Is A NASA Mission to Europa Real?
NASA Wants to Explore Europa On the Cheap, Planetary Society
“Over the past few years, JPL and APL has been working on a reduced-cost Europa concept called the Europa Clipper, which would fly by Europa on the order of 50 times over a few years to map the surface and determine the properties of the assumed ocean and ice sheet. The Clipper had an estimated cost of $2.1 billion, less than half of the originally-conceived Europa Orbiter, which was around $4.7 billion. This would place the Clipper as a “flagship” mission, though on the low side for a flagship.”
not over my dead decadel survey body
“This extra shielding adds weight; and weight adds cost.” – Oh geez…no wonder they arrive at these costs estimates of $1B, which are way, way too high. They don’t understand costs.
Way way too high? Really? Compared to other planetary missions, especially to the outer solar system, they seem quite low.
The JUNO mission cost is $1.1 Billion. The payload manifest I recall seeing for Clipper is more complex, heavier, more power demands. If you started with the JUNO spacecraft bus, you would take advantage of reuse and save maybe $300M +/- $100M in development costs but modifications, adding an RTG, Clipper payload instruments, will take those savings and probably another $1B. No way you accomplish a Clipper mission for under $2B. Also note, if sanity prevails, the mission will be designed to use a Falcon Heavy rather than Atlas V or SLS and save $100M to $400M. While the Falcon Heavy will give you Earth escape velocity, the Clipper may need more delta-V – an off-the-shelf engine, so savings would likely be more on the order of $100M to $200M; still worthwhile, Dr. Morrison wouldn’t mind having an added $100M note in the next year’s NASA budget for SETI to compete after.
What about a nuclear-electric thruster?
That would require a lot of work for a small nuclear reactor to provide enough power for the engines.
For the early SIP or “NIP” that is available, wouldn’t their low impulse engines make maneuvers more challenging? Isn’t high impulse engines preferable for planetary orbital maneuvering?
One has to be able to maneuver to capture, but once in orbit low thrust is fine. NEP can raise the orbit until escape, accelerate along the interplanetary trajectory, decelerate along the transfer trajectory _prior_to_ capture, and progressively change the orbit after capture.
Reactor not needed. See: http://www.lpi.usra.edu/opa…
But if we fund work on a reactor, think of the sensors it could power! and eliminating the need to launch toxic plutonium! (Uranium, if dispersed in a crash, is, for all intents and purposes, nontoxic.)
tack another $1B+plus on the price tag.
The probe needs power anyway. The money would be for developing a technology. We must have a space based reactor if we are ever going to do serious science or human flight BEO. And it would be much safer to launch than an RTG. Compared to plutonium, uranium is essentially nontoxic.
Mr. Peabody and Sherman are in theaters now Rocky 🙂
Never was a big fan of that one but I might. Interstellar and Transcendence – yes.
–
I do not understand the reference to shielding. Unmanned spacecraft electronics are radiation-hardened by other means. It adds a little cost and mass but the impact is quite modes. Has anyone ever heard of Galileo? The spacecraft, that is?
http://www.sandia.gov/LabNe…
Actually, Jupiter/Europa missions are shielded: most of Juno’s electronics are in a meter cubed vault with shielding. The vault is something like 250kg of Titanium, which is well beyond the “little cost and mass”. You’re looking at total doses well in excess of a megaRad (10kGray). and that’s for a mission that avoids most of the dose by clever orbit design AND short life.
Truly rad-hard components are difficult to come by since there’s not much market for them. This is particularly the case for high integration ICs like microprocessors and other VLSI. We’ve come a long way since the CMOS 1802 and Bipolar AM2900 processors of the Galileo era. It’s not just a matter of taking the design and running it on a different fab.
I agree 250Kg of titanium is a significant mass. However it does not seem like enough to require a change in LV or a different LV. I agree that high performance ICs are more radiation sensitive, but I’m not sure it isn’t more reasonable to use lower performance, less radiation sensitive electronics, unless the high performance components can reduce the electronics volume to a lot less than 1 cubic meter.
There’s a lot that comes with the mass of the vault (structure to support it under vibe loads, for instance) Most missions are designed to fit right to the limit of the LV that will get you where you need to go, so in reality, adding shielding mass means “which instruments do you not want to carry”, or “what propellant do you not want to carry”, etc.
In many cases the lower performance electronics are no longer available. I don’t know that it’s really a size issue, either: it’s not like you can practically gang up 1000 radhard 8 bit micros running at 1 MHz from the 1970s to get anywhere near a modern processor: the power consumption alone would be prohibitive; but the workload is not easily partionable.
But how could you need 1 cubic meter of high performance IC’s? That would be a supercomputer. NASA used to do a lot of work in radiation tolerant electronics. Has it all been forgotten?
1 cu meter is everything: boxes to hold the parts, power supplies, cabling, connectors, etc. Juno’s vault is pretty full of stuff.
NASA does do a lot with rad tolerant electronics, but for the most part, they are a consumer of products, not a manufacturer of products. Back in the 60s and 70s, NASA could leverage large DoD demand for high rel parts, etc.; because the consumer demand was tiny: a “solid state TV” in the 70s had very few ICs in it. Today, though, the 8000 pound gorilla in the IC business is high volume consumer products (mobile phones, etc.) which have zero need for high rel or rad tolerance, and neither do the manufacturers. The best hope for NASA is leveraging automotive, which does have a high rel need (a 1 in a million failure rate is very high for engine control computers), although not a rad tolerant need.
