вторник, 30 июля 2024 г.

Long-range high-speed electric airplane

Imagine solar-powered ion-propelled aircraft. Ion propulsion allows flight at high altitudes like 40-50 km. The air is rarefied at high altitudes, that means the aircraft should have high velocity like 1-2 km/s to maintain the altitude. Solar energy allows unlimited range. So, such an aircraft can be long-range and high-speed. 

For high velocity such an aircraft should have enough power like 0.2-0.4 watts per gramm of mass.
If it has some 5 watts per gramm, it might be able to reach the space.

суббота, 16 марта 2024 г.

Non-rocket spacelaunch using solar powered ion engine. It might be possible for small payloads

Imagine a fixed-wing airplane with ion engine and solar panels. Currently it cannot take off from Earth surface due to very low thrust. It is caused mostly due to insufficient power of energy input.

But what if the size of the apparatus decreases. According to Square–cube law, decreasing dimensions n times will lead the surface area decreases n*n times while the volume and mass decreases n*n*n times. This means power-to-mass ratio increases n times. Small enough apparatus might have enough power to take off from the surface, fly in the atmosphere and become a satellite.

Travelling in lower and upper atmosphere seems to be possible. See Ion-propelled aircraft and Atmosphere-breathing electric propulsion.

Photovoltaic is good as an energy source:
1. Virtually unlimited amount of on-board energy.
2. High electric power density - thin-film solar cells might generate some 10 Watts per gram. For comparison Plutonium-238 generates 0.57 Watts of power per gram, that power yet needs to be converted to electricity.
3. Photovoltaic can produce high voltage output just by connecting solar cells in series. High voltage is necessary to power ion engines.
4. Lasers can provide additional power. The lasers can be designed to be safe for eyes.

So, there is a chance, Non-rocket spacelaunch will appear in the near future for small-sized payloads, e.g. several grams.

понедельник, 18 октября 2021 г.

Merge sort with O(sqrt(n)) auxiliary memory complexity (and even less)

In this text an algorithm is described that merges two sorted arrays into one sorted array. Time complexity is O(n), auxiliary memory complexity is O(sqrt(n)), and stable. If this algorithm is used for merge sort, then resulting sorting algorithm will be stable, have O(nlog(n)) time complexity and have O(sqrt(n)) auxiliary memory (and even less for some cases).

пятница, 2 апреля 2021 г.

Sunglasses to better view your smartphone or laptop screen

Sorry, no pictures yet.

The sunglasses are mostly as usual ones - they reduce ambient light and sunlight. But they do not reduce the light from smartphone/laptop screen. As the result the picture on smartphone/laptop screen is more contrast and visible when wearing such sunglasses.

Benefits:

1. Better image on smartphone/laptop screen.

2. Possible to reduce britness of the screen. It will increase battery life (due to lesser discharge) and lifetime (due to lesser charge-discharge cycles).

3. OLED displays can be more durable due to lower display brightness.

How to implement:

1. Filter light by wave length.Now it is possible to increase contrast 3 times.

2. Filter light by time. It will require impulses from the screen (e. g. 1000 Hz) and the sunglasses open and closes according to impulses from display.

3. Filter by polarization. I think it is possible to increase contrast 2 times or more.

среда, 17 февраля 2021 г.

Artificial Hadley cell

 

Artificial Hadley cell is a human-made construction that generates rain in order to produce fresh water.

It mimics natural Hadley cell.

It is ground surface area about 10 km in diameter and tens meters in height.

Artificial Hadley cell absorbs solar energy, heats air, creates upward air stream that in turn leads to precipitation and releasing fresh water.