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Suborbital Spaceflight Picks Up Speed
RocketAcademy writes "The race to develop low-cost, suborbital spaceflight is heating up. On Thursday, Virgin Galactic's SpaceShip Two successfully completed its second powered test flight, reaching a speed of Mach 1.4 and an altitude of 69,000 feet. Meanwhile, XCOR Aerospace has begun posting daily reports on the progress of its Lynx spaceplane, which is expected to begin flight tests sometime around the end of this year. This means one of both companies are likely to begin commercial service by the end of next year. XCOR still plans to move its headquarters to Midland, Texas later this year, but Midland may not be the only suborbital spaceport in the Lone Star state. On Wednesday, the Houston Airport System revealed renderings of its proposed spaceport at Ellington Airport, near Johnson Space Center just south of Houston. Citizens in Space (also based in Texas) has begun training five citizen astronauts to fly as payload operators on the XCOR Lynx and evaluating biomedical sensors for use on the flights. Details of those astronaut activities were also released this week."
Suborbital Spaceflight Picks Up Speed
...then it'd be orbital spaceflight.
suborbital spaceflight is heating up
...and now it's crashing back down through the atmosphere.
Sheesh, this is elementary physics, make your mind up editors!
Moderation Total: -1 Troll, +3 Goat
It's very costly. You have to carry all that weight out of the gravity well and into orbit, up to orbital speeds (~17,000 mph), then get it back down safely (requiring a very expensive thermal protection system). It's why the Shuttle was so expensive to operate and why no one else is doing it that way.
Play around with Kerbal Space Program and you realize just how big the gulf is between suborbital and orbital flights. Getting enough boom to get yourself up to 100km is trivial. You really appreciate the difference in design when you're doing it yourself and seeing just how much more boom it takes to achieve orbit.
I read the internet for the articles.
http://what-if.xkcd.com/58/
a plane flying into space and land by itself should be the real race shouldn't it?
Sometimes the sci-fi vision is prescient. Sometimes it isn't. A flip-phone looks like the original Star Trek communicator. Yay! The new phones don't. Oh well. The 3.5 floppy looked just like the storage used on the original series also. The floppy also came and went.
The Space Shuttle was the closest we've come yet to the sci-fi vision of the space plane to which you refer. It still had to drop a lot of stuff before reaching orbit. I've always wondered to what extent our problems there came because we allowed ourselves to be lead astray by the sci-fi vision. Meanwhile, the Russians continued to perfect un-glamorous but relatively reliable rockets and long duration space flight.
The sci-fi vision is a double-edged sword. It inspires us and stimulates ideas. It can lead us astray if we obsess over achieving objectives that match it in some particular way.
For all intensive purposes, "whom" is no longer a word. That begs the question, "who cares"?
I think a lot of this space plane stuff in the minds of civilians misses that last point. When you don't understand what is really happening you might well assume just getting high up is enough.
Turns out though it is fine for suborbital space flight, which is great for tourists.
Billions on fuel?
Kerosene and LOX are not that expensive. There are a lot of other costs than fuel. Getting out of the atmosphere is easy and relatively cheap, getting up to orbital speed is a whole other ballgame.
A single stage to orbit vehicle is very difficult. The amount of fuel a rocket needs to carry increases exponentially with the ratio of the required velocity change to the exhaust velocity. The options are very limited.
Solid propellants have much too low exhaust velocity for this to be workable.
Kerosene / Oxygen is a typical rocket propellant, but the exhaust velocity is low enough that a single stage to orbit would require an unreasonable ratio of fuel to rocket mass. I don't remember any design concepts for kerosene / O2 rockets for single stage to orbit.
Hydrogen / Oxygen has higher exhaust velocity but liquid hydrogen is very low density so the fuel tanks become enormous, and heavy. There have been design studies for Hydrogen / oxygen single stage to orbit, but it doesn't look very practical - you basically have an enormous flying fuel tank.
The more exotic chemical fuel mixes don't improve things a lot and are too toxic and expensive for atmospheric use. Fluorine / Beryllium / Hydrogen tri-propellant has good specific impulse but is insanely deadly in multiple ways.
Nuclear thermal (like NERVA) could probably do it, but people are understandably unwilling to put 100GW class nuclear reactors in rockets and launch them.
Airbreathing rockets (like ram-jets / scram jets) don't need to carry their own oxidizer and in principal do much better. The problem is that hypersonic ram-jets are very difficult to build and wind up heavy and inefficient. (Mach ~8, only 1/3 of orbital speed, 1/10 orbital energy) is the highest speed ramjet that I am aware of. For various fundamental reasons you expect the performance of ramjets to drop with velocity. Since ramjets also don't work at low speeds, you wind up needing a 3 stage rocket: conventional, scram-jet, conventional, and it ends up not having any advantage over just conventional rockets.
The basic technology for getting things into orbit hasn't changed in over 50 years, and really isn't likely to change - just no clear path. The best approach is probably what Space-X is doing, optimizing the design, and working to make each of the stages recoverable to reduce costs.
The "tourist" sub-orbital rockets don't seem to me to be developing technologies that are applicable to orbital flights. They may attract a few people who are willing to spend $100K for a few minutes of zero-G, but I suspect that most wealthy thrill-seekers will quickly find that a ride in a MIG-29 is a lot more fun and less expensive.
Billions on fuel?
Kerosene and LOX are not that expensive. There are a lot of other costs than fuel. Getting out of the atmosphere is easy and relatively cheap, getting up to orbital speed is a whole other ballgame.
But when you throw away the fuel tank and rocket motor every time you fly... it is very expensive.
Car analogy time: Rocketry is like buying a new car and wrecking it every time you want to travel to the next city.
I'm a good cook. I'm a fantastic eater. - Steven Brust
Anyone else take a look at those renders for Ellington Airport? I just love how the roads and platforms make no engineering sense whatsoever.
Well, you need customers at your spaceport, so therefore you need roads. If you build them, they will fly. Obviously, you'll have full commuter ships leaving for space every 30 minutes, so you'll need four lanes of freeway to deliver all those people, and they're all going to want to park next to the building, so make sure you have a really big terminal. A giant grass bridge over the freeway lets people wander aimlessly beneath the glory of your rocket-filled sky, so make sure to include one of those. And monorails should whiz by giving all the locals a chance to see the future you're providing them as they roll on to their uneventful days ahead.
A spaceport obviously can't serve anybody without support staff, like ticket agents, travel agents, baggage handlers, TSA gropers, insurance salesmen, USO staffers, McFood operators, cart drivers, taxi stand starters, and telephone sanitizers. So you're going to need a lot of lodging to house these people. And they're going to want to live in an interesting place, so stick an F15 on a metal post and now it's an interactive park-museum, fun for the whole family (for at least an hour on a Saturday.)
Now think about all those space customers. If you've been out orbiting hard all day, you're obviously going to want to crash in a nice five star hotel ("crash", "five STARS" - I'm using spaceflight metaphors there, did you get 'em?) at the end of the day. That means you need golfing and pubs and water hazards placed next to a tall building.
See? You're pretty close to an architect already. Just add crowds of people who have no reason to be there whatsoever, and sprinkle liberally with immature trees, and that's practically a bachelor's degree right there.
John