Delta-v budget

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Delta-v budget (or velocity change budget) is a term used in astrodynamics and aerospace industry for velocity change (or delta-v) requirements for the various propulsive tasks and orbital maneuvers over phases of the space mission.

Sample delta-v budget will enumerate various classes of manoeuvres, delta-v per manoeuvre, number of manoeuvres required over the time of the mission.

In the absence of an atmosphere and landings where the ground is hit with some speed, the delta-v is the same for changes in orbit the other way around: gaining and losing speed cost an equal effort.

Contents

[edit] Launch/landing budget

  • Launch to LEO — this not only requires an increase of velocity from 0 to 7.8 km/s, but also typically 1.5–2 km/s for atmospheric drag and gravity drag
  • Re-entry from LEO — the delta-v required is the orbital manoeuvring burn to lower perigee into the atmosphere, atmospheric drag takes care of the rest.

[edit] Stationkeeping budget

Maneuver Average delta-v per year [m/s]   Maximum per year [m/s]
Drag compensation in 400–500 km LEO <25 <100  
Drag compensation in 500–600 km LEO <  5 <  25  
Drag compensation in > 600 km LEO <   7.5
Station-keeping in geostationary orbit 50 – 55
Station-keeping in L1/L2 30 – 100
Station-keeping in Moon orbit 0 [1] – 400
Attitude control (3-axis) 2 – 6
Spin-up or despin 5 – 10
Stage booster separation 5 – 10
Momentum wheel unloading 2 – 6

[edit] Earth-Moon space budget

Delta-v needed to move inside Earth Moon system (speeds lower than escape velocity) in km/s

The return to LEO figures assume that a heat shield and aerobraking/aerocapture is used to reduce the speed by up to 3.2 km/s. The heat shield increases the mass, possibly by 15%. Where a heat shield is not used the higher from LEO Delta-v figure applies.

From\To LEO-Ken LEO-Eq GEO EML-1 EML-2 EML-4/5 LLO Moon C3
Earth 9.3 - 10
Low Earth Orbit (LEO-Ken) 4.24 4.33 3.77 3.43 3.97 4.04 5.93 3.22
Low Earth Orbit (LEO-Eq) 4.24 3.90 3.77 3.43 3.99 4.04 5.93 3.22
Geostationary Orbit (GEO) 2.06 1.63 1.38 1.47 1.71 2.05 3.92 1.30
Lagrangian point 1 (EML-1) 0.77 0.77 1.38 0.14 0.33 0.64 2.52 0.14
Lagrangian point 2 (EML-2) 0.33 0.33 1.47 0.14 0.34 0.64 2.52 0.14
Lagrangian point 4/5 (EML-4/5) 0.84 0.98 1.71 0.33 0.34 0.98 2.58 0.43
Low Lunar orbit (LLO) 1.31 1.31 2.05 0.64 0.65 0.98 1.87 1.40
Moon (Moon) 2.74 2.74 3.92 2.52 2.53 2.58 1.87 2.80
Earth Escape velocity (C3) 0.00 0.00 1.30 0.14 0.14 0.43 1.40 2.80

[2] [3] [4]

[edit] Interplanetary budget

From To delta-v in km/s
Earth Escape velocity (C3) Mars Transfer Orbit 0.6
Mars Transfer Orbit Mars Capture Orbit 0.9
Mars Capture Orbit Deimos Transfer Orbit 0.2
Deimos Transfer Orbit Deimos surface 0.7
Deimos Transfer Orbit Phobos Transfer Orbit 0.3
Phobos Transfer Orbit Phobos surface 0.5
Mars Capture Orbit Low Mars Orbit 1.4
Low Mars Orbit Mars surface 4.1
Earth Escape velocity (C3) Closest NEO Asteroids[5] 0.8 - 2.0

According to Marsden and Ross, "The energy levels of the Sun-Earth L1 and L2 points differ from those of the Earth-Moon system by only 50 m/s (as measured by maneuver velocity)."[6]

[edit] Delta-vs between Earth and Mars

Delta-v's in km/s for various orbital maneuvers using conventional rockets. Red arrows show where optional aerobraking can be performed in that particular direction, black numbers give delta-v in km/s that apply in either direction. Lower delta-v transfers than shown can often be achieved, but involve rare transfer windows or take significantly longer, see: fuzzy orbital transfers. Not all possible links are shown.
Delta-v's in km/s for various orbital maneuvers[7][8] using conventional rockets. Red arrows show where optional aerobraking can be performed in that particular direction, black numbers give delta-v in km/s that apply in either direction. Lower delta-v transfers than shown can often be achieved, but involve rare transfer windows or take significantly longer, see: fuzzy orbital transfers. Not all possible links are shown.

[edit] Abbreviations used

C3 Escape orbit
GEO Geosynchronous orbit
GTO Geostationary transfer orbit
L5 Earth-Moon fifth Lagrangian point
LEO-Eq Low Earth orbit - equatorial
LEO-Ken Low Earth orbit - "Kennedy inclination orbit"

[edit] See also

[edit] References

  1. ^ Frozen lunar orbits
  2. ^ list of delta-v
  3. ^ L2 Halo lunar orbit
  4. ^ Strategic Considerations for Cislunar Space Infrastructure
  5. ^ NEO list
  6. ^ New methods in celestial mechanics and mission design. Bull. Amer. Math. Soc..
  7. ^ table of cislunar/mars delta-vs
  8. ^ cislunar delta-vs


[edit] External links

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