If you want to go to the next level with software defined radio (SDR), there are a lot of choices. The RTL-SDR dongles are fine, but if you get serious you’ll probably want something else. How do you choose? Well, your friends at the European Space Agency Libre Space Foundation have published a paper comparing many common options. True, they are mostly looking at how the receivers work with CubeSats, but it is still a good comparison.
The devices they examine are:
BladeRF 2.0 Micro
Ettus USRP B210
They looked at several bands of interest, but not the HF bands — not surprising considering that some of the devices can’t even operate on HF. They did examine VHF, UHF, L band, S band, and C band performance. Some of the SDRs have transmit capabilities, and for those devices, they tested the transmit function as well as receive.
At this point, most of us are painfully aware of the restrictions that COVID-19 social distancing protocols have put on our daily lives. Anyone who can is working from home, major events are canceled, non-essential businesses are closed, and travel is either strongly discouraged or prohibited outright. In particularly hard hit areas, life and commerce has nearly ground to a halt with no clear end date in sight.
Naturally, there are far reaching consequences for this shutdown beyond what’s happening on the individual level. Large scale projects are also being slowed or halted entirely, as there’s only so much you can do remotely. That’s especially true when the assembly of hardware is concerned, which has put some industries in a particularly tight spot. One sector that’s really feeling the strain is aerospace. Around the world, space agencies are finding that their best laid plans are suddenly falling apart in the face of COVID-19.
In some cases it’s a minor annoyance, requiring nothing more than some tweaks to procedures. But when the movements of the planets are concerned, a delay of weeks or months changes everything. While things are still changing too rapidly to make an exhaustive list, we already know of a few missions that are being impacted in these uncertain times.
Nuclear power is great if you want to generate a lot of electricity without releasing lots of CO2 and other harmful pollutants. However, the major bugbear of the technology has always been the problem of waste. Many of the byproducts from the operation of nuclear plants are radioactive, and remain so for thousands of years. Storing this waste in a safe and economical fashion continues to be a problem.
Alternative methods to deal with this waste stream continue to be an active area of research. So what are some of the ways this waste can be diverted or reused?
Fast Breeders Want To Close The Fuel Cycle
One of the primary forms of waste from a typical nuclear light water reactor (LWR) is the spent fuel from the fission reaction. These consist of roughly 3% waste isotopes, 1% plutonium isotopes, and 96% uranium isotopes. This waste is high in transuranic elements, which have half-lives measured in many thousands of years. These pose the biggest problems for storage, as they must be securely kept in a safe location for lengths of time far exceeding the life of any one human society.
The proposed solution to this problem is to instead use fast-neutron reactors, which “breed” non-fissile uranium-238 into plutonium-239 and plutonium-240, which can then be used as fresh fuel. Advanced designs also have the ability to process out other actinides, also using them as fuel in the fission process. These reactors have the benefit of being able to use almost all the energy content in uranium fuel, reducing fuel use by 60 to 100 times compared to conventional methods.
In the early days of spaceflight, when only the governments of the United States and the Soviet Union had the ability to put an object into orbit, even the most fanciful of futurists would have had a hard time believing that commercial entities would one day be launching sixty satellites at a time. What once seemed like an infinite expanse above our heads is now starting to look quite a bit smaller, and it’s only going to get more crowded as time goes on. SpaceX is gearing up to launch nearly 12,000 individual satellites for their Starlink network by the mid-2020s, and that’s just one of the “mega constellations” currently in the works.
It might seem like overcrowding of Earth orbit is a concern for the distant future, but one needs only look at recent events to see the first hints of trouble. On September 2nd, the European Space Agency announced that one of its research spacecraft had to perform an evasive maneuver due to a higher than acceptable risk of colliding with one of the first-generation Starlink satellites. Just two weeks later, Bigelow Aerospace were informed by the United States Air Force that there was a 1 in 20 chance that a defunct Russian Cosmos 1300 satellite would strike their Genesis II space station prototype.
A collision between two satellites in orbit is almost certain to be catastrophic, ending with both spacecraft either completely destroyed or severely damaged. But in the worst case, the relative velocity between the vehicles can be so great that the impact generates thousands of individual fragments. The resulting cloud of shrapnel can circle the Earth for years or even decades, threatening to tear apart any spacecraft unlucky enough to pass by.
Fortunately avoiding these collisions shouldn’t be difficult, assuming everyone can get on the same page before it’s too late. The recently formed Space Safety Coalition (SSC) is made up of more than twenty aerospace companies that realize the importance of taking proactive steps to ensure humanity retains the unfettered access to outer space by establishing some common “Rules of the Road” for future spacecraft.
Star Trek — as much as we love it — was guilty sometimes of a bit of hyperbole and more than its share of inconsistency. In some episodes, ion drives were advanced technology and in others they were obsolete. Make up your mind!
The ESA-JAXA BepiColombo probe is on its way to Mercury riding on four ion thrusters developed by a company called QinetiQ. But unlike the ion drive featured in the infamous “Spock’s Brain” episode, BepiColombo will take over seven years to get to Mercury. That’s because these ion drives are real.
The craft is actually two spacecraft in one with two different Mercury missions. The Mercury planetary orbiter will study the surface while the magnetosphere orbiter will study the little planet’s magnetic field. Check out a video about the mission, below. The second video shows [Neil Wallace] talking about how the ion propulsion — also known as solar electric engines — differ from traditional chemical thrusters.
While down here there’s room for debate about the suitability of 3D printing for anything more serious than rapid prototyping, few would say the same once you’ve slipped the surly bonds of Earth. With 3D printing, astronauts would have the ability to produce objects and tools on-demand from a supply of inert raw building materials. Instead of trying to pack every conceivable spare part for a mission to Mars, replacements (assuming a little forward thinking on the part of the spacecraft designers) can be made to order out of the stock of raw plastic or metal kept on-board. The implications of such technology for deep space travel or off-world settlement simply cannot be overstated.
In the more immediate future, 3D printing can be used to rapidly develop and deploy unmanned spacecraft. Tiny satellites (referred to as CubeSats) could be printed, assembled, and deployed by astronauts already in orbit. Innovations such as these could allow science missions to be planned and executed in months instead of years, and at a vastly reduced cost.
Humanity has been a spacefaring species for barely sixty years now. In that brief time, we’ve fairly mastered the business of putting objects into orbit around the Earth, and done so with such gusto that a cloud of both useful and useless objects now surrounds us. Communicating with satellites in Earth orbit is almost trivial; your phone is probably listening to at least half a dozen geosynchronous GPS birds right now, and any ham radio operator can chat with the astronauts aboard the ISS with nothing more that a $30 handy-talkie and a homemade antenna.
But once our spacecraft get much beyond geosynchronous orbit, communications get a little dicier. The inverse square law and the limited power budget available to most interplanetary craft exact a toll on how much RF energy can be sent back home. And yet the science of these missions demands a reliable connection with enough bandwidth to both control the spacecraft and to retrieve its precious cargo of data. That requires a powerful radio network with some mighty big ears, but as we’ll see, NASA isn’t the only one listening to what’s happening out in deep space. Continue reading “Serious DX: The Deep Space Network”→