Group items tagged

Is it really true?

Article 1011.6263 doesn't exist

ha it's back! Yes they are talking about GAP since some time in France, and lobbying to put it on a planetary mission.

hehe, a nice controversy? or completely overinterpreted results...?

what the heck is this? sounds strange to me ... would I understand the original paper?

The usefulness of having a robust trajectory :) ... They have to wait 6 more years for another date with Venus ...

"optimised trajectory" of course not, robust definitely! It was the subject of my paper presented at the AAS (the one in San Diego) "Designing robust interplanetary trajectories subject to one temporary engine failure". The problem here is that they do not have enough fuel for a correction maneuver that would allow to come back to Venus earlier, and break for a VOI. A robust scenario could have alloted the best amount of fuel and time to be able to recover from almost all possible unplanned events. In the paper, I introduce some confidence regions such that I get the robust control for p% chance of mission success in case m% chance of problem with the propulsion system.

You should run your method on this scenario and see if you could get a trajectory with a shorter come back time using the same spacecraft.... would be a big selling point for a new trajectory design approach

"At a symposium at the Dutch Spinoza-instituut on 8 December, 2009, string theorist Erik Verlinde introduced a theory that derives Newton's classical mechanics. In his theory, gravity exists because of a difference in concentration of information in the empty space between two masses and its surroundings. He does not consider gravity as fundamental, but as an emergent phenomenon that arises from a deeper microscropic reality. A relativistic extension of his argument leads directly to Einstein's equations."

Leo, do you mean you liked my comment on your question more than Pacome's? Well, the ACT has to evolve and fledge, so no bullshitting anymore, but serious and calculating answers... :-) Sorry Pacome, nothing against you!! I just LOVE this Diigo because it gives me the opportunity for a happy revival of my ACT mood.

haha, today would have been great to show your mood... we had a talk on the connection between mind and matter !!

dark matter :-) ?? could there be loads of them?

A critical view on Prof. Markram's Blue Brain project (in German).

As far as I know it's sort of like "Let's construct an enormous dynamical system and see what happens"... i.e. a waste of taxpayer's money... Able to heal Alzheimer... Yeah... Actually I was on the conference the author is mentioning (FET 2011) and I have seen the presentations of all 6 flagship proposals. Following that I had a discussion with one of my colleagues about the existence of limits of the amount of bullshit politicians are willing to buy from scientists. Will there be a point at which politicians, despite their total ignorance, will realise that scientists simply don't deliver anything they promise? How long will we (scientists) be stuck in the viscous circle of have-to-promise-more-than-predecessors in order to get money? Will we face a situation when we'll be forced to revert to promises which are realistic? To be honest none of the 6 presentations convinced me of their scientific merit (apart from the one on graphene where I have absolutely no expertise to tell). Apparently a huge amount of money is about to be wasted.

It's not just "Let's construct an enormous dynamical system and see what happens", it's worse! Also the simulation of the cosmological evolution is/was a little bit of this type, still the results are very interesting and useful. Why? Neither the whole cosmos nor the human brain at the level of single neurons can be modelled on a computer, that would last aeons on a "yet-to-be-invented-extra-super-computer". Thus one has to make assumptions and simplifications. In cosmology we have working theories of gravitation, thermodynamics, electrodynamics etc. at hand; starting from these theories we can make reasonable assumptions and (more or less) justified simplifications. The result is valuable since it provides insight into a complex system under given, explicit and understood assumptions. Nothing similar seems to exist in neuroscience. There is no theory of the human brain and apparently nobody has the slightest idea which simplifications can be made without harm. Of course, Mr. Markram remains completely unaffected of ''details'' like this. Finally, Marek, money is not wasted, we ''build networks of excellence'' and ''select the brightest of the brightest'' to make them study and work at our ''elite institutions'' :-). I lively remember the stage of one of these "bestofthebest" from Ivy League at the ACT...

Another candidate for analogue gravity ?

New Propulsion Systems

At a meeting of the American Geophysical Union in San Francisco in December, he reported an average figure that was between 0.005 and 0.008 per cent greater than the value for Earth's mass established by the International Astronomical Union. A disc of dark matter around the equator 191 kilometres thick and 70,000 km across can explain this, he says. Harris has yet to account for perturbations to the satellites' orbits due to relativity, and the gravitational pull of the sun and moon. Maybe relativistic GPS could improve this even further? As a side note however, the Juno spacecraft flyby showed an gravity acceleration which matched the calculations, casting doubts on the earlier calculations.

