Mercury "Friendship 7" Commemorative Challenge

[PakledHostage]

February 20th is the 50th anniversary of John Glenn\'s 'Friendship 7' mission. The objectives for that mission were simple yet technically challenging:

'Place a man into Earth orbit, observe his reactions to the space environment and safely return him to Earth to a point where he could be readily found.'

Glenn\'s Friendship 7 capsule splashed down within 5 NM of the destroyer USS Noa on February 20th, 1962 after completing 3 orbits of the Earth. Lookouts on the destroyer sighted the main parachute at an altitude of 5,000 ft from a range of 5 NM. The Noa had the spacecraft aboard 21 minutes after landing and astronaut John Glenn remained in the spacecraft during pickup.

Mission objectives for this challenge are similarly simple yet technically challenging:

1. Launch a chute-pod-decoupler-3LFT-LFE stack into Kerbin orbit. All parts must be stock (see spoiler below for an image showing this stack).

2. Complete 3 full orbits

3. Splash down as close to KSC as possible. Ideally in the ocean east of KSC and within sight of the space centre.

Parts 1 and 2 have been completed by numerous people including myself so I know this challenge is possible, even though I haven\'t completed part 3 yet.

Edit: Clarified that all parts must be stock parts.

[PakledHostage]

[cricket, cricket, cricket....]

Well, I guess I\'m on my own then...

I chose to approach this challenge as a technical challenge requiring pre-calculation of trajectories rather than as a 'trial and error' challenge. Using the atmospheric density and aerodynamic drag equations derived over in the Mini-challenge: max altitude with this supplied spacecraft thread, I wrote a program to predict where my Kerbal 'Friendship 7' capsule would splash down given certain inputs.

My Kerbal 'Friendship 7' rocket was then launched into an initial LKO that was subsequently trimmed into a roughly circular (±200 m), 0 degree inclination orbit during the course of the 3-orbit mission. In keeping with the goals of my mission\'s namesake mission, I also observed the crewmember\'s reactions to the space environment throughout the flight. Bill and Bob reacted to the space environment with a lot of screaming. Jeb, on the other hand, was much less flappable.

During the crew\'s time on orbit, I also ran the numbers to finalize the retrofire sequence that would have to be followed for them to land on target. Given that they were starting from an initial 78.4 ±0.2 km orbit, I determined that a 66.2 m/s delta V deorbit burn would be required. The burn would have to occur at 7 minutes and 32 seconds after they overflew KSC\'s antipode, as determined from the anti-target reticle on the navball.

The de-orbit burn was carried out as prescribed at 1:35:15 MET, and the capsule splashed down off KSC approximately 12 minutes later.

[Klopchuck]

Awesome mission description - definitely shows how much you can do with a basic system. Can you post a youtube video? Or at least some guidance on when and how to get into LKO with good fuel economy?

[r4m0n]

Here goes my first try. No calculations, just tried to guess where I would need to get into the atmosphere to drop in the right place... Got just a bit farther than you.

Tried 2 times after that, but haven\'t gone any closer ;D

Waiting the orbits to complete at low height (even at 10x) is quite a bit slow, but I hadn\'t noticed the planet spinning yet, it was quite a pleasant view

[PakledHostage]

Can you post a youtube video? Or at least some guidance on when and how to get into LKO with good fuel economy?

I\'ll tell you how I do it, but I\'m not an expert on this subject so please take everything I say with a grain of salt:

I start by going straight up then pitch over once I\'m through the densest portion of the atmosphere. Opinions seem to vary on the exact timing, but I don\'t pitch over until upwards of 12000 m - 15000 m. The tricky part is picking the right initial pitch over angle. Too vertical and you\'ll reach your target apoapsis without any horizontal speed. Too shallow and you\'ll waste fuel going fast down low where the air is dense and the drag is high.

Following pitch over, I execute a gravity turn while toggling back and forth between the main view and the map view to keep an eye on my apoapsis. As my apoapsis nears about 10 km below my target value, I pitch over some more to align my thrust with the horizon. By this point, the air is (hopefully) thin enough that the extra drag due to misalignment of my rocket from the direction of travel is minimal. I use the angle that I have to pitch down to align with the horizon as a measure of how well I\'ve executed my gravity turn (less is better).

Beyond that, there\'s currently an exhaustive discussion about maximizing launch fuel economy going on over in the topic=7161.0'>Mini-challenge: max altitude with this supplied spacecraft thread. You might also want to have a look at that.

PH.

Edit: Clarified some wording

[PakledHostage]

Please forgive the bump but I thought I\'d add some more screenshots following some refinements that I made to my re-entry/aero-braking model. They may be of interest to anyone wanting to develop their own re-entry/aero-braking models because they appear to validate Kosmo-not\'s atmospheric density profile:

62.3 m/s delta V deorbit burn at 7:30 after KSC antipode overflight

82.5 m/s delta V deorbit burn at 6:41 after KSC antipode overflight

204.2 m/s delta V deorbit burn at 7:01 after KSC antipode overflight

[Guest meteorite 101]

behold The Atlas D with Friendship 7

let me know if you want the craft

[PakledHostage]

behold The Atlas D with Friendship 7

let me know if you want the craft

Looks freakin\' awesome! Why not post it to KerbalSpaceProgram.net or one of the other sites that hosts add-on parts?