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Parker Solar Probe: Already a Record Setter

Over the sound system in the grocery store yesterday, a local radio station was recapping events of the day as I shopped. The newsreader came to an item about the Parker Solar Probe, then misread the text and came out with “The probe skimmed just 15 miles from the Sun’s surface.” Yipes!

I was in the vegetable section but you could hear him all over the store, so I glanced around to see how people had reacted. Nobody as much as raised an eyebrow, which either says people tune out background noise as they shop or they have little knowledge of our star.

The correct number is 15 million miles (24,1 million kilometers), and it’s still a hugely impressive feat, but I hope the station got the story right later on. I go easy on this kind of thing because it’s easy enough to make a mistake when reading radio copy (I’ve done this myself). Anyway, there is always some listener who calls it in, which I should have but didn’t. I was pushed for time that morning, making choices about squash and rutabagas and thinking about close approaches.

Image: Artist’s concept of the Parker Solar Probe spacecraft approaching the sun. The spacecraft will provide new data on solar activity and make critical contributions to our ability to forecast major space-weather events that impact life on Earth. Credit: NASA/JHU/APL.

After the Parker Solar Probe’s close pass, the spacecraft has gone nearer the Sun than any other craft. The Helios B probe was the previous recorder holder, setting the mark back in 1976. Helios B reached perihelion in April of 1976 at a distance of 43.4 million kilometers (26.9 million miles), inside the orbit of Mercury. A record the Parker probe surpassed with ease.

And the good news about Parker, reflected in the faces in the image below, is that the craft handled the heat and solar radiation without damage. Four status beacon signals are available, the best being the A signal that was received by mission controllers at JHU/APL on the late afternoon of November 7. Our latest mission to the Sun is live and collecting data.

Image: Members of the Parker Solar Probe mission team celebrate on Nov. 7, 2018, after receiving a beacon indicating the spacecraft is in good health following its first perihelion. Credit: NASA/Johns Hopkins APL/Ed Whitman.

Parker is also setting speed records. Again we turn to Helios-B as the previous record-holder, at 70.2 km/s (157,078 mph). At perihelion on November 7, the Parker spacecraft reached 213,200 miles per hour, or 95.3 kilometers per second. By way of comparison, Voyager 1 moves at approximately 17 kilometers per second as it continues to push into interstellar space. Still in the heliosheath, sister spacecraft Voyager 2 is at a slightly more sedate 15.4 km/sec.

But back to the Parker Solar Probe, whose Sun-facing Thermal Protection System, an 11-centimeter thick carbon-carbon composite shield, reached about 820 degrees Fahrenheit, or 437 degrees Celsius. This is just the beginning, for the spacecraft will continue making closer and closer approaches in the course of its 7-year mission. 24 passes by the Sun are anticipated. The spacecraft will eventually close to a scorching 6.2 million kilometers from our star.

Deep space implications? The Parker Solar Probe’s findings will teach us much about the plasma flow leaving the Sun, a solar ‘wind’ that may offer future magnetic sails (magsails) one option for reaching high velocities within the Solar System (though we first must determine whether this highly variable flow can be efficiently exploited by future magsail designs).

The other implication is using a close solar pass in a ‘sundiver’ mission, accelerating a large payload that would be flung outbound in a spectacular gravitational assist, reaching velocities in the hundreds of kilometers per second. We’ll gain a great deal of knowledge about operations close to the Sun through the performance of Parker’s heat shield, all of which should be helpful if we do decide to explore sundiver options for reaching into the Kuiper Belt and beyond.

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{ 25 comments… add one }
  • Antonio November 9, 2018, 16:37

    I wonder what temperature a magsail need to endure in an interestellar voyage. If it’s low enough, we could manufacture the superconducting wire already, and some precursor probe could be built and tested.

  • ljk November 9, 2018, 17:24

    Paul, your grocery store story reminds me of listening to a news blurbs from a local Top 40 radio station in 1990 when the Space Shuttle lofted the Hubble Space Telescope (HST) into Earth orbit. The news announcer referred to the HST as the Hubble Space *Microscope* – and not once, but twice!

