Juno Meets Jupiter...

Lord Jim · Post by **Lord Jim** » Mon Jul 04, 2016 3:28 pm

Fastest-Ever Spacecraft to Arrive at Jupiter Tonight

NASA's Juno probe will attempt to slip into orbit around Jupiter tonight (July 4), shortly after becoming the fastest object ever made by human hands.

As Juno nears Jupiter tonight, the giant planet's powerful gravity will accelerate the spacecraft to an estimated top speed of about 165,000 mph (265,000 km/h) relative to Earth, mission team members said.

"I don't think we've had any human[-made] object that's moved that fast, that's left the Earth," Juno principal investigator Scott Bolton, of the Southwest Research Institute in San Antonio, said during a news conference last week. [Juno's Plunge Into Jupiter Orbit Fraught With Danger (Video)]

The all-time speed record is currently held by NASA's Helios 1 and Helios 2 spacecraft, which launched in the mid-1970s to study the sun. Both probes reached top speeds of about 157,000 mph (253,000 km/h) at their points of closest approach to Earth's star.

For perspective: Bullets cut through the air at about 1,700 mph (2,735 km/h), and the International Space Station zooms around Earth at 17,500 mph (28,160 mph).

Indeed, Juno will be moving a bit too fast for its own good tonight. To slow down enough to be captured into Jupiter orbit, the probe must slam on the brakes, which it will do by firing its main engine for 35 minutes, beginning at 11:18 p.m. EDT (0318 GMT) tonight.

Bolton said he's nervous about this make-or-break maneuver, which Juno will perform on autopilot.

"If that doesn't all go just right, we fly past Jupiter," Bolton said. "Everything's riding on it."

The $1.1 billion Juno mission launched in August 2011. The solar-powered probe is equipped with nine science instruments, which it will use to map the gravitational and magnetic fields of Jupiter and characterize the planet's interior structure, among other tasks.

Juno's observations should help researchers better understand how Jupiter formed and evolved, mission team members have said.

If all goes according to plan tonight, Juno will enter into a 53.5-day orbit around Jupiter. The probe's handlers will then commission the probe's instruments and use them to study the giant planet over the next few months.

The real scientific action, however, doesn't start until October. On Oct. 19, Juno will perform another engine burn to shift into its first science orbit, a highly elliptical 14-day loop that will take the probe within 3,100 miles (5,000 kilometers) of the Jovian cloudtops at closest approach.

Juno will then take Jupiter's measure over the course of more than 30 orbits before ending its life with an intentional death dive into the planet's atmosphere in February 2018. This final maneuver is designed to ensure that no Earth microbes contaminate the ocean-harboring Jupiter moon Europa, which astrobiologists regard as one of the solar system's best bets to host alien life.

http://www.space.com/33336-nasa-juno-pr ... night.html

Scooter · Post by **Scooter** » Mon Jul 04, 2016 3:57 pm

So it's taken only 5 years to get there, which sounds like it could make manned flights possible, but I don't imagine that humans could survive travel at those speeds.

Bicycle Bill · Post by **Bicycle Bill** » Mon Jul 04, 2016 5:16 pm

Scooter wrote:So it's taken only 5 years to get there, which sounds like it could make manned flights possible, but I don't imagine that humans could survive travel at those speeds.

That would make for a ten-year (or more) round trip. I think humans could definitely survive the trip, but whether they would be able to tolerate the ten-year monotony is something else again.

And then there's always this scenario to imagine — let's just say that we *DO* somehow launch a ten-year mission to Jupiter. Three years into the trip, the government changes and someone like Trump takes over and cuts all funding to NASA. Then what happens to those poor bastards stranded out there?

-"BB"-

MGMcAnick · Post by **MGMcAnick** » Mon Jul 04, 2016 5:25 pm

Scooter wrote:" but I don't imagine that humans could survive travel at those speeds."

At one time, in the infancy of steam locomotive travel, it was thought that man would die if he exceeded a mile a minute, 60 MPH. Of course that theory was soon proven wrong. I don't think travel to Jupiter over a five year period is the problem. It's getting BACK that's the problem. It would be a suicide mission. That's another reason Juno will be crashed into the Jovian surface.

If a three stage rocket booster is required to reach Earth's escape velocity of 17,500 MPH, what would it take to escape Jupiter's gravitational pull?

Lord Jim · Post by **Lord Jim** » Mon Jul 04, 2016 7:43 pm

I imagine that the objective of a manned Jovian mission wouldn't be Jupiter itself, but more likely the moon Europa...

Another problem in addition to the planet's gravitational pull is the intense amount of radiation it emits...

datsunaholic · Post by **datsunaholic** » Tue Jul 05, 2016 4:55 am

MGMcAnick wrote:
Scooter wrote:" but I don't imagine that humans could survive travel at those speeds."
At one time, in the infancy of steam locomotive travel, it was thought that man would die if he exceeded a mile a minute, 60 MPH. Of course that theory was soon proven wrong. I don't think travel to Jupiter over a five year period is the problem. It's getting BACK that's the problem. It would be a suicide mission. That's another reason Juno will be crashed into the Jovian surface.

If a three stage rocket booster is required to reach Earth's escape velocity of 17,500 MPH, what would it take to escape Jupiter's gravitational pull?

That's not how it works. You don't need to achieve surface escape velocity to depart orbit-escape velocity is the speed required to depart with no additional propulsion, and the further away, the less the escape velocity is because the gravitational influence eventually becomes infinitesimally small. Plus, you can't land on Jupiter, only orbit, and orbital velocity is already quite high.

kmccune · Post by **kmccune** » Wed Jul 06, 2016 12:10 am

Can someone tell me how a gravity slingshot works?It seems to me like you would lose whatever you gain approaching the gravity well,by moving away from it

Crackpot · Post by **Crackpot** » Wed Jul 06, 2016 1:19 am

They go over it in depth in the Star Trek movie where they go back to the 80s

datsunaholic · Post by **datsunaholic** » Wed Jul 06, 2016 7:56 am

kmccune wrote:Can someone tell me how a gravity slingshot works?It seems to me like you would lose whatever you gain approaching the gravity well,by moving away from it

The velocity or trajectory is changed in relation to the Sun, depending on the approach and departure angles. The velocity in relation to the planet being used for the maneuver is pretty much the same, since the sum of the kinetic energy must remain the same. The planet is also orbiting, so is in motion, so it is impossible for a space probe to approach and depart with the exact same course if it is affected by the planet's gravity.

kmccune · Post by **kmccune** » Wed Jul 06, 2016 10:49 am

Thank you ,that makes sense ,I guess another thing I wanted to ask was,can you rob kinetic energy from a body and actually add speed or is it just a vector change ?I know elevators and such use counterweights ,but all that does is balance things somewhat against the pull of G .( no free lunch

RayThom · Post by **RayThom** » Wed Jul 06, 2016 4:12 pm

The "Gravity Slingshot" explained:

What's not to understand?

kmccune · Post by **kmccune** » Sat Jul 09, 2016 12:19 pm

Thank you ,however what keeps the Earths gravitational pull from robbing what it donated ? Looks like a small high ISP ion thruster would have given the probe enough speed to reach Jupiter and why are the solar panels still attached ,I thought they lost effectivness ,at a distance from the sun ?(I guess its a moot point anyway,since the probe is slated for destruction )

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