# Hohmann equation help

I'm having some slight difficulties in calculating the delta-v in a hohmann transfer equation. I used the equation from wikipedia (which i hope is correct) but whenever i replace the variables i get an extremly small delta-v, is this normal???

$$\Delta$$v=$$\sqrt{}(\mu/r1)$$*($$\sqrt{}(2*r2/(r1+r2)$$-1))

r1=6374000 meters
r2=405500000 meters
$$\mu=9.814$$

my final result was 0.00122149m/s
it seems like a really small number, is this right or i'm i doing something really wrong?

i attached an excel sheet to show you my work.

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Janus
Staff Emeritus
Gold Member
I'm having some slight difficulties in calculating the delta-v in a hohmann transfer equation. I used the equation from wikipedia (which i hope is correct) but whenever i replace the variables i get an extremly small delta-v, is this normal???

$$\Delta$$v=$$\sqrt{}(\mu/r1)$$*($$\sqrt{}(2*r2/(r1+r2)$$-1))

r1=6374000 meters
r2=405500000 meters
$$\mu=9.814$$

my final result was 0.00122149m/s
it seems like a really small number, is this right or i'm i doing something really wrong?

i attached an excel sheet to show you my work.

The problem is your value for $\mu$

$$\mu = GM$$

Where G is the universal gravitational constant and is equal to

6.67300 × 10-11 m3 kg-1 s-2

and M in this case is the mass of the Earth, or 5.97 x 1024 kg

so

4.651 X $10^{14}m^3 s^{-2}$

thanks for that correction.