Huygens Space Probe

[noz92]

On Saturday, 15th January, at 2:00 GMT, the European Space Agency's (ESA) Huygens space probe will land on Saturn's moon Titan.

 

Previously, NASA's Cassini probe flew by Titan, getting a faint glimps of the planets surface, in which geologists believe to be similar to a young Earth. Cassini, carrying Huygens, will drop it's important cargo down to Titan's mysterious surface.

 

For more information on the landing, visit NASA.gov. If you would like to view the landing as it happens, the Science Channel will be showing it live on Saturday a 2:00_A.M. GMT.

[ed84c]

hurrah for huygens!

 

i see nasa havent sabotaged our atempts this time................

 

anyway can i see the science channel over the web?

[Ophiolite]

You can watch NASA TV:

http://www.nasa.gov/multimedia/nasatv/MM_NTV_Breaking.html

[Ophiolite]

The first three photographs show stream beds, a coastline, and a rubble strewn plain that could be Mars or Venus.

http://www.nasa.gov/mission_pages/cassini/main/index.html

[ed84c]

Oh hell its mars allover again.....

 

and can someone tell me wtf is a hypherion?

[Ophiolite]

Helios was the sun god, who pulled the sun across the sky with his chariot. His parents were the Titans Hypherion and Thea, and he had two sisters: Selene, the moon goddess and Eos, goddess of the dawn.

 

http://www.in2greece.com/english/historymyth/mythology/names/helios.htm

 

 

 

Unless you meant Hyperion:

 

http://www.solarviews.com/eng/hyperion.htm

[noz92]

I checked and for some reason NASATV isn't showing it. Instead they'll be showing a program entitled This Week on NASA; Education File with Bill Nye the Science Guy (what every happened to that show anyway?). I guess NASA only shows things that they work on.

 

Does anybody know why NASA's Cassini is carrying the ESA's Huygens?

[Ophiolite]

We have money, you have rockets.

The two cameras were made by JPL.

 

We had a one hour program from ESA HQ interviewing the project scientists. The guy responsible for the penetration experiment said it revealed the surface had the consistency of Crème Brule (with a thin crust).

[coquina]

Congrats to all who participated and made this one a success. I cannot imagine waiting 17 years to see whether a project would succeed or fail.

 

This is just so cool. It brings back memories of when I made parts in my dad's shop that landed on the moon. (OK, ok, I didn't make them, but I filed the burrs off the damned things.)

[ed84c]

Anyone know (for those of us with terrestrial tv) where we can get live/ not live footage of the touchdown, and other wheeling around on titan? Also downloadable sounds from the mic?

[5614]

here:

http://saturn.jpl.nasa.gov/home/index.cfm

 

its the NASA site... images/videos etc

[5614]

oh yeah.... and here:

http://www.esa.int/SPECIALS/Cassini-Huygens/

is the european space agency site

[ed84c]

Anybody know what speed these probes travel at?

[5614]

http://www.esa.int/SPECIALS/Cassini-Huygens/SEMQ1QQ3K3E_0.html

During the following three minutes Huygens had to decelerate from 18 000 to 1400 km per hour.

 

A sequence of parachutes then slowed it down to less than 300 km per hour.

[ed84c]

ok 18 000 then hmmm thats about 10 000 mph

[ed84c]

any idea to what sort of time scale it had to get to 10,000 mph? i mean interms of acceleration

[Ophiolite]

Here are some relevant quotes and links:

 

Huygens is scheduled to reach Titan’s upper atmosphere at about 10:06 CET on 14 January, entering the atmosphere at a relatively steep angle of 65° and a velocity of about six kilometres per second.

http://www.esa.int/SPECIALS/Cassini-Huygens/SEMMDOQ3K3E_0.html

 

 

To gain sufficient velocity to reach Saturn, they had to conduct four gravity-assist manoeuvres by flying twice by Venus, once by the Earth and once by Jupiter. On 1 July, Cassini-Huygens eventually became the first spacecraft to enter an orbit around Saturn.

http://www.esa.int/SPECIALS/Cassini-Huygens/SEMVR53AR2E_0.html

 

 

The descent through Titan’s atmosphere is carefully choreographed, with a series of parachutes deploying at certain intervals to slow the probe’s downward trajectory.

http://www.space.com/searchforlife/huygens_titan_041223.html

 

This link does not give velocities, but is a fascinating look at the orbital paths of Cassini.

http://orbits.esa.int/orbits/science/app/cssn.htm

 

 

A Hohmann transfer to Saturn would require a total of 15.7 km/s delta V, which is not within the capabilities of our current spacecraft boosters. A trip using multiple gravitational assists may take longer, but will use considerably less delta V, allowing a much larger spacecraft to be sent. Such a strategy was used on the Cassini probe, which was sent past Venus, Venus again, Earth, and finally Jupiter on the way to Saturn. The 6.7-year transit is slightly longer than the six years needed for a Hohmann transfer, but cut the total amount of delta V needed to about 2 km/s, so much that the large and heavy Cassini was able to reach Saturn even with the small boosters available.

http://en.wikipedia.org/wiki/Gravitational_slingshot

[ed84c]

also what powered it?

[Ophiolite]

Browse through the esa links provided. You will find answers to questions you haven't even thought of yet.

[Martin]

Here are some relevant quotes and links:

...

...

 

To gain sufficient velocity to reach Saturn' date=' they had to conduct four gravity-assist manoeuvres by flying twice by Venus, once by the Earth and once by Jupiter. On 1 July, Cassini-Huygens eventually became the first spacecraft to enter an orbit around Saturn.

http://www.esa.int/SPECIALS/Cassini-Huygens/SEMVR53AR2E_0.html

 

.....

