Photon Guy

1 hour ago, swansont said:

Any ones that don't require new physics?

None that I can think of, but the point is that just because the lightspeed barrier can't be broken by conventional means doesn't mean it can't be broken period. 

4 hours ago, Moontanman said:

IMHO the main problem of using rail guns to send objects to space would be the enormous friction with the earth's atmosphere. Any object so accelerated would become white hot and evaporate much like a meteor does when it enters the Earth's atmosphere.  Then you would have to include engines to allow the object or package to maneuver to the space station.

You have that same problem with friction and the heat it generates with any sort of spacecraft that reaches escape velocity. Conventional spacecraft are made to withstand the friction and heat with special heat shielding. A spacecraft sent into space by a railgun could have that same sort of shielding, and it could have cooling systems too. Yes it would need some engines and fuel to maneuver to the station as you point out but not the tremendous fuel that you need to reach escape velocity the way conventional spacecraft do as the railgun would take care of that. 

4 hours ago, Moontanman said:

This would be much easier to do if you were launching package from an airless body like the moon.    

But we don't send supplies from the moon to the ISS, we send it from Earth to the ISS. I suppose we could set up a moon base and start mining the moon and producing supplies on the moon that way, but that's a long way off. 

4 hours ago, Phi for All said:

Which supplies can withstand human-squashing forces?

Lots of supplies. Water for instance. And food that you don't mind having squashed. Food remains edible when it's squashed. 

The way I see it, any kind of gun that the police and military have access to citizens should also have access to. So if you want to ban certain guns from citizens, ban them from the police and military too. 

3 hours ago, exchemist said:

But there is no theoretical way to move space itself.  It's a bit like saying we could all fly if we could switch gravity off. Which is sort of true, except that we can't switch gravity off.   

Space itself apparently could be moved by using objects with negative mass. The problem is finding matter that has negative mass which so far only exists in theory but it is a possibility. 

What would be the practicality of using railguns to send supplies into space? The way a railgun works is by using magnets to propel objects at really high speeds so a railgun would no doubt be able to propel a spacecraft at escape velocity and by doing so, it would eliminate the need of fuel to launch spacecraft into space. Such spacecraft would have to be unmanned as the acceleration of a railgun would be too much for people to withstand, they would be squashed like pancakes, but I see no reason why supplies couldn't be sent that way. So the idea is that spacecraft containing supplies could be launched into space and then retrieved by personnel on the ISS, Im wondering how that would work. 

On 8/28/2023 at 2:32 PM, Endy0816 said:

Nothing with mass can travel at or exceed c.

Not by conventional means but there are theoretical ways of breaking the lightspeed barrier, such as if you were somehow able to move space itself and "ride" it, much like a surfer riding a wave. 

On 1/23/2024 at 1:43 PM, swansont said:

 Or just use an electric vehicle.

You could, but that wouldn't have the horsepower of a gasoline vehicle. 

20 hours ago, OldChemE said:

As noted by exchemist many explosives (including gunpowder) have a built-in oxidizer.  The primer in a gun cartridge does not provide oxygen-- it only provides the energy (fire in the case of a primer) to get the chemical reaction started.  So, if you really wanted some sort of similar reaction as your energy source you could use some controlled system that feeds discrete quantities of explosive into a chamber and then ignites the explosive using an electrically generated spark.  Essentially an internal combustion engine but using a powder instead of a liquid.

Well modern cartridges are airtight so they don't get oxygen from the environment. Are you saying that modern gunpowder itself has oxygen in it?

To the best of my knowledge, conventional combustion requires oxygen. When you make a fire in the fireplace you need oxygen for it to burn. You need your fuel source which might be wood that you're burning in the fireplace, you need the energy to ignite it which can be produced by rubbing sticks together although in this day and age you would use matches or a lighter, and you need oxygen which on Earth is abundant enough in the environment. In a different environment without oxygen, such as on the moon, it would not work. You would not be able to start a fire in a fireplace on the moon unless you're able to provide the necessary oxygen somehow because on the moon there is no oxygen in the environment. 

Anyway I was thinking about how to produce tools that use fire or combustion that would be able to function in an environment that doesn't have oxygen such as the environment of the moon. I believe guns would work just as well on the moon or in the vacuum of space as they would on Earth because when the primer is struck it produces the necessary oxygen. A gun fires by the primer being struck by a hammer or pin which in turn ignites the propellant in the cartridge and as the propellant burns it creates the pressure that fires the bullet. Obviously the propellant needs oxygen to burn but the primer provides the necessary oxygen when it is struck. Cars however would not work on the moon. The way a car works is a spark is used to ignite the gasoline in the cylinder which burns and produces the pressure to push up the piston, the upward motion of the piston pushes a crankshaft which turns a series of gears which turns the wheels causing the car to go forward. For the gasoline to burn it needs oxygen which the car gets from the environment so you would need an environment that has oxygen for a car to work. So I was thinking about how to make a car you could drive on the moon or in an environment without oxygen, and how to make other stuff that works by combustion that can be used in environments without oxygen. It works with guns so it should work with other stuff. 