    I did call the station as this was too much to bear. A person whom I am guessing was an intern answered. I told him that the Hubble is a giant telescope, not a microscope, as the two instruments only seem similar with a very brief first glance.

    I could tell in his voice he seemed uncertain if I were right. I told him to please look it up or at least read the newsfeed they undoubtedly received on this story. I must have been successful (or perhaps others had called in as well), because by the third news blurb repeating this event, the Hubble had been restored as a mighty telescope – no offense to any and all microscopes, please note.

    Sad to see that 28 years later, the news media is still having trouble with certain space terminology. And now with all the accessible information at our fingertips, there is even less excuse for such errors, or so I fantasize.

  • Charley November 9, 2018, 18:33

    “The newsreader came to an item about the Parker Solar Probe, then misread the text and came out with “The probe skimmed just 15 miles from the Sun’s surface.” Yipes!

    I was in the vegetable section but you could hear him all over the store, so I glanced around to see how people had reacted. Nobody as much as raised an eyebrow, which either says people tune out background noise as they shop or they have little knowledge of our star.”
    ” Nobody as much as raised an eyebrow,…” To be completely honest, I would’ve been terribly surprised if anybody had raised an eyebrow. I think this just goes to prove that the average individual in the population is not particularly science savvy nor does that individual really care too much about the penetration of sciences into society in general. And people are surprised by this?

    Onto the probe itself, I was will surprised here that the probe will intend to make more than one pass at the sun at increasingly closer distances. So that brings up a question that I have for Mr. Gilster; do you know is there plans to have further gravity assists by the planet Jupiter in the future to reduce the perihelion distances?
    A further question for you, sir, you, you happen to know or do you have someone you could ask as to whether or not these particular gravity assists occur when the planet Jupiter is above the plane of the earth orbit, BUT the spacecraft must approach from the South Pole of the planet Jupiter. I’m being very specific on this because of the fact that this seems to be the geometry that would be required to perform these gradually increasing close approaches to the sun. Could you shed any light on this? Please

    • Paul Gilster November 9, 2018, 21:41

      As far as I know, future gravitational assists are all from Venus. Check the PSP timeline here:

      http://parkersolarprobe.jhuapl.edu/The-Mission/index.php#Timeline

      I know of no gravity assists from Jupiter.

    • AlexT November 11, 2018, 3:58

      …this just goes to prove that the average individual in the population is not particularly science savvy nor does that individual really care too much about the penetration of sciences into society in general…

      I suppose average homo sapience when visiting grossery, usually busy by his own problems and simply do not listen the loud sounded news or advertising. Our bain can perfectly filter informational “noise”.

  • Charley November 10, 2018, 0:58

    “The Parker Solar Probe concept originates from a predecessor Solar Orbiter project conceived in the 1990s. Similar in design and objectives, the Solar Probe mission served as one of the centerpieces of the eponymous Outer Planet/Solar Probe (OPSP) program formulated by NASA. The first three missions of the program were planned to be: the Solar Orbiter, the Pluto and Kuiper belt reconnaissance mission Pluto Kuiper Express, and the Europa Orbiter astrobiology mission focused on Europa.[18][19]

    The original Solar Probe design used a gravity assist from Jupiter to enter a polar orbit which dropped almost directly toward the Sun. While this explored the important solar poles and came even closer to the surface (3 R☉, a perihelion of 4 R☉),[19] the extreme variation in solar irradiance made for an expensive mission and required a radioisotope thermal generator for power. The trip to Jupiter also made for a long mission (​3 1⁄2 years to first solar perihelion, 8 years to second). ”

    Oh … Oh, OK. I had remembered seeing somewhere that the original mission had been intended to be a solar polar mission in which Jupiter would play a part to bring it over the poles of the sun. I did not realize they had revamped the mission and brought it down so that it would get close to the sun in the plane (roughly) of the orbit of the Earth. That’s where my confusion lied in all this; if memory serves me correctly, I think I originally read about it in the scientific magazine Discover and that’s where they originally talked about flying over the pole of the Sun.

    • Andrew Wright November 10, 2018, 13:55

      The Ulysses solar probe launched in 1990 used a Jupiter gravity assist to reach a high inclination orbit and examine the poles of the sun.

