# Tag Info

28

Because of the nature of radioactive decay, Curiosity is going to get a whole lot more than 2 years out of its power source. Curiosity will be getting enough power to keep active for a bare minimum of 14 years (see Specifications> Power Source), though the amount of power it has will steadily decrease over time (from 125 Watts initially to 100 Watts after 14 ...

27

As far as I understand you want the "windmill" to drive a dynamo. Have you ever tried turning a dynamo? It takes some force to do so, and that force is then (partially) turned into electricity. So the dynamo is braking your windmill and unless there is some power input to the windmill (wind), it will eventually come to stop. But there is no wind so your ...

24

To flyby or impact Venus varies from 3.45 to 3.6 km/s from LEO for the optimal time every 19 months. Mars varies from 3.55 to 3.9 km/s for the optimal time every 26 months. So on average, getting to Venus is a little less energy than getting Mars. But not by much. It could even be a tiny bit more in some years. If you also want to get barely into orbit ...

22

Jovian magnetosphere is extremely active and stretches nearly all the way to Saturn. It is indeed in volume the second largest continuous structure in the Solar System, right after the heliosphere. Jupiter's radiation in the radio frequencies is in fact so strong, you can tune in and listen to it between frequencies of other radio stations on AM/FM radio ...

22

For a solid sphere - Absolutely not! This calculation from http://www.aleph.se/Nada/dysonFAQ.html explains why: 8) How strong does a rigid Dyson shell need to be? Very strong. According to Frank Palmer: Any sphere about a gravitating body can be analysed into two hemispheres joined at a seam. The contribution of a small section To the force on the ...

20

No, not really. The atmosphere of Mars is very thin. It has below 1% of the pressure on Earth. That means it has less than 1% of the force of wind on Earth with the same speed. Wind only occures at dawn or dusk. Wind happens when there is a pressure gradient between two areas of an atmosphere. Pressure gradients are caused by temparature- and humidity ...

20

The maximum percentage wasted to noise is approximately 1%. The acoustic efficiency, defined as the ratio of the sound power to the rocket exhaust's mechanical power, for the majority of these data range between 0.2 and 1 percent...with 0.5% as the most probable value. NASA SP-8072 ACOUSTIC LOADS GENERATED BY THE PROPULSION SYSTEM Using the equation for ...

19

Not really. The pressure due to solar wind is approximately 1-6 nPa (See Wikipedia). The pressure due to just the light from the Sun at Earth is actually higher, at around 9 nPa (Source). The mass makes somewhat of a difference, but let's just assume somehow you can get a mass of a 1 square meter windmill at 1 gram. The effective power would be very small, ...

18

This is actually pretty difficult to do, because it depends on where from due to uneven distribution of matter (local parameters), how far from the galactic center due to radial velocity, the direction in which you want to reach escape velocity (how much of the radial velocity can be used), and that it's hard to estimate mass of the Milky Way (global ...

16

If you're asking about interstellar travel, then the answer is pretty simple; For diffuse, unfocused sources of light like the one emitted by stars, photon flux density decreases with the inverse square of the distance to its source, and with it photon pressure (imparted momentum of absorbed or, better yet, reflected photons) on the sail. So you accelerate ...

16

To beam the power to the rocket, especially when needing high acceleration, is not what I will expect to show up in the near future. However, separating the energy source from the propellant is the idea behind the nuclear thermal rocket. Here, energy comes from a reactor, and you can choose more freely in higher performing propellants. Because a NTR is ...

15

It will survive the way that pretty much all space missions survive. First of all, most space missions are speced such that the power at the end of the mission will meet 100% of the demand of the spacecraft. The mission of Curiosity is 2 years, thus, the spacecraft will have 100% of required power after 2 years. Beyond that, its power will decrease. ...

15

You'll need a nuclear reactor for that because the process of dissociation of water into constituent hydrogen and oxygen consumes vast amounts of energy and for an ascent stage you'll also need a very high energy density to provide sufficient thrust. Direct anode/cathode system like you describe (i.e. electrolysis) is wasteful when you don't require ...

15

No, it wouldn't work. In order to drive the treadmill, momentum would have to be transferred from the satellites to the treadmill. The sats would slow down and eventually stop. The "highway" itself wouldn't be stable, either. Since it's moving at a different speed from the satellites, it cannot be moving at circular orbital speed for its altitude by ...

15

A conventional thruster with two liquid propellants requires energy too. But it is chemical energy stored in the propellants. Ion thrusters use no chemical energy at all, all the energy of the ion beam is from the electrical energy used by the thruster. In fact, a conventional rocket engine with a lot more thrust than a ion thruster uses a lot more of ...

