UAV update: GPS jamming, tethered drones, NASA UTM and space planes

June 21, 2017  - By

Drones and Interference

Most UAVs now come with GNSS as the principle sensor for guidance, often with inertial aiding. And high-precision GNSS on a drone enables much quicker high-precision surveying — unless signal interference disrupts things and spoils your day.

Septentrio is now fielding two high-precision receivers that can overcome a good proportion of most common interference. AsteRx4 and AsteRx-m2 receivers, equipped with AIM+, can not only overcome common (but illegal) chirp jammers (which can virtually blot out L1 GNSS signals), but also have a spectrum plotting capability. This spectrum plot can visualize potential onboard interference sources during integration, and help identify onboard jammers.

GoPro Hero 2 camera pick-up monitored by an AsteRx4 receiver

The GPS L1-band spectrum above has been disturbed by a GoPro camera installed without sufficient shielding on a quadcopter close to the GNSS antenna. The three peaks indicate harmonics of 24 MHz — the typical frequency for a MMC/SD logging interface. This problem was fixed in the lab by adding a shielded enclosure for the camera.

Although chirp jammers only transmit at around 10 mW, they are powerful enough to block GNSS signals over several hundred meters on the ground. A UAV is much more vulnerable in the air as jamming signals travel further, without line-of-sight blockage from trees, buildings or other obstacles.

The figure above illustrates how a 10-mW chirp jammer disrupts RTK positioning 1 km away in a high-end receiver. Even a low-end, less accurate and less sensitive consumer-grade L1 receiver loses positioning over several hundred meters. But with AIM+ activated, the AsteRx4 maintains an RTK fix throughout the (simulated) flight and shows no degradation in position.

So, there are two benefits to using these Septentrio receivers on a drone — less likelihood of losing positioning capability from intentional jamming while airborne, and a built-in spectrum plotter.

Tethered Drones

We ran an article recently relating that the U.S. military was interested in tethered drone systems, presumably for short-range reconnaissance. Hard to understand why you might want to intentionally limit the operating range of a drone, but with power supplied from the ground, much longer mission endurance may also have advantages for certain civilian applications too. For instance, inspection of power plants, refinery stacks, on-shore and off-shore oil rigs and other such fixed-location critical installations may benefit from long duration capability, while tethered flight should still allow travel over the whole inspection area.

Well, these same guys — Drone Aviation — just figured out how to adapt DJI Inspire drones to add a tether system. With a massive share of the commercial small drone market, DJI drones are the most common sUAV used in many civilian applications.

So now realtors wanting detailed listing videos, news media, maintenance and insurance people inspecting tall buildings or bridges, and many others in the oil and gas industry, no longer need to worry about losing power during lengthy visual data collection. Maybe in exchange, management of how the tether locates during an inspection may become a concern, but the longer endurance trade-off may also be worthwhile for a lot of applications.

FUSE system.

The Drone Aviation FUSE system comes with a customized power pack and an “automated smart tension control winch case” with 200 feet of tether, and uses 110-volt ground power — which works well when supplied by a portable field generator.

NASA Tests UAV Traffic Management

In the meantime as small drone use increases, including overnight shipping companies who continue to pursue ways to make package delivery by drones in ways acceptable to the FAA, the looming crisis in UAV airspace traffic management (UTM) is getting a lot of attention.

NASA has been cooperating with FAA for some time to investigate potential systems for low altitude drone traffic management, and recently concluded field tests at six FAA test sites across the U.S.

The three-week campaign, known as the Technology Capability Level 2 (TCL2) National Campaign, has focused on flying small drones well beyond the pilot’s visual line of sight over sparsely populated areas at these test sites. Operational test scenarios have included simulation of package deliveries, agricultural surveys, search and rescue, railway inspections and video surveillance operations.

NASA has signed up over 100 industry, academic and government partners for this UTM effort, who are collaborating together, sharing data and using their own resources for this investigation. Companies who are participating and who may have significant interest in the outcome of these tests are planning to fly drones in the national airspace for package and food deliveries, bridge, power line and rail inspections, and agricultural purposes — these include Amazon, Google, Intel, Flirtey, Drone America, Carbon Autonomous and NUAIR.