  • Martin Andersen November 10, 2018, 4:29

    Sadly, most people have no idea of the physics involved. So none reacts to 15 miles. They have no idea of the environment so close to the Sun, they have no idea of distances in the solar system etc.

    • ljk November 12, 2018, 10:25

      Blame a combination of our public education system and a society that still mocks and frowns upon anyone who shows a little too much interest in “smart” subjects. You are allowed to be smart at business and knowing the stats of sport stars, but start knowing too much about the real stars and you will soon find how relatively isolated you are, at least in American society.

  • wdk November 10, 2018, 11:54

    Charley,
    The Dawn mission’s long duration and success seems to make solar electric seem like a modern space appliance now, but I remember when it was dreamed of or planned. On the Solar Probe issue, was involved some solar electric propulsion mission planning in the 80s where we were either looking at Solar Probe mission plan as a model or looking at solar electric as the means.

    Eventually, about a decade later, there was a Shuttle deployed mission with IUS upper stages and a Jupiter flyby as you describe. Maybe over lunch we used to picture it as a shot across Jupiter’s bow from the inner solar system which would be bent back behind Jupiter, canceling most or all of its in-plane (ecliptic) velocity and leaving a residual out of plane
    element – that remainder would define an aphelion of the highly eccentric orbit with perihelion of the Solar Polar Orbiter inward of Mercury and the solar poles visible and from fairly close.

    Admittedly, other missions we were looking at, the trajectories and their objectives, did not blur as easily in memory. I seem to remember Solar Polar Orbiter more as a solar probe too, rather than as a look at the sun’s poles. After all, the spacecraft carried substantial shielding.

    Next time we do a solar polar, etc., I suggest we do it at night.

    • J. Jason Wentworth November 11, 2018, 3:00

      Ulysses was the surviving “remnant”–just as Cassini was the surviving Mariner Mark II mission from the planned CRAF (Comet Rendezvous Asteroid Flyby)/Cassini pair–of the planned two-spacecraft, ESA/NASA ISPM (International Solar Polar Mission). The ISPM was planned to have the two probes (one built by ESA, the other by NASA) conduct out-of-ecliptic Jupiter flybys in opposite directions, so that they would pass over the Sun’s poles more-or-less simultaneously, but in 1981 the NASA probe was cancelled, leaving only ESA’s. It was subsequently re-named first Odysseus, and finally Ulysses (both to honor Homer’s mythological hero, and to refer to Dante’s description in his “Inferno”).

      • ljk November 12, 2018, 10:22

        The 1980s were a rather sparse time for planetary exploration. Yes, there were missions to other worlds in that decade, but so many were the result of having been built and launched in the previous decade and/or the products of spacefaring nations outside of the USA. The Halley Comet probes are one big example here, as NASA sent no vessels to that famous iceball in 1985/1986, a major shame.

        It is also shocking to know that the Reagan Administration seriously considered shutting off Voyager 2 before it encountered Uranus and Neptune, to save money! How much and where would such funds have gone have always been a mystery we thankfully never had to learn.

  • Patrick Underwood November 10, 2018, 14:07

    A sundiver maneuver would be very handy for catching up to Oumuamua.

    • J. Jason Wentworth November 11, 2018, 3:38

      YES…and if necessary, a Sun-diver maneuver could be conducted with a solar sail, to significantly–perhaps very much so, depending on the selected perihelion distance!–increase the spacecraft’s velocity. While most such mission concepts involve solar sails that would emerge, fully-deployed, from the umbra (shadow) of an occulting object, either artificial or natural (small asteroids have been suggested for the latter), a rotating-parachute type of solar sail (the rotation is needed to keep the sail open, as photon pressure doesn’t work entirely like airflow) could be used without an occulter, and:

      The sail could be opened–again like a rotating parachute (rotating atmospheric parachutes aren’t uncommon)–in reefed configuration (even using multiple reefing stages if needed, as is often done with large parachutes in order to minimize the opening stresses). Just as with atmospheric parachutes, the solar sail would have reefing line cutter knives that would cut through the reefing lines after a predetermined period, allowing the solar sail’s canopy to open fully (or open to the next reefed stage, if multiple ones needed to be used). A Jupiter-Sun flyby (or a Saturn-Jupiter-Sun flyby, if needed) with a Sun-diver solar sail perihelion velocity boost (and the sail would continue to generate thrust farther out, in smaller increments) should provide enough velocity to send at least a small probe to ‘Oumuamua.

