View Full Version : Solar Probe Plus

2009-Mar-06, 01:27 PM
Yesterday I got April issue of "Discover" magazine, and naturally tried to figure out which article is April Fools joke. After reading the cover article, about "Solar Probe Plus" to be launched in 2015 and approach within 4 solar diameters from Sun, I was almost certain THAT was the April Fools. To me, the giveaways were "three months travel time to the Sun" and "probe will start with Earth's 18 miles/sec velocity around the Sun, and will shed it using Venus gravity assist". I know that under ideal circumstances, Venus gravity assist will add (or remove) less than a third of that velocity. What article described is flat out impossible.

Still, this morning I googled "Solar Probe Plus". Guess what -- the article was sloppy reporting, but true! The probe is still in early design phase (http://science.nasa.gov/headlines/y2008/10jun_solarprobe.htm?list1065474), so there is no guarantee it will fly in 2015, but that's the plan so far. "Three months travel" is actually time to first perihelion, followed by multiple Venus gravity assists. The probe would take 6.4 years to reach target perihelion of 9.5 soalr radii. Here is detailed information (http://solarprobe.gsfc.nasa.gov/SolarProbe+ME.pdf) (a 39 megabytes PDF).

2009-Mar-06, 02:27 PM
9,5 solar radii? wow. that is quite close.

2009-Mar-06, 08:48 PM
Cool, that's 6.6 million km, right?

I wonder is that the closest thing we've ever sent to the Sun, or has any other probe gone by closer?

I calculate that at that distance the probe will be receiving 700,000 watts per m^2, (compared to ~1,400 w/m^2 in Earth Orbit).

Just looking through the PDF, it seems to say that the surface of the craft will reach ~1,700 degrees k (if I'm reading it right), now that's hot!

2009-Mar-06, 09:02 PM
Yes, it will be by far closest approach to the Sun. So far the record is held by US-German Helios probes (http://en.wikipedia.org/wiki/Helios_probes) -- 0.3 AU, or about 45 million km.