25

Physical First and foremost, the physical reason is that objects accelerate as they approach massive bodies and decelerate as they recede: Parker Solar Probe achieves its peak orbital speed (almost 200 km/s eventually) at its closest approaches to the Sun - as it falls inwards towards the Sun on each orbit it speeds up then slows down again on the way back ...


22

The closer an object to the source of light, the larger the shadow it casts. That's true if we're talking about a point source or at least a compact source of light and "shadow" refers to the "umbra" or area of complete shadowing. But it no longer makes sense in this case where seen from Earth the obscurer (spacecraft) is tiny compared to the "obscuree" (...


22

While the solar corona is very hot, it also has very low density: Wikipedia gives a ballpark figure of about 1015 particles per cubic meter, which, at 1 million Kelvins, translates to a pressure of about 0.01 Pa. That's a pretty good vacuum, comparable to that in low Earth orbit. The low pressure means that the coronal plasma doesn't hold much heat that it ...


14

Spacecraft Overview: "preliminary designs include an 8-foot-diameter, 4.5-inch-thick, carbon-carbon carbon foam solar shield atop the spacecraft body..., radiators for the solar array cooling system, ... actively cooled solar arrays". Low albedo for the heat shield isn't mentioned explicitely. A highly elliptical orbit leads to relatively short periods of ...


10

This test was performed to ensure that the 44 series of solar cells (or "strings") were still connected. After the acoustic and vibration testing, there was a chance that some of the electrical connections could have been broken, so the test used a bar of purple lasers (a "light bar") to verify that the strings were still functioning properly. A laser bar ...


10

You are missing something basic here, which is that the Sun's corona is rather sparse. To take matters to an even greater extreme, consider the intergalactic medium. The temperature of the extremely sparse intergalactic medium can be in the hundreds of millions of kelvins. However, a macroscopic thermometer in this hot medium would not get anywhere close to ...


9

This was addressed directly by Dr Nicola Fox, project scientist for the Parker Solar Probe mission in an interview during NASA's live broadcast of the August 12th 2018 launch - hence the late answer! She explained that for all but one of the seven Venus flybys, there is no plan to use any of the science instruments. This is because they will be powered down ...


8

You have probably seen funnels like the above in shopping malls. Drop a coin in the funnel and it will move slowly at the edge and move faster as it nears the center. This is a good model of a gravity well. Stuff moves a lot faster in the inner solar system.


8

It's using the gravity of Venus alone. Skimming the atmosphere would risk damaging the spacecraft From the NASA blog On Oct. 3, Parker Solar Probe successfully completed its flyby of Venus at a distance of about 1,500 miles during the first Venus gravity assist of the mission. These gravity assists will help the spacecraft tighten its orbit closer and ...


8

Surface contamination is not an issue for Mercury or Venus. It is only considered a Category I (Mercury) or II (Venus) risk, which essentially means don't worry about it too much. Also, its orbit will take it very close to the Sun repeatedly. Eventually it will lose control due to lower fuel and the entire spacecraft will be heated to a more then high enough ...


8

Rockets, especially big ones, create their own artificial, gaseous "wires". Tall cumulus clouds reaching high enough that their upper parts are ice instead of water droplets generate powerful electric fields. The potential difference ("voltage") between the ground and the clouds can be huge, millions of volts. When the electric field strength, typically ...


8

There is some information in this paper although it does not directly address your question. It does mention that the first Venus flyby is at a relatively high altitude (about 2500 km) which may make it less sensitive. I also observe that, since all of the gravity assists are with Venus, once the first Venus flyby is completed, the absolute time doesn't ...


7

The heat shield (TPS) is not meant to protect the spacecraft from dust impacts. The statement is not quite accurate and (from a recent search) seems to have been removed from site. As an engineer on the Parker Solar Probe team, I have been involved in the Preliminary and Critical Design Reviews for the mission which include presentations on Dust Protection ...


7

At 9 hours after launch, the Parker Space Probe's current speed is about 12.4 km/s with respect to the center of the Earth. This is smaller than it was a bit over 8 hours ago when the third stage burn had completed. I calculate the vehicle's velocity was about 14.7 km/s just after third stage cutoff. The vehicle's current velocity (9 hours after launch) ...


7

No, it's much too slow for that. The Parker Solar Probe reaches (or at least approaches) thermal equilibrium on its perihelion passes; your hand passing briefly through a flame does not.


6

Technically this answer doesn't specify what slows it down, but it does explain how it does. I've never done anything with orbital mechanics before today, but I got bored and read a few articles, linked below and made a scale model of the Parker solar probe's final orbit in my program I wrote from scratch! Click Here for Animation What you see here is ...