  • jonW November 10, 2018, 14:45

    So 95 km/s is way faster than figures that usually get quoted for solar system escape velocities, but I realise that PSP gained that velocity very close to the sun in a steeper part of its gravitational well… and it made me realise I had no clue how to figure out how quickly it will be slowed as it recedes from the sun. If it’s going 95 km/s at 15 million miles from the sun, is that enough to escape, and if so with what velocity? Enough to catch ‘Oumuamua, or would a pursuit mission need to dive deeper to get enough speed?

    • jonW November 10, 2018, 21:22

      I checked it out and at 15 million km from the sun, escape velocity is 105 km/s. But as Paul said at the end of the article (I missed it the first time), the closer dives will get PSP up to hundreds of km/s. I am guessing this will be from an unpowered slingshot alone, no powered slingshot?

      • Paul Gilster November 11, 2018, 11:07

        Yes, this assumes no further source of acceleration, either from an engine burn of some kind or even desorption of material from a shielded sail suddenly exposed to direct solar radiation (i.e., rotating out from behind an occulter).

    • wdk November 11, 2018, 11:20

      Jon. W.,
      Comments would not be the best medium to work all that out, but there are some clues. Local escape velocity (based on distance R to center of mass such as sun) is 1.44 (or square root of 2) times the local orbital velocity. The Earth goes around the sun with a local orbital velocity
      just short of 30 kilometers/sec and it’s nearly 150 million kilometers from the sun. Your estimate of Parker’s distance and velocity was 15 million miles and ( 24.1 million kilometers) and 95 kilometers per second. I’d say use the metric distance for calculation.
      Local circular orbit velocity is proportional to square root of ( K/r)
      where the K is effective gravitational constant of the sun or whatever object we are speaking of orbit around (Earth, Moon…). The r is radius for the distance described. We can go further to say that this “K” is based on a universal gravitational constant times the mass of the body
      (Sun, Earth, Moon,…), so K= GM_sun or K_sun.
      So, say Parker’s distance is about 1/6th the distance of Earth’s distance
      to the sun (0.1611 R_sun-earth), local orbital velocity is 2.49 times faster than the Earth’s or around 74.4 or 74.5 km/sec. Escape would
      be about 105.35 km/sec.
      But then at an “infinite” distance, you want to have a velocity greater than ‘Oumuamua’s to catch up someday. That would mean having
      excess energy in a hyperpolic path, meaning you have some excess velocity over escape. We would have to get back to what our interstellar visitor’s velocity was and then select a closing rate…

      • jonW November 13, 2018, 17:45

        Thanks wdk for your detailed answer.

  • J. Jason Wentworth November 10, 2018, 17:49

    After reading this line in the fifth paragraph (“The Helios B probe was the previous ^recorder^ holder, setting the mark back in 1976.”), for a moment I wondered if I might need to change my medication, until I read it again and saw that the word “recorder” was really there… (Having made some howlers of typographical errors myself in various places, I certainly don’t disparage others for making them.) Glaring, factual errors (as opposed to typos, or magnitude errors in copy) in news articles (like the news reference to the “Hubble Space Microscope”) are a different story… I’ve heard two such infuriating news items, on Miami TV stations:

    One was, “Nuclear warhead explodes off the coast of Florida–film at eleven!” (which was actually about a failed Trident II test launch; they *never* carry live nuclear warheads, and neither do routine training launches of any U.S. missiles [only *one* U.S. ballistic missile, a Polaris A-2, ever flew with a live nuclear warhead, in a special test to ensure that its highly-miniaturized warhead would detonate after exposure to flight stresses; it did]). The other one was about an upcoming but delayed “Private Space Shuttle launch” (this report concerned the [ultimately faulty] Intelsat 603 launch on March 14, 1990, aboard a private *rocket*, a Commercial Titan III [it was spectacular from my back yard in Miami!]), and:

