'll need to wait for my freetime block this evening to try it out.

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9 minutes ago, Cunjo Carl said:

Wow, maybe try not being so scathing next time?

Apologies, I did not mean to come across as scathing. Apparently the smiley face wasn't enough. :( I will choose my words more carefully in the future.

Edited by Streetwind
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11 hours ago, bewing said:

I believe this video from @Cunjo Carl shows that you can, in fact, get landed on minmus, and scoot around a bit to take up to 3 biome readings, within the 18/30 launch limit.

 

9 hours ago, Streetwind said:

That is actually using the tier 2 launchpad, with a 140 ton mass limit. No other way to get that massive amount of SRBs fitted otherwise. You can see him upgrade the pad at around 21:30.

He's also using technology not available to @xendelaar. He says he only has the first two nodes, so no thumpers can be used.

For reference, it's possible to land on Minmus, rove around, take readings from 4 biomes, AND return all the science to Kerbin within the 18/30 limit, without patched conics. It looks something like this:

C2i2BXd.pngxIg92JK.png

Not that I would ever recommend doing this; it's tedious and nerve-wracking. But it's certainly possible.

Edited by IncongruousGoat
Formatting
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2 minutes ago, IncongruousGoat said:

Not that I would ever recommend doing this; it's tedious and nerve-wracking. But it's certainly possible.

Great design on that craft! Not applicable to the problem posed in this thread due to the much higher tech involved, but I like the minimalism :)

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38 minutes ago, Streetwind said:

Apologies, I did not mean to come across as scathing. Apparently the smiley face wasn't enough. :( I will choose my words more carefully in the future.

Ah, I didn't realize the tongue face was for tongue-and-cheek here. I was probably too sensitive, it can be hard to read intent through the text some times, and I shouldn't have assumed it so sharply.  Edit: Sorry if I cloudied your day, that wasn't my intent either!

I'm super excited to try a new launcher design this evening. It should be just possible to hit Mun SOI and free return without terrier or shenanigans using a brand new feature in v.1.2. But the new v.1.2. front-face body drag may nullify it.... Ah, I can't wait!

Edited by Cunjo Carl
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Wow. So many great replies! It makes me feel warm and fuzzy inside when i read all the great suggestions everybody's giving.  This community is the greatest!

I'm currently swamped at work so i dont have time to reply properly at the moment.. or even play ksp for that matter. 

I will answer most questions in a day... i hope.  Thanks again for all the suggestions. I thought my mission was a lost cause.  

You guys made my day! :) 

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I just wanted to also check -- I know you don't have wheels, but one trick/tip in the early game to hit up the KSC campus for science points in all its biomes is to make a craft that rolls all over the place. Have you done that already? I think it falls well within Streetwind's limits for cheating. ;p

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