Talk:Cassini–Huygens

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Former good articleCassini–Huygens was one of the Natural sciences good articles, but it has been removed from the list. There are suggestions below for improving the article to meet the good article criteria. Once these issues have been addressed, the article can be renominated. Editors may also seek a reassessment of the decision if they believe there was a mistake.
In the news Article milestones
DateProcessResult
January 29, 2005Featured article candidateNot promoted
December 16, 2005Good article nomineeListed
January 31, 2006Peer reviewReviewed
July 17, 2009Good article reassessmentDelisted
In the news A news item involving this article was featured on Wikipedia's Main Page in the "In the news" column on September 15, 2017.
Current status: Delisted good article

High traffic

On 26 April 2017, Cassini–Huygens was linked from Google, a high-traffic website. (See visitor traffic)

A Big Rocket[edit]

This sentence in the second paragraph of the Introduction: "Launched aboard a big rocketTitan IVB/Centaur on October 15, 1997, Cassini was active in space for more than 19 years, with 13 years spent orbiting Saturn, studying the planet and its system after entering orbit on July 1, 2004." could use some work. Some spacing corrections and I'm not sure that the term "a big rocket" is really encyclopedic.

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misson progress[edit]

Can please add somebody the very nice mission progress from the German Wiki with is real nice to follow up. The special dates here mention can also be added, but atm it is a bit 'staccato'. Thanks in advance -- LAZA74 (talk) 11:52, 23 December 2017 (UTC)

Why was it launched on Titan IV[edit]

Titan IV says "It (C-H) was the only use of a Titan IV for a non-DOD launch." - it would be nice if this article explained why. Perhaps it was the only US launcher that could launch the ~23,000 kg mass of the 3rd stage Centaur to get it out of earth orbit ? - Perhaps it was originally intended to be launched on Shuttle-Centaur until that was canceled ? - Rod57 (talk) 13:58, 17 January 2018 (UTC)

The Cassini-Huygens probe was launched by the Titan IV-Centaur (rocket) because it was the world's ONLY unmanned rocket with enough overall energy to send the (heavy) space probe off our planet and into a trajectory that would take it to Saturn. Now the Titan IV is no longer made, and all that we had have already been expended.
A little bit of history here: A Saturn V or a Saturn IB-Centaur could have done the job, but the last Saturn V was fired in 1973 to launch the Skylab, and the last Saturn IB was fired in 1975 to carry the Apollo-Soyuz mission. No Saturn IB - Centaur was ever built.
After the Space Shuttle Challenger self-destructed in 1986, all considerations of putting a Centaur rocket into a Space Shuttle were discarded. Also, this was after an upgraded version of the Centaur had been planned and designed. The new Centaur was going to carry 75 percent more LOX and liquid hydrogen than the previous version, and over $750 million had been spent on the R&D for this new rocket. The idea at that time had been to have enough energy to send Cassini on a straight shot to Jupiter, and thence a gravitational assist to Saturn - exactly what had been done by Pioneer 11, Voyager 1, and Voyager 2.
After all of this, the Titan IV-Centaur did not have enough energy to send Cassini on a straight shot to Jupiter, and thence to Saturn. A lot of careful planning was done, including a lot of computer simulations, and those showed that it was possible to use the rocket to send Cassini inwards towards Venus, fly past Venus once, and then over a year later, past Venus again, and then months later, past the Earth once, gaining enough momentum to reach Jupiter with enough velocity to continue on to Saturn. This basic trajectory to Jupiter is called "V-VEGA" = "Venus-Venus-Earth-Gravity-Assist". [The previous space probe, Galileo, had used "VEEGA" = "Venus-Earth-Earth-Gravity-Assist" to reach Jupiter, but with a lower velocity at Jupiter, so that it could go into orbit there.]
47.215.180.7 (talk) 08:35, 18 January 2018 (UTC)

Gravity assist details[edit]

Gravity assist includes :

Cassini's speed related to Sun. The various gravity assists form visible peaks on the left, while the periodic variation on the right is caused by the spacecraft's orbit around Saturn. The data was from JPL Horizons Ephemeris System. The speed above is in kilometers per second. Note also that the minimum speed achieved during Saturnian orbit is more or less equal to Saturn's own orbital velocity, which is the ~5 km/s velocity which Cassini matched to enter orbit.

but that graphic shows Venus gravity assists of nearer 3.0 km/s rather than the 7.0 km/s quoted in the article. - Rod57 (talk) 14:15, 17 January 2018 (UTC)

The firing of the retrorocket to put Cassini into orbit[edit]

The firing of the retrorocket to put Cassini-Huygens into orbit around Saturn is not completely described.
Nowhere in this article does it say really how long that small rocket was burned. I just remember that it took quite a while, but I cannot remember if it was for 60 minutes, 90 min., 120 min., or whatever. I do know that 460 newtons is not very much thrust. In describing other space missions, thrusts are described in kilonewtons, meganewtons, and giganewtons.
One newton is the amount of constant force that will accelerate one kilogram of mass by one meter per second per second. That is tiny. A related tiny unit is the unit of pressure, the pascal, which is one newton per square meter.47.215.180.7 (talk) 08:54, 18 January 2018 (UTC)

It was a 96 minute burn. Do we need that level of detail? If so, what else is missing? I'm afraid I'd have to dig for a citable reference; I work on the mission and happened to have the relevant spreadsheet in front of me. I'm sure the timeline is out there in a public and citable form, but I 'd have to look. Relatively speaking, 460 N is quite a bit. You're thinking in terms of the rockets launch vehicles use. For the spacecraft itself, much lower thrust and acceleration is fine (actually, often good; I'd hate to put a deployed magnetometer boom or solar array under 20 m/s^2 of acceleration.) Fcrary (talk) 23:33, 20 January 2018 (UTC)