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High-Power HAPS

Table of Contents

SkyScroll has a large surface area at high altitude, which is perfect for providing power to stratospheric payloads

HAPS Background
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High Altitude Pseudo Satellites (HAPS) are airborne platforms for providing communications or Earth-observations from the stratosphere. They operate in a relatively stable part of the atmosphere, well above normal air traffic.

For communications applications, HAPS offer several potential benefits over satellite, including 5G-smartphone compatibility, lower latency, higher bandwidth, lower costs, and being more environmentally friendly.

Power Limitations
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However, most current proposals for communications HAPS are significantly power constrained. According to a recent funding solicitation from ARIA “300W is significantly beyond capability of state-of-the-art platforms”.

SkyScroll has the potential to offer 10x to 100x the power availability, with 3kW or 30kW potentially available to a telecoms payload.

image description
An AI rendering of SkyScroll-based HAPS, delivering high-bandwidth communications capacity from the stratosphere.

The SkyScroll Difference
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Most LTA craft can only carry a small payload into the stratosphere, where atmospheric pressure is ~10 times lower. To allow for gas expansion, normal LTA craft can only be ~10% full of lifting gas at take off.

SkyScroll’s compound LTA platforms are different. They marry one or more conventional airships with a purpose-specific component, the “raft”, which serves three key purposes:

  • Provide gas expansion volume, enabling the airships to 100% full of lifting gas on take off
  • Act as a payload at take off, but become neutrally buoyant at the target altitude
  • Provide a flat base of very large surface area, to maximise interaction with sunlight

A SkyScroll-Based HAPS
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Typically a SkyScroll-based HAPS would consist of an inflatable raft joined to two communications-capable stratospheric airships.

The raft would:

  • share lifting gas with the airships, and provide power to them.
  • be covered with thin-film solar cells to generate power
  • incorporate interleaved battery cells to store a portion of the electrical energy generated, for use in the hours of darkness.

When covered with thin-film PV cells, the raft can provide power equivalent to a large ground-based solar power station.

Estimated Power Availability (Worst Case)
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The following table summarises estimations of the scale and electrical power of a SkyRaft-based system, flying at 18km altitude at latitude of 50°N, for a range of airship dimensions

Airship Length Airship Diameter Maximum Surface Area of Raft (m2) Maximum Width of Raft (m) Mean Power in 8hrs Daylight Dec 21st (kW) Mean Power in 16hrs Darkness Dec 21st (kW)
75 18 25,000 500 600 200
100 24 60,000 900 1,500 500
125 29 125,000 1,400 3,000 1000
150 35 215,000 2,000 5,000 1,600

The above results are based on the following assumptions and parameters:

  • Solar input on 21st December, the shortest and darkest day of the year in the Northern Hemisphere
  • “Raft” of areal density of 1kg m-2 , including
    • Gas envelope with strength reinforcement, covered with thin-film solar cells
    • Interlaced lithium-metal, lithium-sulphur, or lithium solid-state pouch cells, storing up to 500Wh kg-1
    • Lightweight wiring looms and control circuitry
  • Expected depth of horizontal raft at 18km of ~18m
  • Incorporating sufficient battery cells to store ⅔ of the 8-hours of daylight power, to cover 16 hours of darkness
  • Airship dimensions scaled from the 140m “Stratobus” semi-rigid HAPS airship