[2012-Nov-27] Turns out I AM a rocket scientist.

[Luemas]

As interesting as this was, I believe it's impossible to have sex in space because the air pressure/gravity is too low to maintain an erection.

[Peon]

As interesting as this was, I believe it's impossible to have sex in space because the air pressure/gravity is too low to maintain an erection.

http://www.msnbc.msn.com/id/14002908/ns ... lications/

Although zero-G could be a boon for saggy body parts, Bonta said males might notice a "slight decrease" in penis size due to the lower blood pressure that humans experience in microgravity.

you're just worried about your slight decrease

[Destructicus ҉̵̞̟̠̖̗̘̙̜̝̞̟̠͇]

Took me a while to figure out that (1e - 3 kg/ml) actually meant (1*10^-3 kg/ml)

[Destructicus,̵̡̩̭̪̱͎͙̮̖́͞.̧̭͙̻͎̣̳̥͙̤͔͖̻̗̞̙̼̩̀́͝,̶̧̼̟̜̱̥̗̜̖͈̠̹́]

also v=0.000781250

[Destructicus,̵̡̩̭̪̱͎͙̮̖́͞]

also v=0.000781250

m/s

[Destructicus,̵̡̩̭̪̱͎͙̮̖́͞.̧̭͙̻͎̣̳̥͙̤͔͖̻̗̞̙̼̩̀́͝,̶̧̼̟̜̱̥̗̜̖͈̠̹́]

I'm gonna go ahead and be a nitpicker.

The equation input to wolfram alpha [(5ml*(10^-3kg/ml)*12.5m/s)/80kg] was incorrect. The correct equation is (5ml*((e^-3)kg/ml)*12.5m/s)/80kg, with the solution being ~.0389 m/s, or roughly 82% the speed of a cassette tape.

Data is often displayed as XE-3, which actually means X*10-3. Furthermore, the density jizz is very similar to that of water, which is 10^-3 kg/ml. If your claim were correct, jizz would weigh 0.248936 kg/ml, which is definitely wrong.

[GUTCHUCKER]

Zalgo is here, and he's a fucking quadruple poster.

[gmalivuk]

Next up: assuming a linear speed gain, how many times would you have to wank to reach light speed?

As has been said, this breaks physics, but if you're okay doing that, just divide.

If you don't want to do that, you have to take a step back and use momentum, which is different in relativity than in Newtonian mechanics. Relativistic momentum can increase linearly and indefinitely, it just no longer would correspond to a linear or boundless increase in actual velocity.

Incidentally, if you go against the advice of the votey and use the rocket equation anyway, you get 0.00078122558 instead of 0.00071825000. This is because the rocket equation assumes a continuous release of mass, so the later bits are released from something that is already moving slightly in the opposite direction, and the earlier bits are released from something more massive than it ends up being.

The new result is 99.997% as much as the one in the comic, though, which most would probably consider close enough.

[brossa]

These calculations only hold true if the axis of thrust passes through the center of mass; othwise you'll just induce a spin. It would be tough to orient the 'exhaust nozzle' to align thrust with COM due to design constraints of the hydraulic systems which result in drastically reduced thrust over a range of exhaust vectors, but fortunately it is easy to arrange matters such that a second individual 'receives the transmission' in a more favorable geometry, and in an inelastic fashion. Drafting an appropriate two-body configuration is left as an exercise for the reader.

[Peon]

Next up: assuming a linear speed gain, how many times would you have to wank to reach light speed?

As has been said, this breaks physics, but if you're okay doing that, just divide.

If you don't want to do that, you have to take a step back and use momentum, which is different in relativity than in Newtonian mechanics. Relativistic momentum can increase linearly and indefinitely, it just no longer would correspond to a linear or boundless increase in actual velocity.

Incidentally, if you go against the advice of the votey and use the rocket equation anyway, you get 0.00078122558 instead of 0.00071825000. This is because the rocket equation assumes a continuous release of mass, so the later bits are released from something that is already moving slightly in the opposite direction, and the earlier bits are released from something more massive than it ends up being.

The new result is 99.997% as much as the one in the comic, though, which most would probably consider close enough.

Due to the lack of precision of the given values, the calculation can't be taken to that many digits anyway: Both methods give an equal value of 8*10^-4 m/s because only one significant figure is known. You can't get something more precise from something less precise.

[lurpa]

Once again reminded of the sad absence of nerd ladies.... Got to the bottom of the comic after solving the problem, and laughed.

[gmalivuk]

These calculations only hold true if the axis of thrust passes through the center of mass; othwise you'll just induce a spin.

This is true for prolonged thrust, but the linear momentum calculation in the comic holds for a single ejaculatory impulse, whether or not being off-center also imparts some angular rotation to the body afterwards.

[nobody]

Was it "by how many standard deviations is my ejaculate unusually copious?"?

[brossa]

This is true for prolonged thrust, but the linear momentum calculation in the comic holds for a single ejaculatory impulse

I pity the rocket engineer whose burn time is zero.

Static tests of the engine system in question demonstrate that as a result of some (to us, in retrospect) truly baffling decisions by the engineers in the design phase, under real-world conditions thrust is produced in five to ten short bursts (mean of seven) over a period of multiple seconds. Calculations are complicated by the fact that ~40% of the propellant is consumed (delivered?) in the first pulse, with remaining pulses showing variable timing and diminishing mass flow. Thixotropy and particulates in the propellant mean that accurate computer modeling of engine performance is perpetually 'five to ten years in the future'. Meanwhile, the aforementioned static tests show shocking variability between individual engines w/r/t propellant volume, total burn time, and nozzle velocity. With further research time and funds, it may be possible to lower the number of pulses or the overall burn time, but to date resources have been devoted mostly toward the opposite goals, as well as to maximizing propellant mass and minimizing the turn-around time between launches. And something about pineapple juice.

[ghori92]

Tell me what inspired this sudden realisation? And also shed some light in Pascal's Law so I know how much of a scientist you are. But it's nice to see the feedback you have received.