NASA is currently assessing the data gathered during these recent tests, but plans are already in place for the next phase of tests — flying drones in denser traffic over more populated areas and also determining UAV/UTM responses to larger manned aircraft.

And in related activities elsewhere, at AUVSI XPONENTIAL in Dallas last month the International Civil Aviation Organization (ICAO), an agency of the United Nations that coordinates aircraft operations between member countries around the world, announced a Request for Information (RFI) on UTM systems. The intent of the RFI is to advance international progress towards worldwide UTM adoption by first gathering the best ideas from governments and industry.

BVLOS Demonstration in France

In an effort to demonstrate practical, readily implemented Beyond Visual Line Of Sight (BVLOS) drone operations in France, Delair-Tech recently flew a UAV for 30 miles, simulating powerline inspection. Delair used a regular, commercial 3G cell-phone network to control the drone for this test – an innovative demonstration that long-distance drone operations can be safe and simple to achieve.

Delair drone inspects powerlines in France.

Delair-Tech acquired Gatewing — which was previously owned by Trimble — in 2016 and has also signed strategical distribution agreements with Trimble. The business not only includes the manufacture, turn-key operation and support of drones, but also includes data analysis and reporting. And in a sign that commercial drone operations are becoming more commonplace in France, and that there is likely a preference for local suppliers, the purchasing conduit for government agencies across the country has selected the Delair DT18 and DT26X as the choice for French government agencies purchasing fixed-wing unmanned aerial vehicles.

Unmanned Space Plane?

DARPA recently selected Boeing to complete advanced design work for the Experimental Spaceplane (XS-1) program — a new class of hypersonic aircraft aimed at rapid turn-round, low-cost access to space.

Artist’s concept of the space-plane.

The XS-1 program is expected to create a reusable unmanned aircraft, around the size of a business jet, which would take off vertically like a rocket and fly at hypersonic speeds. The vehicle would fly to a high suborbital altitude and release an expendable upper stage, deploying a 3,000-pound satellite to polar orbit. The reusable space plane would then return and land horizontally and — this is a key requirement for the program — be prepared for the next flight within hours or a few days.

The XS-1 technology demonstration will therefore aim to fly 10 times in 10 days, with the final flight carrying the upper-stage payload delivery system. Its hoped the program will promote a commercially offered service with costs as low as $5 million or less per launch — a small fraction of the cost of today’s launch systems. The XS-1 technology demonstrator’s propulsion system will be an Aerojet Rocketdyne AR-22 engine, a version of the Space Shuttle’s main engine, which would be fired on the ground 10 times in 10 days to demonstrate propulsion readiness for flight tests.

Phase 3 objectives include 12 to 15 flight tests, currently scheduled for 2020. After multiple shakedown flights to reduce risk, the XS-1 will to fly 10 times over 10 consecutive days, at first without payloads at speeds as fast as Mach 5. Subsequent flights are planned to fly as fast as Mach 10, and deliver 900lb to 3,000lb payloads into low Earth orbit.

So, high-end receivers to help deal with both external and internal jamming, tethers for DJI drones enabling longer inspection flight capability, NASA testing and industry collaboration towards an air traffic system for drones, long-range drone operations using 3G cellular networks in France, and even a research program to develop an unmanned space plane — nothing ever stands still in the ever-evolving world of unmanned aircraft.

Tony Murfin

GNSS Aerospace

This article is tagged with and posted in OEM, Opinions, UAV/UGV

About the Author:

Tony Murfin is managing consultant for GNSS Aerospace LLC, Florida. Murfin provides business development consulting services to companies involved in GNSS products and markets, and writes for GPS World as the OEM Professional contributing editor. Previously, Murfin worked for NovAtel Inc. in Calgary, Canada, as vice president of Business Development; for CMC Electronics in Montreal, Canada, as business development manager, product manager, software manger and software engineer; for CAE in Montreal as simulation software engineer; and for BAe in Warton, UK, as senior avionics engineer. Murfin has a B.Sc. from the University of Manchester Institute of Science and Technology in the UK, and is a UK Chartered Engineer (CEng MIET).

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