Envisioning the world of 2100

Discussion in 'Science and Technology' started by RAMA, Aug 9, 2012.

  1. sojourner

    sojourner Admiral Admiral

    Joined:
    Sep 4, 2008
    Location:
    Sojourner
    airplanes =/= rockets. You have lots of bad assumptions there. I've seen your tactic of taking an absurd position on a subject and trying to make it look reasonable in other threads. No one buys it. When you want to talk about the subject earnestly, get back to us.
     
  2. gturner

    gturner Admiral

    Joined:
    Nov 9, 2005
    Location:
    Kentucky
    I can't help it if you can't conceive of doing anything the least bit different from the way they did things in the 1940's, no matter how inefficient it is.

    The cost to build the mobile launch platform for the SLS is about $300 million dollars. Even through the project was started for Bush's Ares program, it won't be completed till 2016, and just the modifications from the Ares configuration are budgeted for 1000 man years of design and construction work. That gives you the ability to launch a rocket every few weeks, at maximum, because each rocket has to be assembled in the VAB, loaded onto the mobile platform, rolled out, and then sat on the pad for a few days.

    If the SLS flies 45 times, the mobile launch platform alone adds $10 million to the cost of each launch, or about two million dollars per seat. There's no engineering breakthrough that's going to lower the cost of a steel tower by some factor of three, so cheap space flight cannot ever happen as long as you use a big giant tower for the launch. And that's not even figuring in the VAB, which would have a replacement cost somewhere in the $5 to $10 billion dollar range, and which eats up over a hundred million a year.

    When space flight advocates talk about a future with $100 a pound to orbit, or even $10 a pound, you can't keep using a launch tower if it alone is adding more cost than that. Even if the rockets were free, the cost of maintaining the support equipment required for the vertical launches keeps the price per launch hardly better than buying an airliner, using it once, and throwing it away.

    And if there's an explosion on the pad, which could certainly happen, the entire sytem will be grounded for the several years it will take to build a new tower. As in-depth NASA studies found, the tower will not in any way survive a pad explosion. Not surprisingly, they found the most likely cause of a pad explosion was a collision with the launch tower, which became a major worry with the Ares design. Of course you could build several towers for redundancy, but then you've spent over a billion dollars.

    We got to this point because the early small rockets are trivially easy to raise, and when the space race started in earnest we just threw money at the problem. The Russians didn't build and transport their Soyuz vertically because they couldn't afford to, whereas we could afford to do almost anything. SpaceX took a page from the Russians and became the only US launch provider that doesn't build their rockets vertically, just standing them up prior to launch, and not coincidentally is by far the lowest cost provider.

    If they were extremely confident in their engine start, they could lift the nose up with just 30 SuperDracos, and they're already going to use eight of those in the Dragon capsule just as abort engines. They don't need to do that because their rocket is small enough to raise vertically right at the launch pad, but as rockets get bigger that operation becomes much more difficult and expensive, and eventually impractical.

    So, a question: How many Orion capsule abort motors would it take to raise the entire SLS to vertical while its fully fueled? About six. If you use twelve you could lift the entire rocket, including the SRBs, and flip it vertically in the air. The abort motor is the tiny little thing on top of the stack. Lifting and fipping are infinitely easier than getting such a vehicle to go supersonic, and then getting it all the way to outer space.
     
  3. Crazy Eddie

    Crazy Eddie Vice Admiral Admiral

    Joined:
    Apr 12, 2006
    Location:
    Your Mom
    You'd need a hell of a lot of JTO rockets to pull that off, and the risks would not outweigh the benefits.

    I think that simply dropping the rocket out of a carrier aircraft makes a lot more sense to accomplish that, especially since the air-dropped launch allows you to always launch your rocket from the equator and potentially at a relatively high altitude which can increase your mass fraction by reducing drag and saving some fuel.
     
