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2200000N (1 Raptor) / 1,300,000*0.4 kg (Total weight adjusted to fuel loss) = 4.2 m/s^2 (acceleration)

Delta-V (to travel to Jupiter) = 9000 m/s

9000 m/s / 4.2 m/s^2 = 2,142 s (1 Raptor engine burning time: 1.8 hours)

SpaceX Raptor engine mass flow = 650 kg/s

2,142 s * 650 kg/s = 1,392,300 kg

Gravity assist could probably reduce required propellant by half, but is it still too heavy?

When traveling to other planets, maybe a classical 3-stage design is better than SpaceX's revolutionary 2-stage design?

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  • $\begingroup$ Earth comparison: 14-ton fuel truck - can bring - 28-ton of fuel (1/2 ratio) - compare to 1/20 in Starship. $\endgroup$ Commented Feb 17, 2023 at 22:44
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    $\begingroup$ close-voting as duplicate. You've tried to use this method before on the site and been told about the rocket equation. $\endgroup$
    – Erin Anne
    Commented Feb 17, 2023 at 23:32
  • $\begingroup$ This question is about the design of spacecraft limitations, when increasing fuel capacity would not increase your payload capacity. $\endgroup$ Commented Feb 17, 2023 at 23:49
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    $\begingroup$ @TheMatrixEquation-balance that is sorta what the rocket equation tells you, for any chemical rocket getting to Jupiter involves getting deep into the exponential curve of increasing fuel mass. $\endgroup$ Commented Feb 17, 2023 at 23:55

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You're not accounting for the weight of the Starship decreasing as fuel burns off.

You need to use the Tsiolkovsky rocket equation:

$$\Delta v = v_\text{e} \ln \frac{m_0}{m_f} = I_\text{sp} g_0 \ln \frac{m_0}{m_f}$$

$m_0$ is the initial mass of Starship, fully fueled (1300 tons). $m_f$ is the final mass after propellant consumption, i.e. the dry mass of Starship (100 tons). $v_\text{e}$ is the rocket exhaust velocity, about 3600 m/s for the Raptor engine, and $\ln$ is the natural log function.

So for those figures (gleaned from a very quick glance at Wikipedia and probably wrong), the potential delta-v works out to about 9233 m/s. Payload mass would add to both the initial and final mass figures, reducing the mass ratio and thus the $\Delta v$.

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  • $\begingroup$ Now I can see why it is not recommended to reference Wikipedia as a source. They have changed Starship's propellant specifications recently. $\endgroup$ Commented Feb 18, 2023 at 1:14
  • $\begingroup$ Wikipedia has had the 1200 t number for years now. $\endgroup$ Commented Feb 18, 2023 at 2:30
  • $\begingroup$ @ChristopherJamesHuff - They did have "Starship Interplanetary" with 1900-ton propellent capacity. Now I don't see it on Wikipedia. $\endgroup$ Commented Feb 18, 2023 at 3:40

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