According to inverse.com aboard starship "Its use of liquid oxygen and methane as rocket fuel means astronauts can fly to Mars, refuel using the planet’s resources," but can we go further? That's what I aim to answer with this question.
Yes, But it Depends on the Details
In 2019 Elon Musk responded to the same question on Twitter: How Much Delta-V Does a Fully Fueled Starship in space have with a 100T Payload?
Elon's answer was, "Approximately 6.9km/s".
Now at the time he said that, Starship was about 120 tons, and the Raptor engines had a lower ISP. This would likely be a worst-case scenario.
An expendable Starship would be a lot lighter, and that's what you'd likely use for deep space missions. That Starship wouldn't need fins, a heat shield, or the sea-level Raptor engines. This is similar to the configuration of the Lunar Starship, except it also has landing legs, an elevator, human living facilities and a ring of emgines for lunar landing.
Lunar Starship can go from fully fueled in LEO to the Gateway, then to the Moon's surface, then back to the Gateway. That's roughly 9 km/s.
Given that, a 'Lunar' Starship without landing legs, the elevator, landing engines and a standard payload bay will be well over 9 km/s. With a smaller payload it could be 10 to 12. I'm being intentionally non-precise because of ongoing improvements to Starship. We don't really know the final weight of Starship yet or the final performance numbers for the engines. But 6.9 to 12 kilometers per second depending on payload and configuration seems about right.
So where could Starship go with that?
- 6590 km/s gets you to Jupiter intercept.
- 7700 km/s gets you to a Saturn intercept.
- 8490 km/s gets you to Uranus intercept.
- 8600 km/s gets you to a Neptune intercept.
Those are direct transfers, without using planetary slingshots. And those are essentially flybys. It takes a lot more energy to make it into orbit.
At Jupiter, Callisto is easiest to attain orbit around, and it would take a total of approx 11,800 km/s to go direct from Low Earth Orbit to Low Callisto Orbit. At Saturn, Titan orbit is also close to 12,000.
So, an expendable Starship could deliver a 100T payload to the intercept orbit of every planet except for Mercury. It could also put 100T into Low Venus Orbit. With no payload, an expendable Starship might be able to achieve orbit around Callisto or Titan.
It could easily send 100T of payload completely out of the solar system.
If we allow for slingshot manoevers we could do considerably better.