Minimum delta-V for low sun orbit?

[thereaverofdarkness]

MINIMUM DELTA-V FOR LOW SUN ORBIT

MINIMUM SUN PERIAPSIS

About how much delta-v does it take to get a rocket into a scraping orbit of the sun? Looking for some good estimates from all of you nerdy Kerbals (Nerdals?). Also challenge below:

Simple challenge: get a spacecraft into an orbit over "Kerbol" as low as possible to its surface. Minimum submission: a pic from assembly building showing total delta-v and TWR of each stage, a map pic from final orbit showing apoapsis, and a pic from final orbit showing the gorgeous sun horizon along with remaining delta-v. You can get a cheap and easy delta-v reading with the flight engineer chip from the Kerbal Engineer mod, available in the Spaceport. Feel free to show maths for delta-v and TWR if you don't feel like modding your client. I might also be willing to gather readings myself if you provide the craft file (emphasis on might!).

Scoring: 1,000,000 points base score for a successful sun orbit divided by the square root of the apoapsis in km - max score 100km apoapsis for scoring purposes.

Additional modifiers:

1.) added points for: lightweight science equipment +50k, goo +100k, materials bay +150k, MPL +500k, antenna +50k/100k/150k (higher for more advanced antenna), solar panels +50k/100k/150k for tiles/small pivotal/gigantor. Each listing here can only be obtained once per craft, with a maximum of 1,100,000 bonus points added to base score before delta-v calculation.

2.) higher thrust propulsion is ideal here. no score bonus for using ion propulsion. +100% score if LV-N or other types of NERVA atomic engines are your weakest engine, +250% if LOX rockets are your weakest.

3.) minimum TWR on any stage confers a 25% score bonus times how many times it is over Kerbin gravity, for example if the lowest TWR stage starts with a Kerbin TWR of 2.5, you get a 62.5% bonus to score. Max penalty for lowest thrust stage being under TWR of 1 is -25% to score for a TWR of 0.

4.) you lose 50% score if you leave off with a maneuver node and do not actually complete the maneuver

all percentage bonuses cumulative

I will be calculating TWR with the formula thrust (kN) divided by (mass (tons) times 10). This gives an answer slightly different from actual Kerbin TWR but is an easy way for me to get accurate decimal points, which Kerbal Engineer doesn't give.

Refueling mid-flight is allowed, provided you document the refueling operation and show how much delta-v was gained through refueling.

Accepted mods:

1.) Kerbal Engineer

2.) MechJeb

3.) FAR (Ferram Aerospace Research)

4.) Kethane

5.) structural and aerodynamic parts from B-9 Aerospace and KW Rocketry

6.) B-9 or KW engines that are within stock technology - LOX rockets, jet engines, NERVAs, noble gas ion propulsion

7.) engines and structural or aerodynamic parts from other mods accepted on a case-by-case basis

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LEADERBOARD

1.) ihtoit: (1,250,000/10)*0.7506*0.5 = 46912.5

2.) thereaverofdarkness: (1050000/39492.73519)*3.5*1.01096 = 94.1

3.)

Edited January 20, 2014 by thereaverofdarkness

[mythbusters844]

To answer your question (How much delta v to low sun orbit): ALOT.

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First off, making a maneuver node is a nightmare. The corona makes the node impossible to see, and the node freaks out and glitches, making it impossible.

Second off, a 1 day burn with an ion engine.

Third, the 20 km/s of delta-V that's required. I have no idea how you can get this much. The entire launch vehicle has less than that.

So, I'm giving up on this hard (but fun) challenge.

[ihtoit]

I'll have a go.

Prescribed mission profile:

Dawn launch to prograde low orbit (stage)

1 orbit then dawnbreak escape to sub-Kerbin solar orbit (stage)

apoapse burn to 100km periapse (ion/electric so LONG burn)

retrograde burn at periapse to circularise (ion/electric so another LONG burn)

All manoeuvres manual, using Mechjeb info (not control)

Edits for pictures: to follow, but to report: I used a one-man capsule rather than radio since I started a new game and didn't bother putting a geostationary satellite up first. Initial dV was 24km/s, LKO@100km left me with 21km/s before circularisation so I figured, might as well just go straight for escape. Did that, ended with a spare rocket stage and 14km/s ion stage. Burned the rocket stage and ended up with 6Gm periapse, grazing altitude of 59km would require apoapse burn (from 13Gm) of 5.7km/s.

So, nowhere near as much for a grazing elliptical orbit as you think it does, particularly if you start with a retrograde escape trajectory to slow you down a chunk to begin with!