6

It won't transmit data when it is at the closest points, but those periods are pretty small. Take a look at this image seen from this report to see how these will work. 1 degree can transmit Ka science data, 3 degrees can transmit X-band science data. The key thing to pay attention to on this chart is the green line, where it goes down to near 0 there will ...


6

Solar Probe Plus will be protected by an 11.4 cm (4.5 inch) carbon composite shield during it's closest approaches. Furthermore, the highly elliptical orbit will ensure that it won't remain close to the sun for long, although it will be long enough to heat up considerably. Also of some note is the very narrow profile. The satellite won't have to have much ...


6

As one scientist said to me "It would be a sin to fly by Venus and not do science". So, yes, scientifically valuable data will be collected during the Venus flybys. (As it turns out this data collection will be very limited - see Dr. Fox's answer below - to the extent that the "short answer" is "none") HOWEVER, designing and building a spacecraft that ...


5

Let's take a look at the instruments, as seen at JHU APL's site. Solar Wind Electrons Alphas and Protons Investigation- Measures solar wind particles. Might do a bit of science at Venus with how the solar wind reacts to Venus. I personally don't know much about the science value of this, but as @gerrit mentioned, it is currently being done by Mars Express. ...


5

This was difficult to answer until I figured out that this mission used to be called "Solar Probe Plus" and all the early studies were done under that name. From here: As part of the TPS Risk Mitigation effort, two potential ceramic coatings were found that met the requirements of the Solar Probe+ mission. Ceramic materials that are ...


5

I added this to a special page to Where is Roadster, you can find the Parker Solar Probe info here. The current location is 7,338,815 miles (11,810,682 km, 0.079 AU) from Earth, moving away from Earth at a speed of 27,043 mi/h (43,522 km/h, 12.09 km/s). By the way, that is CRAZY fast. For comparison, to get that far Elon's Tesla Roadster took about 2 ...


4

The Parker Solar Probe keeps its heat shield towards the sun at all times, even at aphelion: Source: NASA/JPL During part of the cruise/downlink portion of the first pass, the heat shield is pointed near Earth: Source: Here's the orbit NASA's Parker Solar Probe will take around the sun, Science News (Youtube) But the HGA (High Gain Antenna) used to ...


4

@Machavity's answer is correct. This is just some addition, interesting data. I had downloaded the data for Parker Solar Probe from Horizons before the launch. They had state vectors for a complete (planned) mission there (Revised: Aug 24, 2018) from launch until 2025-Aug-31 09:19:00. Currently Horizons is showing a much shorter span because it is now based ...


4

You are correct in your assumption that larger launch windows require higher fuel margins on the rocket. Therefore, the main reason for such a large launch window is not because they just want to, but because it allows for some flexibility in the actual launch point. Should they have to abort the countdown and need to recycle, they need some time (usually ...


4

At Parker Solar Probe’s closest approach to the Sun, temperatures on the heat shield will reach nearly 2,500 degrees Fahrenheit, but the spacecraft and its instruments will be kept at a relatively comfortable temperature of about 85 degrees Fahrenheit. Source is here, admittedly it's far shorter than I had hoped. In addition to the quote stating the ...


4

For your goal, molten metal is not suitable, or at least, has no benefits. Metals are generally good conductors of heat. So all that heat from the Sun will be distributed quickly throughout the metal blob, until all sides are at equilibrium temperature. That will be a bit lower than the temperature from direct insolation (the sphere will radiate heat in ...


3

New launch schedule: Rescheduled to lift off at 3:31 a.m. EDT on Aug. 12, 2018. Scrub Announcement Video: "Parker Solar Probe Launch Postponed". There will be live coverage on the NASA Kenedy YouTube Channel. Current live stream: "NASA Live: Official Stream of NASA TV's Media Channel". To me, this makes it sound like the margins for the energy budget ...


3

@uhoh - Mistake, no. Poor phrasing, perhaps yes. It looks like the APL fact sheet is implying that the Solar Probe Plus heat shield must survive extreme temperatures, radiation, and dust impacts otherwise the the rest of the spacecraft will ablate near perihelion at closest approach. If the heat shield is facing directly towards the Sun so that this ...


3

Parker Solar Probe is designed to operate completely autonomously during the data collection periods of its orbits for exactly this reason - the RF noise from the Sun swamps reception. From here: For several days around the Nov. 5 perihelion, Parker Solar Probe will be completely out of contact with Earth because of interference from the Sun’s ...


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