Is Helios 1 really the fastest object ever made by man?

[fsgregs]

Hi all. Last week, I discovered an entry on the Guinness World Records website claiming that Helios 1 achieved a speed of 252,800 km/hr in 1976, during one of its orbits of the Sun. (see http://www.guinnessworldrecords.com/), go to the science page and locate the link to fastest spacecraft). That makes it by far, the fastest object ever built by man.

According to NASA, however, the fastest spacecraft and fastest man-made objects are the Voyager spacecraft, which are traveling at about 50,000 km/hr out of the solar system.

In fact, I have searched on Google and failed to find any other collaborate reference to Helios being the fastest object ever made by man. If it is true, I want to incorporate it into my educational activities. It is obviously a fascinating fact and is 4 times faster than Voyager. If it is false, I am surprised Guinness would include it. They are supposed to be strict in posting their world record claims.

Any thoughts, anyone?



Frank

[granthutchison]

Frank:
I've never understood this claim that the Voyager probes are moving faster than anything ever built. You've got to ask "Relative to what?"
The figure of ~50000km/hr is for "departure from the solar system", and you'd think that would be quoted relative to the Sun, as the stable centre of the solar system. But the Earth is 150 million km from the Sun and goes around once a year (~8766 hours). 2 times pi times 150 million kilometres divided by 8766 hours reveals that, almost without exception, every object ever built by man travels twice as fast relative to the Sun as the Voyager probes are currently moving.

The Helios satellites got to be the fastest because they made the closest approaches to the Sun. They followed orbits with aphelia ~1AU and perihelia ~0.3AU: that's a semimajor axis of 0.65AU and an eccentricity of 0.54. Mean velocity is sqrt(GM/a), which comes out to be 37km/s = 133200km/hr, and perihelion velocity is sqrt(1+e) times that, or ~165300km/hr. Hmmm. From that, I'd guess that the Guinness figure is quoted relative to the Earth, at some time when Earth and Helios 1 were almost opposite each other during the satellite's perihelion passage - Earth going 100000km/hr one way, and Helios hitting 165300km/hr in almost the opposite direction would bring the vector sum out comfortably in the vicinity quoted by Guinness.

Grant

[fsgregs]

Grant:

Wow, that relativity perspective is mind-boggling. Of course you are right. I never really thought about it in relation to Voyager. I presume NASA wanted Voyager's speed relative to a "stationary" Earth, or perhaps the speed is supposed to be relative to the Sun. Frankly, I haven't a clue. Thanks for straightening us all out about the relative speed of things.

In summary, it does look like Helios may be the fastest man-made object relative to the Earth ever built.

Ah, Einstein ... why did you have to open this can of worms? It was so much simpler when everyone thought the Earth was the center of all things!

Regards,

Frank

[maaf]

Perhaps what was meant by the statement that the Voyager is the fastest ever man built probe is that it's the probe with the largest specific mechanic energy (it is, energy per unit mass) ever built, which means it's the probe that will have the largest residual speed after it has completely escaped from the Solar System.

But it isn't so much remarkable, since most of currently Voyager kinetic and gravitational potential energy was stolen from planets during swing-by maneuvers.

[Cormoran]

Fsgregs,

Um....the one to blame is Galileo, I think..... or Kepler.....or Tycho Brahe...or possibly some greek fellow....

Don't blame Uncle Albert for it....

Cormoran

[fsgregs]

Hi Cormoran:

My reference to Albert was about his advancement of Relativity, although I admit it does read like I was attributing him with the Heliocentric theory. Sorry for any confusion.

Strange, but I just ran across a reference that gives Eager Allan Poe credit for "first" making reference to space, time and matter as "relative" to one's position. It was on public radio and I tuned in too late to catch everything said, but Poe apparently in some writing, did point out some of the ideas regarding relativity that Einstein later more fully developed.

Interesting ... very interesting

Frank

[granthutchison]

The simple idea of "relative motion" is much older than Einstein and Poe, and goes back at least as far as Galileo, who asked his readers to imagine various experiments carried out on dry land and then on a ship sailing across a calm sea, precisely to demonstrate that things at motion in one frame of reference may be at rest (or in a different state of motion) in another.

Grant