And these are not angled to create lift they are perfectly in line and only used to create drag for passive stability. The only surfaces on a rocket that could potentially create lift are the stabilization fins at the base of a rocket. Rockets use massive amounts of thrust to punch a hole through the atmosphere to go up.
Rockets don’t glide gently through the air like an airplane.
If the COT and COM are not perfectly aligned, the craft will pivot around the COM. COL very far behind of COM → Very hard to correct course likely to flip up or nosediveįor both rockets and airplanes we have to line up the COT to push through the COM.COL further behind of COM → More stable.COL closely behind of COM → More maneuverable.COL inside COM → Excessively maneuverable needs constant course correction.COL ahead of COM → Flips or turns uncontrollably.Positive lift.Īngle your hand down slightly. Hold your hand horizontal with your finger tips pointing into the wind.Īngle your hand up slightly. Has nothing to do with with engines / thrust. The center of lift is the point where the sum total of all lift generated by parts - principally by wings, control surfaces, and aerodynamic fuselage parts - balances out and the aggregate direction their force will act on a craft while in an atmosphere. For your typical rocket, COT sits perfectly centered at the base of the rocket behind a perfectly centered COM perfectly in line with the centerline of the rocket. It is the midpoint where thrust from engines balances and the direction in which it is acting. The center of thrust is displayed as a vector. Hence it indirectly resembles the center on which the downward force of gravity acts.Ĭenter of Thrust (COT) – Thrust Force Vector It is also where the downward force of gravity pulls down on the rocket or plane. (!) The Center of Mass of an object is a static property of an object.
The point in space where your finger is placed to balance the object is where the center of mass is located. Let’s look at the various centers and vectors next.Ĭenter of Mass (CoM) – Indirectly represents the Gravity Force Vectorīalance an object on the tip of your finger. A force is a vector it acts on a center and pushes in a certain direction with a certain amount. Now we can look at forces acting on a craft in atmosphere (aerodynamic forces of lift and drag) under gravity (force of gravity) using its engines (force of thrust). Either use ‘mass’ or ‘(force of) gravity’, but definitely not ‘weight’, okay? Let’s agree not to use the word ‘weight’ anymore. Hint If you see the word ‘weight’, simply substitute it for ‘force of gravity’. Weight is a force (N) and represented by a vector.For interplanetary rocket design, we need to be more accurate, so: Coyote is 6 times less on the Moon than on Earth.Īs I am not likely to leave the planet anytime soon kilograms will do just fine 1kg weighs not much really, 10kg weighs quite a bit more and 1000kg weighs a lot. The force exerted by a 50kg ACME anvil dropped on Wile E. The Moon’s gravity is 1/6th that of Earth’s gravity. Even though on earth we express weight in kilograms, it really should be expressed as a force in Newton (N). Weight is an indicator of how heavy an object ‘feels’. Thousand kilograms is called one ton or tonne (1t). In space, there is only Thrust and the Gravitational pull from planets.īefore we start looking at these forces, let’s get something out of the way first. There are four forces acting on a craft when in the lower atmosphere within gravity: Thrust, Weight, Lift and Drag.ĭrag and Weight = Bad, although they do come in handy at times.įorces during atmospheric vertical take-off. What engines to use? How much fuel to take? What shape should the craft be? Stack decouplers or Radial decouplers? Solid booster or Liquid Fuel Engine? Let’s start with some basic concepts.
#Kerbal space program service bay how to
Kerbal Space Program – How to build a rocket
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