[Success]: Asteroid Capture - Rondevouz with Roche challenge

[SirJodelstein]

This is a report for my attempt at NovaSilisko's excellent Rondevouz with Roche Scenario challenge. The objective is to relocate a 600ton-asteroid from a 13.000km orbit around Eve to a low Kerbin orbit (because some administrator decided it would be way easier to study the thing in LKO). Also, this is my first mission that will lead me out of Kerbins sphere of influence

Mission Constraints and Planning

- Mission restriction: The asteroid may not enter any atmposphere (or must be protected with a large heat shield during atmosphering maneuvers)

- Mission optional goal: Recover a three-man-crew orbiting around Eve (this is the crew of the botched "Roche Expedition 1" mission, whose failure made the administrator come up with the great idea to bring the asteroid home).

- I want to do the mission in one launch, with only stock parts. My heaviest lifter can launch 200 tons to LKO. To see if this is even possible, i made some quick calculations with a spreadsheet calculator.

- The final stage captures the asteroid (with a stabbing device that comes with the mission). If i understand the delta-V-maps which i have never used before, it takes about 1310 m/s to escape from Eve LKO (reduced by 500m/s for the 13000km orbit), 80m/s to intercept Kerbin and another 950m/s to establish a low orbit around Kerbin assuming no aerobraking. Total return dV requirement: 1840m/s

- 1840m/s with 10 atomic drives, 600 tons of dead weight and the rest fuel would require 165 tons of fuel. Bringing that to Eve would require more 30 tons of fuel, and we have not jet counted anything else (fuel tank dry weight, command pods, stuff, snacks, RCS etc), and have no fuel for Eve operations. Well, scrap that, back to the drawing board

- 1840 m/s with ion drives requires about 30 tons of fuel. Great! Oh wait, we want to push 600 tons of dead weight. Even if i bring 60 Ion engines, we could only accellerate at a whopping 30kN/600ton= 0.05m/s² (or even less if counting engine+fuel+electricity support mass). Not going to happen.

- Aerobraking! Lets remove most of the 950m/s for Kerbin LKO establishing from the equation (and remember to bring a big shield for the precious rock). 1000m/s with 6 atomic engines and 30 tons of stuff => 90 tons of fuel. Bringing that to Eve with 1000m/s remaining for asteroid rondevouz operations => 40 tons of fuel. Total: Engines 13.5t, Fuel: 130t, Stuff: 30t = 173t. => Time to start building !

(some hours later)

"Here we go, Launching "EIVAARRK" (Experimental Interplanetary Vessel for Asteroid Approach, Rondevouz and Return to Kerbin) mission!"

=> SSTE (single stage to explosion)

(some hours later)

"Here we go, Launching "EIVAARRK" (Experimental Interplanetary Vessel for Asteroid Approach, Rondevouz and Return to Kerbin) mission!"

=> disintegration on gravity turn

(some days later)

"Here we go, Launching "EIVAARRK" (Experimental Interplanetary Vessel for Asteroid Approach, Rondevouz and Return to Kerbin) mission!"

=> LKO orbit achieved

=> Shield won't dock in cruise configuration

Enough of the prologue, here is the final totally polished EIVAARK mission rocket. It has just some untested last-minute changes, so everything is totally fine. What could possibly go wrong?

* 144t fuel, 190 tons, 670 parts

* small crew rescue ship included

* innovative asteroid-protecting aerobrake-shield

* reliable lifter stage (1 of 3 launch attempts usually succeeds)

Mission Report Part 1: Launch and Kerbin escape Video (12min, download for better quality)

Well, let's say the launch was the easiest part. Almost 1 full X-32 fuel tank remained from the launching stage, which granted me some unplanned "free" dV. I learned a lot about interplanetary travels that i did not know before. Who knew that the delta-V map assumes ballistic (non-homann) transfers for Eve? These require a somewhat different launch window. And those mid-flight plane-alignment burns for Homann transfers really stink (370m/s for those tiny 2.1° inclination? come on!) Oh, and while escaping Kerbin can be done with just 850m/s and a Mun gravity-assist, that does NOT mean that it's just 80m/second from just outside Kerbins SOI to Eve. Anyway, after countless tries of fiddling with maneuver nodes and consulting various KSP travel calculators, i got the EIVAARRK with Scott Kerman at the helm on a ballistic transfer to Eve with an encounter sheduled in about 40 days. Even without the asteroid, turning this 200-ton-hulk without RCS takes forever, and the accelleration is not that great (1000m/s in 10 minutes). I split the escape burn in three parts to increase the accuracy of the burns (and to practice splitting a long burn, since with the asteroid attached this ship will accellerate at less than 0.5m/s².

Mission Report Part 2: Eve Arrival, Aerobraking and Crew Rescue Video (download for higher resolution)

After some minor in-transfer course corrections totalling in at about 30m/s, Scott reaches Eve and does two rounds of aerobraking. The final plane alignment took about 75m/s, pushing the Apoapsis back out to 13000km another 500m/s. Scotts decouples the small crew rescue craft, collects the three stranded Kerbals (its Bill, Bob and Jeb!) from their disfunctional command pod and heads back to the main ship. Someone forgot to put RCS thrusters on the ship (duh!), so re-docking is handled by Jebediah, with Bill, Bob and Scott watching from command seats on the main craft. Next up: Asteroid approach and stabbing!

Everything is going really good so far. Took some tries to get the aerobraking depth right, but other than that, the mission is progressing way to smoothly. Lessons learnt: Don't forget RCS thrusters, pay attention to your target's orbit direction (first attempt had me going in the opposite direction around Eve), dont do sketchy docks with Kerbals sitting in command seats, interplanetary-speed aerocapturing altitude for eve is about 69km.

Part 3: Asteroid Capture and a Kraken attack Video

Some minor burns put the Eivaark onto a close approach to the Asteroid. The shield is decoupled, Bill examines the Asteroid in EVA to find the stabbing spot. Scott carefully aligns the ship into stabbing position, and goes in for the kill. The docking forces eject the Scott and Bob (and one of the 4 shield ports), which suffer a Kraken attack but eventually reccover and return to the ship. Jeb arrives with the shield and undocks the rescue craft. Some minutes later, the shield is docked in position, and we are ready for departure. According to the data readouts, the combined craft has about 1100m/s dV remaining, which should be enough for a comfortable return to Kerbin. Woo!

Part 4: Finale - Return to Kerbin Video

About 100 days later, a ballistic return window opens. One long 15-minute burn (about 600m/s) puts the EIVAARK with Roche on an intercept with Kerbin. Some minor course adjustments direct the ship into Kerbins atmosphere for aerobraking at about 32km. The shield works perfectly, the one missing docking port makes not much of a difference. A second round of non-scorching aerobraking at 42km bring the Apoapsis down to 175km. With loads of fuel remaining, the final circularization burn is completed, and the crew gathers for the obligatory "mission completed" photo.

This was an awesome scenario mission. You should go and check it out!

Edited June 18, 2013 by SirJodelstein
Part 4

[SirJodelstein]

Part 3 added. Looks like this mission might go successfull after all!