> could allow for crewed missions to Mars to be completed within 2 months. As it stands today with commonly used propulsion systems, a trip to Mars takes aroun

> could allow for crewed missions to Mars to be completed within 2 months. As it stands today with commonly used propulsion systems, a trip to Mars takes around 9 months. Both numbers are pulled out of thin air. The Hohmann transfer time between 2 planets is about half a year. Which year, you ask? The year of the inner planet, or of the outer planet. Well, it's the average of the 2 years. A Martian year is about 2 of our years, so the average is 1.5 years, divided by 2 it's 9 months. But if you are willing to burn more fuel, you can cut down the travel time. The delta-v between Earth orbit and Mars is surprisingly low. From the Moon transfer orbit to the low Mars orbit it is 2.5 km/s. The rule of thumb is that a rocket can achieve twice the delta-v of its exhaust velocity. In the case of the SpaceX Starship, the exhaust velocity is 3.7 km/s, twice that is 7.4 km/s, about 3 times the delta-v needed for the Hohmann transfer. SpaceX states they will be able to get to Mars in 6 months [1]. Musk went further and claimed that the Starship could get to Mars in as little as 80 days, and this fantastic Stack Exchange post [2] explains that maybe 80 days is slightly too optimistic, but 90 days is doable. Now this design here claims that the rocket can achieve an ISP of 5000 seconds, which means an exhaust velocity of 50 km/s. With such an exhaust velocity, basically they can pick any random number and claim they can get to Mars that fast. The shortest path between the two orbits, the radial one, is about 75 million km long. At 50 km/s, it takes 1.5 million seconds, or 17 days. Of course, this is for a one-way trip, but presumably in the far future we could preposition fuel in Mars orbit for the return trip. Maybe they thought half a month will sound too wild, so they went for the 2 month number to make it sound more realistic. The problem is that compared to the 3 months doable by SpaceX, it's not all that impressive. [1] https://www.spacex.com/humanspaceflight/mars/ https://www.spacex.com/humanspaceflight/mars/ [2] https://space.stackexchange.com/questions/57568/elon-musks-its-travel-time-to-mars-estimate https://space.stackexchange.com/questions/57568/elon-musks-i...