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I made an R7 replica to launch a Vostok? Voskhod? Whatever. The KV-1 pod. However, once I reach about 7,000 meters the rocket tips over past the 90 degree vector too early. Upon booster separation, It pitches to the 270 degree vector, and by that time I reverted to VAB

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All the spherical pods have crazy amounts of drag.  This makes them trivial to reenter safely with, but very difficult to launch.  You can fit gigantic, unrealistic fins at the back of the rocket (you'll need them on the core stage, not the side boosters) but still the drag is so severe it will really slow down the booster and require a lot more propellant than the other pods.

The better solution is to use a fairing to hide the pod from aerodynamic drag until almost in space.  If you're in career/science mode and don't have fairings yet - unfortunately the best strategy is just to wait and use the other pods until you do.

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  • 2 weeks later...

While I never built anything reality-inspired (parts tend to be too high up in the tech tree for my preference), I did a lot of experimentation with KV pods and can state with absolute certainty that you can, in fact, launch a KV-1 pod to space without a fairing, but it requires a completely different rocket design methodology than a Mk1 command pod.

  • You need a strong lower stage. Looking at an image of an R7, that seems to be the case already, but what I'm saying in particular is that whatever stage you mount your fins on, DO NOT DROP THAT STAGE until you're well above 50 km altitude. Anything lower and the rocket will flip from the air resistance. The longer that stage stays on during ascent, the better, vacuum Isp be damned.
  • Use gimbal engines, not non-gimbal ones. A reaction wheel is NOT strong enough to counteract flipping. Once you reach around 55-60 km, even a single Terrier has enough gimbal to keep you from flipping by brute-force overpowering the aero forces on the KV pod, even if you don't have a reaction wheel (though not having a reaction wheel means you won't have roll control).
  • High AoA is your enemy.  Lock SAS to prograde once you begin the gravity turn and use time-to-apoapse to control your trajectory (ie. throttle up to push it further away to make your trajectory steeper, throttle down to let the AP closer to flatten out your trajectory), not steering at crazy angles.
  • Keep the rocket short and squat. Remember physics class: torque equals force times lever. The taller the rocket, the further away the KV pod is from the CoM, which makes the pod's aero drag pull the rocket sideways into a flip even harder.



This craft can go to the edge of Kerbin's SOI and back without reaction wheels and no flipping during launch.

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On 1/18/2021 at 9:59 PM, The wizard of me said:

I made an R7 replica to launch a Vostok? Voskhod? Whatever.


Post a screenshot!  We can help you sort this out.

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  • 2 months later...

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