# delta-v for a trip to Bennu asteroid

101955 Bennu has a mean diameter of 490 m (1,610 ft; 0.30 mi) and was the target of the OSIRIS-REx sample return mission. What is the delta-v using a Hohmann transfer orbit to do a round trip from low Earth orbit and then to "land" on 101955 Bennu, and then return to Earth, and is it within the SpaceX Starship's range?

I was also going to ask, "How long a duration would be required for such a mission?". But then I realized the orbital period of 1.1955 years, which leads to a 6.12 year period between consecutive close approaches of Bennu's orbit and Earth's orbit.

Since the asteroid has a longer period then Earth, as do the two Hohmann transfer orbits, one must make (x-1) trips around the sun in (x) years to get back to the Earth ... which I assume is why the OSIRIS-REx mission was a 7 year long mission, which included 3 years at the asteroid....

So the minimum time for an asteroid visiting mission might be much better for an asteroid with about a 2 year period, and might take something like 2.5 years more or less like a mission to Mars using Hohmann transfer orbits. One can save time using more than the minimum Delta-V for the orbit transfers...

• trajbrowser.arc.nasa.gov/… might be informative. Note that the eccentricity of Bennu's orbit means actual transfers are generally quite different from ideal Hohmann transfers. Nov 10, 2021 at 23:55
• @ChristopherJamesHuff thank you very much! That information would easily qualify as a complete answer. There are many 101955 Bennu trajectories that would have a reasonable Delta-V, and some are even a reasonable time mission, where reasonable is about a year. Earth Departure Mar25 2024, $\Delta V=4.36$, asteroid arrival Oct01-2024, $\Delta V=2.2$, Asteroid departure Oct21; $\Delta V=1.77$ Earth reentry Mar25 2025 at 13.06 km/sec. Total $\Delta V=8.33$ Nov 11, 2021 at 14:34
• Starship's $\Delta V$ with 25ktons of cargo is claimed to be 8.30. From the trajbrowser.arc.nasa.gov/… website; there are some missions less than 1.5 years with a $\Delta V\approx 7.2$ If @ChristopherJamesHuff wants, he can answer; else wise I'll combine these last three comments into an answer.... Thanks!!! Nov 11, 2021 at 16:50