Saturday, March 09, 2013
A few days ago (I think), NASA released a new tool with little fanfare that is simply fantastic, a 'trajectory browser' that lets one plan an interplanetary mission to any planet or asteroid. It looks a tiny bit intimidating at first but is easy to get used to.
Let's start with something simple: a mission to fly by Venus. First I'll unclick NEO, type "Venus" in the custom list, select one-way flyby, launch year 2014 - 2016, max duration 2 years, max delta V 7.0 km/s (delta V is the change in velocity, which then translates into how much fuel you need), minimize delta V (we want this to be cheap), and now search.
Here's the result!
We leave in May 2015 and fly by in October, for a total 120 days to get there. Delta V is 3.45 km/s, and we fly by Venus at a bit over 10 km/s.
What's even more fun is that you can select view to see an animation of the probe leaving Earth and making its way to the destination.
All right, now we want to actually orbit the planet, but we don't need to come back, a typical orbiter mission. Change it to one-way rendezvous, and now we get this result with delta V just over 4 km/s. This time it's a 1.23 year mission leaving in 2014, apparently the best way to arrive there without too much delta V. If we don't care about delta V (we have a larger budget and can use a bigger rocket) we can go with this trajectory, which only takes 80 days (yes, Venus is that close) and delta V is 5.74 km/s.
And finally, a two-way rendezvous mission to Venus in 2015. Once again we don't care about delta V, and end up with 6.98 km/s. The mission goes as follows: leave Earth in June 2015, arrive at Venus September the same year, stay for 20 days, and now it's time to come back on a fairly long trip that does from October until June the next year. Still, that's a total of just 355 days compared to the 501 days for Dennis Tito's planned 2018 Mars flyby (and that doesn't include 20 days in orbit).
And now for something completely different: what would be the quickest asteroid flyby we could manage if we didn't care about delta V? Change some parameters, make max mission duration 0.1 years, and we get a number of results that say 16 days. The first one for example is a mission that starts January 10 2015, and finishes just 16 days later with a flyby of an asteroid that was already fairly close to us. It's pretty easy to arrange such a mission if you don't need to come back, and don't care about a budget.
Now what about the minimum duration for an asteroid rendezvous followed by a return to the Earth? The tool seems to think the minimum duration would be 25 days, once again if we don't care about delta V (if we have a max 7.0 km/s the lowest mission duration is 100 days). That 25-day mission involves leaving the Earth on May 8 2028, flying for 10 days to an asteroid that is flying very close to the Earth, staying for 5 days and then coming straight back for another 10 days. Total delta V is 10.78 km/s which is huge - remember our first Venus flyby which was just 3.45.