[LMB] Light-flyers and groundcars

Walter Bushell proto at panix.com
Wed Apr 12 02:41:39 BST 2017

> On Apr 9, 2017, at 7:39 PM, Howard Brazee <howard at brazee.net> wrote:
>> On Apr 9, 2017, at 12:54 PM, Walter Bushell <proto at panix.com> wrote:
>>>> yup - once you are in orbit you are half way to anywhere
>>>> the problem is that continous thrust (even minmsucle one) is HARD
>>> That’s because our only current options are rockets or solar sails.  We know that the Vorkosiverse is not so limited.
>> Different Universe with different laws of Physics.
> Within limits.   There are a couple of new features that have been added, without really breaking stuff like having continuous thrust with rockets HARD.   

Hey, the laws of Physics in fiction are imposed by the Author. Here they needs of the story triumph over
the law of physics of our Universe. 

Continuous thrust at high level would seem to 
need change of a reasonable fraction of mass to energy and then getting rid of the heat.

The reason that ionic propulsion is used is that it has a very high specific impulse. For the same change in 
momentum it’s best to take it in the *shortest* time, in general, that the crew and equipment can stand, because
you have the increased velocity longer.

The trouble with high specific impulse is that the thrust per unit of exhaust goes up with the speed of the 
ejaculated propellant[1] but the energy required goes up with the square of the speed of the exhaust.

[1] Some critics have stated that rockets are phallic symbols.

More information about the Lois-Bujold mailing list