14

The "much deeper" drilling would have to be rougly 900km to get near to the core. No drilling of this scale has been ever attempted on Earth. Lower gravity will make it easier but not much easier, and you will have to have pumping stations from time to time - no pipe will withstand 900km long column of water, even in Lunar gravity. On top of the ...

14

Human powered vehicles used within domed or cavern cities would seem to be extremely plausible. One way to look at it is a simple bicycle is less complex than a powered vehicle. The power source (aka a Human) is extremely complex and maintenance intensive, but given that we already have a functioning human and want to get that human to some other place, a ...

14

The second table here essentially answers your question. Venus transfer from Low Earth Orbit is 3.5 km/s, Mars transfer is 3.6. This will allow you to impact either body (on Venus you will need to make sure your vehicle is tough enough to actually impact, rather than dissolving in the atmosphere, but that's not really the point). In either case, you can ...

13

Consider the Earth and moon to start out with. Obviously we can extract energy through tidal power (which is a real thing, although the economic question is non-trivial). This is possible because the Earth is spinning faster than the moon orbits. However, this tidal power is rate-limited. As long as we're using water as the working fluid, the theoretical ...

13

The ISS has a number of thermal management systems. The most visible part are the radiators attached to the main truss (they are the two sets of 3 white panels just to the left and right of middle, and yes, there's a tear towards the end of the first one on the right side) Those panels are part of the External Thermal Control System (ETCS), if I'm not ...

13

It is what your velocity would be at a sufficient distance from Earth that its gravity doesn't matter, squared. That velocity is $v_\infty$, so $C_3=v_\infty^2$. It can be calculated at any distance from Earth as your specific energy (energy per unit mass), times two: $C_3 = v_\infty^2 = v^2-{2\mu\over r}$ So wherever you are, use the magnitude of your ...

13

NO As a rule of thumb: if you think you invented either a way to generate infinite energy or infinite propellant: you are wrong. But [...] No. Always. Your craft will gain a velocity vector of e. To retrieve the bullets you need to apply to them a velocity vector of -e. If you do this using a liquid, the liquid will accelerate by e. If you do ...

12

There are at least two problems with solar photovoltaic cells (not considering concentrators) in the outer solar system: the low power of the sun, and the low temperature of the cells. For the Cassini mission to Saturn (9–10 AU from the Sun), NASA investigated solar as an alternative. They calculated the surface area that would be required, and concluded ...

12

Currently existing, and for leaving the atmosphere? No. It's always a rocket engine of one kind of another, whether for vertical launch or horizontal, solid fuel or oxygen-hydrogen. Developed - definitely yes. Solar sail is only viable in space, considering solar wind it catches is a miniscule fraction of physical (air) wind force, meaning it would be torn ...

12

The answer is a clear no because Hubble Space Telescope (HST) uses a fixed focal length of 57.6 m. The only thing you'd achieve by re-purposing it as a solar concentrator would be to melt its focal plane assembly and likely everything around it. HST is a Cassegrain reflector and its mirror assembly is utterly unsuitable to applications where adjustable focal ...

12

No: The heat produced by atmospheric reentry isn't a happy side effect of returning to the earth, it's a byproduct of the fact that your satellite/orbiter has enough kinetic energy to be circling the earth every 90 minutes and you want it to stop doing that and come down. To have something you've made for the purpose of harvesting energy reenter the ...

12

Considering fuel consumption or energy expenditure may be misleading, because of the huge change in mass over the flight as fuel is expended. 2/3 of the fuel is expended by the first stage, which only produces 1/3 of the total velocity, for example. Another way to look at the question is through delta-v expenditure; according to Bob Braeunig's simulation ...

12

Consider the windmill as a system. If there is no wind blowing on the windmill, there is no energy being input into the system. If you pull power out of the windmill, energy is being output from the system. With an output and no input, whatever energy is in the system will be drained and not renewed.

11

This question is intriguing because of the nature of the thermal cycles. This is the maximum theoretical efficiency of a thermal cycle (Carnot cycle), no ifs, ands, or buts about it. You can obtain very low temperatures from space, because space is at a low temperature. You'll often hear the Cosmic Microwave Background (CMB) cited for this, but that's ...

11

Well we don't yet have the actual proof that there's an "abundance" of 3He (Helium-3) embedded in the Lunar regolith that would make any "mining" worth our trouble. All we have so far is the indication that there might be, as shown by the trace amounts of 3He detected in the regolith samples extracted by the Apollo missions. Current estimates are that there ...

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