On 1/9/2024 at 11:37 AM, exchemist said:

You can't just recycle it, because of "entropy", but you may be able to get some further use out of it, depending on the circumstances. The basic problem is that heat energy is the kinetic energy of random motion of atoms and molecules. It is thus in a sense "disordered" and cannot be completely re-ordered again. All non-reversible processes lead to an increase in entropy, which means (loosely speaking) a dispersion of energy in a way that cannot be completely recovered. 

However waste heat from many processes can be put to further use. For example waste heat from power stations can heat homes, commercial greenhouses, or swimming pools. And heat pumps can raise the temperature of heat energy from ambient air or the ground to something useful for home heating, although some extra energy has to be put in to do that.

High temperature heat energy has lower entropy than low temperature heat energy, so the higher the temperature the more uses it can be put to. Machines like car engines and power station turbines are "heat engines", which rely on converting high temperature heat energy into mechanical work. However, due to the disordered nature of heat energy, they can't convert 100% of it, so there is always waste heat rejected from any heat engine, usually more than half of it in fact. 

I've tried to explain this in simple words, but really you need to read about the second law of thermodynamics and a bit about the concept of entropy, to see what the limitations are. 

So it sounds like what you're saying is that chaos cannot lead to order. That's what you seem to be saying to a certain extent when you talk about how heat is disordered and can't be re-ordered. The concept of entropy is associated with disorder, randomness, or uncertainty, in short, its associated with chaos. But chaos can lead to order, sometimes. 

There is the concept that if you have an infinite number of chimpanzees with an infinite number of typewriters there is a chance that one of them might write Shakespeare. If you randomly press keys on a keyboard there is a chance, however slim, that you could write the complete works of William Shakespeare. That would be an example of how chaos, pressing keys at random, can lead to order. 

On 1/9/2024 at 4:57 PM, Ken Fabian said:

Optical Rectenna can convert Infrared radiation - radiant heat - directly into electricity but in practice so far the yields are extremely low. Like an antenna does with longer (radio) wavelengths - like the old "crystal radio" that powered itself from the radio waves. Not sure how that works in entropy terms - heat loss in the conversion?

Of all the out there possibilities this would be one I'd like to see get some serious attention because if they can be made to work we could not only make electricity from waste heat but from radiant heat of all kinds, including down-radiation from clouds and atmosphere by night as well as from sunshine by day.

That would work wonders for electric cars. 

I believe heat is one of the greatest losses of kinetic energy. For instance, whenever energy is transferred some is lost in the form of heat. Take for instance when you fire a gun, when you pull the trigger it causes a hammer or pin to strike the primer which sets off the propellant. The propellant is the source of the gun's power. When the propellant is set off it burns and expands, releasing kinetic energy which forces the bullet out of the cartridge, down the barrel and out the muzzle. However, at the same time tremendous heat is produced which is why guns get hot when you fire them. Same thing with cars, a car works by the gasoline being ignited in the cylinder which in turn produces kinetic energy that forces up the piston which turns a series of gears which in turn causes the wheels to turn and the car to move forward. However, tremendous heat is being produced with that too which is why car engines get really hot when you run them and need cooling systems to keep from melting. 

Anyway, I was thinking if there was some way to recycle heat back into usable energy. Usually heat is a nuisance but I was thinking if there was a way to make it into something useful. Maybe turn it back into potential energy somehow. 

When are we going to start using hall thrusters?

On 10/30/2023 at 2:54 PM, zapatos said:

 I'm not sure why you are having such a difficult time with this.

Im not having a difficult time. 

2 hours ago, Janus said:

In order to reach LEO, a fully loaded shuttle needs all the fuel in that large external tank, plus two solid fuel boosters.

As I pointed out in an earlier post, you need about 2.2 km/sec of delta v to enter a trans-lunar orbit from LEO.  Even if the entirety of the cargo capacity of the shuttle was extra fuel, the SSME's wouldn't be capable of getting the shuttle up to this speed.

Once at the Moon, your shuttle would be moving ~ 0.8 km/sec slower than the Moon, and would need to do another burn in order to be able match speeds and enter orbit around it.

Then to return, another burn is needed to re-enter another trans-lunar orbit in order to get back to Earth.  Once back, the shuttle will be moving at ~2.2 km/sec more than LEO orbital speed.  The shuttle can't hit the atmosphere at this speed, so it will need to do another burn to shed enough for re-entry.

So, this works out to at least 6 km/sec total delta v for the trip.  This jumps the fuel requirements to 2.8 times the mass of the empty shuttle. Adding a lander would increase this fuel requirement. (some thing the equivalent of the Apollo LEM, would require ~20% more fuel.

