NASA's 'Inspirational' Mars Flyby

astroengine writes "The idea of slingshotting a manned spacecraft around Mars isn't a new one. In the 1960's, NASA carried out a feasibility study into an 800-day flyby mission to the Red Planet. And it would have been awesome. AT&T/Bellcomm mathematician A. A. VanderVeen was working for NASA in 1967 and came up with 5 possible launch opportunities between 1978 and 1986 — two windows in 1979 and 1983 provided the shortest transit time between the planets. But launch mass and fuel requirements were a constant issue. So VanderVeen turned to physics to find an elegant, and scientifically exciting, solution: add a Venus flyby to the Mars trip. Mars, Earth, and Venus align with the sun five times every 32 years, but Venus and Mars alignments happen more frequently making double (Earth-Venus-Mars-Earth) or even triple (Earth-Venus-Mars-Venus-Earth) flybys a viable mission. Unfortunately, the flyby never happened."

Comments

Re:About launch mass

[DerekLyons]

I never completely understood the need of launching massive ships from Earth whenever we want to leave it. Whenever we wanted to travel the seas, we did not build a massive caravel inland then painstakingly dragged it all the way to the coast. We reasoned it made more sense to build it in a dry dock, that way it only requires a tiny push to get it into the ocean.

I can't tell if you're actually that stupid or if you're pretending to be stupid to make a point. I mean seriously, you can't grasp the difference between a shipyard (dry dock) that you workers can walk to and needs no especial support - and LEO where everything comes with a launch price cost tagged onto it?
 

Wouldn't anyone at NASA think that making a "Space Dock" made sense?. Make a bunch of tiny trips to lower earth orbit and build the ship there, so you can make a larger ships to travel further. Mass would not be such a big issue (granted, fuel would be), but at least the escape velocity problem would be non-existent.

No, space docks don't make any sense - they don't save you any money, in fact they cost you *more* because of the need to support your assembly on orbit. Mass is still a big issue because you have to pay to boost it. Escape velocity is still a problem, because you still need to boost the fuel to LEO and the mass of your spacecraft beyond LEO.
 
Yes, eventually we're going to have to face the on-orbit assembly issue, but we're a long way from that. We're still in the 'canoe' phase - which you *can* build inland and carry to the water.

Re:About launch mass

[FatLittleMonkey]

The problem is that working in space is hideously expensive. So that the cost of engineering out as much mass as possible to allow you to do everything in a single launch is, bizarrely, cheaper than launching a bunch of heavier-but-simpler-&-cheaper parts to assemble in orbit. For example, right now we can't even launch ship and fuel on separate rockets, which seems a pretty basic skill for a space-faring civilisation.

As we do more in orbit, particularly as private companies actually start operating human-space-flight (even if it's just to provide in-orbit services for NASA/DOD/ESA/JAXA/CSA/etc), we should see techniques developed to make operations in space cheaper. At some point we'll reach the cross over where assembly is always cheaper than single-launch. After that, someone will inevitably start building a "space-dock".

It's like reusable launchers. Logically, using a launch vehicle 100 times should be cheaper than using it once and throwing it away; look at aircraft, who would build a single-use plane? But so far we haven't been able to figure out how to make refurbishable craft cheaper than disposable ones.