Delta-v to overcome atmospheric and gravity drag at 13km?

In summary, launching from a higher altitude, such as 13km, can save a significant amount of delta-v required to reach normal LEO orbital velocity due to reduced atmospheric and gravity drag. However, estimating the exact amount saved can be difficult and time-consuming, and most launch sites are still located close to sea level for practical reasons.
  • #1
Treva31
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Wikipedia says that:

Atmospheric and gravity drag associated with [space] launch typically adds 1.3 to 1.8 km/s to the launch vehicle delta-v required to reach normal LEO orbital velocity of around 7.8 km/s (28,080 km/h).

Does anyone know, or know how to calculate/estimate/simulate the delta-v required to overcome atmospheric and gravity drag (excluding the 7.8 km/s for orbital velocity) if you were launching from 13km altitude? ie a commercial jetliner.

I'm guessing it would be a lot less since its already only around 0.1 atm pressure up there.
I also suspect its very difficult to work out.
 
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You can simulate a trajectory numerically, and optimize launch angle, acceleration profile and so on for the reduced atmospheric pressure and some rocket model. Takes a lot of time.
To get a lower estimate on the saved delta-v, you can take a sea-level lauch profile, estimate air drag along its flight path and reduce this accordingly.

Many countries have access to mountains with a height of at least 4 km, but most launch sites are close to sea level: access via ships or highways and a safe landing zone for potential debris are more important than some kilometers of air.

There is more than 1/10 sea-level pressure at a height of 13 km.
 
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  • #3
mfb said:
You can simulate a trajectory numerically, and optimize launch angle, acceleration profile and so on for the reduced atmospheric pressure and some rocket model. Takes a lot of time.
To get a lower estimate on the saved delta-v, you can take a sea-level lauch profile, estimate air drag along its flight path and reduce this accordingly.

Many countries have access to mountains with a height of at least 4 km, but most launch sites are close to sea level: access via ships or highways and a safe landing zone for potential debris are more important than some kilometers of air.

There is more than 1/10 sea-level pressure at a height of 13 km.

Yea that's probably close enough, thanks :)
I'll post my workings here when I've done it.
 
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1. What is "Delta-v" and why is it important in overcoming atmospheric and gravity drag at 13km?

"Delta-v" refers to the change in velocity required to achieve a certain goal, in this case, overcoming atmospheric and gravity drag at 13km. It is an important concept in aerospace engineering as it helps determine the amount of propellant needed for a spacecraft to reach its desired destination.

2. How is the "Delta-v" calculated for overcoming atmospheric and gravity drag at 13km?

The calculation of "Delta-v" for overcoming atmospheric and gravity drag at 13km involves taking into account several factors, including the mass of the spacecraft, the specific impulse of the propulsion system, and the force of gravity and air resistance at that altitude. These variables are used in a formula known as the Rocket Equation to determine the required "Delta-v".

3. What are the challenges of overcoming atmospheric and gravity drag at 13km?

The main challenge of overcoming atmospheric and gravity drag at 13km is the significant amount of energy required to counteract the forces of air resistance and gravity. This means that a spacecraft must have a powerful propulsion system and carry a sufficient amount of propellant to achieve the necessary "Delta-v". Additionally, the design and aerodynamics of the spacecraft must also be carefully considered to minimize drag and maximize efficiency.

4. How does the density of the atmosphere at 13km affect the "Delta-v" needed to overcome drag?

The density of the atmosphere at 13km plays a significant role in determining the amount of "Delta-v" needed to overcome drag. The higher the density, the greater the drag force acting on the spacecraft, and thus, the higher the "Delta-v" required to overcome it. This is why spacecraft typically perform a "gravity turn" maneuver at around 13km, where they tilt their trajectory to gradually reduce the effects of atmospheric drag.

5. Are there any other factors that impact the "Delta-v" needed to overcome atmospheric and gravity drag at 13km?

Yes, there are other factors that can impact the "Delta-v" needed to overcome atmospheric and gravity drag at 13km. These include the shape and size of the spacecraft, the altitude and speed of the spacecraft, and the presence of other external forces such as solar wind or magnetic fields. All of these factors must be taken into account when calculating the required "Delta-v" for a successful spacecraft mission.

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