Shoot for the sun!

[boolybooly]

CarolRawley, did you get back to Kerbin OK?

[DeadlyPear]

Right now I am traveling about 2,200 m/s and I have nearly a full tank of fuel.

Hopefully It is enough to eventually get back to Kerbin.

Ok here we are going past the sun. I missed it by about 5 degrees. Which is about 1,178,062,500 meters. Now that may be alot, but I still passed it.

EDIT: Ends up I have failed to get back to Kerbin. Third times the charm?

[Salda007]

Good news, everyone!

Bill, Bob, and Jeb returned from their marathon solar-approach mission this morning, touching down at something like 8:45 this morning. A press conference is planned for late tonight, once the Mission Director gets around to getting his slides in order.

[boolybooly]

EDIT: Ends up I have failed to get back to Kerbin. Third times the charm?

Too bad DeadlyPear, getting back is trixy, nice screenies and log of doom though . Say when you do it and I will make a metagame of it and move your name up to the roll call of star pilot dudes !

Grats Salda007.

Booly, a question for you. In your attempts, did you go to escape by flying directly upwards? Suddenly I realized that going to a low parking orbit and then burning to escape from there is more fuel efficient. Should have known that, but I was never interested in straight-up velocity contests so I never thought about it.

Flown this way, the same rocket I used previously cut the round trip time to a little less than a year. Aiming is quite tricky, for now I settled to going in an elliptical orbit and then finishing the acceleration when I was in the 'straight' section pointing to the Sun. (This is suboptimal). Trimmed a bit by eye with RCS on the outbound leg, final error a little more than 2 degrees (I flew half a million km to the side).

At first I used the orbit technique thorfinn but then I tried the straight burn and found that used less! But my orbit skills leave a little to be desired, pointing the apogee the right way takes a little finesse. Will have to experiment, I made a couple of attempts with 11x5 today and missed the space center by a few hundred meters each time : reentry angle is so trixy.

[nivvydaskrl]

Whelp, I did this one in 388 days, with all stock parts: 30 tanks of liquid fuel and 12 boosters. I circularized my orbit with 5 tanks of fuel remaining in my top stage, and shot all but about 2 and 1/3 slingshotting and then boosting sunwards. I wound up with an outbound velocity of about 1,800 m/s, and got there in 88 days.

The return trip was a lot slower, as by the time I had about 450 m/s of velocity toward Kerbin, I was down to about 1/2 tank of liquid fuel, which I wanted to hold on to for end phase maneuvering. As KSC is on the sunwards side of Kerbin and re-entry heat and G forces are concerns for creatures which AREN\'T 99% insane, I decided the 'treat Kerbin like a dartboard' approach was best, and tweaked my trajectory such that the green line intersected Kerbin at the general area of KSC. I landed maybe a couple hundred meters away, if that.

Pics follow:

[Thirster]

well, using a rocket with only basic parts (see first picture), I managed to orbit out there past the sun (see second picture),

third and fourth were of the voyage out and passing of the sun, unfortunately I woke this morning with a stack error, so I never got to land. Will attempt again

oh an interesting point was I calc\'ed the speed at apo at about 1.8m/s and a total mission time of 87 or so years.

here ends my first post to these forums. long time lurker tho

[Guest Jebediah Kerman]

This is pretty close to it, as close as you can get without it taking up the whole screen pretty much. The point is around 13600 M.

After I passed it, my ship is pointing back at the home planet.

A picture from the map view, after passing it I think.

[boolybooly]

nivvydaskrl what can I say, so close and yet so far?! Definitely a worthy landing and good shot to boot. Might have to consider that technique myself.

Props to thirster for being insane enough to even think about orbiting Kermin at that range, tell your PC it owes you one fat lady singing!

Jebediah Kerman, good job your ship is not made of wax is all I can say! Excellent stellar screenies. Let the world know when you make touchdown.

[CarolRawley]

If your still wondering about me getting back, i didn\'t even use any engines

Anyway, I had no RCS fuel left

[nivvydaskrl]

nivvydaskrl what can I say, so close and yet so far?! Definitely a worthy landing and good shot to boot. Might have to consider that technique myself.

The fun part is, I did most of my re-entry adjustment at around 1 billion meters out. If I\'d taken the time to refine a bit at 10 million meters, plus burned laterally towards KSC before hitting atmo, I probably would have been on the terrain.

Going 3,000 m/s at 15,000m altitude, however, tends to make you panic and dump your stages FAST!