  4. gturner

    gturner Admiral

    Joined:
    Nov 9, 2005
    Location:
    Kentucky
    Well, it's definitely different. I prefer the carrier aircraft idea for all reasons except size. The Stratolaunch being built in Mojave can only carry a Falcon 4 or Falcon 5, and it's the biggest yet (about 200K lbs thrust). Something like the B-1 or British Vulcan would scale up quite nicely, and the Vulcan's thick low-aspect ratio wing is structurally an easy thing to scale up tremendously. Thrust isn't a problem because you can use as many engines as it takes, perhaps using GE-90's with about 3 times the thrust that the Stratolauncher's old 747 engines use. You could even design for supersonic flight using something like a vast array of GE F-404's we'll be retiring with the F-18 B's and C's. But the cost would probably be several bilion and you're probably not going to get much beyond the payload capability of a Falcon 9 or Falcon H, which while nothing to sneeze at shouldn't be the end point of space launch. However the Stratojet also shows that you can hang something like a fully fueled Falcon horizontally from some hardpoints and it's good for 1.4 or so G's with a human-rated safety factor, otherwise they wouldn't be able to fly with it. That means there really are no significant structural penalties in a horizontal lift-off. Hypersonic flight vehicles that pull several G's with pressurized tanks tend to be pretty tough.

    What I'm trying to get around is the size limits on reusable launchers set by the carrying capacity of crawlers, the tower height, and the processing building, and the scaling laws likely are part of what makes the SLS cost/LEO pound so much higher than the Falcon 9 or Soyuz. Part of that is the engines, structure, and manufacturing, and part of that is the tower, VAB, and vertical processing. Once you severly cut engine, structure, and manufacturing costs, as SpaceX has done, you're left with the vertical operations costs. If you start re-using the entire rocket, as SpaceX intends to do, the vertical costs will start to dominate the bottom line. The Falcon 9, Soyuz, and Zenit avoid that by being fairly short and doing as little as possible upright, with a simple boom that raises the rocket. That gives way pretty quickly to a tower as the rocket size increases, and tower costs would probably follow a cube or fourth power law versus height. At some point most of your employees are tower-painters.

    In contrast, a single maneuver right after lift-off is pretty simple. You know the rocket's launch mass and moment of inertia and can exactly calculate the thrust profile and impulse required. A lot of military missiles use a stage 0 booster and post-launch maneuver just to avoid back-blast from the main engine. The Navy even launches ICBM's from underwater. Some of the rocket hobbyists already have difficulties erecting their towers and rockets, and then have to climb precarious extension ladders for launch prep. If they'd add some high-thrust low-impulse solids they could leave it horizontal, blast it ten or twenty feet in the air while rotating, fire one opposite motor to kill the rotation, and then ignite the main motor, using anything from a simple timed sequence to a sophisticated control system (which the BATF really frowns on). It might be fun to play with some Estes motors and a simple controller just to show something weird and new in a hobby launch.

    Doing something like that on the Falcon 9 would only take two Orion abort motors (which have 500,000 lbs thrust each and a 5.5 second burn). It's pointless on the Falcon, but they're not blowing a billion dollars on facilities. Air-starting the first stage shouldn't be shocking because we've been air-starting second and third stages, in flight, since the 1940's.

    If you go liquid fueled for all the motors, you could have an intact abort and landing capability, and only about half the main engines at the base would need to rotate to lift the back end. If you want to avoid the weight penalty of liquid engines at the forward end, just use expendable solids, although that would probably rule out an intact landing unless you went ahead and seperated the stages and did an upper-stage fuel burn till it was light enough to set down. It's really not a major engineering challenge, and the result would have vastly more control authority in pitch and yaw.
     
  5. sojourner

    sojourner Admiral Admiral

    Joined:
    Sep 4, 2008
    Location:
    Sojourner
    :guffaw::guffaw::guffaw:

    Seriously? If you think this is true, go post the idea on nasaspaceflight.com where the engineers actually hang out. I would love to see the reaction you get.
     
