Electrically Powered Helicopter / Drone For FireFighting And Rescue Operations

Introduction & Rational:

Most modern Fire Fighting Firetrucks, have the limitation that their ladders cannot extend beyond a certain height (due to physical & practical limitations). Thus in cases where a fire occurs in a highriser building, the fire department / crew have no alternative but to use the stairways of the said building. But there are many recorded incidents / scenarios where this approach as well to not have had been feasible (for example not possible to reach the floors above the "fire line", in cases where the fire had had reached / breached into the stairways...)

In the recent past itself there were several such highrise fires, where the fire departments / crew were rendered helpless, as they could not reach and rescue the victims.

R&D Goals / Targets:

Thus this R&D project intends to develop an electrically powered helicopter or drone, that can reach any high-riser building and engage in either firefighting and / or rescue operations from the relative safety of the outside of the building.

This helicopter or drone will thus be a barebone shell, that will only house the electrical motors, batteries, pilot & cockpit, one or two firefighters / rescue personnel and a fireproof layer/ outer skin  ex : Fiber Glass or if feasible Aerogels.

(The feasibility of using a thin water cooled / soaked layer -holding about 10-20 litres/ 10-20 kg of water- will also be looked into, as part of this R&D project. Thus in the presence of excessive heat, it would be the water that will absorb the heat and vaporize... Wherein fresh water could be pumped/ fed from the vehicle's water tanks, thus preventing the structure's temperature to exceed 100 ºC, -which is a temperature that is within the safe zone / will not structurally weaken the airframe metals/ carbon fibres-)

This firefighting Platform Vehicle would be fitted with an additional/ detachable / external water tank (larger capacity). And for personal rescue operations, the detachable water tank could be left on the ground...

The necessity to operate this helicopter / drone via electricity emanates from the fact that, it may be required to go into thick smoke (for example to rescue personel from a rooftop of a burning building/ highriser). Thus even though it would be possible to provide the pilot and the rescue team with breathing equipment, it may not be that much feasible to do such, with a turbo engine (however refer to Solution 2, for a possible alternate solution that may / might work...)

To make this rescue helicopter / drone as safe as possible for it's operators and the personnel at its close viscinity:

1. In the case of a drone, all fan blades will be placed inside ducts (aka ducted fans). 

2. In the case of a helicopter rotor, a lightweight / sufficiently rigid casing / duct will be constructed to cover the outer perimeter of the blades (which will act as a guard rail). Thus effectively this helicopter rotor will function inside a large protective duct/ guard rail. Thus even if a sudden gust of wind pushes the helicopter against the building, it would be the above protective perimeter duct/ rail that will come into contact / collide with the building (and not the rotor blades).

Solution 1 : Electrically operated:

Considering the torque to weight ratios, the best/ optimum motors to use would most likely be those built around Neodymium magnets. If for example in the case of rotating a helicopter rotor, if more power is required, then multiple such motors can be connected via gear wheels to the rotor shaft.

The next issue that would need to be resolved would be, what does one do when the batteries starts to run low? (As high power motors are extremely power hungry and can drain batteries at high rates).

One possible solution would be to have an additional battery pack on the ground. But what does one do when that pack as well runs low? For usually it takes at least half an hour to one hour (or more) to even fast charge a rechargeable battery... (There do exist, very fast battery recharging technologies, for example using suitable coolants / refrigerants, but whether such are currently available commercially, needs to be investigated...)

Thus as part of this R&D project, would like to investigate the feasibility of powering this rescue helicopter or drone, from / via a ground truck generator (mobile diesel generator used for power backups). Now a power cable will run from the generator, to the rescue vehicle, and if so required, to hold the weight of this cable (say at every 100 meters height) smaller drones will be deployed. Thus the sole purpose of these smaller drones will be to stabilize and hold the weight of the main power cable (prevent the power cable drifting in the gusts of wind, and offload the power cable weight from the main rescue vehicle). The smaller drones themselves can be powered from the ground truck generator...

This ground power, approach has the added advantage / benefit, that it may also be able to provide sufficient energy to power an additional set of drones and submersible water pumps (say at 100 meters height intervals) to hold / lift / provide a permanent water hose / line / connection, to the firefighting vehicle. Otherwise each time the firefighting vehicle runs out of water, it would have to come back to ground level to refill.

Firefighting Helicopter with protective guard rail & ground power

Ground power generator & Water pump

This rescue vehicle will have the option of powering it's (high power) motors, either via the ground truck generator, or if so required from it's internal batteries (for example when / if, it becomes necesary to disconnect from the ground power cables, when it is required to reach the roof of a building on fire). Thus when / if the rescue vehicle disconnects from the power cable, the smaller drones will keep the power cable in place, at a safe distance from the burning building.

