Typical delta V (velocity increment) value(s) for various space manoevres

Knowledge about Δv value(s) for the various manoeuvres performed by the spacecraft is necessary to generate a Δv (pronounce: delta-v) budget. Below, some typical velocity increment values are given for various space manouevres subdivided over three broad categories:

  • Launch into Low Earth Orbit (LEO)
  • Impulsive shot manoeuvres
  • Constant low thrust space manoeuvres

In case you require more detailed data you need to revert to orbit analysis. All values are taken from lecture notes "Aerospace Design & Systems Engineering Elements I, Part: Spacecraft (bus) Design and Sizing", B.T.C. Zandbergen, TU-Delft, LR, November 2015.

Launch into Low Earth Orbit (LEO)

Table: Required Δv for launch into LEO

Manoeuvre

Δv, km/s

Launch into LEO (including drag and gravity loss)

 

 

Moon surface into Low Lunar Orbit (LLO)

 

LLO to Moon surface

 

Mars surface to Low Mars Orbit (LMO)

Low Mars orbit to Mars surface

9.2-10.2 (depending on vehicle size and ascent trajectory)

2.0-2.6 km/s (2.2 km/s for Apollo ascent stage

1.6-2.9 km/s (2.5 km/s for Apollo descent stage

4.1-5.7 km/s

4.7 km/s (including effect of atmospheric drag


Impulsive shot manoeuvres

Table: Typical Δv value(s) for impulsive shot manoeuvres

Manoeuvre

Δv, km/s

Orbit transfer:
                     LEO to GEO
                     LEO to GEO
                     GTO to GEO (1)
                     GTO to GEO (2)
                     LEO to Earth escape
                     LEO to translunar orbit
                     LEO to lunar orbit
                     GTO to lunar orbit
                     LEO to Mars orbit

                     LEO to Mars transfer orbit
                     LEO to solar escape

Orbit control:
                     Station-keeping (GEO)

                     Station keeping in Moon orbit

                     Station keeping in L1/L2

Drag compensation:

                                    (alt.: 400-500 km)
                                    (alt.: 500-600 km)
                                    (alt.: >600 km) Attitude control:
3-axis control Auxiliary tasks:
                                    Spin-up or despin
                     Stage or booster separation
                     Momentum wheel unloading


3.95 (no plane change required)
4.2 (including plane change of 28 deg)
1.5 (no plane change required)
1.8 (incl. plane change of 28 deg.)
3.2
3.1
3.9
1.7
5.7

3.4 (depends on relative position of Mars)
8.7


50-55 m/s per year

100-400 m/s per year

30-100 m/s

 

< 100 m/s per year max (<25 m/s average)
< 25 m/s per year max (< 5 m/s average)
< 7.5 m/s per year max

2-6 m/s per year

 

5-10 m/s per manoeuvre
5-10 m/s per manoeuvre
2-6 m/s per year


Constant low thrust space manoeuvres

Because of gravity loss, low thrust-to-weight (T/W) propulsion systems suffer a loss in performance equivalent to increasing the effective missionΔv. For example, the impulsive Δv for a high T/W transfer from LEO to GEO is 4.2 km/s; for a low T/W transfer, the effective Δv is about 5.9 km/s. However, even with gravity losses, low T/W propulsion systems can still out-perform high T/W impulsive systems, because the very high specific impulse of some low T/W systems (greater than 1000 s) more than compensates for the increase in effective Δv.

Table: Typical Δv value(s) for constant low thrust (acceleration < 0.001 m/s2) orbit transfer (propellant mass is negligible)

Manoeuvre

Δv, km/s

Transfer time

LEO (200 km altitude) to GEO (no plane change)

4.71

a is 0.001 m/s2:
~54 days

LEO (200 km altitude) to GEO (including 28.5 deg. plane change)

5.97

 

LEO to MEO (19150 km altitude; no plane change)

3.83

a is 0.001 m/s2:
~44 days

LEO to Earth escape:

 

 

Initial acceleration-to-local gravitational acceleration: 10-2

5.82

 

Initial acceleration-to-local gravitational acceleration: 10-3

6.66

 

Initial acceleration-to-local gravitational acceleration: 10-4

7.08

 

Initial acceleration-to-local gravitational acceleration: 10-5

7.43

 

LEO to Lunar orbit

~8

months-year
 ~2.2 years

LEO to Mars orbit

~15

 

Next figure illustrates the effect of the thrust-to-weight ratio (as a measure for the vehicle acceleration) on mission Δv for low thrust LEO to GEO transfer. With decreasing thrust-to weight ratio, the mission Δv increases.

Figure: Low thrust LEO-to-GEO orbit transfer including 28.5 degrees plane change

 
Note: A thrust-to-weight ratio of 0.1 corresponds to an initial acceleration of about 1 m/s2.

Travel time calculation example:
Taking a(n) initial thrust-to-weight (T/W) ratio of 0.001 (initial acceleration of 0.01m/s2 ) to achieve a velocity increment of 5.9 km/s and assuming a constant acceleration leads to a transfer or travel time of about 6.8 days. For a spacecraft with an initial weight of 20000 N (~2000 kg mass), we find for the required thrust level a value of 20 N. Assuming a specific impulse of 2000 s this gives then a mass flow of ~ 1g/s. Multiplying by the travel time, this gives a propellant mass of 616 kg. On the other hand, using the rocket equation, we find an initial-to-empty mass ratio of 1.34 or an empty mass of 1489 kg. This leads to a propellant mass of 511 kg, which is ~ 100 kg below the propellant mass estimated assuming a constant acceleration. Since mass flow of propellant is constant, we find for the travel time 511kg / 1 g/s = 511000 s = 5.91 days.

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Name author: SSE
© 2017 TU Delft

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