Light from a distant galaxy can be strongly bent by the gravitational influence of a foreground galaxy. That effect is called strong gravitational lensing. Normally a single galaxy is lensed at a time. The same foreground galaxy can – in theory – simultaneously lens multiple background galaxies. Although extremely rare, such a lens system offers a unique opportunity to probe the fundamental physics of galaxies and add to our understanding of cosmology.
One such lens system has recently b [...]
Can you find the comet? True, a careful eye can find thousands of stars, tens of constellations, four planets, three galaxies, and the central band of our Milky Way Galaxy -- all visible in the sky of this spectacular 180-degree panorama. Also, if you know what to look for, you can identify pervasive green airglow, an earthly cloud, the south celestial pole, and even a distant cluster of stars.
But these are all easier to find than Comet 252P/LINEAR. The featured image, taken in el Leoncito [...]
Expedition 48 is moving ahead with preparations for an upcoming spacewalk. New science also is under way aboard the International Space Station after being delivered last week.
A new U.S. spacesuit was unpacked from inside Dragon and will be used during an August spacewalk to install a Commercial Crew docking port. An older U.S. spacesuit will be returned to Earth inside the Dragon for refurbishment.
Housed inside the trunk of the Dragon space freighter is the International Docking Adapter [...]
Using NASA’s Hubble Space Telescope, astronomers have conducted the first search for atmospheres around temperate, Earth-sized planets beyond our solar system and found indications that increase the chances of habitability on two exoplanets.
Specifically, they discovered that the exoplanets TRAPPIST-1b and TRAPPIST-1c, approximately 40 light-years away, are unlikely to have puffy, hydrogen-dominated atmospheres usually found on gaseous worlds.
“The lack of a smothering hydrogen-heli [...]
Did the two most famous satellite galaxies of our Milky Way Galaxy once collide? No one knows for sure, but a detailed inspection of deep images like that featured here give an indication that they have. Pictured, the Large Magellanic Cloud (LMC) is on the top left and the Small Magellanic Cloud (SMC) is on the bottom right. The surrounding field is monochrome color-inverted to highlight faint star streams, shown in gray. Perhaps surprisingly, the featured research-grade image was compiled with [...]
The Space Show, hosted by David Livingston at www.TheSpaceShow.com, will have the following guests this week:
1. Monday, July 25, 2016, 2-3:30 PM PDT (21-22:30 GMT)
Hermes Project for using cell phones for getting data directly from space with Rishabh Maharaja as guest.
Rishabh Maharaja is currently the deputy flight operations team lead for the EO-1 mission at NASA’s Goddard Space Flight Center and an adjunct professor for the Astronautical Engineering Department at Capitol Technolo [...]
Several years back I suggested a type of compensating nozzle that should be inexpensive to build and test. Unfortunately the ones I made for demonstration with compressed air were hit and miss as I didn’t have the theory quite right. Hit and miss is not good enough for serious companies, so I mostly dropped the idea for a while. I thought a few of my acquaintances in the business might do something with the idea for a while. Now I think the idea has been mostly forgotten as unworkable.
A few years back I did finally find the missing part of the concept and did nothing about it as I thought at the time that others had picked it up and moved on. Since I don’t think that has happened, I am going to repost the concept.
On the left is the engine with the notch showing on the right side. The notch allows the atmosphere to enter the bell to compensate for over expansion at lower altitudes. At higher altitudes and in vacuum the exhaust gradually uses the whole bell with some losses through the notch. This will allow a nozzle to be optimum at sea level when most are over expanded. It will also be nearly as good as a full diameter high expansion nozzle in regimes with the exhaust under expanded.
The missing ingredient in the prior concept was appreciation for the momentum of the exhaust at the notch site. The momentum, especially with the rounded notches that I was advocating before, would prevent the atmosphere from entering the notch in a controlled manner. The addition of a sharp edge at the notch to assure a clean break and a slight reverse on the notch edge to direct the exhaust inwards controls the momentum of the exhaust in a manner that allows the atmosphere to interact and provide pc/pa compensation at a range of back pressures.
A compensating nozzle allows lower pressure engines to operate more efficiently in a launch vehicle. They should allow a payload increase of 1-5% depending on the vehicle and the assumptions going in. For a VTVL that wants to operate at very low pressures in the landing phase, a compensating nozzle would be a very important upgrade, though the successes of Blue and SpaceX take some of the edge off that argument.
This is a public domain concept as I described it here years ago. So anyone that wants to see what I am talking about can build a quick and dirty nozzle to use with shop air. The ones have done were an air chuck and fiberglass. About $10.00 in materials. I know it works at 135 psi. Then you can try a higher pressure gas if it might be useful to you or someone you know.
Are stars better appreciated for their art after they die? Actually, stars usually create their most artistic displays as they die. In the case of low-mass stars like our Sun and M2-9 pictured above, the stars transform themselves from normal stars to white dwarfs by casting off their outer gaseous envelopes. The expended gas frequently forms an impressive display called a planetary nebula that fades gradually over thousands of years.
M2-9, a butterfly planetary nebula 2100 light-years away [...]
Lights sprawl toward the horizon in this night skyscape from Uludag National Park, Bursa Province, Turkey, planet Earth. The stars and nebulae of the Milky Way are still visible though, stretching above the lights on the northern summer night while three other planets shine brightly. Jupiter is at the far right, Mars near the center of the frame, and Saturn is just right of the bulging center of our galaxy.
Because the panoramic scene was captured on July 6, all three planets pictured were h [...]