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Joris _

Elon Musk: SpaceX signs "biggest" commercial launch deal ever - The Write Stuff - Orlan... - 0 views

blogs.orlandosentinel.com/...mmercial-launch-deal-ever.html

launcher spacex

shared by Joris _ on 17 Jun 10 - Cached
LeopoldS liked it
  • ore than half of his company’s manifest of about 30 launches are purely commercial
  • His statement challenges critics of private space companies whom have maintained that there is not enough commercial business to support them
  • lower launch costs for the government
duncan barker

Top 10 Ridiculous Patents - 4 views

top-10-list.org/...top-ten-ridiculous-patents

pure class

shared by duncan barker on 19 Aug 10 - Cached
Dario Izzo liked it
  • duncan barker on 19 Aug 10
     
    My favorite is the "Device to Sense if a Pedestrian Was Hit by a car" invention
santecarloni

Space-time cloak could hide events : Nature News - 3 views

www.nature.com/...news.2010.611.html

phy cloak space-time

shared by santecarloni on 19 Nov 10 - No Cached
LeopoldS liked it
  • santecarloni on 19 Nov 10
     
    I think they are taking it a bit too far....
  • ...1 more comment...
  • Luzi Bergamin on 19 Nov 10
     
    I'm a little bit surprised as well about the crude story of the burglar, pure nonsense, of course! But the paper is deadly serious, Alberto and Paul are my best collaborators in metamaterials and optics, they are not this type of TV-show scientists as Leonhardt etc. But as Alberto told me: just put the name "cloak" in the title and you're in all the news. It's not science, it's kindergarden :-(.
  • LeopoldS on 20 Nov 10
     
    is my memory wrong or isn't this what you have already mentioned as theoretically possible a few years back when discussing this, Luzi?
  • Luzi Bergamin on 21 Nov 10
     
    Very well possible that I mentioned this. In fact I was one of the first who took spacetime transformations in transformation optics seriously. But first, my name is not Leonhardt and I don't work at Imperial, that's why nobody cites me and second I most probably found the idea too stupid to be published. You see the two reasons why I'm not successful in science...
LeopoldS

Spaceflight Now | Atlas Launch Report | Air Force spaceplane is an odd bird with a twis... - 3 views

spaceflightnow.com/...100402x37update

spaceflight suborbital defence

shared by LeopoldS on 06 Apr 10 - Cached
  • LeopoldS on 06 Apr 10
     
    Juxi are you following this one? any idea on its purpose?
  • Ma Ru on 07 Apr 10
     
    Not that I'm an expert in the field in any way, but there are two things I could think of: 1) possibility of bringing the payload back means that it can collect huge amounts of data which wouldn't be possible to be transferred via radio in reasonable time and/or you can bring back data you don't want to be intercepted by enemy 2) I remember reading somewhere that possibility of re-entry from orbit means you can strike any country without violating the airspace of the neighbouring countries. As the project is now managed by military, a purely civil purpose can be safely ruled out in my opinion.
pacome delva

Photonic Thermos | Physical Review Focus - 0 views

focus.aps.org/st14

phy thermodynamics insulator

shared by pacome delva on 19 Oct 09 - Cached
  • The pure vacuum of a thermos is not the best possible insulator for keeping your soup warm. Last year a team found theoretically that a structure known as a photonic crystal could block heat flow even more effectively than vacuum.
annaheffernan

Laser shines a new light on isotope separation - 0 views

physicsworld.com/...ew-light-on-isotope-separation

shared by annaheffernan on 07 Jul 14 - No Cached
  • annaheffernan on 07 Jul 14
     
    A new method of separating nuclear isotopes that exploits the slight differences in their electronic energy levels has been developed by physicists in the US. The energy-efficient separator was used to create isotopically pure lithium-7, which is used in some nuclear reactors. Good news for any future nuclear powered space missions perhaps? It could potentially replace the current (and much less energy efficient) methods that were developed in the 1950's
Nina Nadine Ridder

To save on weight, a detour to the moon is the best route to Mars - 1 views

phys.org/...ht-detour-moon-route-mars.html

technology space lunar_base fuel Mars_missions

shared by Nina Nadine Ridder on 15 Oct 15 - No Cached
Ethan Evan liked it
  • Nina Nadine Ridder on 15 Oct 15
     
    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."
  • Alexander Wittig on 16 Oct 15
     
    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
Paul N

New derivation of pi links quantum physics and pure math - 5 views

phys.org/...-pi-links-quantum-physics.html

science INF PHY

shared by Paul N on 11 Nov 15 - No Cached
  • Paul N on 11 Nov 15
     
    In 1655 the English mathematician John Wallis published a book in which he derived a formula for pi as the product of an infinite series of ratios. Now researchers from the University of Rochester, in a surprise discovery, have found the same formula in quantum mechanical calculations of the energy levels of a hydrogen atom.
  • Ma Ru on 11 Nov 15
     
    This is insanity, Max. Or maybe it's genius.
Luzi Bergamin

[1107.0167] Nonlinear transformation optics and engineering of the Kerr effect - 9 views

arxiv.org/1107.0167

PHY nan optics metamaterials

shared by Luzi Bergamin on 04 Jul 11 - No Cached
LeopoldS liked it
  • Luzi Bergamin on 04 Jul 11
     
    The best paper on transformation optics written ever :-)
  • ...2 more comments...
  • jmlloren on 05 Jul 11
     
    Finally something worth to read in the MM field!. The idea is excellent, congratullations. However, I think there is a typo or mistake in the definition of l=3x10-13 m, the "waist" of the laser beam. Seems clear that 0.3 pm is too small for being a waist of any laser beam.
  • Luzi Bergamin on 05 Jul 11
     
    Thanks for your commendation. Of course, the problem with nonlinear transformation optics is the same as with linear: it's very easy to come up with theoretical descriptions of devices that have the most absurd properties, but it will be extremely hard to fabricate them. But if you have any good suggestion, please shoot! About the laser beam: Pekka made the simulations, since I am not a "Comsolist", but still I think the numbers are correct. You are right that we should not call this a laser beam. Our problem was the following: we need to have a very simple model that can be simulated exactly (full Maxwell equations) but naturally exhibits self focusing. The Gaussian beam was the simplest solution. Since our model is purely classical and moreover we do not take into account diffraction effects, the parameter "l" is of minor importance. Taking "l" much larger gives almost the same picture but requires much more computer power to simulate. I guess that's why Pekka chose an unnaturally small number.
  • jmlloren on 05 Jul 11
     
    Concerning the fabrication... as usual, no idea. I agree that this is the main drawback of MM, and certainly difficult to overcome. I would double check that number, because its value is related with the beam shape of Fig. 1 A. I believe that the simulations are correct, it's just a detail.
  • LeopoldS on 06 Jul 11
     
    wow ... still publishing despite babysitting and new job!!
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