The IIS Express

[bobvanx]

>The shuttle is in a shallow climb when it is accelerating the fastest because velocity relative to the center of gravity of the planet is the goal.<br /><br />One day we'll stop trying to apply our instinctual grasp of aerodynamics to spaceships. The Orbiter is not in a "shallow climb." It's in a perigee raising maneuver. From the ground, that looks like a shallow climb. In space it looks like... well, I don't know, I don't have the tools for that, yet. So I'm at the inbetween place, where what I have doesn't work, and what will work, I don't yet have.<br /><br />/warning/snide comment alert/warning/<br /><br />Oh! You'd put the spaceship on the BACK of the wing! Well, I'm sure that the extra 20 feet closer to space will make all the difference.<br /><br />/end warning/begin apologies/eh, I had to be sarcastic for a moment/Please don't be offended/sheesh what a weak apology/end apologies/<br /><br />You really don't seem to realize just how non-helpful the atmosphere is for reaching orbit. For reaching space, it's relatively easy to ignore. But to orbit, it's inconvenient in a couple of really important ways:<br /><br />It's not deep enough. 10 miles or so is all you've got to work with. If it were 50 miles deep, then there'd be lots of reasons to look into flying to the edge of space.<br /><br />It gets your spaceship too hot. At the speeds required to orbit, the atmosphere burns stuff up.

 

[bobvanx]

Aleta over at XCOR helped clear alot of this up, for me. They've got all the software to model all this stuff. For orbital spaceships, the atmosphere is so very much not your friend. A system designed to use it does so at great mass and performance penalties.<br /><br />The optimal flight path really is to pop out of the atmosphere ASAP and then tip into your perigee-raising maneuver.

 

[marcel_leonard]

<font color="yellow">I do not think that is correct at all Leonard. </font><br /><br />Is<br />That<br />A<br />Fact?<br />Don't<br />Everything<br />You see on the<br />Internet !!! <div class="Discussion_UserSignature"> "A mind is a terrible thing to waste..." </div>

 

[halman]

bobvanx,<br /><br />Apparently, you take things very litterally. I did not say anything about 'flying into space'. The shuttle can only increase its velocity by accelerating parallel to the the planets center of gravity, which means having the engines pointed opposite the direction that the pilot wants it to go. A slightly nose-up attitude provides a somewhat faster climb than if the nose is pointed at the horizon, which is desired to get out of the atmosphere as fast as possible.<br /><br />This model of launch has been considered the optimal for over 50 years by many educated persons involved in spaceflight because it utilizes an air-breathing vehicle to carry the rocket-propelled vehicle to an altitude where air resistance is minimal. A vertically launched rocket suffers the penalty of gravity removing 20 miles per hour of velecity every second. In addition to that, the rocket cannot accelerate at its maximum because atmospheric effects known as Maximum-Q will begin buffeting the vehicle severely enough to rip it apart. Max-Q effects are a product of velocity and air density, and are negligable above 60,000 feet. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[bobvanx]

>I did not say anything about 'flying into space'.<br /><br />But you'd like to. <img src="/images/icons/wink.gif" /><br /><br />Seriously, neither did I. I know you're thinking about flying to the edge of space. You'll also note that those 50 years' worth of geniuses always had little ships making the final part of the trip, on the back of big fly-back boosters. A long, slow wing at 50k feet isn't going to help something as massive as a Shuttle stack make it into orbit. It will however, help make a nice crater.

 

[bobvanx]

> Max-Q effects are a product of velocity and air density, and are negligable above 60,000 feet. <br /><br />Thanks, I'm glad you report that. That's exactly why a different set of geniuses have their vehicles come up out of the atmosphere before making the acceleration to orbital velocity.<br /><br />It's also why rockets don't take off horizontally, because they'd do just like you say, tear themselves to bits before they got out of the atmosphere.

 

[marcel_leonard]

<font color="yellow">A long, slow wing at 50k feet isn't going to help something as massive as a Shuttle stack make it into orbit. It will however, help make a nice crater. <br /></font><br /><br />I can see by your remarks college physics must have significantly brought down your grade point average. Halman is right when he says:<br /><br /><font color="orange">A vertically launched rocket suffers the penalty of gravity removing 20 miles per hour of velecity every second. In addition to that, the rocket cannot accelerate at its maximum because atmospheric effects known as Maximum-Q will begin buffeting the vehicle severely enough to rip it apart. Max-Q effects are a product of velocity and air density, and are negligable above 60,000 feet.</font><br /><br />You are basing your conclusions on the assumption the we use the current shuttle model, and not a vertical paradymne. This is the same reason 19th century areonautics failed to produce a viable airplane, and why the Wright Bros. succeeded. They realized that you don't need to use the mechanics of birds in order to sustain flight. As we move further into the 21st century we will discover other means; other than rocket sciences in order to achieve high earth orbit...<br /> <div class="Discussion_UserSignature"> "A mind is a terrible thing to waste..." </div>

 

[najab]

Air launch will work for small rockets, but it is not the way to go for large payloads. The simple fact is that we aren't likely to be able to build an aircraft big enough to <b>land</b> with a multi-million pound payload any time soon.<p>Unless your carrier aircraft can return to base with a fully loaded and fueled rocket in the case of an launch abort, you aren't going to get many customers - they aren't going to take kindly to deliberately dumping their payload into the Atlantic because the wind was stronger than you predicted.</p>