Solution 2: Turbo (air breather) Engine operated:

Now an alternative solution to building an electrically operated system from the ground up, would be to use an existing helicopter and modify it for this firefighting and rescue operation. This approach would yield a working end solution, in the shortest time frame (as the amount of R&D required would be significantly reduced, than in the case of Solution 1).

But now, we face the issue/ problem of addressing as to how to resolve the case, of preventing the "air breather" turbo engine from malfunctioning / shutting down in the precense of excessive atmospheric CO₂ / sooth...

Thus as an alternate solution, would like to investigate the possibility of deploying an expandable duct that will be held in place via drones. Thus if this duct can be expanded to a length of say 15 or 20 meters, it should be possible to suck in air, sufficiently away from any smoke/ sooth of a burning building. Thus in this approach, if / when required, the pilot of the helicopter will be given a mechanism to deploy the above ducting, and allow the turbo engine, to breathe through / via this duct. This duct would be made of rigid ducting material, from the turbo intake upto the protective rotor perimeter rail (the region susceptible to rotor downdraft), and there onwards in a flexible / expandable design that can be extended to upto 15 or 20 meters via drones.

In this case, the drones will be powered from the alternators (electrical system) of the helicopter. Most likely to hold the weight of this duct, and prevent if from getting swayed in wind gusts, at least 2 drones of sufficient size may be required...

Stabilisation if the Firefighting vehicle:

Now in either of the above Solutions (electrical or turbo), in the case of utilizing a helicopter rotor, it would be required to stabilize the rotor, against differential pressure gradients (for example when one side of the rotor blades enters thicker smoke). Otherwise, these differential pressure gradients would lead to sending the helicopter into sharp spins, which the pilot would find extremely difficult / impossible to control via reflex responses alone. Most modern commercial helicopters with advanced electronic instrumentation navigation and control systems have such stabilisation controls in-place.

For auto stabilisation of the helicopter / rescue vehicle, would like to investigate a few approaches. But in this regard, would like to first check on the existing prior art via a PCT / WIPO search and proceed, according to the search report (aka depending on what prior arts already exists).

And if electrically operated drone approach is selected (to power the main fire fighting platform), then standard drone stabilisation algorithms could be utilized...

Water Cooled Airframe :

A firefighting vehicle with a sufficiently water cooled airframe (via a thin water soaked "epi/exo dermis" layer), should theoretically be capable to even enter directly into a fire and remain intact, as long as the water cooling system can be replenished, with the water that steams out (aka airframe temperature, would not / should not rise above 100 ºC, due to the latent heat absorption of water... ). This would be one of the reasons as to why electrically powered, firefighting vehicles would be investigated as well in this R&D project. 

Do have a few design ideas (would like to test), which should be capable of cooling the helicopter rotor blades and / or the drone fan blades, as well.

Potential practical issues / limitations:

Considering the fact that a 100kWh rechargeable battery could weight in the range of 500-600 kg, and that a helicopter capable of lifting 3-4  metric Tonnes, would require a powerplant in the range of 500-700 kW, the battery weights/ battery capacity (how long the onboard batteries would be able to supply power), would most likely be a potential issue / limitation.

Thus in most likelihood, in the Electrically Powered, Firefighting Vehicles, the onboard battery would most likely have to be utilized, only for emergency operations / maneuvers. Thus in most likelihood, it would / may require to adopt the path of, ground power / mobile backup generator option (discussed earlier in this article). We have to understand here, that unlike in the case of lighter drones (or drones developed for 1 or 2 passengers), in this R&D, we will be focussing on a Vehicle / Platform that can have the capacity to lift heavy loads (in the range of atleast 2-3 metric Tonnes). Thus in most likelihood, the ground power plant based approach, would be the the most viable option (for Electrically powered Firefighting helicopter/ drone).

Follow on project - Part II -

As a follow on project would like to investigate, the feasibility of operating an unmanned / remotely operated drone or helicopter (with a water cooled airframe), that can be deployed to engage in attending fires of hazardous and or potentially explosive nature. Have a few ideas in mind (for example provide water cooling for certain sections / portions of the power cords etc), so to safely provide remote power/ external generator power, to this firefighting vehicle (which in most likelihood, would have to operate in close proximity to, open fires/ high temperatures).

(If in the future if / when, hybrid power units also becomes commercially available / feasible, that would also open up another avenue, that could be possibly be looked into...).

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