Difference between revisions of "Duna"

Revision as of 06:45, 15 August 2016

Duna
Duna as seen from orbit.
Planet of Kerbol
Orbital Characteristics
Semi-major axis		20 726 155 264 m [Note 1]
Apoapsis		21 783 189 163 m [Note 1]
Periapsis		19 669 121 365 m [Note 1]
Orbital eccentricity		0.051
Orbital inclination		0.06 °
Argument of periapsis		0 °
Longitude of the ascending node		135.5 °
Mean anomaly		3.14 rad (at 0s UT)
Sidereal orbital period		17 315 400 s
		801 d 3 h 50 m 0.1 s
Synodic orbital period		19 645 697.3 s
Orbital velocity		7 147 - 7 915 m/s
Physical Characteristics
Equatorial radius		320 000 m
Equatorial circumference		2 010 619 m
Surface area		1.2867964×1012 m2
Mass		4.5154270×1021 kg
Standard gravitational parameter		3.0136321×1011 m3/s2
Density		32 897.302 kg/m3
Surface gravity		2.94 m/s2 (0.3 g)
Escape velocity		1 372.41 m/s
Sidereal rotation period		65 517.859 s
		3 d 0 h 11 m 57.9 s
Solar day		65 766.707 s
		3 d 0 h 16 m 6.7 s
Sidereal rotational velocity		30.688 m/s
Synchronous orbit		2 880.00 km
Sphere of influence		47 921 949 m [Note 1]
Atmospheric Characteristics
Atmosphere present		Yes
Atmospheric pressure		6.75500 kPa
		0.066667 atm
Atmospheric height		50 000 m
		6.7×10-8 atm
Temperaturemin		-123.15 °C 150 K
Temperaturemax		-40.15 °C 233 K
Oxygen present		No
Scientific multiplier
Surface		8
Splashed		N/A
Lower atmosphere		5
Upper atmosphere		5
Near space		7
Outer space		5
Recovery		5
↑ 1.0 1.1 1.2 1.3 The distances are given from the body's center, not from the surface (unlike ingame)

Duna is the fourth planet from Kerbol and the fourth-largest planet. It is the Mars analog for Kerbal Space Program. It has one tidally-locked and large natural satellite, the moon Ike. Duna is a terrestrial planet with a red-brown surface and polar ice caps similar to that of Kerbin.

Using a ballistic insertion burn from 100km, with proper aerobraking, a round trip from Kerbin to orbit around Duna and back requires ~1700 m/s of LKO delta-v, a relatively low amount compared to other interplanetary destinations. Duna's orbit has nearly the same inclination as Kerbin around Kerbol, making the planet one of the easiest to encounter.

In-game description

Topography

A topographic map of Duna made with the ISA MapSat plugin

Duna's terrain ranges in altitude from 124 to 8264 meters. Its mountain ranges are a peril to landing craft, due to their steepness and the limited aerobraking that is possible in Duna's tenuous atmosphere at such altitudes.

Duna has several craters. They appear quite eroded, presumably by the wind.

Several maria (large regions of dark soil) are around several hundred meters altitude. Their low altitude allows for more aerobraking, and the flatness of the terrain makes them easy but boring landing locations. These may have been lakes when the planet may have had liquid on its surface in the past.

Duna's surface contains 3 anomalous features.

Biomes

Duna has 5 biomes.

Biome list

Duna In-game biome map as of 1.2

Poles Highlands Midlands Lowlands Craters (Currently found in the border of poles, not actually in "craters").

Atmosphere

Temperature and pressure of Duna's atmosphere as a function of altitude.

Duna has a thin, cool atmosphere with a mass of approximately 3.0×10¹⁵ kilograms, a datum level pressure of 6.755 kilopascals (0.067 atmosphere), and a depth of 50,000 meters. Compared to the atmosphere of Kerbin, Duna's atmosphere has 1/15^th the mass, 1/15^th the surface pressure, and 1/9^th the surface density. The datum level pressure on Duna is equivalent to that at an altitude of 14,975 m on Kerbin. The pressure at the top of Duna's highest mountain peak is only 2.4 kPa.

The average molecular weight of Duna air is 42 g/mol, and its adiabatic index is 1.20. Although the composition of Duna's atmosphere is unknown, these values suggest that it may consist largely of carbon dioxide.

Like all other atmospheres in the game, Duna's atmosphere fades exponentially as altitude increases. The scale height varies with altitude, which is a change from pre-1.0 versions of the game. The pressure-altitude profile is globally constant and independent of temperature. The following table gives the atmospheric pressure at various altitudes above the datum level.

The surface of Duna is cold, with a globally averaged datum level temperature of approximately -23 °C. Air temperatures decrease with increasing altitude to an altitude of 30 km. Between the altitudes of 30-45 km lies an isothermal layer, having a temperature of -123 °C.

Air temperatures vary with latitude and time of day. At the equator, datum level temperatures vary between a nighttime low of -20 °C and a daytime high of -2 °C. At the poles, the temperature varies between -90 °C and -85 °C. Since Duna has no axial tilt, there are no seasonal temperature variations.