A good part of the Shuttle's mass is there for re-entry and landing, and would be dead weight as far as the majority of the trip is concerned, so you'd be burning a lot of fuel to get something to the Moon that is of no use when you get there.

Well then I would say it's a good thing we retired the shuttle. We're better off using rockets such as Atlas V that we used to get the Curiosity rover to Mars. 

5 hours ago, Eise said:

Yes, thanks for the explanation, I really needed that .

Your OP was about the Space Shuttle. It was not able to reach escape velocity. And for reaching the moon one does not need the 'full escape velocity': reaching the point where the gravitation of earth an moon exactly cancel is enough. But then, for the return trip, you still need fuel to reach that point again, against the gravity of the moon.

But we have built spacecraft that do achieve escape velocity. I don't see why the shuttle couldn't do that considering the fact it could reach altitudes where Earth's escape velocity is very low. As for leaving the moon, the moon's gravity is much weaker than Earth's so it would take far less fuel. And you could just put the shuttle in orbit around the moon and use a lander to get to the moon's surface the way they did with the Saturn V rockets. 

On 10/10/2023 at 4:15 AM, Eise said:

It couldn't. Orbiting earth means that the space shuttle did not escape earth's gravity. Why else would it keep in its orbit? Apollo could travel to the point where the gravitation of the earth and moon exactly cancel. Getting over that point means that it 'falls' to the moon. But the moon itself neither escapes earth's gravity, otherwise it would fly away. Escaping earth's gravity for space vehicles means that gravity fields of other objects (planets, moon, sun, ...) have (much) more impact than the gravity field of the earth. 

All you have to do is build a spacecraft that can achieve escape velocity. Once you reach escape velocity you're guaranteed to not fall back to the Earth, regardless of the gravitational effect of other objects such as the moon. That's how probes such as Voyager work.  

I know the space shuttle was retired in 2011 but could a space shuttle go to the moon? I know back when we did send people to the moon it was with the Saturn V rocket and from what I heard you need a powerful rocket such as the Saturn V to make it to the moon. But if a space shuttle can escape the Earth's gravity, which it obviously can, I see no reason why it couldn't make it to the moon. 

On 10/8/2023 at 12:51 AM, zapatos said:

So is the National Park Service. If you distrust an agency simply because they are government funded and run you are probably not making a fair assessment.

The National Park Service does not send people into space, which can be very risky. If the space industry was run by private businesses they would be far less likely to take unnecessary risks that can result in people being killed, because they wouldn't want the backlash. 

On 10/8/2023 at 6:00 AM, swansont said:

LOL

History is rife with examples of corporations causing environmental damage, and harming (even killing) people, without going out of business as a result. Union Carbide India Limited killed thousands in Bhopal in 1984, paid a settlement and renamed itself. Still in business. Exxon, Shell and ARCO are still around, despite serious incidents. TEPCO, owner of the Fukushima reactor, is still there.

Well a private corporation would be far more reluctant than a government organization to take unnecessary risks which would jeopardize people because they wouldn't want the backlash which would result in, if not the company going out of business at least the loss of lots of money, especially if they're competing with other private corporations. 

The company of Remington that makes guns, there was a time they were making faulty products that were unsafe, some of their guns would even fire without the trigger being pulled. To the best of my knowledge thankfully nobody was killed as a result but they did lose lots of business and as such they had to take certain actions such as firing some of their higher up managers. 

On 10/8/2023 at 8:18 AM, Sensei said:

When you have virtually a monopoly on the market, almost nothing can throw you out of it. Your company is the market.

That's why a single company should not hold a monopoly in the space industry, there should be multiple companies just like it is with airlines. 

8 hours ago, StringJunky said:

This wouldn't happen in a private company, with profit as it's core motive?

If a disaster such as Challenger happened with a private company the backlash against the company would be so severe that it would go out of business. As such, a private company would not take such a risk. 

8 hours ago, zapatos said:

That was two decades ago. What do you know about them today?

I know that today they are a government funded and government run organization just as they were back then. 

3 hours ago, zapatos said:

Can you please expand on which aspects of NASA you find untrustworthy?

It's the management of NASA that I don't like. It's because of how careless and impatient the managers can be that we had disasters such as Challenger and Columbia. With Challenger the engineers knew there was something wrong, they knew about the faulty 0-ring and they warned management but management decided not to listen to them and went ahead with the launch anyway. One of the engineers even knew that Challenger was going to blow up before it happened but management wouldn't listen to him. Just to satisfy their own egos and impatience they decided to throw safety out the window and it cost lives.

With Columbia they knew that some of the crucial heat shielding had been damaged and they could've launched a rescue mission with Atlantis or they could've even allowed some of the crew members to do a spacewalk and repair the damage but they didn't, and that too cost lives. 

