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Posted by: Toma B Jan 24 2006, 08:43 AM

There was statement that recently launched New Horizons is the fastest spacecraft to leave Earth. The velocity was 16.2 km/s relative to the Earth according to "Jonathan's Space Report".

So:
New Horizons is fastest to leave Earth at 16.2 km/s (relative to Earth).
Voyager-1 is fastest to leave Solar System at 17.374 km/s (relative to Sun).

Now that is OK. but what is this?
Today's "Astronomy Picture of the Day" features launch of New Horizons and in text bellow image is one particularly interesting link to "Guinness world of records"...
http://www.guinnessworldrecords.com/content_pages/record.asp?recordid=46995
There "Mr. Guinness" claims that the fastest spacecrafts ever, were two Solar probes "Helios 1&2"...According to him those spacecrafts had speed of 252,800 km/h which is staggering 70.2 km/s...BUT RELATIVE TO WHAT?????
Can somebody explain this?

Posted by: ugordan Jan 24 2006, 08:53 AM

It's all relative...

Personally, I wouldn't get that much excited about the "fastest ever" claims.

Posted by: Alan Stern Jan 24 2006, 09:01 AM

Relative to the Sun, I suspect. They were in very tight solar orbits.

Posted by: edstrick Jan 24 2006, 10:21 AM

The fastest spacecraft ever, relative to what it's primarily interacting, may well have been the Galileo entry probe. The 70 km/sec figure would have been heliocentric orbital speed at perihelion, I presume...well inside Mercury's perehelion.

A more significant "figure of merit" would have been the toltal "Delta-V" of a spacecraft due to powered flight.

Posted by: odave Jan 24 2006, 02:52 PM

Here's a pointless activity for the space sim jocks - though after hearing about http://www.cnn.com/2003/TECH/ptech/07/02/popsci.stereo.kill/ I know that people do invest a lot of time in apparently pointless activities.

If you wanted to build and launch a spacecraft with the sole purpose of exiting the solar system and beating Voyager 1's sun-relative speed, what combination of today's launch vehicles and gravity assists would you use, given a spacecraft mass equivalent to V1?

I'd fiddle about with it myself, but I think the learning curve would outstrip the amount of free time I have.

Posted by: ljk4-1 Jan 24 2006, 02:59 PM

A solar sail vessel could pass Pluto's orbit in just five years and outdistance Voyager 1 shortly after that. It could reach the nearest star in "only" a thousand
years or so. And this is just with solar light. With a powerful enough laser... fuggedaboutit.

http://www.planetary.org/solarsail/faqs.html

Posted by: tasp Jan 24 2006, 03:15 PM

I can't find the thread here right now, but the manhole cover blasted with a nuke might rate a mention in this thread.

Posted by: ljk4-1 Jan 24 2006, 03:24 PM

Here ya go:

http://www.unmannedspaceflight.com/index.php?showtopic=1955&hl=manhole

How much of that manhole cover could have survived into space anyway?

Posted by: ugordan Jan 24 2006, 03:47 PM

The shortest answer is : probably nothing. It was moving so fast and in the densest part of the atmosphere that even if it somehow survived being vaporized by friction, it would likely have fallen back down some distance away, probably not reaching very high up in the first place.
Keep in mind just how powerful friction is even up there, tens of kilometers up in the atmosphere where all those meteors get disintegrated, let alone here at the surface...

Posted by: RNeuhaus Jan 24 2006, 03:57 PM

Ulysses still holds as the fastest escape velocity from Earth: 15.17 km/sec versus to NH 12.3 km/sec relative to Earth.

Fastest Earth Departure Speed
The fastest escape velocity from Earth was 54,614 km/h (34,134 mph), achieved by the ESA Ulysses spacecraft after deployment from the Space Shuttle Discovery on October 7, 1990. It was en route to an orbit around the poles of the Sun via a fly-by of Jupiter.


http://www.guinnessworldrecords.com/content_pages/record.asp?recordid=46996

Ulysses was launched by the Space Shuttle Discovery on 6 October 1990 at 11:47:15 UTC. The Payload Assist Module (PAM-S) which propelled Ulysses away from the Earth toward Jupiter.