12 new NIAC 1 studies - many topics familiar to us ... please have a look at those closest to your expertise to see if there is anything new/worth investigating (and in general to be knowledgeable on them since we will get questions sooner or later on them)
Principal Investigator Proposal Title Organization City, State, Zip Code
Atchison, Justin Swarm Flyby Gravimetry Johns Hopkins University Baltimore, MD 21218-2680
Boland, Eugene Mars Ecopoiesis Test Bed Techshot, Inc. Greenville, IN 47124-9515
Cash, Webster The Aragoscope: Ultra-High Resolution Optics at Low Cost University of Colorado Boulder, CO 80309-0389
Chen, Bin 3D Photocatalytic Air Processor for Dramatic Reduction of Life Support Mass & Complexity NASA ARC Moffett Field, CA 94035-0000
Hoyt, Robert WRANGLER: Capture and De-Spin of Asteroids and Space Debris Tethers Unlimited Bothel, WA 98011-8808
Matthies, Larry Titan Aerial Daughtercraft NASA JPL Pasadena, CA 91109-8001
Miller, Timothy Using the Hottest Particles in the Universe to Probe Icy Solar System Worlds John Hopkins University Laurel, MD 20723-6005
Nosanov, Jeffrey PERISCOPE: PERIapsis Subsurface Cave OPtical Explorer NASA JPL Pasadena, CA 91109-8001
Oleson, Steven Titan Submarine: Exploring the Depths of Kraken NASA GRC Cleveland, OH 44135-3127
Ono, Masahiro Comet Hitchhiker: Harvesting Kinetic Energy from Small Bodies to Enable Fast and Low-Cost Deep Space Exploration NASA JPL Pasadena, CA 91109-8001
Streetman, Brett Exploration Architecture with Quantum Inertial Gravimetry and In Situ ChipSat Sensors Draper Laboratory Cambridge, MA 02139-3539
Wiegmann, Bruce Heliopause Electrostatic Rapid Transit System (HERTS) NASA MSFC Huntsville, AL 35812-0000

Eh, the swarm flyby gravimetry is very similar to the "measuring gravitational fields" project I proposed in the brewery

More arguments for a lunar base? "They found the most mass-efficient path involves launching a crew from Earth with just enough fuel to get into orbit around the Earth. A fuel-producing plant on the surface of the moon would then launch tankers of fuel into space, where they would enter gravitational orbit. The tankers would eventually be picked up by the Mars-bound crew, which would then head to a nearby fueling station to gas up before ultimately heading to Mars."

There was a paper with a very similar concept (reaching Mars via DRO) at the AAS meeting in January by Conte et al. First, the total Delta V required for a trip Earth -> LLO -> MLO is higher than Earth -> MLO. The trick is that Earth -> LLO requires less Delta V than Earth -> MLO and hence less mass has to be carried along *from Earth*. Essentially what both approaches have in common is that they say "if there's a free gas station orbiting the moon, it's cheaper to fly empty and fill up there on the way". The AAS paper actually does a decent job at estimating the "real" cost by also including estimates of the cost of a lunar base. https://pure.strath.ac.uk/portal/files/44275737/Conte_etal_AAS2015_Earth_Mars_transfers_through_Moon_distant_retrograde_orbit.pdf

From the section Science & Environment Scientists are claiming a stunning discovery in their quest to fully understand gravity. They have observed the warping of space-time generated by the collision of two black holes more than a billion light-years from Earth.

According to their Nature article, they can detect "a tunnel less than 1m across, buried 2m underground" just from its gravitational difference. Using a device that they predict could cost ~100 € in mass production. UK researchers have built a small device that measures tiny fluctuations in gravity, and could be used to monitor volcanoes or search for oil. Such gravimeters already exist but compared to this postage stamp-sized gadget, they are bulky and pricy.

Einstein's theory of gravity, General Relativity (GR), has been tested precisely within the Solar System. However, it has been difficult to test GR on the scale of an individual galaxy. Collett et al. exploited a nearby gravitational lens system, in which light from a distant galaxy (the source) is bent by a foreground galaxy (the lens). Mass distribution in the lens was compared with the curvature of space-time around the lens, independently determined from the distorted image of the source. The result supports GR and eliminates some alternative theories of gravity.

Paper at http://www.nature.com/nature/journal/v548/n7669/full/nature23463.html?foxtrotcallback=true

Loss of connectivity in the multisensory integration cortical areas after short term microgravity experience, which could explain astronauts decrease of performance in sensorimotor tasks and spatial working memory. However, the effect should wear off after a few days in microgravity and after adaptation to incongruent vestibular information. ISS experiment needed...