So that's what I don't like about NASA, how they can be so utterly careless and ignore danger and as such it leads to disaster. 

On 10/5/2023 at 11:11 AM, zapatos said:

https://www.pewresearch.org/science/2023/07/20/americans-views-of-space-u-s-role-nasa-priorities-and-impact-of-private-companies/#:~:text=The private sector has become,companies to accomplish its missions.

Well that's good. While Im a really big fan of space exploration, I am not a fan of NASA. I don't really trust how NASA is run and I wouldn't mind if NASA was completely dissolved, or at least greatly down graded, and the space industry was taken up by private businesses. 

On 10/5/2023 at 4:42 PM, RomanRodinskiy said:

It seems to me that in the future the boundary between upper-atmosphere flight, which is already considered space, will be erased. For example, this is indicated by the transition of some state air forces to air-space forces. As spaceflight technology becomes cheaper and more widespread, the boundary defined by commercial flights will rise. Nevertheless, let us remember that earlier attempts have been made to fly mediocre flights in near-space by airlines to reduce the cost of conventional commercial flights. Such programs failed, but this is a rather mediocre example.

So by upper atmosphere I take it that means the Thermosphere. I've never heard of airplanes flying that high. 

In the movie 2001 the now defunct airline company Pan Am had gone from the airline industry into the space industry. We know that won't happen now since Pan Am went out of business in 1991 but I've been thinking of the possibility of other airline companies and private businesses in general going into the space industry. To the best of my knowledge in the USA the only organization that sends people into space is NASA which is entirely government funded. It would be better if private companies would take up the space industry since that way the space program wouldn't rely entirely on government funding and there would be more opportunities for people to go into space not to mention more opportunities to develop technology used in space. 

Well in terms of science fiction cases of  planets with really strong gravity in which, as a result, the inhabitants of such planets are super strong, an example would be with the series The Orville. In The Orville there is a little girl with such tremendous strength that she can smash through walls and pry open big metal doors and bulkheads. The girl, whose name is Lt. Alara, is the chief of security on The Orville and the reason she is so strong is because she is a Xalayan, a fictional race from the planet of Xalaya which has a really strong gravity. The gravity on Xalaya is so strong that a human who stepped out on the surface would be crushed flat like a pancake without special protection such as a gravity suit. A metal can from Earth that's thrown onto the surface of Xalaya would instantly be flattened. Now The Orville is a spoof on science fiction and its not supposed to be taken seriously, even by fictional standards, but still that would be a science fiction example of a planet with really strong gravity having really strong people. 

Sometimes in science fiction they have planets that have very strong gravity and as a result the people from such planets are really strong. For instance, people from a planet that has twice the earth's gravity would be able to perform tremendous feats of strength while on Earth or while on any planet or environment that has gravity around the same level as earth's gravity, able to bend steel bars and lift cars and so forth. Im wondering though just how realistic that would be in real science. Let's say Earth did have twice the gravity, would we all evolve to be super strong? Or is that just in science fiction and not in real science?

On 7/17/2023 at 6:58 PM, swansont said:

What is a “radioactive spider” anyway? Merely irradiated? What about it is radioactive, and how, specifically, did that happen? The comic says it “absorbed a fantastic amount of radioactivity” which is good copy but is nonsensical, technically speaking 

You would have to ask Stan Lee if you want to know exactly what kind of radioactive spider we're talking about when we're talking about the spider that bit Spiderman.

On 7/17/2023 at 8:49 PM, mistermack said:

I have access to water when I need it, without having to lug around lots of water. And I don't have to lug lots of hydrogen around either. Having water available in water mains is pretty good. No lugging involved. Just turn on the tap.

If an alien world had an oxygen-rich atmosphere, that means it would be sure to have plants that photosynthesise, and that would mean rain on land and oceans of water. So making water available would be a similar process to what we do on Earth. 

So can you have access to good drinking water without having to lug large amounts of water around, when you don't have running water? Let's say you're out in a desert. Or let's say you are in an area that does have water in the form of oceans and rain, is it drinkable water? The water in our oceans is not drinkable for various reasons, not the least being that it contains way too much salt. That's the problem with water that you find in nature, it could not be the drinkable kind. 

On 7/15/2023 at 2:18 AM, exchemist said:

OK. So someone had not thought it through, evidently. That happens a lot in some sci-fi, which is why people like me can find some of it rather irritating.

There is also the fact that science can "ruin" science fiction. For instance, back when Spiderman first came out the story was that he was bitten by a radioactive spider and that's how he got superpowers. Today, with all the scientific discoveries we made since, we know that if you're bitten by a radioactive spider you will die when the radiation goes through your bloodstream and all. Back then, though, they didn't understand all the stuff about radiation that they do now.