New answers tagged

1

Orbital insertion is hard enough with ships where the initial stages can be aimed in directions favorable to the final orbit. This design calls for a fixed launch direction, which would be a terrible waste of on-board fuel for all but those satellites whose orbits coincide with the gun's trajectory. Even that can be overcome with fuel. The real issue is ...


4

One more nasty factor: What is the expansion speed of your propellant. Take the Jules Verne approach and your spacecraft falls far short no matter how much powder you put in the gun because the expansion velocity is too low. Your craft will never exceed the expansion velocity of the propellant. Note, however, that you don't have to use explosives (or ...


63

Other answers don't mention the fact that no single impulse (e.g, like being fired from a gun) can launch a projectile into orbit. A purely ballistic projectile fired from a gun must either crash back into the planet, or it must escape from the planet altogether. In order to achieve orbit, at least two impulses must be applied to the projectile. The first ...


11

I think the heart of the question is whether one could arrange a continuous combustion of propellant along the length of the barrel. In that way the acceleration occurs along the length of the barrel in a more gentle way. Since the expanding gases from the propellant in a shell casing expand and the pressure of the expanding gases declines along the way it ...


31

Anything launched into orbit by such a gun needs to travel at orbital velocity (in fact above orbital velocity) in the lower atmosphere. That's generally undesirable, to put it mildly: there will be really serious heating.


0

Let's say you have got such gun. Next logical step will be to install on the satellite a smaller gun that would shot-back several small shells and so accelerate the satellite, indeed? If this small on-board gun would use really many small shells (size of molecula) then your are getting just a traditional rocket. Apparently it is not much difference for ...


16

Aside from the interior ballistic aspects of these various projects, it was quickly realized that any satellites launched by gun would have to withstand high g-loadings during firing of the gun and the size and mass of the satellite would be greatly constrained by the dimensions of the bore of the gun and the maximum impulse which could be provided by the ...


0

Actually, a smilar approach was just recently proposed by S. Hawking and others. Using electromagnetic waves, as you correctly observed traveling through space with the speed of light, they plan on accalerating a light sail by shooting it with a laser based on earth. That kind of fits your discription of a "magnetic launcher". As the previous answer already ...


3

Speed of light has nothing to do with why maglev is fast. Maglev is faster because it levitates the train so there's no friction with the track. In space, there's no friction to begin with. So the "lev" in "maglev" makes no sense in space. You already levitate there. That being said, electromagnetic launch (in a sense of a railgun or something) is just ...


1

The rocket nozzle is mounted on a bearing that can tilt a small amount in two directions - allowing it to steer the direction of the exhaust and so the direction of thrust. Thrust vector nozzle The gimbal linked in the article is for the sensor platform used to measure the direction, although now you would use a solid state 3d acceleration sensor instead of ...


2

Air friction is roughly proportional to the (magnitude of the relative) velocity squared. Power is equal to force times velocity (the time derivative of work, which is force times distance). Since the force is proportional to the velocity squared, then the power will be proportional to the velocity cubed.


0

It turns out you cannot use an accelerometer to determine the attitude of a rocket at any time other than when it is experiencing the normal force from the earth. This is explained in some detail in this article: Thinking About Accelerometers and Gravity. The key point from the article is this line: "An accelerometer never senses gravitational acceleration ...


1

As @EntropicallyDriven mentions, matter-wave interferometry can be used for inertial navigation. Better clocks (in terms of both performance and size / weight / power) would help with pulsar navigation.


2

One possible application of AMO physics would be inertial guidance systems based on atomic interferometers--similar systems are currently being investigated for missile guidance and have shown much higher accuracy than other methods. Inertial navigation systems don't rely on a network of GPS satellites, which obviously wouldn't be present on Mars (yet!)



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