An optimal speed per altitude profile minimizes gravity and aerodynamic losses during orbital launch
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Retrieved data supports the concept that balancing speed and altitude during an orbital launch profile helps manage and minimize losses caused by gravity and aerodynamic drag.
# Optimal speed per altitude for orbit launch
Tags: launch, rockets, aerodynamics, launch-trajectories
- Score: 9
- Views: 11000
- Answers: 2
- Answered: yes
- Asked by: Antzi (13135 rep)
- Asked: 2014-11-20
- Edited: 2020-08-31
- Site: space
## Question
On Kerbin, rockets have an optimal speed depending on altitude for maximum fuel efficiency, as
You can save fuel by being close to your terminal velocity during ascent. Lower velocity wastes delta-V on gravity, higher is wasted on air resistance
See http://wiki.kerbalspaceprogram.com/wiki/Basic_maneuvers
I searched for a similar chart on earth but couldn't find any. Can someone give me an approximation of ideal speed for real rockets on earth, or maybe a few other planets ?
## Answers
### Answer by Hobbes (score: 12 [ACCEPTED])
If the optimal speed is terminal velocity, this is the formula you need:
$V_t= \sqrt{\frac{2mg}{\rho A C_d }}$
where
- $V_t$ is terminal velocity,
- $m$ is the mass of the falling object,
- $g$ is the Earth's gravity|acceleration due to gravity,
- $C_d$ is the drag coefficient,
- $\rho$ is the density of the fluid through which the object is falling, and
- $A$ is the projected area of th
# Fuel-optimal thrust profile for an orbital ascent on a planet with an atmosphere
Tags: launch, orbital-mechanics, orbital-maneuver, launch-sequence, launch-vehicle
- Score: 3
- Views: 247
- Answers: 1
- Answered: yes
- Asked by: InquisitiveInquirer (1642 rep)
- Asked: 2017-09-21
- Site: space
## Question
This is a continuation of a previous question posted a few months ago. If we consider a SSTO vehicle launching from a planet with an atmosphere, would it be fuel optimal to have a period of lowered thrust whilst going through the thickest part of the atmosphere (even if we ignore dynamic pressure constraints), in order to minimize the largest losses from drag? If so, would a fuel-optimal thrust profile for an ascent into orbit consist of an initial period of maximum thrust, a second period of lowered thrust, a third period of maximum thrust, a fourth period of zero thrust (coast phase), and a fifth and final period of maximum thrust in order to circularize the orbit?
## Answers
### Answer by SF. (score: 4)
Essentially, yes. Providing you can output enough thrust and the atmosphere is so dense that your atmospheric drag losses during that relatively short period would outpa
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