Starship Asterisk*

Last week included one of the few times in history that humanity launched something completely off the Earth, moving away so fast that it will never return.

LoneStarG84 wrote:

Last week included one of the few times in history that humanity launched something completely off the Earth, moving away so fast that it will never return.

What were the others?

http://en.wikipedia.org/wiki/Prandtl-Gl ... ingularity
[E]xtreme atmospheric conditions are produced which may give rise to a vapor cone, shock collar, or shock egg of visible condensation....Since heat does not leave the affected air mass, this change of pressure is adiabatic, with an associated change of temperature. In humid air, the drop in temperature in the most rarefied portion of the shock wave (close to the aircraft) can bring the air temperature below its dew point, at which moisture condenses to form a visible cloud of microscopic water droplets. Since the pressure effect of the wave is reduced by its expansion (the same pressure effect is spread over a larger radius), the vapor effect also has a limited radius....These condensation clouds were frequently seen during Space Shuttle launches around 25 to 33 seconds after launch when the vehicle is traveling at transonic speeds.

Then Juno will be instructed to dive into the thick atmosphere of the Jovian giant, taking as much data as it can before it melts.

NoelC wrote:I'll Echo Orin's comment... Why, if we're sending something all the way to Jupiter, after the orbital phase does it have to be a one-time drop into obvlivion? Haven't the Mars rovers shown us that a well-designed, durable probe can keep good scientific observations coming back for a long time? Is it that we just don't know enough about what's happening in Jupiter's atmosphere yet to even try such a feat (e.g., via a smart glider or even a powered plane)?

NoelC wrote:
I'll Echo Orin's comment... Why, if we're sending something all the way to Jupiter, after the orbital phase does it have to be a one-time drop into obvlivion?

NoelC wrote:
Is it that we just don't know enough about what's happening in Jupiter's atmosphere yet to even try such a feat (e.g., via a smart glider or even a powered plane)?

• 1) a heat shield,
  2) deceleration strengthening,
  3) some sort of parachute (or wings) and
  4) a communications system able to reach all the way back to Earth.

http://en.wikipedia.org/wiki/Galileo_%28spacecraft%29 wrote:

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<<An atmospheric probe was released from the Galileo spacecraft in July 1995, entering the planet's atmosphere on December 7. It parachuted through 150 km of the atmosphere, collected data for 57.6 minutes, and was crushed by the pressure to which it was subjected by that time (about 22 times Earth normal, at a temperature of 153 °C). It would have melted thereafter, and possibly vaporized. The Galileo orbiter itself experienced a more rapid version of the same fate when it was deliberately steered into the planet on September 21, 2003, at a speed of over 50 km/s, to avoid any possibility of it crashing into and possibly contaminating Europa—a moon which has been hypothesized to have the possibility of harboring life.

The 339-kilogram atmospheric probe, built by Hughes Aircraft Company at its El Segundo, California plant, measured about 1.3 meters across. Inside the heat shield, the scientific instruments were protected from ferocious heat during entry. The probe had to withstand extreme heat and pressure on its high-speed journey into the Jovian atmosphere, traveling at 47.8 km/s.

The probe was released from the main spacecraft in July 1995, five months before reaching Jupiter, and entered Jupiter's atmosphere with no braking beforehand. The probe was slowed from its arrival speed of about 47 kilometers per second to subsonic speed in less than two minutes. This was by far the most difficult atmospheric entry ever attempted; the probe had to withstand 230 g and the probe's 152 kg heat shield, making up almost half of the probe's total mass, lost 80 kg during the entry. NASA built a special laboratory, the Giant Planet Facility, to simulate the heat load, which was similar to that of an ICBM-style straight-down reentry through a thermonuclear fireball. It then deployed its 2.5-meter parachute, and dropped its heat shield.

As the probe descended through 150 kilometers of the top layers of the Jovian atmosphere, it collected 58 minutes of data on the local weather. It only stopped transmitting when ambient pressure exceeded 23 atmospheres and temperature reached 153 °C. The data was sent to the spacecraft overhead, then transmitted back to Earth. Each of 2 L-band transmitters operated at 128 bits per second and sent nearly identical streams of scientific data to the orbiter. All the probe's electronics were powered by lithium sulfur dioxide (LiSO₂) batteries that provided a nominal power output of about 580 watts with an estimated capacity of about 21 ampere-hours on arrival at Jupiter.

The probe included six [specialized sounding] instruments for taking data on its plunge into Jupiter:

• an atmospheric structure instrument group measuring temperature, pressure and deceleration,
  a neutral mass spectrometer and
  a helium-abundance interferometer supporting atmospheric composition studies,
  a nephelometer for cloud location and cloud-particle observations,
  a net-flux radiometer measuring the difference between upward and downward radiant flux at each altitude, and
  a lightning/radio-emission instrument with an energetic-particle detector that measured light and radio emissions associated with lightning and energetic particles in Jupiter's radiation belts.

