Rockets

[KPN]

A rocket is fired from a Launchpad with an initial velocity of 8000m/s. Ignoring atmospheric drag,
what delta-v is required to circularise the orbit of a projectile fired horizontally from the Earth’s
surface?

And what will the resulting orbit altitude then be?

[Snark]

Hello, and welcome to the forums! 

Moving question to "Science & Spaceflight", since that's a general real-life-science question and not about KSP per se.

[Gaarst]

Depends in what direction you fire. Because of the rotation of the Earth, firing West on the Equator will get you to the ground, East on the Equator will get you 2170 km up, North or South on the Equator 300 km, and wherever else somewhere in between. Say you fire East on the Equator because everyone launches East on the Equator in math problems, you are in an orbit with an apo at 2170 km and a peri at the point you fired your projectile (I've assumed 0 m for the calculations).

Then you need 520 m/s of dV to circularise into a 2170 km circular orbit.

[Nightside]

Why does this  “rocket “ have an initial velocity and no acceleration? To me that is just a projectile.

 

 

[Gargamel]

7 hours ago, KPN said:

Ignoring atmospheric drag,
what delta-v is required to circularise the orbit of a projectile fired horizontally from the Earth’s
surface?

Well, the way I read this, you have already achieved orbital velocity at sea level, in an atmosphericless environment.

There just seems to be a lot of info missing from these questions.....

7 hours ago, KPN said:

A rocket is fired from a Launchpad with an initial velocity of 8000m/s. Ignoring atmospheric drag,
what delta-v is required to circularise the orbit of a projectile fired horizontally from the Earth’s
surface? 

To me, a rocket is fired from a launch pad vertically, not horizontally, so these seem to be two completely unrelated statements.