  6. gturner

    gturner Admiral

    Joined:
    Nov 9, 2005
    Location:
    Kentucky
    I've been discussing it in threads filled with NASA people. Former MSC flight directors blog too, you know, and just last night I was having an interesting discussion with one of the engineers who had the numbers of the Columbia foam strike before most others did. Of course nobody has plans for this type of launch, since we have lots of money to throw at the high-expense, low-risk path, but making a flight vehicle change course by 90 degrees isn't exactly difficult, though some people obviously think it's inconceivable.
     
  7. gturner

    gturner Admiral

    Joined:
    Nov 9, 2005
    Location:
    Kentucky
    I'll add that 9 out of 10 aerospace or control engineers would agree that the horizontal orientation is easier to control than a vertical rocket steerred from the back, because it would be like hovering a Harrier instead of balancing a broomhandle. There's no question that horizontal touch-down is much easier, not even requiring a digital flight computer to control orientation, because you've got full pitch, roll, and yaw authority, no big instability due to gravity wanting to tip you over, and you've got a big fat landing gear spread to set down on.

    The problem with rear steer is that if your nose tips left, you drift left, and have to shift the base left to stay balanced, and further left to kill your drift and return to your original position, and then you have to shift to the right to kill the horizontal motion. The control problem is so difficult that NASA didn't even attempt rear steering with the lunar module, instead keeping the engine pointed through the center of mass, using side-mounted thrusters to keep the vehicle's orientation locked to a vertical gyro, also to move it around in X and Y. By comparison, horizontal take-off is a no-brainer. Once you're up, there are no precision requirements for the pitch maneuver because there's nothing you can crash into, much like the way a submarine-launched ICBM can dance around all over the place right after it clears the water. Compared to clearing the tower with a rear-steering tail-sitter (and there are very strict limits on allowable launch-area winds because of that), it's like doing a bellyflop compared to a ballet.

    The advantage of the tail-sitter is of course simplicity, at least at first blush, because you just light the motor and only have two axes to contol (ignoring roll). It's based on a missile, not an easily controllable flying machine with oddles of thrust. We do it the way we do because spaceflight developed from missile programs instead of aviation programs. Or as Admiral Gehman, who lead the Columbia investigation, summed up the fatal, underlying flaw in NASA culture, “We do it this way, because this is the way we’ve always done it.” As rockets became bigger and more unwieldy, we just threw money at ground support instead of suspecting that there might be a simpler option. The large tail-sitting rocket is simpler, but the large tail-sitting rocket system is not.
     
  8. sojourner

    sojourner Admiral Admiral

    Joined:
    Sep 4, 2008
    Location:
    Sojourner
    Oh for fuck's sake. Please don't try and move the goal posts. We're not talking about the inherent control advantages between vertical and horizontal flight. We're talking about the engineering fuck whittery of a rocket that takes off vertically while lying on it's side and THEN transitions 90 degrees before trying to achieve orbit. Like I said, go to nasaspaceflight.com and post this idea. See what kind of reaction you get. There's a difference between "I have talked to NASA people" and "I brought up this idea with them".
     
  9. gturner

    gturner Admiral

    Joined:
    Nov 9, 2005
    Location:
    Kentucky
    Why would NASA be interested in an idea that would throw most of them out of work and render much of their support structure obsolete, or can't you see that obvious consequence? They will build whatever the Senate tells them to build. They're not even trying to build a re-usable rocket anymore, much less innovate.

    Apparently you also never saw the DC-X fly. It did loops. NASA didn't go for it. In fact, what they did go for is way crazier than horizontal launch, lighting two giant solids on the bet that they wouldn't have a differential thrust problem in a vehicle with no abort system at all, while using a piggyback configuration with wings where the aerodynamics and structural complexities were mind-boggling. They made whole chains of decisions on the Shuttle that carried greater risks and greater complexity than lifting a rocket into the air with rockets and then aiming it, which is something rocket folks have done ever since guidance systems were developed.

