To mitigate the effect of unknown and constantly changing ground winds, the terminal guidance algorithms employ continuous (real-time) reoptimization of the final turn. But this is not the only novel idea Snowflake utilizes to achieve an unprecedented accuracy. The networking version of Snowflake, Snowflake-N, developed in cooperation with another research and development center at NPS, Center for Network Innovation and Experimentation (CENETIX) enables communication between multiple descending ADSs, ground weather stations and operator/user, who can reside anywhere in the world (global reach).
The most current and robust network / communication architecture is presented in Fig.O. Its key component, the portable ground target weather station (Fig.Pa), was developed and employed to measure ground winds (magnitude and direction) and uplink them to the descending Snowflakes along with current altitude settings. The target weather station (TWS) is based on a portable Kestrel-4000 weather device (weighting only 3.6oz), which was slightly reprogrammed to be able to constantly output all necessary information. In terms of accuracy, Kestrel-4000 is capable of measuring wind’s direction within 5º, speed – within 0.1kts and atmospheric pressure – within 0.1psi (or 1ft). The TWS communicates with a descending Snowflake-N via miniature computer and 900MHz FreeWave radio module residing in a Pelican-1150 case somewhere nearby (Fig.Pb). This short-range communication between Kestrel and TWS computer utilizes the advantages of a Bluetooth interface.
Figure O. The most current communication architecture for Snowflake-N ADS.
Figure P. Portable weather station on the vane (a) and its computer / communication set (b).
In turn, a TWS FreeWave radio passes information from TWS on to the ground control station (GCS). The GCS gathers information from multiple target weather stations and broadcasts it to multiple descending Snowflake-N. Depending on what specific target was assigned to each particular Snowflake-N, the latter only accepts weather data from its own target. If the target during ADS descent was reassigned, Snowflake-N starts listening to weather data pertaining to that newly assigned target. Once Snowflake-N receives a new piece of data, it responds back to the ground station (via 900MHz FreeWave radio available on board) with its current parameters. Therefore, the GCS has full situational awareness of all target weather stations and Snowflakes all the time. If GCS is connected to the internet (via Ethernet, wireless or satellite link), this information becomes available globally. Figure Q features the GCS' 900MHz FreeWave radio set (a) and a small, lightweight, satellite terminal (b) allowing accessing Inmarsat’s Broadband Global Area Network service (BGAN) available worldwide. Once the first Snowflake-N reaches the ground it broadcasts an estimated wind profile to the remaining ADSs in the air to improve their touchdown accuracy.
Figure Q. The GCS' 900MHz radio set (a) and Hughes BGAN terminal (b).
The Snowflake-N payload can also include a standard Blackberry 8310 cell phone, which communicates with the autopilot via Bluetooth-Serial module. That allows sending and receiving packages of data via the AT&T GSM network to the Internet directly. In this case, the TWS can also include a Blackberry / Bluetooth module bundle allowing them to be clients of the network as well and therefore talk to Snowflakes directly. The communication architecture for this case is shown in Fig.R, while Fig.S features Kestrel/Blackberry/Bluetooth module bundle.
Figure R. The Snowflake-N communication architecture relying on GSM network.
|Figure S. The target weather station posting its data via Blackberry cell phone (on the back).||Figure T. Blackberry Curve 8310 handheld with Snowflake control interface.|
As shown in both Fig.O and Fig.R the operator/user can monitor the mission (using a common Google Earth tool) and/or exert control at any moment via computer (Internet), via GSM handheld, or via voice portal to change any mission parameters (Fig.T shows the developed GSM handheld interface).
Originally developed for the single purpose of communicating with the target weather stations to enable better touchdown accuracy of the Snowflake ADS, the developed architecture allows doing much more. In addition to Snowflake-N ADS' unique capability of delivering supplies with high accuracy in hostile and hazardous environments, the system could also be used as an innovative individual temporary “node” of ad hoc self-forming tactical network or a hub for a short-term aerial-ground network. On one hand, it is a slowly descending aerial node, which is capable of receiving data from the unattended sensors, once it gets in the range of wireless link, and sending information out through manned-unmanned network-on-the-move, before hitting the ground.
On the other hand, it is a perfect platform for bringing in nuclear radiation or chemical sensors close to the source, which otherwise is inaccessible. While collecting and feeding data out, remotely-controlled (in terms of target assignment) Snowflake-N could also bring a new set of disposable unattended sensors for the next step of data collection.
Several Snowflake ADS gradually descending in geographically distributed areas would enable largely distributed in time and space networking capability with sensors and small unit operators. Placing a small base station in Snowflake ADS payload would allow having highly undetectable wireless cell physically existing within 2-4 seconds of burst transmission. Then another cell or cluster pops-up 10-15 miles away from the source to receive some information temporary stored in UAV, air balloon, or ground vehicles relaying tactical information across network-controlled battlefield. Several parafoils during the descent could comprise a short-term mesh for reaching further into the area without network coverage.