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2

Why does Government Space Agencies (all) not run behind Reusable Launch Vehicles when they know slight hike in budget can significantly contribute to Cut High Costs on Launch? Politics. This year's legislative assembly has to justify the slight hike in budget, while some future legislative assembly, if anyone, has to answer for the higher future launch ...


0

In general, liquid propellants are so difficult to work with and so dangerous, and the rocket engines so difficult to design and build, that commercial engines only barely exist (and seem to be in the territory of rumor, possible Kickstarter scams, and dead Geocities links). Most efforts are more like amateur-operated-and-funded research programs than ...


0

One variable not mentioned here is the increasing ∆V of ion thrusters on satellites. On the starling launches 60 satellites all just take off and find their own orbits. The better electric propulsion gets, the less important it will be to lift into exactly the right orbit.


3

Launching from international waters. In addition to the factors mentioned in other posts, there's an additional benefit from launching from the ocean: you can launch from international waters. This could be handy if you're launching a rocket that uses some form of material or process that is illegal or heavily regulated for civilian use in your home country....


9

Early in the development of the Polaris missile system, there was a lot of work on launching a missile from underwater. Polaris was a nuclear deterrent to rapidly launch multiple missiles from a fully submerged submarine. Staying submerged until a boat-load of launches were complete was a key goal: the boat was to be very difficult to track and destroy ...


35

Sea Dragon The very large rocket was probably Sea dragon and the advantages were more on allowing a massive vehicle to be built at all rather than inherent advantages in starting underwater. (image credits) Building the launch vehicle on a slip way and floating it to the launch site bypasses a number of size constraints in building and moving large ...


9

You might be thinking of the Sea Dragon project, although this never got past the conceptual / early planning stages. Some of the advantages of a sea launch are that you can be far away from habitation and the water can provide cooling and acoustic damping during launch. But the disadvantages are also serious. You are even more at the mercy of the weather ...


1

Gravity will not keep a species out of space, although it can make it incredibly expensive. A resource-limited species might not be able to make it to space, though--I'm thinking of Jovians. Chemical rockets suffer the tyranny of the rocket equation, if you need more than 30km/sec to attain orbit I don't think you're doing it, period. However, that's not ...


0

In Russell Borogove's answer, they assert "Linear increases in gravity require exponential increases in the size and expense of the rocket, so at some point it becomes impractical." That is the physics answer, but it's slightly different from an economics perspective. A more precise statement would be that if the only variables are payload and gravity, then ...


-2

If gravity is higher, the density of the atmosphere would be higher as well, and probably also to a greater altitude as well as less would have evaporated into space. So hydrogen or helium balloons would rise up more rapidly or lift more weight to possibly higher altitudes. Maybe this would be the main way of accessing space travel on this imaginary planet....


8

A (very high) upper limit is defined by the thrust to weight ratio of the first stage engine itself. The engine without a tank and a payload would not be able to lift off if the thrust is smaller than its weight measured under the high gravity. An engine build for such an extreme gravity would need more structal weight than at Earth's gravity. The ...


4

Note that you seem to be assuming chemical propulsion. Nuclear propulsion would work against even stronger gravity, but there are major safety problems.


17

As this article points out, rockets quickly get impractical. For example, at 10 times earth gravity, the rocket's mass is comparable to the planet's mass, so that's definitely some sort of limit! But who said we have to use rockets? Suppose we build a monorail completely encircling the planet at some convenient height $h$ above the ground, and accelerate ...


61

There's no "bright line" at which space travel would become impossible; a slightly stronger gravitational pull would require bigger and more expensive rockets. Linear increases in gravity require exponential increases in the size and expense of the rocket, so at some point it becomes impractical1. At some point there's a theoretical barrier (no material ...


6

It appears that the 20 engines are all accounted for. (Note that the chart from Wikipedia lists engine 2048 twice (once with powerhead 6007 and once with powerhead 6021).) Here is the list of engines, their planned usage, and their last Shuttle flight. 2043 / none at present / STS-108 L SSME 2044 / SLS launch # 4 / STS-133 C SSME 2045 / SLS launch # 1 / ...


4

I think it's just barely possible that 1850s technology could achieve a crewed suborbital launch above the Kármán line, similar to the first crewed Mercury missions, but that anything beyond that would not be possible. Without modern rocket engines, the best propulsion option is a black powder rocket. This has a specific impulse of about 80 seconds (a ...


4

This depends on how stable your rocket is. If your rocket is aerodynamically stable, meaning its center of pressure is behind its center of mass, the rocket will likely be turned to its velocity vector (zero angle of attack) by aerodynamics alone. A gravity turn is optimized for the least manual maneuvering possible. Any launch trajectory besides a perfect ...


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