This puff piece on Marshall contains a troubling assertion…one which needs to be knocked down before it becomes widely accepted as the gospel truth:
Work to find a propulsion system for a ship to travel through the solar system, a Mars ship, has been underway for the past few years. Using chemical rockets like those that powered the Saturn Five and the Space Shuttle aren’t feasible for a Mars trip. Using cumbersome chemical rockets would make a Mars ship 95% fuel, and the round trip would take nearly two years. What’s needed is something more efficient, and at the Propulsion Center, that something may be electric propulsion.
Someone at Marshall is obviously looking for funding for their pet project, by positioning electric propulsion as a sine qua non for manned exploration of Mars.
Electric propulsion is not needed for manned missions to Mars. Currently available chemical propulsion technology will get humans to Mars in 5-6 months. While it’s sensible to explore long-term advanced propulsion technologies, delaying manned expeditions by another decade and spending tens of billions of dollars on propulsion R&D so that we can shave maybe a month off of the transit time is foolish when we have a serviceable alternative available to us today. As others have noted, it’s akin to asking Columbus to wait to cross the Atlantic until steam-turbine ships became available.
Remember, “not feasible” is not the same as “cannot be done”. And certainly I don’t think they’re advocating sending PEOPLE directly via electric propulsion (spiralling out/in takes too long). But study after study has conclusively shown that you get lower IMLEO by sending the cargo portion of the mission using electric. And since IMLEO is a primary cost driver, and the $$/yr for a Mars mission are limited, the electric vs. chemical trade becomes less clean in terms of how long the program takes.
Of course, if we could get the radiophobes out of the way…
– Eric.
I dunno — I read “aren’t feasible” as “cannot be made to work” rather than “works but isn’t practical”.
But sure, send the cargo via ion drive, or solar sail, or multiple Earth-moon slingshot passes, whatever — so long as it arrives before the crew that intends to use it. And so long as the *desire* for exotic propulsion doesn’t get converted into a *need* which keeps us from sending people there at all. It may be a nice-to-have at some point, but it isn’t required to get us there.