    In 1992, the crew of the STS-49 Space Shuttle mission–on the orbiter Endeavour’s maiden flight–serviced the comsat in its low orbit, and it was sent on to its planned geostationary orbit. When I called the TV station to politely point out that Intelsat 603 would be launched aboard a private expendable launch vehicle, not a private Shuttle (there was–and still is, at least to date–no such thing), they reacted rudely and dismissively, and said–in so many words–that the distinction was irrelevant (which I took to mean: “Our viewers are too ignorant and/or stupid to know or care”). Also:

    Perhaps the other patrons in Paul’s grocery store were followers of Heraclitus, who taught that the Sun was about twelve inches in diameter; in that case, the Parker Solar Probe passing within 15 miles of it would not have been particularly astounding. :-)

    • Paul Gilster November 11, 2018, 11:08

      The thought of shopping for vegetables amidst patrons of Heraclitus is rather pleasing, even if they would have been so off-base when it came to the size of the Sun…

      • ljk November 12, 2018, 10:15

        At least Heraclitus had some excuse, plus he also gave the idea some thought, even if he came to some very wrong conclusions.

        I am sure if you asked a random sampling of modern people on the street, the majority would be found to have given very little thought to the subject, if at all. Just so long as that big yellowish ball of light and heat comes up in the morning and keeps shining, right?

        I have always been charmed by the ancient Greek natural philosopher – whose name escapes me at the moment – who once went on a sailing expedition past the Pillars of Hercules to see if the Sun would hiss when it set in the ocean!

  • Kamal Ali November 10, 2018, 23:12

    Why are not sundivers used to greatly reduce time to visit planets? Is it shielding cost? Is it that they would then pass the planet so fast that we would not be able to take proper photos? It’d be great if we could develop good solutions to the heating costs because then we would have solutions for 100km/s or greater – perfect for planet 9. I really want that to exist because it would give us a intermediate interstellar target: ie on the order of 500AU to 1K AU (Yes, i realize 1LY is 64K AU so we would have a few more orders of magnitude to go )

    • Alex Tolley November 11, 2018, 13:21

      Because the velocity at perihelion is much higher than it is further out in its orbit. So a craft falling from 1 AU might be traveling at high velocity near the sun, but would be back to the starting velocity at 1 AU. This buys you nothing. Using the Oberth effect by adding acceleration at perihelion does have advantages, but it depends on how much acceleration can be added. A sundiver deploying a high performance solar sail does allow for higher velocities at higher multiples of AUs from the sun. In Solar Sails by Vulpetti et al, a chapter on fast sails shows that a craft can reach 70 km/s at > 9 AU with a complex sundiver trajectory using sails with loading at 2 g/m^2. With even lighter sails, cruise speed can exceed perihelion speed.

      At this point, we are nowhere near being able to manufacture such high-performance sails, but we are getting there. Beamed energy sails make even more interesting flight profiles, which I think my prove the most tractable way in the relatively near term to get very high velocities and short flight times. I also think we should consider hybrid systems to increase mission flexibility and capabilities. So far we only have chemical launch and Earth escape, followed by ion drives as a “hybrid”.
      As the Benfords have shown, a carbon sail with microwave beams with some ablation will accelerate faster than 1 g. This indicates that theoretically a sail could be launched from the ground on a beam, but more importantly, fast accelerations are possible in space, eliminating the slow spiral to escape velocity of current solar sails.

      I have proposed before that sails with concave sunward surfaces could also act as concentrators for solar thermal rockets, using readily available volatiles as a propellant. The recent suggestion that holographic technology could offer the same capability for modifying light paths using a flat sail gives me hope that this might be a mechanism to make such photon sails and solar thermal rockets a viable approach. (Metamaterials for sail construction might offer a similar technology to holographic printing.) The possible design space for various propulsion technologies acting in concert must be huge. What I am hoping to see is a huge reduction in cost, especially launch cost, so that far more science and exploration craft can be launched.

  • wdk November 14, 2018, 11:34

    Erratum. One at least.
    Just noticed that in an earlier comment to JonW on escape trajectories, etc. that I dropped a digit out of the square root of 2. That’s 1.414 vs.
    1.44 typed.

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