DailyDirt: Actually Getting People Into Space...

from the urls-we-dig-up dept

There are only a handful of vehicles that have launched people into space (or even just provided shelter) for space-faring people. A few more ships and space stations would be nice to see, and there are a few in various stages development (unfunded proposals, ahem). If you're interested in people (not just robots) exploring outer space, here are just a few links on some of the ships that might transport more folks to at least the edge of space. After you've finished checking out those links, take a look at our Daily Deals for cool gadgets and other awesome stuff.
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Filed Under: dream chaser, elon musk, jeff bezos, lifting body, manned missions, re-usable rockets, rockets, space, space exploration, spacecraft, suborbital
Companies: blue origin, nasa, sierra nevada, spacex

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  1. identicon
    Anonymous Coward, 8 Apr 2016 @ 6:07am

    Re: Cheap Launch System

    There are a few problems with your suggestion. The first is that it can't put a vehicle into orbit (on it's own). Or rather, it can but the orbit would be one that intersects with the Earth at some point, which isn't a useful orbit. The velocity needed to enter orbit has two components, the velocity needed to reach a certain altitude and the velocity needed to remain at that altitude. Let's call them launch velocity and orbital velocity (and yes, I'm talking vectors, not scalars). This system can essentially only impart the launch velocity. You need to have another system to impart the orbital velocity. The lower the orbit you're targeting the higher lower the launch velocity required, but, ironically, the higher the orbital velocity required, so the less use this system would be. To reach low Earth orbit, this system could impart around a sixth of the needed velocity. Now how long does that tunnel have to be? Well, just to get to LEO, you need a speed (yes, scalar now) of around 1.4 km/sec. Suppose you will accept an acceleration of 3g or roughly 30 m/s/s. Using the good old acceleration equations, it will take roughly 47 seconds in the tube to acquire that speed, over a distance of approximately 33 kilometers. Slightly longer than you envisioned. Of course you could increase the acceleration, but the higher you go, the fewer people who will live through the experience... Plus that's only to LEO and you only have a sixth of the velocity you need... Next there's what happens when you exit the tube. You encounter atmosphere. At this speed, that will be something akin to hitting a brick wall when travelling in a car, in terms of acceleration. Here is where your inertia will come in handy, though strictly speaking it isn't inertia that counts in overcoming air resistance, it's the ratio of mass to cross-sectional area. For the same shape, mass scales with the cube of length, while cross section scales with the square, so larger size is a benefit. Still, unlike a rocket, your speed will be highest where the air is thickest, which means the air resistance will be ferocious. Not only will this mean you need a significantly higher speed than would be need on an airless planet with that same gravity, but there will be enormous heat problems (remember those ceramic tiles on the shuttle? Needed because of heating from air resistance. At 6 times the velocity, admittedly, but in air maybe one hundredth the density. To make matters worse, this system can't launch straight up because 33 km up and down is impossible (either because we can't build something that tall, or because the Earth is too hot at that depth, while a turn at the end to deflect the launch vehicle would impart a high enough lateral acceleration to kill any crew members. Eventually the curvature of the Earth would take the surface far enough away from the launch vehicle that would be travelling straight-ish, but it does mean that the vehicle would travel a far greater distance in the densest part of the atmosphere than a rocket does. Rockets don't require heat shields in the launch because they are never travelling fast enough in the air at any particular density to heat up enough to require shielding. (As they accelerate, they rise and the atmospheric density drops).

    And no, the launch vehicle will not "coast into orbit". This is not a launch system, just part of one at best. You would still needed an enormous rocket to impart the orbital velocity.

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