Duna's north pole

Duna's atmosphere appears to have a reddish or brownish color, both from the surface and from space. The atmosphere has this color even over the poles, where the surface is white.

Atmospheric flight

The thickness of Duna's atmosphere makes it suitable for aerocapture from a high-speed interplanetary intercept. The periapsis altitude required for a successful aerocapture depends on the spacecraft's drag characteristics, its approach velocity, and the desired apoapsis of the resulting orbit. The most effective periapsis for aerocapture is best determined experimentally; however, for a Hohmann transfer originating from Kerbin, it appears that the target range lies between 10 km and 20 km.

Although parachutes will deploy on Duna, the atmosphere is so thin that they are usually unable to slow a craft to a safe landing velocity and must be assisted with engines. Parachute performance can be particularly troubling when attempting to land in highland areas. Attaining the same vehicle descent rate on Duna that a vehicle would have on Kerbin requires about 2.5 times the parachute area.

Below 5 km Duna's atmosphere is thick enough to allow wings to generate enough lift for aerodynamic flight. Jet engines don't work for want of oxygen, but other propulsion methods work well. Performing a horizontal landing with a plane is also possible.

An ascent to low Duna orbit from the surface typically requires around 1400 m/s in Δv to reach a 55 km altitude traveling at roughly 900 m/s.

Orbital statistics

The synchronous orbit of Duna is at an altitude of 2 880.00 km above Duna. The speed of the satellite is 306.88 m/s and it has an orbital period resonating with 1 Duna day (18.2 hours or 65517.859375 seconds). However, this is the same altitude at which Ike orbits, so unless a ship's orbit is perfectly precise, it will eventually be captured by Ike.

For a semi-synchronous orbit of ½ Duna day (9.1 hours or 32758.9295 seconds) an orbit of 1 695.87 km above Duna is needed with a velocity of 386.65 m/s.

Observation of Ike

An animation of an orbit viewed from Duna

Ike's orbit keeps it directly above a short range of Dunaian longitudes. The average Duna longitude that Ike tends to stay directly above (at the Zenith) is 6 degrees east, but the eccentricity of Ike's orbit causes the exact longitude to oscillate between about 2 degrees and 10 degrees east and makes Ike appear to grow slightly larger and smaller to an observer on the surface of Duna. The latitude at which Ike is in the Zenith also oscillates between 0.2 degrees south and 0.2 degrees north due to Ike's orbital inclination, making Ike appear to rotate upwards and downwards as viewed from the surface, but due to the extremely small orbital inclination, this effect is nearly imperceptible. These phenomena together are known as libration. The oscillation in Ike's position above the horizon allows areas from 88°W to 80°W and 92°E to 100°E on Duna to observe Ike rise and set at least partially across the horizon, as can any areas north of 89.8°N or south of 89.8°S.

Interplanetary travel

From a 60 km altitude orbit around Duna, the requirements for attaining an intercept trajectory of other celestials are:

Reference frames

Gallery

• 

  Parachute descent down to Duna surface.

• 

  ISA satellite in orbit over Duna being used to map the planet surface.

• 

  Duna's surface at Dawn.

• 

  Duna and Ike.

• 

  A topographic height map of Duna made with the ISA MapSat plugin.

• 

  A color map of Duna.

• 

  A lander on the northern pole of Duna.

• 

  Duna at sunrise.

• 

  A rover at the edge of one of the "sinkholes."

• 

  A small probe orbiting Duna.

• 

  Ike partially eclipsing Kerbol. Note the dimmer light and the solar panels not charging.

• 

  Duna seen from Ike.

• 

  Duna and Ike as seen from a space telescope.

Changes

1.0.5

• Changed atmosphere characteristics

0.90

• Added biomes

0.21

• Art Pass

0.18

• Minor art pass

0.17

• Initial Release

Trivia

• According to former developer NovaSilisko, Duna's appearance was inspired by the theory that ice ages on Mars may have brought the ice caps much closer to its equator. ^[3]
• Duna's name may be either a reference to its desert landscape or a reference to the Frank Herbert novel Dune.
• The low-lying areas near Duna's equator make a shape resembling Europe.

Spoiler: Anomalous features

• On the surface of Duna, there is a large monument carved in the likeness of a Kerbal face, alluding to the infamous "Face of Mars" discovered in the Cydonia Mensae region of Mars during the 1970's.
• Buried deep under the surface, there is a small camera, similar to the design on the Curiosity rover.
• One anomalous feature on Duna is a small, pyramid-like hill emitting an SSTV signal. When decrypted, it shows a diagram-like image of three figures standing next to the hill itself, which was originally part of the developer's story but later scrapped.

References

1. ↑ KSP Delta V Planner
2. ↑ Transfer calculator
3. ↑ NovaSilisko's answer in “Duna's ice caps are too big”.

v t e Kerbol System Kerbol Moho Eve Kerbin Duna Dres Jool Eeloo (The Sun)   Gilly Mun Minmus Ike   Laythe Vall Tylo Bop Pol