Rodolfo

Posted by: PhilCo126 Jan 24 2006, 05:12 PM

I guess it's pretty difficult to come up with the current speed of the Voyagers and Pioneers ( via Radio doppler but their signal is very faint ) ... but shouldn't we take the distance Earth-Moon as basic measurement?
( Apollo CSM did it in 90 Hours, Pioneer 10 in 11 hours, New Horizons in 9 hours ... don't know about the Helios spacecraft )

Posted by: remcook Jan 24 2006, 05:37 PM

"I guess it's pretty difficult to come up with the current speed of the Voyagers"

http://voyager.jpl.nasa.gov/mission/weekly-reports/index.htm

Posted by: Alan Stern Jan 24 2006, 06:23 PM

NH left Earth at 16.2 km/sec.

Posted by: djellison Jan 24 2006, 08:53 PM

Who's up for Top Trumps. I think Alan just won.

Doug

Posted by: BPCooper Jan 24 2006, 09:14 PM

NH is fastest to be propelled away from Earth. The other probes got it from other gravity weels (Helios from the Sun). NH will not exceed Voyager's speed, which it obtained during its flybys.

Posted by: Bob Shaw Jan 24 2006, 11:06 PM

Doug:

Not fair! Alan had his own rocket!

Bob Shaw

Posted by: David Jan 24 2006, 11:27 PM

Er... and you were stuck with one you made out of a soapbox?

Posted by: djellison Jan 24 2006, 11:55 PM

My Estes two-stage Mongoose would shame an Atlas V any day of the week

Doug

Posted by: ljk4-1 May 2 2006, 06:18 PM

Via Solar Array to the Outer Planets

New Scientist is covering the work of Rudolph Meyer (UCLA), who envisions a vehicle that sounds for all the world like a cross between a solar sail and an ion engine. And in a way, it is: Imagine a flexible solar panel a solid 3125 square meters in size, and imagine this ’solar-electric membrane’ weighing no more than 16 grams per square meter, far lighter than today’s technology allows. I’ll be anxious to see the paper when it’s published in Acta Astronautica, but the gist of the design seems to be this: the solar membrane would power an ion engine array which, conventionally enough, draws xenon ions through a powerful electric grid to create thrust.

The membrane, stabilized by additional ion engines at the corners, could reach remarkable speeds. Meyer talks about 666,000 kilometers per hour — that’s one year to Pluto, and an obvious invitation out into the Kuiper Belt. No show stoppers here, but clearly a design heavily dependent on advances in thin film arrays. I always listen to Geoffrey Landis (NASA GRC) about such matters; he is, after all, the man Robert Forward declared to be his successor in interstellar studies. And Landis is quoted as saying of Rudolph’s idea, “…the extremely high-energy ion-propulsion vehicles he proposes may be a practical alternative technology for future missions to the edge of interstellar space.”

Full article here:

http://www.centauri-dreams.org/?p=638

Posted by: djellison May 2 2006, 06:28 PM

Yes - but how long to accelerate to 666000 kph ?

Doug

Posted by: ljk4-1 May 2 2006, 06:34 PM

I don't know. If anyone can find the paper or even just more
information on the plan, please post it here, thanks!

Posted by: Bill Harris May 2 2006, 07:11 PM

...but, as importantly, how long to decelerate from 666000 kph ?

--Bill

Posted by: tty May 2 2006, 07:38 PM

Also the payload would probably have to have some kind of spaced multiple shielding. At 185 kms-1 even micrometeorites would be deadly.

tty

Posted by: dvandorn May 2 2006, 08:12 PM

Yeah -- you'd end up with a pretty ragged, hole-ridden sail/solar panel by the time you got out to the Kuiper Belt. How are you going to create a really, really thin/lightweight sail/solar panel that can stand up to the high-energy dust impacts it's going to face? Gonna redirect some of that energy into intense magnetic fields that divert dust particles electrostatically?

Before we get too involved in discussions of new propulsion technologies, I will make the cautionary noise, here, that when Mike Griffin went before Congress last week, he was asked point-blank about new propulsion technology research. He said that NASA's immediate goals (including the full range of VSE goals) do not require any new propulsion technologies. He said that almost every NASA program, with the exception of the Shuttle/ISS wind-down, has been cut or delayed, including propulsion technology research. He said that there will be *no* new propulsion research for a decade or more.