That said, there are rad tolerant/hard parts being developed: Xilinx SIRF parts for instance.
Radiation hardening is a relative thing. The estimate for Europa Clipper is a total dose of 2.8 Mrad. That’s worst case model with a factor of two design margin (a standard for JPL/NASA mission assurance) inside a standard 100 mil Al electronics box. (OPAG presentation by B. Goldstein, Jan. 13-14, 2014.) Space-rated electronics are typically rated to 50 krad, with some up to 200 krad. You can go above that, but it isn’t easy. Shielding is one way. More radiation-hardended parts help, but it limits the parts you can use, which is a hit to performance, mass and/or power. I understand they can do some really impressive things with ASICs, but they are very expensive even by NASA standards.
Galileo, by the way, was designed to 150 krad inside 300 mils of Al, survived about 600 krad, had multiple radiation-related problems (but none fatal.) The electronics that did so is 1970s technology (19, RCA 1802 processors with 16 kB of memory each and a clock speed of 200 kHz.) Newer chips get most of their improved performance by packing more components into each square inch of chip, which makes them more radiation sensitive.
The other concern is instrument noise. Many types of detectors get high background noise in a hard radiation environment, which requires additional shielding. For example, the mass estimate for the UVS instrument being developed for the European JUICE mission to Ganymede is “5.2 kg (plus 9.7 kg TaW shielding)” (OPAG presentation by R. Gladstone, Jan. 13-14, 2014.)
Build two identical buses with complementary instruments and launch on a (by then) proven Falcon Heavy. Adjust trajectories to phase their arrivals.
Given how cheap FH’s are. Why not give them one launch each? That gives you an insane amount of mass to play with. Which means you can build cheap. Solid steel beams instead of ultra-light grid trusses machined out of titanium blocks. Heavy shielding instead of expensive hardened electronics. Etc.
Separate launches mean you can build one simpler, earlier. Feed what you learn into the second.
I assume this mission will require a Plutonium-238 based Radio Isotope generator. We are running out quick…and, the way things are going over in the Ukraine, I doubt will be able to buy any more Pu-238 from Russia in the foreseeable future. The DOE better get crackin’.
Also, does anyone know when the NASA/Glenn Research Advanced Sterling Engine generator is going to be flight ready? Is it possible it could be used on this proposed Europa mission?
Good points. We need a program to produce U-238. But public support is needed for any program using radioactive materials.
The Europa Clipper concept would use five MMRTGs (550 We.) As of FY14, NASA and DOE have funding to restart production. New Pu238 won’t be available for some time (~2022) but the current supply (including some DOE was holding in reserve, but has now released because production is being restarted) is enough for the one MMRTG the Mars 2020 rover needs and the five Europa Clipper would need, but not a whole lot more. The ASRG project has been dropped by NASA’s Planetary Science Division, so no more-efficient power supplies can be expected in the near future, but some level of development is continuing at Glenn. (based on information presented by J. Green, OPAG meeting, 13-14 Jan. 2014.)
Fcrary, thanks for the feedback and info. Very informative. I am sorry to hear about the cancellation of the ASRG program, as that sounded really promising. I wonder if they were having trouble getting the vibrations down to the levels that NASA required? Glad to hear that GRC is still working on it…but it definitely sounds like it is on the back-burner.
Or just bite the bullet and build a space-rated fission reactor.
[It even makes them safer to launch, since you have no radioactivity until they are turned on (in space.)]
How are we ever going to send people to Mars without a space-rated reactor? Unlike the SLS, most of the money would be spent on development; building more units would not be anywhere near as expensive. And relative to plutonium, U235 is extremely safe. We could even buy it from Iran.
I should point out, at the scale we are talking about, it’d be a very inefficient reactor. (Laws of thermodynamics and all that.) So it probably wouldn’t produce any more power/kg than a RTG, maybe less given how simple RTGs are. But it solves the plutonium problem (and I assume, the extra cost of ground-side handling) once and for all.
It also doesn’t give you any better power/kg than solar, until you get beyond Mars’ orbit. So NEP has no advantage over SEP. It does, however, solve the problem of night and winter for solar while on the surface. It also produces more waste heat per kilogram than solar, which is useful on Mars (and the moon at night.) But probably not so much for a free-flying facility whose main problem is getting rid of heat.
We _can_ launch plutonium, but there’s a real pucker factor. It’s so incredibly toxic that inhaling just one 5 micron particle can cause lung cancer. Even diluted in the atmosphere of the entire earth the plutonium in the Cassini RTG would, in theory, result in about one extra cancer death. Highly enriched U235 _is_ fissionable and has to be kept secure from terrorists, but it is no more toxic than depleted uranium, which can be found on the shelf in most college EM labs, is sometimes used as a glaze on ceramics, and can be purchased without a license. There is simply no possibility that it would harm anyone if dispersed. http://depletedcranium.com/…
A space reactor is normally not started until after launch so contains no highly radioactive fission products. I agree a small reactor is not very efficient but a reactor design could be scalable to much larger capacities then an RTG. I recall the JIMO proposal included a reactor to provide the power for moving around the Jovian system.
I was fairly bummed by the cancellation of the ASRG, but perhaps by some miracle an uptick in deep space probe mission interest in the future will give them a reason to revive the project. You’d think dramatically more efficient use of plutonium supplies would be a worthwhile endeavor.
Or developing a reactor and eliminating the plutonium.