    In contrast, horizontal launch wouldn't take but a couple of days to design, and Mythbusters could film it for an episode. You could do it with only two pre-determined fixed burns, one slightly forward of the center of mass that lifts and rotates around the center of percussion relative the thrust location (the majority of the Wiki references for the math on that are me), and one to slow the rotation after 90 degrees. I wouldn't use just one lift and rotate motor for structural reasons, but that's all there is to it.

    By the way, the DC-X burned because it was a tail sitter that had a landing leg failure, and a re-usable tail sitter tips all the way over when that happens. A horizontal lander would just drop one end several feet and get dented. It's also a given that tail sitters can't have nice, shock absorbing landing gear like an airplane because then the gear wouldn't be stiff enough to hold it vertically without wobbling and tipping problems, which means they have to set down very, very gently. Almost all of Elon Musks problems with grasshopper are probably going to stem from the combination of balance and stiff narrow landing legs.

    I don't know if any SpaceX engineers read where I comment (lots of former NASA and Rockwell people do) but the blogger who runs the site runs into Elon Musk pretty often. Maybe he'll mention it sometime.
     
  10. sojourner

    sojourner Admiral Admiral

    Joined:
    Sep 4, 2008
    Location:
    Sojourner
    Nevermind. Come back when you're serious.
     
  11. gturner

    gturner Admiral

    Joined:
    Nov 9, 2005
    Location:
    Kentucky
    Come back when you have a counter-argument that isn't "It can't be done because we've never done it that way." If rocket people thought like that, there wouldn't be any rockets, because among the things said to be crazy were liquid fuel, lighweight turbopumps, swiveling engines, staging, vacuum operation, liquid hydrogen handling, and monocoque tanks, while the list of things that were thought to be essential were tail fins, launch rails, streamlined boat-tails, pointy noses, and parachutes. The 400 foot launch tower made out of pretty red trusswork: also not essential. It's a flying machine. It can fly on its own - unless your thinking is stuck in a tiny little box that dates back to the 1940's.

    The Merlin 1D has a thrust to weight ratio of about 160:1. That means that if you wanted, you could have a completely seperate set of engines that are used only for 30 seconds, and you'd only pay a 1% mass penalty. It might end up lighter than adding elaborate tail-end landing legs and the fuel burn to transition from a horizontal return flight, bleed off the airspeed to zero, and gently touch down (a horizontal landing can kiss a runway at a hundred miles an hour, since it's not going to tip over).

    And speaking of hover, pressure fed engines are even lighter than pump driven engines, and many months ago I thought about a demonstrator that was like a ball with thrusters aimed all around, so that it could rotate freely in the air on any axis while always having enough thrusters aimed vertically to maintain the hover. You can't do that with jet engines except by redirecting the exhaust because they don't have a thrust-to-weight ratio that allows for carrying many extras, and their throttle response is too slow. The SDI program actually had something almost similar, a missile that hovered horizontally and able to translate in any direction while remaining pointed at a fixed target. It could also, of course, pivot in any direction too, while hovering. Rockets don't have any problem doing that.
     
  12. Byeman

    Byeman Lieutenant Junior Grade Red Shirt

    Joined:
    Oct 28, 2012
    That is totally wrong. Spacex and SNC don't do anything different or use different techiques than the existing contractors at the launch site. Technicians are interchangeable. Most if not all of Spacex's workforce came from existing contractors.
     
  13. Byeman

    Byeman Lieutenant Junior Grade Red Shirt

    Joined:
    Oct 28, 2012
    No. It is not feasible and a bad idea. The engines for supporting the front of the vehicle would be useless mass after rotation. The launch vehicles are not designed to loads horizontally. They can't even support themselves horizontally when loaded with propellant.
     
  14. Byeman

    Byeman Lieutenant Junior Grade Red Shirt

    Joined:
    Oct 28, 2012
    Your math uses bogus assumptions. Too many to even point out.

    It is one thing to think of a small horizontally launched vehicle. It is completely asinine to think of one the size of the Saturn V.
     