BTW, he also said that, since Congress and this Administration refused to give NASA any additional monies to repair damage to Michoud, the Stennis Space Center, and the Kennedy Space Center incurred during last year's hurricane season, he was even stealing from the Shuttle/ISS funds to cover a roughly half-billion-dollar repair bill.

-the other Doug

Posted by: ljk4-1 May 2 2006, 09:19 PM

What a frightening and depressing statement. Does Griffin think that just
because he won't let NASA engineers and space scientists develop new
concepts of propulsion that other equally talented and visionary people
in other countries won't pursue this course? Or that he might drive US
talent to more receptive places?

The next time I hear Griffin or anyone else say that the USA must remain
at the forefront of space exploration and technology, I will remember this
statement.

It will be sadly ironic if in 2025 we have a handful of astronauts on the
Moon while the other space nations are sending probes to every planet
in the Sol system and beyond.

Posted by: djellison May 2 2006, 10:08 PM

He has no money. Having been told to do X things, by date Y with Z dollars he has no options left but to cull a lot of other programs. It sucks, it is very wrong, but it is the only thing that he can do given the parameters than have been handed down to him from on high.

Doug

Posted by: Stephen May 3 2006, 01:41 AM

Why blame Griffin? These engineers and space scientists cannot develop new concepts of propulsion if Congress won't provide NASA with the funding necessary to allow them to proceed.

Unless, of course, you would prefer Griffin take more money from (say) space science to make up the shortfall.

Well, America has already sent probes "to every planet in the Sol system and beyond", has it not? By sending probes out to those same planets those other space nations would merely be catching up.

What I presume you *really* mean--if, that is, those other nations are really going to steal a march on America--is that by 2025, when America (may) have "a handful of astronauts" plodding around on the Moon (much as once upon a time it had a handful paddling around in LEO aboard the ISS--until it was decided LEO was too boring a place and the Moon a more exciting destination) those other nations were planning to send astronauts of their own to destinations more exciting than the boring old Moon: "every planet in the Sol system and beyond".

That may well happen. After all, once upon a time Spain and Portugal led the way in Europe's exploration of the world, finding routes around the Cape of Hope to India and across the Atlantic to the New World. Yet eventually they were eclipsed by other European nations such as France and Britain. America (and Russia) would be merely following in their footsteps by commencing the world's exploration of outer space only to be eclipsed in time by johnny-come-latelies.

======
Stephen

Posted by: ljk4-1 May 4 2006, 11:40 AM

My concern is that the VSE is going to become Apollo Mark 2, where it takes
away resources for real science missions just to put a few extra humans on
the Moon for slightly longer stays.

Then the politicians of 2020 or so decide it is not worth the effort, or the public
gets bored again, or both, and we end up with a few more flags and footprints,
the Moon is abandonded for another 40 years, manned Mars missions get
pushed even farther into the distant future, and robotic planetary missions
lose the momentum they had regained in the 1990s and 2000s. All for yet
another stunt to show the world just how great the USA is.

Posted by: djellison May 4 2006, 11:49 AM

'going to become'

It's already happened.
http://planetary.org/programs/projects/sos/

Doug

Posted by: Stephen May 5 2006, 06:56 AM

That sounds an awful lot like the grumbles you used to find (and maybe still find) on Usenet about the Apollo missions not being real science missions, usually from those seeking to show how unmanned missions do "real science" ever so much better.
If the VSE were only "another stunt to show the world just how great the USA is" America would not be sending people back to the Moon. It would be sending them straight to Mars instead.

The real danger from the politicians to the VSE (IMO) is that:

1. They may wind it back before the first CEV is even sent to the Moon (much as their funding cuts forced changes to the Shuttle and the ISS).
2. If the Moon is reached, the politicians--be it the president or Congress or both--may give NASA an unwelcome choice: you can keep going to the Moon or you start heading to Mars, but not both at the same time.

That last choice is arguably what happened to Apollo. The Apollo program died because America was not prepared to pay for a manned lunar program *and* the development of the Shuttle at the same time. NASA was allowed to do one or the other but not both. That naturally meant an invidious choice had to be made.

