Models and Measurements

WLPT:

The Process

L= Lander.

A= Aircraft

The Energy Storage

Energy storage plays a critical role in the Venus power beaming architecture; first, to store the harvested energy on the maneuverable aerial platform, and second, to store this energy on the lander, as it is beamed from this platform. The lander battery supports operations, while the aerial platform is ascending to recharge its on-board batteries. The Russian Venera series and Vega 1 and 2 Landers using conventional lithium primary batteries survived for <2 hours. Notable advances have been made at JPL in the development of high temperature primary batteries, which can provide low power levels for up to 30 days at surface temperatures [11]. For this architecture, high temperatures rechargeable batteries are needed to support extended surface missions for up to 60 days, at power levels of 10 W or more.

Lander Energy Storage

The lander would use LiAl-FeS battery for energy storage.

Assumptions for sizing:

Example-

To provide 5 W continuous power for 11.6 hours (the time required for a powered aircraft to recharge and return to the transmission power), the stored energy and mass would be given by-

Lander battery stored energy = (11.6 hours)(5 W)/(0.6) = 97 Wh Lander battery mass = (97 Wh)/(80 Wh/kg) = 1.2 kg

Aerial Vehicle Energy Storage

The aerial vehicle would use sodium-nickel chloride with beta-alumina solid electrolyte for energy storage.

Assumptions for sizing-

*For the aerial vehicle, a heater is required to keep the battery sufficiently warm and operational when the vehicle ascends to the cooler altitudes of the atmosphere during the energy harvesting point.

Example-

If an aircraft transmits 1 kW laser output, the battery is required to provide a total of 3 kW for a period of 2 hours (2 kW are estimated for the input to the laser and 1 kW is estimated to power the aircraft). The stored energy and mass would be given by:

Aircraft battery stored energy = (1.15)(2.0 hours)(3 kW)/(0.6) = 11.5 kWh

Aircraft battery mass = (11.5 kWh)/(90 Wh/kg) = 128 kg

*This analysis can be used to scale energy storage sizing to other average power levels that would be available to the lander.

WLPT transmitter

1022 nm laser would maximize power transmission below the cloud decks and the surface of Venus.

Aerial vehicle Platform

Choosing Preferable aerial vehicle-

*Multiple aerial platforms can be used to achieve an average power of 10 W available to the lander.

The aircraft has the advantage that it can return to transmit power much sooner than the balloon since it does not necessarily need to circumnavigate the planet. The minimum time between flyovers can be determined by the time required to recharge the battery. This can be increased by using a larger solar array, potentially increasing the power available to the lander. Hence, WLPT is the most preferable way, with options for transmission from either a series of balloons or an aircraft. Although using a balloon may be possible, issues with pointing and control, combined with uncertainty over wind patterns make this option difficult to implement.

One of the prime advantages of an aircraft is that it possesses sufficient control authority (using standard aircraft control surfaces), to move between altitudes for alternately harvesting/transmitting, as well as to stay on target for beaming to the lander. Once the landed mission is completed (e.g., failure due to high-temperature exposure), the aerial asset would have the opportunity to perform continued science investigations, assuming it outlives the lander. The specific altitude for the aerial vehicle would be chosen to optimize efficient energy transfer while minimizing exposure to the most extreme temperatures found immediately above the surface. It would be preferable to implement a type of station-keeping flight pattern over the target, to avoid circumnavigation scenarios and maximize the transmission time to the lander (i.e., flying in a circular path over the lander, to maintain continuous pointing of the beaming laser to the laser power converter). A true solar-powered aircraft could fly against the winds and maintain its position above a fixed landing site. These earlier studies focused on aircraft flying at high altitudes (65+ km) and at high solar angles, to ensure sufficient availability of solar energy to power the propulsion system. This particular scenario was determined to be feasible.

*Blackswift Technologies has experience in the conceptual design of Venus aircraft and is the proposed lead for this feasibility study. High-temperature components (such as motors produced by Honeybee Robotics) would considered in the conceptual design activity.

assumptions-

*There was not sufficient time to fully evaluate this assumption. So, some data were not developed. There are several things to be developed, in particular the amount of power required to fly against the wind of Venus at the lower altitudes, as well as to transition from lower to higher altitudes. This aircraft mass is very similar to that proposed in the Venus Aerial Maneuverable Platform (VAMP) concept, by Northrup-Grumman. VAMP is a hybrid vehicle that gets most of its lift from buoyancy and only some from aerodynamics The VAMP concept contemplates aircraft in the 90 to 880 kg range. This concept may be difficult to implement, however, at higher temperatures and higher wind speeds. If this is the case, two or lower mass aircraft could be employed as part of the overall mission to reduce its size and provide for redundancy.

Concept aircraft

a) solar airplane designed at NASA Glenn Research Center, b) Variable Altitude Maneuverable Platform (VAMP) designed at Northrup-Grumman, c) Dynamic soaring aircraft concept developed at BlackSwift Technology and d) Bioinspired Ray for Extreme Environments and Zonal Exploration (BREEZE) concept developed at the University of Buffalo.

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