[boolybooly]

Dudes I made it... I tried a hybrid of direct drop and aerobraking. One aero braking pass to take the speed off the ship and then tweak apogee to just drop straight down onto the KSC terrain. Not exactly easy but getting better. Went about 1000m/s both directions.

Out there...

Aerobraking pass...

Apoapsis adjustment...

Kerplunk...

The ship was a bit simpler than the behemoth I was using. Still needed lots of struts and boosters though. It was 2+4+4 LF stages with a booster section of 12x (SRB+2LFT+LFE) (double 6x radial symmetry) and a bunch of SRBs under it to give it a kick. Also T8 winglets on the lowest LFT. I fired up the two rings of 6xSRB independantly. Went for the vertical burn.

Beat that!

[nivvydaskrl]

I think my rocket was as follows:

S0: Command pod, parachute {stack decoupler S1}

S1: 1x RCS tank, 6x RCS block, 6x LFT, 1xLFE, {1x stack decoupler S2}

S2: 1x RCS tank, 1x tricoupler, 3x ( 4x LFT, 1x LFE, 1x RCS block, {2x radial decoupler S3} )

S3: 1x SFB, 1x {stack decoupler S4}

S4: 2x LFT, 1x LFE, 1x moveable fin, {1x radial decoupler S5}

S5: solid fuel booster

Note: When I say something like 3x (------ {2x radial decoupler S3} ) what I mean is everything inside the parenthesis is symmetried, including the 2 stage 3s, so stage 3 is repeated six times.

It comes out to 30 liquid fuel tanks, 12 boosters, 6 fins, 9 RCS blocks, 2 RCS tanks, 10 liquid fuel engines, plus decouplers, pod, chute, and struts. It was just under 122.3 units of weight overall -- six engines would barely lift it, but to prevent topple-over and inefficiency, I fired off the 3 S2 LFEs with the S5 boosters and the S4 LFEs. This gave a really nice accelleration curve.

The design is expandable -- throw 2 more LFTs in tri-symmetry on the S2 core and the S4 radial boost stacks, a fin in tri-symmetry on the S2 core, and an advanced SAS right before the tricoupler in the S2 core. This will get into a 200m by 200m orbit with fuel still left in the S2 core stage, and a full load of fuel in the six tank S1 stage; plenty for getting to the sun and back. However, the S2 stack hates going in a straight line. The ASAS will keep it on course to establish orbit, but at the expense of about a full tank of RCS fuel. You could probably add another RCS tank in there somewhere -- I\'m pretty sure there\'s the lift capacity for it lost in a rounding error somewhere.

I do establish orbit first, then do successive burns when on the opposite side of the planet from Kerbol until escape velocity. Once I\'m on an escape vector, I modify my heading on the accelleration burn towards the star to correct for any inaccuracies. I\'m hoping the correction is costs less than I save by using Kerbin to boost my velocity.

I might do another shot soon using the beefed up version of my rocket. Having a full 6 cans of gas will probably cut several months off the journey! Dumping all my RCS fuel before I start my outbound burn would probably help a little, too.

[DeadlyPear]

I say we have more or less mini-challenge where we attempt to get there and back to Kerbin with the least amount of parts.

My ship (I believe) had about 23 parts.

Time to actually get back to kerbin though....any tips? I end up flying past kerbin by about 500 milion meters or so each time.

[boolybooly]

Good idea Deadly.

Tip, returning to Kerbin.

If its a tip you want then I can tell you what I do, which is to drop out of warp about 5000M-1000M out or so and then check periapsis value and try a very short retro burn, as short as I can make it, with the ship oriented with a 5° bias* to one of the major axese ie 0°-180°,90°-270°, and see if the PE figure increases or decreases. If it decreases I carry on giving short burns until it starts increasing and then stop, if it increases I switch to the opposite direction on the same axis. Then when it is at its minimum I switch to the perpendular axis and try again. When the PE disappears you are heading for Kerbin so then you pick your preferred orbit axis, usually 90° for me and make a short burn to bring the PE figure back, which should be below 100,000m.

Then go to timewarp until you see a green line at Kerbin and slow down again to make burns on the 0°-180° axese with a larger bias, to flatten that green line so it is on the ecliptic as you see it in map view. That way you will pass over KSC in orbit, though since the KSC is on the sunward side of Kerbin 24/7 at the moment (tidally locked?), frankly any return orbit will take you over it.