Compare that to the present situation since the VSE was announced. NASA is presently in more or less the position it would have faced in 1972 had the Shuttle been given the go-ahead while at the same time it has also been authorised to keep sending Apollo missions to the Moon for a few years longer--*but* without being given the funding necessary to fully cover both. It goes without saying that one consequence would surely have been that other NASA programs, especially expensive unmanned ones like Viking and Voyager with no connection to Apollo or to the Shuttle, would have been hit as NASA took funding from them to make up the shortfall in the Shuttle and/or Apollo programs.

======
Stephen

Posted by: ljk4-1 May 8 2006, 02:54 PM

G. Landis had a similar idea to Meyer's one year to Pluto drive in 1989.


The Landis paper online:

http://www.sff.net/people/geoffrey.landis/lightsail/Lightsail89.html


The Centauri Dreams article:

http://www.centauri-dreams.org/?p=652

Posted by: ugordan May 8 2006, 04:04 PM

As Arthur C. Clarke used to point out - when something hits you in space, it doesn't really matter whether it's travelling at 10 or 1000 km/s. Either way, you're toast

185 km/s probably doesn't require additional shielding. You just have to hope that every dust grain that hits you is microscopic. If it's not -- you'll buy the farm anyway.

Posted by: djellison May 8 2006, 04:06 PM

Well - consider a 1 gramme projectile at 10km/sec - that's 50,000 joules of energy

Consider it moving at 185 km/sec - that's 17112500 joules, or 342 times as much (i.e. 18.5 ^2 )

Doug

Posted by: ugordan May 8 2006, 04:13 PM

That's true, but consider what are the odds of flying into a one-gram chunk (assuming you're not flying by a comet - in which case 200 km/s doesn't give you a big science op)? Present multi-layer protective blankets are IIRC designed to withstand micron-sized (or whatever) dust impacts. A 1-gram dust grain would punch through the shielding in both cases and would potentially be disastrous to the s/c. IMHO, it would be unfeasible to add shielding mass such that it would specifically protect the s/c against such large and statistically unlikely impacts.

Which reminds me of "whipple-shields" used on Stardust - how large impactors were they designed to hold?

Posted by: djellison May 8 2006, 04:16 PM

I wasn't suggesting we would encounter 1 gramme particles - I was just using that as a simple figure from which to demonstrate the way the energy ramps up with the square of the velocity.

Doug

Posted by: ugordan May 8 2006, 04:19 PM

You mean velocity?

Posted by: djellison May 8 2006, 04:23 PM

Oop- yes

Doug

Posted by: DonPMitchell May 10 2006, 10:37 PM

I believe it is the case that it takes far more energy to send a probe to the Sun than it does to send a probe out of the solar system. The third cosmic speed is about 17 km/sec. But to cancel the Earth's orbital speed and fall into the Sun would require reaching about 30 km/sec.

Posted by: mchan May 11 2006, 01:49 AM

If one were not permitted to cheat and use one or more gravity assists.

Posted by: Phil Stooke May 11 2006, 03:18 AM

No, that would just be the method.

Phil

Posted by: djellison May 11 2006, 07:46 AM

Yes - it seems unintuitive at first, but the number of flybys and the fuel mass ratio of Messenger show just how difficult Mercury is.

Doug

Posted by: edstrick May 11 2006, 11:03 AM

"...square of the velocity...."

When we're dealing with speeds of tens of kilometers per second, I'm inclined to think of the kinetic energy in terms of the "square of the ferocity"!

Zip-CRUNCH!

Posted by: mchan May 11 2006, 08:41 PM

I had interpreted "energy" in the post as the C3 "energy" for injecting into a solar orbit. The C3 for a direct trajectory to intersect the Sun's surface is greater than, say, a VEEGA trajectory to a Jupiter gravity assist back towards the Sun. I hesitate here because I don't know if it is possible to get the required inflection without going into Jupiter's atmosphere.

Posted by: Bob Shaw May 11 2006, 09:23 PM

You can actually get *very* close to the 'surface' of Jupiter and still be out of it's atmosphere, the pressure of which drops of rapidly with altitude (unlike, say, Mars). Of course, if you get it wrong, it's a problem...

Bob Shaw