Unmanned development build (manned build used the same staging but smaller side tanks, losing about 40 tons and nearly 2km/s dV off the pad):

the manned version: note the dV remaining on stage (ion) and the dV required for an apoapse burn from 5.6Gm-59km periapse/13.3Gm apoapse (navball):

So a grazing elliptical orbit of the sun from the pad in change out of 13km/s dV. You're welcome

Edited January 20, 2014 by ihtoit

[Armchair Rocket Scientist]

My guess as to the best mission profile is:

1. Launch to Kerbin escape trajectory.

2. Either directly or after gravity assists from Kerbin and/or Eve, get a Jool encounter.

3. Use a gravity assist from Jool to kill your orbital velocity, dropping you into a sun-grazing orbit (Ulysses did this in real life, although it did a plane change instead of dropping its periapse.

4. Use more gravity assists from Kerbin and Eve to get your apoapse as low as possible.

5. Burn to Low Kerbol Orbit.

According to this: http://forum.kerbalspaceprogram.com/threads/41652-A-more-accurate-delta-v-map doing this with a direct transfer from Kerbin would require 38 km/s of dV. For comparison, Tylo landing and return is only 15 km/s. Moho? 19 km/s. Eve? 20 km/s.

I would say this breaks the "Is this challenge possible?" rule, but someone did pull off a Jool "landing" and return: http://forum.kerbalspaceprogram.com/threads/50242-Jool-accent-the-imposible-chalenge (the dV requirements for this are about the same as for this challenge IF you can shave off a few km/s with gravity assists, and the TWR and atmo isp issues don't apply). Nevertheless, this is pretty much the hardest thing you can do in KSP. There's really no point in having a scoring system, because if you pull this off at all you (and your computer) will be elevated to deity status.

A more reasonable challenge might be "least dV to reach a kerbolcentric orbit with a PERIAPSE of less than 100 km." Then it becomes more about clever piloting and less about building ships that would make Whackjob's monocle fall off.

[thereaverofdarkness]

Wow, I knew it would be difficult, but I didn't know it would be THAT difficult.

I adjusted the challenge and took out scoring for delta-v expenditure, and instead have the score based on your apoapsis height.

[thereaverofdarkness]

Here's my own submission:

http://imgur.com/a/7x83p#0

It took me 4806 delta-v to reach initial orbit. I made a final apoapsis of 1,559,676,133km, which has a square root of 39,492.73519. My base score is 1,050,000 (+50k for little solar panels). I get a 250% score bonus for having only LOX rockets, and a 1.096% score bonus for a minimum TWR of 1.0274

(1050000/39492.73519)*3.5*1.01096 = 94.075

[stormtroopr1977]

Mission Debrief

(unnecessary, please proceed to the calculations if un-interested)

The mission involved sending 1 man (with TAC life support installed) to a low sun orbit and returning him to kerbin safely. the mission began by launching the main body of the rocket into an orbit of about 100000m. Once in orbit, The rocket motors were ejected from the lifting stage leaving only fuel tanks. Following this, a series of refueling missions were launched. The final of these contained no fuel, but contained the pilot, Jebediah Kerman. Once the pilot was on board and the rocket was refueled, a series of burns were performed to bring the rocket's orbit to the very edge of kerbin's influence before a final burn which would allow it to achieve escape velocity out of the sphere of influence. This burn continued for half an hour until the periapse of roughtly 100,000,000m. after two orbits, it was deemed safe to approach the sun at a lower altitude and the periapse was lowered to 3,000,000. Science was gathered at this altitude, and the solar satellite was assembled and deployed. At the following apoapse, a burn was initiated which brought the rocket into an encounter with kerbin. During this burn, the fuel in the outer stages was expended and those stages were ejected. The rocket then performed a series of course corrections and an aerobraking maneuver through Kerbin's Atmosphere. during aerobraking, the rocket sustained moderate damage. After establishing a 100,000m orbit around kerbin, a transport ship ferried up a probe containing communications equipment to the rocket. Jebediah kerman boarded this transport ship following the docking of the communications gear and transmission of science data. The transport ship then returned to Kerbin and was recovered. At this time, the rocket in orbit was determined to be unusable in future missions due to damage sustained during aerocapture and was de-orbited.

http://imgur.com/a/4cOa6

Scoring Calculations

The closest i came in my attempt was 3080585. I didnt want to get any closer with deadly reentry turned on. so, that was a base score of 569.7487772. I also had 350,000.00 points from various science equipment. I had 9 Lv-N Atomic Rocket Motors as my power, so I believe that is +100% of 350569.7488= 701139.4976. I had a TWR of 0.193 at its lowest, so that is a -4.825 % penalty.(667309.5168)

So I believe that my final score is 667,309.5168?

*note* I also returned the ship to Kerbin's orbit and retrieved the crew.. bonus points?

[zarakon]

I got a very low solar orbit before using LV-N with droptanks followed by ion engine with droptanks. I think I used somewhere in the neighborhood of 40km/s dv. I could have done better if I had taken less solar panels, since you barely need any when you're that close to the sun, but I still got close enough that I think I was unable to timewarp and math errors resulted in constantly losing altitude