Electric Airplanes

[CardsFan]

Not sure, but there was an episode where at the end it was revealed that the ETs were carnivorous and liked the taste of human flesh.

They had a book. "To Serve Man". Unfortunately man (we) did not findout until too late it was a cook book.

 

[Out-to-Lunch]

Out in space, the only way to have propulsion is via Newton's Third Law of Motion. You have to carry something with a mass, then eject it backwards to get a force to push you forward.

I guess you can carry a lot of batteries, then eject them out the rear to move forward. However, it would be cheaper to carry slugs of lead to shoot out the rear, as they are cheaper than batteries. Won't work as well as burning and expelling propellants though.

True. But the propulsion can be done electrically. This is actually standard practice, called Ion Propulsion: https://www.nasa.gov/centers/glenn/about/fs21grc.html

 

[Koolau]

True. But the propulsion can be done electrically. This is actually standard practice, called Ion Propulsion: https://www.nasa.gov/centers/glenn/about/fs21grc.html

I recall talk of ion thrusters perhaps 40+ years ago. In theory, electrical power within the solar system is virtually unlimited with enough solar panels. Using the electrical power to operate enough ion thrusters could make travel within the solar system possible. I recall one proposed scenario in which the ion thrusters (of the future) would be powerful enough to accelerate space craft at g (9.8 m/sec or 32 ft/sec) which would provide artificial gravity. Half way to the space craft's destination, it would be turned 180 degrees and the reverse thrust at g would slow the craft down as it approached its destination. BUT batteries (as such) wouldn't likely be any significant part of the process (brief storage of excess solar power only) due to weight issues.

I believe ion thrusters are used to stabilize satellites in their orbits now as they remain relatively low power. YMMV

 

[NW-Bound]

The concept of ion thruster was advanced way back in the early 1900s!

I have read about them being used to steer a space craft, but have not looked into what the state of the art can accomplish.

Found this on Wikipedia:

Ion thrusters in operational use typically consume 1–7 kW of power, have exhaust velocities around 20–50 km/s (Isp 2000–5000 s), and possess thrusts of 25–250 mN and a propulsive efficiency 65–80%, though experimental versions have achieved 100 kW (130 hp), 5 N (1.1 lbf)...

A force of 25-250 mN is 2.5-25 grams of force. And 5 N is 1.1 lb as noted above. Still, because the spacecraft is already moving at a high speed, generating a force of merely 1.1 lb to accelerate it further takes 100 kW.

There's not enough battery capacity on board to provide the power, and it has to come from solar panels.

The fundamental problem remains: What is the source of the ions that you are shooting backward? The material to be ionized to eject is not unlimited. They use xenon gas, and the spacecraft has to carry it from launch.

For spacecraft at an already high velocity, an ion thruster is about the only way to accelerate it further. The force is small, but when applied for a long duration will get the job done.

Ion thrusters create small thrust levels (the thrust of Deep Space 1 is approximately equal to the weight of one sheet of paper compared to conventional chemical rockets, but achieve high specific impulse, or propellant mass efficiency, by accelerating the exhaust to high speed.

The Deep Space 1 spacecraft, powered by an ion thruster, changed velocity by 4.3 km/s (2.7 mi/s) while consuming less than 74 kg (163 lb) of xenon. The Dawn spacecraft broke the record, with a velocity change of 11.5 km/s (41,000 km/h), though it was only half as efficient, requiring 425 kg (937 lb) of xenon...

 

[sengsational]

I'm not going anywhere on an ion drive ship... I'm going to wait for warp drive, or at least an Epstein drive (which breaks fewer laws if physics).

 

[NW-Bound]

According to some science-fiction movies, if you find a wormhole, you can just walk right across it to another planet in the universe.

But if you find a wrong one, it may lead you to a sun that burns you to a crisp. Or to a planet with those ETs who carry the book "To Serve Man".

 

[ejman]

Whatever humankind knows to build, it has to conform to the laws of physics as we know them.

Agree, except for the part "as we know them". That assumes we already know all there is to know about the laws of physics. I would amend your statement to read "Whatever humankind knows to build it has to conform to the laws of physics - period"