Zear Dynamics "Cronus VI"

[Ranzear]

So after seeing so many orbital and escape-velocity craft that more resemble the N1 than a feasible real-life spacecraft, I started stacking what I found decidedly more realistic in terms of arrangement and payload.

Firstly, I constructed a Command and Service module arrangement much like the Apollo missions, using the RCS module and an SAS module. I felt this much better simulated a real mission package. To this I added a small fuel tank and medium engine for de-orbiting. This final stage has enough ?V to drop out of most orbits the platform can reach.

Under this came the second stage, intended for the exoatmospheric phase, with its own medium engine and two standard tanks. Through testing I found this arrangement provides enough ?V to push into a 40k orbit with about a quarter the available fuel and a 150k orbit with just three quarters of the available second stage fuel.

Then came the real design nightmares. It was so incredibly difficult to stack enough large fuel tanks to break out of the atmosphere under this payload without breaking the main first stage engine under the weight when set on the pad. Additionally and instead I found that six Midsize solid fuel boosters were needed to really get the whole thing going at any more than a limp past 40km.

So then some major assembly concerns came in. Using radial decouplers meant the midsize boosters wouldn't quite reach below the main engine to support the whole craft as required. Getting crafty I used a stack decoupler on each solid booster as a 'foot' which detaches in the same stage as the booster is activated.

So after this massive assembly could finally stand under its own weight, I took to flight testing it. If a full power launch is attempted from the pad the best case would cause decoupling of the first stage fuel tanks and an aborted launch, or at worst the main engine tends to plow upwards through the stack with the boosters shortly behind it. Launching at minimum throttle solved this issue, but then advancing the throttle too quickly would cause the whole stack to collapse from the thrust anyway. I think I managed to, in trying to mimic the Saturn V which had exactly this problem, be the first person to encounter Pogoing in KSP!

So assuming you get off the pad and up to full throttle properly, when the solid boosters shut down and you decouple them... they take the main engine with them because of their low position and angle. I found you must decouple the main boosters while they are still running for them to clear the craft without incident, specifically in the final few seconds of their fuel.

I find it interesting that this very realistic design has very realistic problems, like barely being able to handle its own power output or issues with booster separation. I could drop the number of solid boosters to four or stack some dummy legs under the main assembly, but that wouldn't be any fun now!

It does do one thing very well: It gets a usable amount of thrust into a stable orbit, and is probably a great setup for attempting transfer orbits too.

So as it is, this craft has a very strict flight profile, and not following it will cause catastrophic malfunction. I'll use a second post to put together a Flight Manual. Failure to follow these instructions will generally result in dead Kerbalnauts (then again, so does playing KSP in general).

Requires: Wobbly Rockets 1.06

[Ranzear]

Flight Manual:

Warning: Failure to follow these instructions will result in catastrophic, spectacular, and hilarious failure of the spacecraft. This craft has some gentle stability issues and per the moniker of the Wobbly Rockets pack does have a little bit of a wiggle when attempting to maneuver before first stage separation.

Liftoff

Warning: Excessive time spent on launchpad will cause malfunction.

1. Reduce throttle to 0%. Launch at greater than 10% throttle will cause malfunction.

2. Engage SAS

3. Cycle the first two dummy stages.

4. Activate stage 9 to initiate launch.

5. While monitoring G Force gauge, slowly advance throttle to 50% as needle drops to top of green arc (2G). Advancing throttle too quickly will cause malfunction.

6. Continue monitoring G Force gauge while advancing throttle. Do not exceed 75% before G Force gauge falls below and then maintain below 1.5G (between middle and top marks of green arc). Exceeding 75% throttle before G Force meter has stabilized below 1.5G will cause malfunction.

7. Monitor Solid Booster fuel level. Separate boosters at minimum possible fuel level. Solid booster separation may cause a change in craft stability. If separation not enacted before fuel cutoff do not separate boosters until main engine fuel cutoff and in sequence with first stage separation or malfunction (detachment of main engine) will occur.

Note: Best performance is achieved by advancing throttle as aggressively as possible and separating boosters at the very last second before shutdown.

Maneuvering

8. Begin maneuvers for desired orbital path. Recommend immediate but gradual pitching to 30 degrees above horizon for low orbit or continuing vertical ascent until 25-30k altitude and pitching to 45 degrees for 100k+ orbits. Reduce throttle as necessary if overshooting lower altitude targets. Excessive rolling of the spacecraft to promote directional stability will cause malfunction.

9. Activate stage 5 for First Stage Separation. Allow first stage to clear second stage engine before activating stage 4 to engage Second Stage engine or destruction of reusable components may result.

10. Utilize Second Stage for orbital maneuvers. A full burn of second stage should achieve escape velocity in a nonvertical flight profile.

11. Activate stage 3 for Second Stage separation once all fuel spent.

Deorbit and reentry.

12. Reduce throttle and activate stage 2 to activate Third Stage engine. Third Stage has a high degree of thrust efficiency but a very small fuel supply. Be precise when utilizing for deorbit burns. Third Stage is still fairly capable of recovering from an escape velocity trajectory.

13. Activate stage 1 to separate command capsule from service module for reentry. Separation before shutdown of Third Stage engine will cause loss of control and malfunction.

14. Activate stage 0 to deploy parachute around 1000-2000m altitude, depending on reentry speed (higher=higher). Activation of parachute after separation before shutdown of Third Stage engine will cause malfunction.

This craft also has a tendency to malfunction just because it wants to. Don't be alarmed if it blows up for no apparent reason.

A malfunction on liftoff may be identified by any of the following and will prompt an abort procedure.

1. Main engine showing more than one fuel tank active. Indicates separation of first stage sections.

2. Main engine separation from first stage due to incorrect timing of booster separation.

3. Entry of engine or booster components into crew cabin.

LIFTOFF ABORT PROCEDURE:

1. Reduce throttle to zero. Do not separate solid boosters if still operating.

2. Notify Zear Dynamics main office in writing of a malfunction event and the nature of the event. Please include the seventeen digit malfunction code readout displayed in the cockpit.

3. Apply hard and full flight control input in one direction. Separate solid boosters and first and second stages in sequence. Command capsule is very likely to evade much of the resulting shrapnel, though the parachute module may not.

4. Third Stage engine may be used in atmosphere to maneuver away from debris and into a safe trajectory.

5. Reduce throttle to zero before separation of command capsule.

6. When Service Module clear, deploy parachute at altitude between zero and 3000m. Deployment of parachute below 100m may promote ineffectiveness.

Screenshots:

[Heimdall]

very impressive in precision of execution and beautiful visually.

[Ranzear]

Best circular orbit I've attained is 1302km with a little over 2/3rds fuel left in the Third Stage tank. Whether I have enough to deorbit will be another story for another day because I accidentally separated the command module.

Also I didn't feel like waiting ~80 minutes for a post-burn perigee to find out

[Velo]

I loved the immersiveness of the manual. And the rocket looks good, and functions as advertised.

[Damonjay]

Welcome To KSP Forums Velo

Keep posting

[SteevyT]

That was one of the greatest user manuals I have seen.

[RedRockets]

A great Rocket and thank you for taking the time out to create such a detailed manual.

RRs

[Commander Zoom]

Glad for the bump. Love the manual.