294 reputation
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bio website ericmenze.com
location Minneapolis, MN
age 29
visits member for 1 year, 11 months
seen 2 hours ago

I'm a Computer (Web) Programmer/Analyst based in Anchorage, AK and Minneapolis, MN. I use (among other things) ASP.NET, C# and SQL Server.

I build things. Bicycles, computers, websites, guitars, cars, motorcycles, sound sytems... lots of things.


Mar
27
comment How to calculate the velocity needed for a rocket to get to a L1 point (escape a body without orbiting)?
And, (finalish question) - if I got a small rocket precisely to L1 and used the surface rotation timing, how much velocity/energy would it take for lunar capture? Or would it just speed past the moon unless slowed down significantly? Would it need to get much closer to the moon than L1 to actually be captured with the KE from earth's rotation?
Mar
27
comment How to calculate the velocity needed for a rocket to get to a L1 point (escape a body without orbiting)?
Also, one of the things I'm confused about is atmospheric orbital speed: if the balloon setup sat at 100km altitude for long enough to synchronize with the atmosphere at that height (what little of it there is); would it speed up to the orbital rotation at that height (I.E. track the same geostationary location once settled), or slow down, or ?
Mar
27
comment How to calculate the velocity needed for a rocket to get to a L1 point (escape a body without orbiting)?
Nailed it. Would this be correct for solar gravity inclusion: $V_e = −Gm(\frac {M_e} {r_e} + \frac {M_l} {LD−r_e} + \frac {M_s} {SD-r_e})$ and $V_{L1} = −Gm(\frac {M_e} {d_{L1}} + \frac {M_l} {LD−d_{L1}} + \frac {M_s} {SD-d_{L1}})$ ?
Mar
25
comment Can relativistic momentum (photons) be used as propulsion for 'free' after the initial generation?
But the mass of the mirror is not infinite, and so with enough photons, you could move the mirror (as the other SO question alludes to), correct?
Mar
24
comment Can relativistic momentum (photons) be used as propulsion for 'free' after the initial generation?
So light bouncing off a mirror selectively transfers energy only if they aren't attached?
Mar
24
comment Can relativistic momentum (photons) be used as propulsion for 'free' after the initial generation?
I see, so energy would need to be added to keep the thrust constant. Does a laser get redshifted every time it bounces off something? I.E. if you pointed a green laser between two calibrated mirrors it would eventually be red?
Mar
24
comment Rocket propelled by a giant monochromatic laser
Posted: physics.stackexchange.com/questions/104970/…
Mar
23
comment How to calculate the velocity needed for a rocket to get to a L1 point (escape a body without orbiting)?
Sure - in theory, I get that. However, that 'fast enough' is orders of magnitude more energy than it takes to just get to an orbital height; indeed this article reports that in getting to LEO, 93% is spent increasing the horizontal speed, and 7% is raising the altitude. Since I don't even have very good odds to get the 7% it will take to get to the altitude, let alone the 93% it would take just to fall at the same rate that the surface of the earth does, then it seems that any thrust in the horizontal direction will be wasted. permanent.com/space-transportation-earth-moon.html
Mar
20
comment How to calculate the velocity needed for a rocket to get to a L1 point (escape a body without orbiting)?
Rockets usually take up their own oxidizer; for example Black Powder in model rockets and Liquid Oxygen in full scale ones, so they don't need 'air' to operate. I'm still confused as to how, say, a rocket engine is changing any of the horizontal kinetic energy from the 1 rev/day orbit, or utilizing it to move in the vertical direction.
Mar
20
comment How to calculate the velocity needed for a rocket to get to a L1 point (escape a body without orbiting)?
Can you explain the process by which horizontal kinetic energy is converted to vertical potential energy, without a ramp or some similar structure? I don't think $KE_{horizontal}$ or lack thereof has any effect on the height an object will reach, unless we're leaving Earth's rotating reference frame or something.
Mar
20
comment Rocket propelled by a giant monochromatic laser
If photons have non-zero effective mass, then why wouldn't a mirror on the rocket and on earth give perpetual free momentum as the photons bounce back and forth?
Mar
20
comment How to calculate the velocity needed for a rocket to get to a L1 point (escape a body without orbiting)?
Simplified for only the normal vector, and just reaching the Earth-Moon L1 from rest on earth's surface: $PE_{i} + KE_{i} + E_{rocket} = PE_{L1} + KE_{L1}$, so $0 + 0 + E_{rocket engine} = PE_{L1} + 0$, or $E_{required} = PE_{L1}$. I'm lost on how to calculate the Potential Energy at L1, since $PE = mgh$ doesn't really work (g = 0?). Your equation above doesn't seem to care about the mass of the object, a 100kg object surely has more PE at L1 than a 1kg object. Can you elaborate?
Mar
20
comment Rocket propelled by a giant monochromatic laser
From answers.yahoo.com/question/index?qid=20100521204409AAk1lkq, $m_{photon} = \frac {h*f} {c^2}$? Seems bizarre, and the conservation of momentum could be used to calculate it. How do you account for the Tsiolkovski Rocket Equation, based on the (rest) mass and velocity of the exhaust? Does it not apply in this situation?
Mar
20
comment How to calculate the velocity needed for a rocket to get to a L1 point (escape a body without orbiting)?
I think you're thinking of an orbital insertion; in my case I don't want or need any additional 'horizontal' velocity; unless it can be used to increase the vertical. I just want to reach the highest point I can.
Mar
20
comment How to calculate the velocity needed for a rocket to get to a L1 point (escape a body without orbiting)?
Wouldn't launching off-normal (straight up) 'add velocity' at the expense of some altitude? What angle would maximize altitude from Earth's surface?
Mar
20
comment Would it be economical to add a counterweight to rocket launches?
Example: Take a fully loaded Saturn V rocket at 2,800,000kg, and add a counterweight that will reduce its effective weight for the first 10 seconds to 400,000kg and detach. It burns 2,100,000kg of fuel in the first stage in 161s, so 13,000kg/s of fuel is lost. Without the counterweight, the first 10 seconds would net a $\Delta v = 4,440m/s*\ln(2,800,000/2,670,000) = 211m/s$. With the counterweight: $\Delta v = 4,440m/s*\ln(400,000/270,000) = 1745 m/s$, or roughly Mach 5.1.
Mar
19
comment Would it be economical to add a counterweight to rocket launches?
I should add that I wasn't counting on the acceleration from the counterweights to be of much importance in and of themselves; the 63 m/s velocity difference would pale in comparison (I think) to how fast the onboard rocket engines could accelerate the lessened (or non-zero) effective mass. Is there a way to calculate this?
Jan
28
comment Could the Heisenberg Uncertainty Principle turn out to be false?
The Heisenberg Uncertainty Principle is an unfalsifiable claim? All of (good) science is falsifiable. See the first paragraph: en.wikipedia.org/wiki/Falsifiability
Jun
25
comment Would it be economical to add a counterweight to rocket launches?
How about four steel cables, each holding 100 tons? Some bridge reinforcement cables are rated for more than this.
Jun
25
comment Would it be economical to add a counterweight to rocket launches?
Further, I do refer to wikipedia. Since you seem to be of the opinion that this has been answered therein, could you provide a wikipedia link that properly addresses this question?