Yet to me not to expect discussion of the launchers on a forum mostly dedicated to such technology seems a odd stance to take.
Quote from: Star One on 03/13/2019 04:27 pmYet to me not to expect discussion of the launchers on a forum mostly dedicated to such technology seems a odd stance to take.Too often discussions of launchers in the science forums has gone the way of thinking about what ifs, "if we do multiple launches and stack elements in orbit..." These are fine discussions and there are boards to vet and debate these kinds of issues. However, they are outside the realm of options being considered by the project teams. I believe that the discussions on the science board should be among the options being considered by the project teams.So I support discussions of the implications of different commercial launches here, whether ice giant missions should have SEP stages, etc., in the science boards.I write this knowing that the head of NASA has just suggested in orbit stacking of elements for the first Orion moon launch. That now makes this legitimate to discuss on the Orion, SLS, and Falcon Heavy boards.
More interesting to me is the fact that we have often been told in this section of the forum that a launch cost saving of $10M to $20M doesn't matter to science missions, since it's a tiny fraction of the total mission cost. Yet here we have an important instrument on a multi-billion dollar mission getting canned because it's $8M to $16M over budget. So the question is, does $10M to $20M matter to a science mission or not?
Glaze said that cost alone was not the reason for removing ICEMAG. “The emphasis is not so much on the overall cost growth but on the other risks that were inherent in the design and the approach that was going forward,” she said. “Most of the concern had to do with the future risks and the fact that instrument was not stabilizing.”
So the question is, does $10M to $20M matter to a science mission or not?
Margaret Kivelson, a professor emerita at the University of California, Los Angeles, will lead the effort to develop a simplified magnetometer to replace ICEMAG. The instrument will measure Europa’s magnetic field and gather data on the ocean’s depth and salinity. Kivelson previously led the magnetometer team on the spacecraft Galileo, which orbited Jupiter in the 1990s. She is credited with discovering the ocean beneath Europa’s ice shell.ICEMAG’s estimated cost had grown to $45 million—nearly three times its proposed price—according to NASA headquarters. Sophisticated internal sensors had vexed the ICEMAG science team and led to much of the extra expense. The new magnetometer will do away with those sensors, using simplified components instead. The downside is that the new sensors will likely lose calibration over time and drift in response to temperature variations. The team is now devising strategies to compensate for these effects.
“We are gearing up for one last review needed for confirmation of the mission by NASA,” Pappalardo says. “That is where NASA says that you are ready and cleared to go build the instruments and spacecraft.” In April, the project will go through its “delta preliminary design review” (PDR)—a reevaluation of certain elements of the spacecraft that had given NASA pause.
Once completed successfully, the project will go through another review at NASA headquarters called “key decision point C.” The agency will commit to the calendar and cost determined during the PDR, and the process of finalizing design and fabricating the hardware can begin.[...]After the April design review, Clipper will likely enter the final design and fabrication phase in August. If all goes well, it will lift its first inch from the launchpad in 2023.
When Culberson was defeated for reelection last year, things looked grim. He still had a few tricks up his sleeve, however. “Before I left,” he says, “I won the support of a number of my House colleagues to be sure that they would protect those missions.” And tying Clipper to SLS should help.
In its place, NASA will fly a “facility magnetometer” that will collect some of the same magnetic field data as ICEMAG in the vicinity of Europa, an icy moon of Jupiter. The agency subsequently said Margaret Kivelson, a planetary scientist at UCLA who also is the new chair of the Space Studies Board, will lead the development of the magnetometer.<snip>Robert Pappalardo, project scientist for the mission, said in an April 23 presentation at an Outer Planets Assessment Group (OPAG) meeting here that challenges with the sensors’ fiber optic cables, which are sensitive to the temperature and radiation conditions at Jupiter, “essentially brought on its downfall.”<snip>The increased errors of the [replacement] fluxgate magnetometers, [Pappalardo] said, “does put at risk” some of the key, or Level 1, science requirements of the mission, notably estimating the thickness of Europa’s ice shell as well as the depth and salinity of the liquid water ocean beneath the ice. Other Level 1 science requirements aren’t affected, he emphasized.
The project has been looking at a number of options for the non-SLS option. Speaking at a National Academies committee meeting in March, Barry Goldstein, Europa Clipper project manager, said one option under consideration would be a launch on a SpaceX Falcon Heavy equipped with a Star 48BV kick stage. That trajectory, known formally as Delta-V Earth Gravity Assist 3-Minus, involves a launch in November 2023 and an Earth flyby in October 2025 prior to arrival at Jupiter in September 2029.The travel time of a little less than six years is only slightly shorter than some other alternatives previously studied. However, it has the advantage of not requiring any gravity assist flybys of Venus, with the spacecraft getting only slightly closer to the sun on its trajectory than the Earth. “That solves a world of problems on thermal management,” Goldstein said. “We no longer have the challenge of the thermal problems that we had getting close to Venus.”A second advantage, he said, is that it offers a backup launch window roughly a year later, whereas with the Venus flyby trajectory the mission would have to wait until 2025 if it can’t launch in 2023. “We’re not 100 percent there yet, but things are looking very positive” for the new trajectory, he said.
a launch in November 2023 and an Earth flyby in October 2025 prior to arrival at Jupiter in September 2029.
https://www.lpi.usra.edu/opag/meetings/mar2019/Findings.pdfHere’s a recent report from OPAG which also addresses the recent termination of ICEMAG. I’m surprised to find out that the cancellation of certain risky instruments seems to be new process and I am pleased to see others call for transparency regarding this new approach towards keeping science missions within their cost caps.
Has there been any further news from the OPAG meeting this month? Aside from the ICEMAG and FH/EGA-trajectory options being unveiled?
Quote from: redliox on 04/29/2019 02:22 amHas there been any further news from the OPAG meeting this month? Aside from the ICEMAG and FH/EGA-trajectory options being unveiled?The OPAG presentation was entirely focused on the impact on the magnetometer measurements. The launch/trajectory options were from an earlier meeting this year (CAPS?).
And in regards to ICEMAG, basically the improved electronics and optronics turned out to be sadly vulnerable to Jupiter's radiation whereas another, presumably off-shelf or 'traditional', magnetometer could manage but only, slightly better at best, at Galileo's detection levels? 'Clipper will basically finish the job Galileo never properly finished to begin with.A wonky (yet functional) magnetometer would only imply there was an ocean below whereas the radar would solidly confirm it.
-You're going to hear some low level (i.e. not very public) grumbling about the overall capabilities of the mission and whether it will really provide the science that the community wants. Some of that was voiced at OPAG last week by people who wish that NASA was building an orbiter instead of a flyby mission. Some of these people are in denial, because there simply was not enough money to build the orbiter. But certainly some science was lost when going from orbiter to flyby.
Quote from: zubenelgenubi on 04/27/2019 07:20 pma launch in November 2023 and an Earth flyby in October 2025 prior to arrival at Jupiter in September 2029.Why does it take 4 years from EGA(not launch!) to Jupiter arrival? A transfer orbit with 5.5AU AP and 1AU PE has period of ~6 years, so even Hormman transfer will only take 3 years. Does it actually pass AP when encounter with Jupiter? But what's the purpose?
Short man, Large dream/I send my rockets forth between my ears/Hoping an inch of Good is worth a pound of years
.perhaps even more available if the Gateway payloads get offloaded to commercial alternatives, by 2023.
