# Difference between revisions of "Duna"

Duna is the fourth planet of the Kerbol star system. It is the Mars analog for Kerbal Space Program and is mostly red with polar icecaps. It has one natural satellite, the moon Ike. Due to Ike's size and proximity, Ike and Duna are tidally locked to each other.

## Topography

 A topographic map of Duna made with the ISA MapSat plugin Duna is a iron-rich planet which has greatly varying land altitude, the consequence of which is very difficult judgment of a safe landing position. Its mountainous ranges are a peril to landing craft, especially considering the thin atmosphere, where very little aerobraking can be done safely. It is important to slow one's ship down before coming into the atmosphere, to ensure a safe descent. There are several maria, or large regions of Dark soil at, exactly 0 meters altitude. These are ideal landing locations due to their low altitude, and thicker atmosphere for aerobraking. Its two poles are very expansive and are the result of a thin atmosphere. The central regions make a shape resembling Europe.

## Atmosphere

A comparison of the atmospheres of Duna and Kerbin

Duna's atmosphere begins at 41,446 m. It is only 20% as dense as Kerbin's at altitude 0 and is even less dense (relative to Kerbin) at higher altitudes.

Like all atmospheres in the game, Duna's atmosphere fades exponentially with increasing altitude (with a scale height of 3000 m). In general, the atmospheric pressure on Duna at an altitude expressed in meters is:[1]

${\displaystyle p_{d}=0.2\ e^{-altitude/3000}}$

Parachutes work at lower efficiency than on Kerbin, making powered descent necessary when landing from orbit (unless your craft is a glider or just a pod with a parachute).

The following table gives terminal velocities at different Duna altitudes. These are also the velocities at which a ship should travel for a fuel-optimal ascent from Duna, given the game's model of atmospheric drag.[2]

Altitude (m) Velocity (m/s)
0 212
1000 231
2000 252
3000 274
5000 324
8000 418
10000 495
13000 638
15000 756
20000 1.16×103

## Orbital Statistics

The geosynchronous orbit of Duna is at an altitude of 0.00 m above Duna. The speed of the satellite is 0.00 m/s and it has an orbital period resonating with 1 Duna day (18.2 hours or 65517.859375 seconds). However, this orbit is not possible since it intersects with Ike's SOI.

For a semi-synchronous orbit of ½ Duna day (9.025 hours or 32490 seconds) an orbit of 0.00 m above Duna is needed with a velocity of 0.00 m/s.

## Reference Frames

 Warp 5x, 10x 50x 100x 1000x 10,000x 100,000x Minimum Altitude above atmosphere 60 km 100 km 300 km 600 km 800 km

## Changes

0.17
• Initial Release

## Notes

1. A nuclear engine has a specific impulse of 220 in 1 atm, 800 in vacuum, and the following at various Duna altitudes:
 altitude (m) 2 100 300 500 1460 2420 3000 4272 5000 10000 specific impulse 684.1 687.8 695.1 701.8 728.7 748.2 757.3 772.1 778.1 795.9