Fastest probe.

[qso1]

I've seen a few postings on New Horizons in which its stated that it is the fastest unmanned probe to date. I responded to one thread in which I mentioned one probe reaching 107,000 mph as I recalled, it was the probe that went into Jupiters atmosphere as part of the Galileo mission. I recalled a solar probe in the mid 70s called Helios. I could recall a speed of 145,000 mph but since I could not verify that, I didn't mention it. I cannot find that thread now. I was unable to supply a source until now.<br /><br />The Helios probes are the record holders of the fastest manmade objects. The 40 some thousand mile an hour velocity for NH may be the fastest Earth escape velocity of an unmanned craft.<br /><br />That I did point out because these days, the mainstream media does not fact check as much on space exploration reporting as it once did. And indeed, according to the link, the Helios probes hold the record by far...158,000 mph.<br /><br />http://www.guinnessworldrecords.com/content_pages/record.asp?recordid=46995 <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[john_316]

How fast will New Horizons be once it gets the Jupiter Gravity assist?<br /><br />Will it reach 158,000 mph or more?<br /><br />I sure don't know and I dont know how fast its going at the moment either. <br /><br /><img src="/images/icons/smile.gif" /><br />

 

[henryhallam]

<font color="yellow"><br />How fast will New Horizons be once it gets the Jupiter Gravity assist?<br /><br />Will it reach 158,000 mph or more? <br /></font><br /><br />No, nowhere near that fast. (Although the peak velocity at closest approach to Jupiter will probably be fairly high)<br /><br />The record of "fastest unmanned probe to date" is referring to the inital speed upon Earth departure.<br /><br />Helios holds the speed record because it had a perihelion which was relatively close to the sun, something like 0.3AU IIRC. As we all know, the lower your orbit is at periapsis, the faster you go when you are at periapsis.<br /><br />Similarly the Jupiter entry probe that Galileo released built up speed as it approached very close to (and even "inside") Jupiter.

 

[mlorrey]

The origins of the statement are likely that NH is the fastest to reach the edge of the solar system. If you'll recall, the Pioneer and Voyager probes spent time doing flybys of Saturn and the other jovians (in the case of the Voyagers), while NH is going directly to Pluto after a speedup flyby of Jupiter. Also note that at the time of the flyby of Jupiter, the NH probe will pick up several km/sec. Wikipedia has this to say about the 'fastest probe ever' claim:<br /><br />"Once it receives a gravity-assist from passing Jupiter, it will be the fastest spacecraft ever launched. The record-holder prior to New Horizons is Voyager 1, currently traveling at 17.2 km/s (38,400 mph) relative to the Sun. Other spacecraft, such as Helios 1&2, can also be measured as the "fastest" objects, due to their orbital vectors relative to the Earth at launch. But, because they remain in solar orbit, their velocity relative to the sun is slower than the five probes, including New Horizons, that achieved solar escape velocity (and overcame a far more massive gravity well than Earth's)."<br /><br />So, as Helios was faster wrt Earth, they both went downhill, passing inside the orbit of Mercury. Going downhill is always easier than uphill..

 

[bpcooper]

NH is the fastest launched spacecraft in history. It was propelled away from the Earth faster than any, i.e.<br /><br />It will not, however, reach the speeds of Helios, or that of and subsequently pass Voyager (but it will pass Pioneer 10/11). <br /><br />Voyager is the fastest on escape, having picked up its speed from flybys of the largest planets. <div class="Discussion_UserSignature"> <p>-Ben</p> </div>

 

[CalliArcale]

Eh, it's all relative. <img src="/images/icons/wink.gif" /><br /><br />That is, of course, the stickler in these sorts of records. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[qso1]

A minor correction of my own post here:<br /><br />I did mention 145,000 mph for Ullyses in the original posting I did on this subject. I meant to say Helios and later found Helios had achieved 158,000 mph according to Guiness folks.<br /><br />Like CalliArcale said, its all relative. Mainly because when these speeds are reported, its almost never reported as to what they are relative to (Earth, Sun, Jupiter?). <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[waxy]

As einstein would probrably say...<br />The New Horizens is holding still, the solar system is spinning<br />and moving around it.<br />

 

[vogon13]

Another way of stating this (I think) :<br /><br />What's the lightest spacecraft launched on the largest rocket?<br /><br />IIRC, Voyagers were launched on Titan IIIC, Helios the same, and New Horizons on a severely souped up Atlas.<br /><br />The Voyagers massed around a ton, while Helios I and II and New Horizons were about half that.<br /><br />Earth departure speed would seem to be the more relevant criteria (to me at least). That the Galileo probe accelled a great deal as it plunged into the atmosphere of Jupiter is on par with the Helios crafts at perihelion.<br /><br />In my view in light of all this, it seems NH is the winner, but I would grant a caveat that others would look at this from their own perspective.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[nexium]

" fastest Earth escape velosity" I'm not sure what that means. Long ago, someone wrote that the escape velosity from Earth's surface is 39,000 miles per hour. If you are at L1 or L2, escape velosity (from L! or L2) is only a few hundred miles per hour if you pick the right time and right direction. Occasionally L1 is going the same speed as Earth's equator, rarely more than 2000 miles per hour different than the closest point on Earth's equator.<br />If our space craft is going toward the sun at 5000 miles (or most any other speed) per hour and it is crossing Pluto's orbit, we might say it is below Earth's escape velosity, as it will hit Earth sometime in the far future if it does not hit something else first, or get an orbit change. For most other directions at 5000 miles per hour with respect to Pluto's orbit, it will never hit Earth, unless it's orbit is perturbed. Pluto's orbit is moving less than 1000 miles per hour with respect to the center of the sun. Likely all orbits of planets in our Solar System are moving less than 1000 miles per hour with respect to the center of the Sun. Please refute, comment and/or embellish. Neil

 

[henryhallam]

The minimum escape velocity from the Earth's surface is about 11200m/s (about 25000 mph). If you give an object some "upwards" speed and throw it away from the Earth, it will obviously slow down as it is attracted by the Earth's gravity. This is why a ball will come down again if you throw it in the air. The deceleration decreases the further away the object gets. If it is initially thrown at anything less than 11200m/s then at some point its speed will decrease to zero and it will start to fall back down again. If it is thrown at exactly 11200m/s, it will reach zero speed at "infinite" distance. There is nothing to stop you throwing it faster if you want to get somewhere in a hurry!<br /><br />The "fastest Earth escape velocity" means simply that New Horizons is the mission which left Earth at the highest initial speed. It is no more complicated than that.