[Dave Lev (OP)]

What is the source of energy for the orbital motion?

Based on Newton's second law of motion the orbital motion of an object must consum energy:

https://en.wikipedia.org/wiki/Momentum
Newton's second law of motion states that the rate of change of a body's momentum is equal to the net force acting on it. Momentum depends on the frame of reference, but in any inertial frame it is a conserved quantity, meaning that if a closed system is not affected by external forces, its total linear momentum does not change.
Therefore, "in any inertial frame it is a conserved quantity, meaning that if a closed system is not affected by external forces, its total linear momentum does not change".
Therefore, if the Astronaut was not effected by any external forces/energy it is expected that "its total linear momentum does not change"
However, the gravity bends its linear momentum.
Therefore, based on Newton's second law of motion, that astronaut must get external force/energy - even if it is called gravity, and he does't feel it.
Hence, do you finally agree that in order to change the linear momentum of any object/astronaut - by gravity or by rocket - that force must come with real energy.

Based on the Conservation_law, the total quantity of energy in an isolated system does not change.
https://en.wikipedia.org/wiki/Conservation_law
"the conservation law of energy states that the total quantity of energy in an isolated system does not change, though it may change form.."

As based on Newton's second law of motion, in order to bend/change the linear momentum of an object into orbital motion, energy must be invested, and as based on the conservation law of energy the total quantity of energy in an isolated system does not change then what is the source of energy for the orbital motion?

[Halc]

Locking this topic now since all of this has been discussed.

Based on Newton's second law of motion the orbital motion of an object must consum energy:

Newton's 2nd law says no such thing. It doesn't mention energy or orbital motion at all.
Your general inability to distinguish energy from force, potential, momentum, etc, aside, all this has been discussed in other topics.

Therefore, based on Newton's second law of motion, that astronaut must get external force/energy

This is wrong, as it has been explained so many times before. Newton's law says nothing about energy being required to alter the momentum of the astronaut (him not being a closed system).
Please learn some basic physics before repeating this nonsense assertion yet again in another topic.