On May 31, NASA announced its 2018 plan to send the Parker Solar Probe within 4 million miles of the sun— seven times closer than any previous spacecraft.
To learn more about the Parker Solar Probe and what NASA may learn from humanity’s first visit to our star, R&D Magazine spoke to Jonathan Lunine, the David C. Duncan Professor in the Physical Sciences and the director of the Cornell Center for Astrophysics and Planetary Science at Cornell University.
While Lunine is not involved in the Parker Solar Probe mission, he is involved in several other NASA missions, currently serving as an interdisciplinary scientist on the Cassini mission to Saturn and a co-investigator on the Juno mission to Jupiter. He is also the principal investigator of the proposed Enceladus Life Finder mission.
R&D Magazine: What do you think NASA will learn from the Parker Solar Probe?
Lunine: What we want to learn is ultimately, how the sun works. This mission will get closer to the sun than any spacecraft before it; it will actually be in what’s called the ‘inner corona’ of the sun. The corona is this very hot outer atmosphere. This is not inside the sun in the sense of inside the disc that we think of as the sun. The corona is an interesting region because it is actually much hotter than the surface of the sun. Speeds of the particles are the equivalent of a temperature of a million degrees Kelvin. The question is— why does the corona get that hot? This is also the region where particles are accelerated to become the solar wind. It is the region where you have coronal holes and flares bursting out to make coronal mass ejections. Therefore, it is a really important and fascinating region of the sun, which is ultimately the departure point for solar wind and for energetic events that have an effect on our technologies.
R&D Magazine: Are you saying the data we gather during this mission will have an impact on how we live on Earth?
Lunine: Yes, it will because it will give us the ability to predict better when such events will occur. We’ll never have the ability to stop such events, the energies are extraordinary. Being able to predict them and their intensity ahead of time is the key to protecting technologies.
R&D Magazine: How much risk is involved, since we are getting closer to the sun than ever before?
Lunine: Every mission that goes to a new environment has some amount of risk associated with it because all we can do is predict the environment and design the spacecraft to that prediction. In the case of the Parker Solar Probe, the temperature that the front of the spacecraft will experience at the closest approach at the end of the mission is something like 1,400 degrees Celsius, which would be a temperature that a spacecraft could not operate at if it did not have this carbon fiber heat shield. That heat shield is crucial and it also means that it is crucial to keep that spacecraft pointed in the right way. The way that shield protects the instruments and the electronics, is by creating a shadow behind it. The spacecraft orientation is critical in this.
Also critical is that the solar panels have to be canted backward at the close approach because if they were faced on to the sun they would overheat and fail. The spacecraft orientation and the spacecraft configuration are absolutely crucial in making this mission a success. I think, as with other planetary missions, the whole concept of redundancy and the concept of safe mode will all be important in ensuring that this mission is a success.
R&D Magazine: Assuming that this mission is a success do you think it will lead to subsequent missions working to get even closer to the sun?
Lunine: Certainly one of the points that is important to recognize is the Parker Solar Probe will be operating possibly at the same time as another mission, a joint U.S./European mission, a solar orbiter that will not get as close to the sun, but will provide a global view at the same time. The two of those together, if successful, will stimulate more missions. Whether would be trying to go even closer or trying to do something at the poles of the sun, it is hard to know.
Solar probe is a mission that has been recommended since 1958 by the National Academy of Sciences. People may be thinking about doing a mission beyond that, but I think getting this mission completed is going to be a real milestone in the history of spaceflight. As for using this technology elsewhere, there are lots of heat shield technologies in different places for different purposes.
R&D Magazine: Throughout your career, did you ever believe we would be able to get this close to the sun?
Lunine: This mission is one of the ones I remember when I was on the NASA Space Science Advisory Committee, which no longer exists under that name. That was in the 1990s and it seemed to be a very ambitious mission at the time. The technologies available to protect the spacecraft were such at the time that it did not seem to be very compelling as a mission.
I think this mission design really optimizes the science and is in improvement over what we saw 20 years ago. My assumption was, yes, we would certainly see a solar probe, but probably not in the 1990s or the period immediately thereafter.
Understanding the sun not only will tell us an enormous amount about how our own planets interact with solar wind and energetic events, but also about extra solar planets. The very close extra solar planets, the ones with very short orbit periods, are orbiting within the outer coronas and the very intense inner part of the solar wind. This is going to be a tremendous boon to understanding the environments that those planets experience as they orbit their parent’s star.
R&D Magazine: Will this mission lead to more knowledge about whether other planets outside of Earth can be habitable?
Lunine: It will certainly tell us more about those planets in relation to their stars because they are much, much closer than the Earth is to the sun. There have been other missions that have told us a lot about the Earth’s interaction with the solar wind locally at the position of the Earth. What we’ve been missing is what happens much closer to the sun where the solar wind is actually generated and in the corona itself. That is the key to getting a better handle before these events arrive at work.