#### steve_bank

##### Contributor

Issues

1. Energy

The show stopper. Energy density and mass.

2. Life Support

The Laws Of Thermodynamics would seem to say resources like O2, H20, and human waste can not be recycled indefinitely.

3. Gravity

Constant 1g acceleration may solve that, but then in comes energy consumption. As velocity increases at 1g distance per second goes up and the work goes up. The ISS has demonstrated long term physilogical changes with zero/low g.

4. Heat

How do you get rid of heat? The oly means is radiation. Mass goes up for radiators along with energy.

5. Psychology

What happens to a crew spending a long time in deep space with no Earth to look down at? Boredom. No variation in people. How long before a social meltdown?

6. Maneuvering

Deep space is not necessarily empty. There can be dust, gas, and objects. At say .5C how do you turn or slow down quickly? There will be reaction forces on the structure and on people. Any high speed gas and dust are abrasive. I saw a piture of a micrometeroite strike on a shuttle window. It looked like heat vaporized a neat hole in the window, not deep enough to penetrtae all the way..

7. Stopping at a destination

All the kinetic energy gained has to be lost and that will be heat.

8. Navigation

Last but not least how do you now where you are at any time to what accurcay in going to a point in space, given that all obseved refernces are in motion. Again, accuracy required ad attainable.

9. The X Factor

I believe the term came out of Edwards during the breaking of the sound barrier. Despite thorough plann9ng and analysis there may be unknown variables. X in algebra usually representing the unknown to be solved for.

I coded somethin so I could look at plots or velocity, mass, time, and energy.

For constant acceleration dv = a*dt, change in velocity. Change in velocity is linear with time.

For Newtonian mechanics there are two ways to calculate energy. Assumptions are fuel with zero mass And 100% engine efficency.

Using work F = 1kg * a, Ework is F*Distance. For a straight line Ework is F*meters, Joules. If not a line then the it requires the work integral. ∫F∙dl.

The other is equating kinetic energy added to energy used, assuming 100% efficiency.

Tje two methods correlate. For 1g acceleration over 1000 days 357.75 peta Joules kinetic enrgy vs 357.39 work. Peta is 10^15. Compare to yearly energy in Joules for the USA.

https://en.wikipedia.org/wiki/Energy_in_the_United_States

Coded in Scilab, it can be ported to other tools or implemented as a spreadsheet macro, or a graphing calculator.

Relativistic mass is calculated vs velocity to see where it may become a factor, if any. It looks like up to around .5C relativistic mass if it applies is not a factor. The time step is 1 day, a shorter step will increase the calculated peak relativistic mass.

Feel free to pick it apart.

clear

light_year = 9.5e12 //km

C = 3e8 //m/s

a = 9.8 //1 g

Ndays = 1000

dt = 60*60*24 //seconds per day

dv = a*dt //change in velocity m/s

m0 = 1 //kg

F0 = m0*a // force Newtons

vel = 0

E0 = 0 // energy

Ew = 0 // work energy

s = 0 // distance meters

watts =(F0*dv)/dt //E/t Joules/second

for i = 1:Ndays

day(i) = i

dist(i) = s/1000 //km

ly(i) = dist(i)/light_year

v(i) = vel

ke(i) = E0 *(10^-15) //petajoules 10^15

we(i) = Ew *(10^-15)

ds = vel *dt // change in distance

s = s + ds

watts(i) =1e-6*(F0*ds)/dt

vel = vel + dv

E0 = .5*m0*(vel^2) //Joules

Ew = Ew + (F0*ds)

if(vel < C) // no divide by zero

mr(i) = m0/sqrt(1- (vel/C)^2); //m relative

mdif(i) = (mr(i)/m0)*100

else

mr(i) = 0;

end//if

pc_c(i) = (v(i)/C) * 100 // percent C

end//for

mprintf("ENERGY KINETIC PJ %.4f WORK %.4f\n",max(ke),max(we))

//mprintf("%e %f\n",v,pc_c)