A Hohmann transfer to Saturn would require a total of 15.7 km/s delta V, which is not within the capabilities of our current spacecraft boosters. A trip using multiple gravitational assists may take longer, but will use considerably less delta V, allowing a much larger spacecraft to be sent. Such a strategy was used on the Cassini probe, which was sent past Venus, Venus again, Earth, and finally Jupiter on the way to Saturn. The 6.7-year transit is slightly longer than the six years needed for a Hohmann transfer, but cut the total amount of delta V needed to about 2 km/s, so much that the large and heavy Cassini was able to reach Saturn even with the small boosters available.

http://en.wikipedia.org/wiki/Gravitational_slingshot

 

....

This link does not give velocities, but is a fascinating look at the orbital paths of Cassini.

http://orbits.esa.int/orbits/science/app/cssn.htm

 

this is so elegant.

 

instead of boosters and onboard thrust having to change the speed by a total of 15.7 they were so adept at using gravity-assist that they got it down to only 2 km/sec!

 

the same strategy was used with Gallileo (to Jupiter and Jovian moons)----the mission was originally funded to reach a nearby goal with no idea of going to Jupiter (and the resources for propulsion were accordingly very limited) but they figured out that with barely more "push" than needed to get to Venus they could get to Jupiter, so they re-planned the mission using gravity assist.

 

Gallileo used essentially the same sequence of flybys! To get to Jupiter it used its fuel to SLOW itself so it would fall IN towards Venus----then passing twice by Venus, once by earth, and one very close flyby of Jupiter to get into a highly elliptical orbit around Jupiter.

 

Later Gallileo used flybys of the moons to round the ellipse out, by gravity assist as well. But the main sequence of gravity assist maneuvers (twice Venus, plus Earth, plus Jupiter) is what I wanted to point out because it is very similar to what is described for Cassini trip to Saturn.

 

An obvious difference though is that Gallileo was using Jupiter gravity to catch up with Jupiter (by falling in very close and slowing down) whereas Cassini was doing the more intuitive "slingshot" of falling in close and speeding up. But both plans used Jupiter gravity to save on Delta Vee.

[Martin]

This link does not give velocities' date=' but is a fascinating look at the orbital paths of Cassini.

http://orbits.esa.int/orbits/science/app/cssn.htm

 

http://en.wikipedia.org/wiki/Gravitational_slingshot

 

that esa link gives a nice animation, and you can set the date so if you set it to be sometime around May 1998 you see it get a gravity assist from Venus

after you type in some date then it starts from there and advances rapidly from day to day----showing positions of probe and all the planets

 

Here are some sample dates to plug into the box

May 1998 the first flyby Venus, picks up some energy,

July 1999 second gravity assist encounter with Venus

August 1999 assist encounter with Earth

 

November 2000 a boost from Jupiter

[ed84c]

so what do RTGs do exactly other than 'thrust things' ?

[Sayonara]

Toni: no religious opining in science threads pls ta.

[Martin]

Anybody know what speed these probes travel at?

 

Ed you are asking a general question about "these probes" so that means you are looking to get a rough idea----and order-of-magnitude estimate.

 

because they travel a whole range of different speeds

 

and a given probe will typically be going fast, like 30 km/second, while it is near the earth and in the inner solar system and then it will slow down as it swing wide out towards some planet like Jupiter and Saturn in the outer solar system

 

If anyone ever wants to get a grasp of the basic speeds in the solar system then there is a real simple rule. Most of the planet speeds are roughly circular so just focus on circular orbit

 

circular orbit speed falls off as the square root of distance from the sun

 

so you need to memorize only one speed: earth goes 30 km/second

 

and then a planet that is 4 times farther from sun must go half the speed which is 15 km/second

 

and a planet that is 9 times farther from sun (than earth is) must go one third the speed, so it must go 10 km/second

 

so roughly speaking "these probes" are going 10 to 30 kilometers a second

 

(one that is near earth and on the trip out to Jupiter, say, would have some extra speed to boost it outwards----so more than 30----and by the time it gets to Jupiter it would have been slowed down by the drag of the sun's gravity to less than 10 km/second. Might seem to be barely moving, compared to Jupiter. But a good rough estimate of the range of speeds relative to the sun is 10-30 km/second, if it is missions outwards from the earth.)

 

Only a modest percentage of the speed is due to artificial propulsion.

Most of a craft's speed comes from gravity and the fact that it is launched from a platform (earth) already going 30 km/second.

 

If you are excited by speed you should read about the Gallileo mission to Jupiter and its moons. In its first encounter with Jupiter, the probe fell in very close so it was really traveling when it was at the "bottom" of that loop. the engine (as usual) was only used to make a small ADJUSTMENT in the speed, at that time.

 

In the Gallileo mission the onboard propulsion used a form of HYDRAZINE fuel which does not require oxygen. It is a so-called monopropellant.

this is typical. The lunar lander of the Apollo mission used a type of hydrazine to take off from the moon for the trip back.

 

It is so much the fuel-of-choice for long missions that, although I dont know about Cassini, I would guess that Cassini spacecraft is using hydrazine for pretty much everything (after the initial departure from Earth)

 

any reference, like encyclopedia or dictionary, can tell you about hydrazine (anything you dont know already)----it is an unstable compound of Nitrogen and Hydrogen (which can have hydrocarbon pieces attached). It will burn if you happen to have a supply of oxygen, but it will also just decompose and turn back into nitrogen gas and hydrogen gas and whatever, releasing energy, because the molecule just likes to go to pieces (similar to common explosives like TNT)

[noz92]

The speed of the Huygens probe after it had released it's parachute was aproximitly 200 km/h