of the energy spectrum of tritium decay that the neutrino might
be a tachyon
The neutrino would have to have imaginary rest mass
E^2 = (pc)^2 - (mc^2)^2 on mass shell
phase speed E/p of quantum wave is slower than light
& signal speed? faster than light
zero energy E at finite momentum p has infinite group & signal? speed
Obviously of extreme interest. Too soon to know if it's not an error of some kind.
Check out specific impulse of tachyon
beam rocket propulsion.
"The higher the specific impulse, the less propellant is needed to produce a given thrust during a given time. In this regard a propellant is more efficient if the specific impulse is higher. This should not be confused with energy efficiency, which can even decrease as specific impulse increases, since propulsion systems that give high specific impulse require high energy to do so. ...
In rocketry, where the only reaction mass is the propellant, an equivalent way of calculating the specific impulse in seconds is also frequently used. In this sense, specific impulse is defined as the thrust integrated over time per unit weight-on-Earth of the propellant:
is the specific impulse measured in seconds
is the average exhaust speed along the axis of the engine in (ft/s or m/s)
is the acceleration at the Earth's surface (in ft/s2
In rockets, due to atmospheric effects, the specific impulse varies with altitude, reaching a maximum in a vacuum. It is therefore most common to see the specific impulse quoted for the vehicle in a vacuum; the lower sea level values are usually indicated in some way (e.g
For rockets and rocket-like engines such as ion-drives a higher Isp
implies lower energy efficiency: the power needed to run the engine is simply:
is the actual jet velocity.
whereas from momentum considerations the thrust generated is:
Dividing the power by the thrust to obtain the specific power requirements we get:
Hence the power needed is proportional to the exhaust velocity, with higher velocities needing higher power for the same thrust, causing less energy efficiency per unit thrust.
However, the total energy for a mission depends on total propellant use, as well as how much energy is needed per unit of propellant. For low exhaust velocity with respect to the mission delta-v, enormous amounts of reaction mass is needed. In fact a very low exhaust velocity is not energy efficient at all for this reason; but it turns out that neither are very high exhaust velocities.
Theoretically, for a given delta-v, in space, among all fixed values for the exhaust speed the value ve
is the most energy efficient with respect to the final mass, see Tsiolkovsky
On Sep 22, 2011, at 2:46 PM, Gary S. Bekkum
Your opinion for the record?
Should shake up the community if true.
Does this imply a second metric?