  15. Byeman

    Byeman Lieutenant Junior Grade Red Shirt

    Joined:
    Oct 28, 2012
    Wrong on all accounts. When is comes to impractical, it is your idea.
    a. OSC and Delta IV are horizontally integrated vehicles.
    b. Wrong on the Dracos. To lift the whole vehicle requires nearly the same thrust as the main engines. For example, using a Falcon 9, the thrust of all nine engines would need to be directed down. And to maintain control, some of the Merlin engines would need to mounted near the nose. Not puny Dracos.
    c. Lifting and flipping is not easier than vertical assembly building.
     
  16. Byeman

    Byeman Lieutenant Junior Grade Red Shirt

    Joined:
    Oct 28, 2012
    Wrong, the structure can not take the propellants much less thrust of the abort motors. And solids would be unworkable since they can not be controlled.

    Also, booster engines are not the same as upperstage engines and many are not air startable.

    All your examples of horizontally integrated vehicles, not one of them are fueled until vertical.

    This idea is just plain stupid.
     
  17. Byeman

    Byeman Lieutenant Junior Grade Red Shirt

    Joined:
    Oct 28, 2012
    Another assinine post
     
  18. Byeman

    Byeman Lieutenant Junior Grade Red Shirt

    Joined:
    Oct 28, 2012
    1. Wrong, there are no "people who have direct experience with aviation processes" in the Carolinas and the KSC people are getting jobs.

    2. Huh? KSC is an aerospace facility. There is little difference in the work that happens there vs what happens in other aerospace facilities including aircraft factories across the country. Actually machining is a small amount of the work and workforce in manufacturing. Aerospace companies assemble hardware, they mostly out source machining. You basically don't know how the aerospace industry works

    3. Huh? The point was these few jobs were the only "specialized" ones at the space center and they are related to outside jobs, meaning they could be hired more easily, which did occur. You are not following the argument.

    4. Wrong, Delta IV and Antares are. Thor did it 50 years ago. Also, the assembly "process" is the same. The vehicles are aligned and then bolted together

    5. No different than Atlas and Delta. Atlas III and Delta III tested systems for Atlas V and Delta IV.

    6. Unsubstantiated.

    7. Wrong, they are not that "special" and the workers still have their basic aerospace skills

    8. No, not even close. The point is that there is no new technology in a Falcon 9 or Dragon or newer than Delta IV or Atlas V. Ethernet doesn't count since there issue with it.

    9. They are, They are taking jobs that usually done by teenagers to make ends meet. The area doesn't have enough jobs to absorb the lost of the KSC jobs.

    10. Your response shows you know less. Most machinists I know say they can operate any machine with a little OJT. And the ones at the Delta and Atlas plants are actually doing that.

    11. Shallow? That would be yours. Your posts show a complete lack of knowledge about aerospace business and launch operations.
     
    Last edited: Nov 16, 2012
  19. gturner

    gturner Admiral

    Joined:
    Nov 9, 2005
    Location:
    Kentucky
    Then how are they going to load a Falcon 4 or Falcon 5 into the Stratolaunch? As Elon Musk said, the extra structure to let them do that is pretty trivial. It's a fuel tank. Almost all cylindrical fuel tanks that have to take heavy pounding are horizontal. You can certainly thin one so that it can't, and the original Atlas couldn't even support itself vertically without the pressure of the fuel.

    And most booster engines are not air-startable because it wasn't a design requirement. That's a pretty easy thing to do. You just add ignitors, as they did to make an air-startable Merlin. Often when they take an upper-stage engine to use as a first-stage booster engine, they remove that capability because it's not needed.

    No, that would create a disaster because the nine engines would be at one end of the rocket, accelerating it at about 3 G's. You want to use half the lift-off thrust on one end, and half up toward the other end. The easiest place to put the engines is the interstage, which is otherwise mostly empty space.

    I bet you used to run around shouting "A 747 is too big to fly!!!"
     
  20. sojourner

    sojourner Admiral Admiral

    Joined:
    Sep 4, 2008
    Location:
    Sojourner
    You really need to stop conflating aircraft with rockets. It's embarrassing.