When a rocket is launched then how much speed till it needed to just enters into space, like how much speed needed to take off, how much speed it needed to travel that 100 km (to reach karman line) , can you tell me with breakdown in change of speed in different stages of rocket launch.
Here is how a rocket’s speed changes at each stage while going from the ground to space.
(Values are approximate but very close to real rockets like Falcon-9, GSLV, PSLV, etc.)
How much speed a rocket gains until it enters space? (Stage-by-stage breakdown)
First point to remember:
Space begins at 100 km,
but reaching 100 km does NOT need very high speed.
Most of the speed comes later to reach orbit, not just space.
Below is the full speed journey.
Stage 1: Liftoff (0–20 km altitude)
At the moment of liftoff:
- Speed = 0 km/h (standing on the ground)
As the rocket rises through thick atmosphere, speed increases slowly.
Typical speed at 20 km:
→ 1,500 – 2,000 km/h
Reason:
Most energy is spent fighting gravity and air drag.
Stage 2: Mid-Ascent (20–50 km altitude)
Air becomes thinner → rocket can accelerate faster.
Speed at 50 km:
→ 4,000 – 6,000 km/h
Note:
The first stage booster usually separates around this phase.
Stage 3: Reaching Space (50–100 km altitude)
Now the rocket is above most of the atmosphere.
Speed when it crosses 100 km (enters space):
→ 6,000 – 8,000 km/h
Important:
A rocket does NOT need orbit speed (28,000 km/h) just to touch space.
Reaching space = height
Orbit = height + extreme sideways speed
Stage 4: After Entering Space (100–200 km altitude)
Second stage or upper stage fires to gain orbital velocity.
Speed in this phase:
→ from 8,000 km/h
→ to 20,000 km/h
Stage 5: Final Orbit Insertion (~200 km altitude)
To stay in stable Low Earth Orbit (LEO):
Final speed needed:
→ 27,000 – 28,000 km/h
This is why rockets still accelerate after crossing 100 km.
Easy Summary (Means, in simple words)
- 0 km/h → liftoff
- 2,000 km/h → 20 km
- 6,000 km/h → 50–100 km (entering space)
- 20,000+ km/h → higher in space
- 28,000 km/h → needed to stay in orbit
Author
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Aditya Raj Anand (Msc Physics student) is a dedicated book author and the founder of Science laws a well-regarded blog that deliver science related News and Education. Aditya holds a Bachelor of Science (B.Sc.) in Mathematics, currently doing Master in Physics. A discipline that has fueled his lifelong passion for understanding and demonstrating complex scientific principles. Throughout his academic journey, he developed a deep interest in simplifying challenging concepts in science and making them more accessible to a wider audience. He is written science for more than 5 years. He has served as a writer, editor and analyst at science laws since its inception.
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