Aerobraking.

Use the above technique* to get the PE figure down to something between 35,500m and 40,500m and you will be set for aerobraking.

With aerobraking the deeper you go the lower and faster the resulting eccentric AP, so the more you have to burn to hit KSC. If you aerobrake too high though you wont make orbit unless you can do a retro burn...

EDIT Another tip about escape velocity.

Another thing I have been figuring out is limiting outward bound velocity so I don\'t have to use too much fuel on the turnaround. Its easy to over burn on the way out.

I have been using a velocities table to check escape velocity per altitude and made a few experiments and found I don\'t need to be much more than 100-200 m/s over escape at 500km to be travelling at 600-700m/s by 1000M and keep that all the way out. I am guessing that its not directly proportional either. The amount of velocity you lose leaving Kerbin should decrease the faster you go, as you take less time to travel out of the gravity well. So if you give it more welly you can end up going a bit quicker than you bargained for... ;D

[Cannon_Fodder]

I have made it to the Kerbol a few times. The problem has been getting BACK to Kerbin. First missed the gravity well and just blew on by. 2nd I managed to get into the gravity well but wasn\'t able to get back. Just flew off. I am hoping 3rd time is the charm.

3rd -5th all failed the 'Get Home' part of the challenge. I have also come to the realization that it is NOT the rocket\'s fault. I am sure with a better operator it will do just fine.

[boolybooly]

See above tip CF, given much against my own best interests in the space race, you just have to burn semi-perpendicular to flight path on one of four headings and see if the PE goes up or down until it goes down, rinse>repeat etc

PS my latest round trip with drop to KSC terrain (339.01.08) was using.

1 P

1 CM

1 ASAS

30 LFT 2+4 + 12x2

13+1 LFE

12 SRB

14 DC

12 LDC

37 S

It adds up to 144.55 weight if I did my sums right.

[Cannon_Fodder]

I think a big part of my problem is I am too impatient and trying to make those fine adjustments while I am still close to a billion meters out. I might give it another try but try to wait until I am a bit closer.

[thorfinn]

I think a big part of my problem is I am too impatient and trying to make those fine adjustments while I am still close to a billion meters out. I might give it another try but try to wait until I am a bit closer.

The farther you are, the easier it is. If you can see the periapsis marker in the map, you can judge what effect your velocity changes are having.

I used translational RCS (much more controllable than rotating the whole craft) to get a perigee in the hundreds of km while still in the solar neighborhood (at 13-14 million km).

[Cannon_Fodder]

Then I go back to my original assessment of 'I suck at this.'

Maybe I will try a few more times. [hint to HarveteR]It would be really cool if I could save the game when I was at the sun.[/hint]

[thorfinn]

Then I go back to my original assessment of 'I suck at this.'

Well, if you don\'t use RCS it\'s really a mess. I don\'t know how Booly manages that (more patience than I have, I suppose.)

[boolybooly]

Easy peasy, vectored burns, if you are on say a 270° heading but at inclination of only 5° that is sine of 5° times thrust ie only 0.08x total burn goes to lateral thrust, one twelfth. You can do micro burns that tweak PE by 4,000m at 1000M.

Vector addition was one of the few things I learned from open university daytime TV in the summer hols when I was a bored teenager.

[nivvydaskrl]

Yeah. I burned off all my RCS before doing my main burn back to Kerbin. The way I modified my vector was doing minimum-thrust burns directly towards Kerbin, with a slight (less than five degrees) offset to modify my vector. At one billion kilometers, this is a good way to get your periapsis on the same screen as Kerbin. At shorter ranges, finer tweaks are possible, until you can get it so your orbital vector puts you smack dab on KSC.

[killernooby]

Well, I made to the sun...

I burned too a standstill at about 142000K.(I was messing about in orbit)

Then decided to go the sun:

It was a long trip and I think Bill was eaten. I\'ll have to figure out how to get Jeb home, as Bob will probably be the next to be taken by space madness(and being locked in a capsule with Jeb for 247 days won\'t help).

[DeltaBravo]

Successfully made it to the Sun after 177 days. Unfortunately, I gravity sling shotted around Kerbal at about 26Mm, tossing the crew into deep space.

[Causeless]

Successfully made it to the Sun after 177 days. Unfortunately, I gravity sling shotted around Kerbal at about 26Mm, tossing the crew into deep space.

Lies, that\'s impossible. You can\'t get energy from nothing, you must have used thrust.