Total data returned from the probe was about 3.5 megabits. The probe stopped transmitting before the line of sight link with the orbiter was cut. The likely proximal cause of the final probe failure was overheating, which sensors indicated before signal loss.

The atmosphere through which the probe descended was somewhat hotter and more turbulent than expected. The probe was eventually completely destroyed as it continued to descend. The parachute would have melted first, roughly 30 minutes after entry, then the aluminum components after another 40 minutes of free fall. The titanium structure would have lasted 6.5 hours more before disintegrating. Due to the high pressure, the droplets of metals from the probe would finally have vaporized once their critical temperature had been reached, and mixed with Jupiter's liquid metallic hydrogen interior.>>

Chris Peterson wrote:Juno isn't going to burn up because the atmosphere is hot, but because it will become a meteor.

NoelC wrote:

Chris Peterson wrote:
Juno isn't going to burn up because the atmosphere is hot, but because it will become a meteor.

So what, they couldn't design an orbiter to continue to send useful data / pictures for longer than a year?

NoelC wrote:
Is it going to run out of gas? Maybe become brain damaged from the radiation belts?

NoelC wrote:
My question still stands, though at a higher level: Why drop it in and burn it up?

http://en.wikipedia.org/wiki/Galileo_%28spacecraft%29 wrote:
<<Galileo arrived at Jupiter on December 7, 1995. Galileo's prime mission was a two-year study of the Jovian system. The spacecraft traveled around Jupiter in elongated ellipses, each orbit lasting about two months. Once Galileo's prime mission was concluded, an extended mission followed, starting on December 7, 1997; the spacecraft made a number of daring close flybys of Jupiter's moons Europa and Io. The closest approach was 180 km (112 mi) on October 15, 2001. The radiation environment near Io in particular was very unhealthy for Galileo's systems, and so these flybys were saved for the extended mission when loss of the spacecraft would be more acceptable. The uniquely harsh radiation environment at Jupiter caused over 20 anomalies. Despite exceeding its radiation design limit by at least a factor of three, the spacecraft survived all the anomalies. The quartz crystal used as the frequency reference for the radio suffered permanent frequency shifts with each Jupiter approach. Galileo's cameras were deactivated on January 17, 2002, after they had sustained irreparable radiation damage. NASA engineers were able to recover the damaged tape recorder electronics, and Galileo continued to return scientific data until (once its fuel supply was nearly depleted) it was deorbited in 2003, performing one last scientific experiment —a measurement of the moon Amalthea's mass as the spacecraft swung by it.>>

NoelC wrote:So what, they couldn't design an orbiter to continue to send useful data / pictures for longer than a year? Is it going to run out of gas? Maybe become brain damaged from the radiation belts?

My question still stands, though at a higher level: Why drop it in and burn it up?

LoneStarG84 wrote:

Last week included one of the few times in history that humanity launched something completely off the Earth, moving away so fast that it will never return.

What were the others?

tytower1 wrote:
Look out Jupiterians [sic] here we come ,don't take this as a sign we intend to bomb you , trust us on this !!

http://en.wikipedia.org/wiki/Demonym wrote:
<<A demonym, also referred to as a gentilic, is a name for a resident of a locality. The word demonym comes from the Greek word for "populace" (δῆμος demos) with the suffix for "name" (-onym). A demonym is usually – though not always – derived from the name of the locality; thus, in English, the demonym for the people of Italy is Italian, though the one used for the people of the Netherlands is Dutch.>>

• Code: Select all

  Planet  	Demonym
  ------------------------------------------
  Mercury:  Mercurian, Hermean
  Venus:    Venusian
  Earth:    Earthling, Terran, Terrestrial, Tellurian
  Mars:     Martian
  Jupiter:  Jovian
  Neptune:  Neptunian
  Saturn:   Saturnian
  Uranus:   Uranian

Chris Peterson wrote: it is an important aspect of the mission that it not be left dead in orbit.

NoelC wrote:

Chris Peterson wrote: it is an important aspect of the mission that it not be left dead in orbit.

That's the first I've heard of conscientious space exploration. And I can't immediately think of justification for it. Isn't it really only around the Earth that we have to worry about space junk?

NoelC wrote:That's the first I've heard of conscientious space exploration. And I can't immediately think of justification for it. Isn't it really only around the Earth that we have to worry about space junk?

Rob wrote:Oops, Chris is faster on the draw

rstevenson wrote:
Art was being serious (he does that from time to time to throw us off)....