 

[bobvanx]

Actually, I'm basing these conclusions on the assumptions from the posts in this thread from you and halman. Writings of ET's with wings, heavy-lift vehicles, long thin wings for high-altitude flight (go back and read the comment about not using a swept wing), all the data about the weight of the shuttle... so these are my conclusions, yes, but they are based on the system that's being proposed.<br /><br />There could very well be a flyback booster idea that would work. But the major fly in the ointment in <b>this</b> idea (it seems to me) is that when you get this massive vehicle up to 50k (60k, whatever, it doesn't matter much) and let it go at non-swept wing speeds, it's going to drop like a stone.<br /><br />All the way down.<br /><br />Making a big boom.<br /><br />When it tries to orbit through the lithosphere.<br /><br />Oh, excuse me, unless you switch to a "vertical paradigm" and your orbital vehicle boosts straight up... oops, there's that 20mph vertical penalty again. Which halman has been trying desperately to avoid. <br /><br />If you did have a flying launch platform, now you're out of the densest part of the atmosphere, so you don't have to throttle back for the 20 seconds or so (there being no Max-Q) and your engine bell can be optimized for vacuum.<br /><br />PS maybe you can work on sticking to discussing the ideas presented. Thanks.

 

[bobvanx]

>Unless your carrier aircraft can return to base with a fully loaded and fueled rocket in the case of an launch abort<br /><br />Both Pegasus and SS1 have this capability. So that can give us a sort of baseline. The carrier is by far the largest mass of the system.

 

[najab]

><i>The carrier is by far the largest mass of the system.</i><p>Even if we assume that the carrier is going to be purpose designed to take off, fly to 50,000ft and land (no requirement for long distance, endurance or fuel economy), and that its weight is kept to an absolute minimum, to carry a launch vehicle of more than a few hundred thousand pounds loaded weight would take a <b>massive</b> aircraft.</p>

 

[scottb50]

To begin with you don't really need a Shuttle vehicle and the external tank wouldn't have to carry nearly as much as the Shuttles does. Figuring a vehicle 1/2 the mass of the Shuttle and having to accelerate from 50,000 ft from mach .75 to mach 25, as opposed to mach 5 for the Shuttle you would still need at least half as much propellant, or about 750,000 pounds, for the vehicle and propellant.<br /><br />Use 747 wings attached to a carrier, somethhing like the Skycrane idea and it could be under a million pounds or so, which would be doable. <div class="Discussion_UserSignature"> </div>

 

[bobvanx]

You know what, I've lost sight of the goal. I think. Were halman and leonard trying to get an Ariane Heavy or Shuttle-class payload into orbit?<br /><br />Or are we discussing just any air launch to orbit?<br /><br />Or are we trying to figure out, within the context of the foreseeable future, just how big a payload could be air launched?

 

[halman]

bobvanx,<br /><br />I should apologize for the confusion. I started out using the shuttle as an example, and then jumped ship because the shuttle configuration is very unweildly for airborne launching. I was trying to use tho shuttle originally because of the numbers are readily available.<br /><br />In regards to the shuttle falling down at seperation, due to a lack of velecity, I agree that it will lose some altitiude. However, if the nose is held above the horizon, the thrust will overcome gravity, and the velocity will build quickly.<br /><br />I do not forsee a carrier wing cabable of landing with a fully loaded and fueled shuttle on its back. However, since the primary reason for using a winged lifting body is gliding ability, I do not see a problem with the wing and the shuttle returning seperately.<br /><br />I believe that this method will ultimately be used for launching 100,000 pound plus payloads. Probably not for at least 20 years, but in less than 50. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[bobvanx]

Apology is not sought, but thank you. And I sure appreciate the clarification!

 

[bobvanx]

>I believe that this method will ultimately be used for launching 100,000 pound plus payloads. Probably not for at least 20 years, but in less than 50.<br /><br />Huh. Don't I recall some of your posts over on the space tether/elevator threads? Anyway, if I had money, that's where I'd put it, for lifting large masses and volumes, on a space elevator.<br /><br />Airlaunch for smaller, people carriers, and elevator for cargo. That's my prediction, for the way space access wil shape up.

 

[halman]

bobvanx,<br /><br />20 years ago, fusion power seemed just around the corner. Several nations were pouring billions into new tokamak designs, plasma temperatures were acheiving stability in the realm needed to support the reaction, and reactions of measurable duration were being reported. So where are the fusion reactors? I can't believe that the market for power has collapsed, and fusion was supposed to be clean, no harmful waste, no hard radiation. There are wind turbines going up all over the place, and no mention of fusion in the popular press.<br /><br />I cite the above to support my position that the technology required to build a space elevator may be just around the corner, but when we will get to the corner is anyone's guess. I would dearly love to see a space elevator built, but the economics may well prove to be the biggest obstacle. Not to mention the possibility that more mass will be coming down from space than going up to it, if predictions of space manufacturing turn out to be realistic. This is not to say that a space elevator will never be built. Far from it! I am certain that someday one will be constructed. However, I also am certain that we cannot afford to wait until the technology and the economics are in place for what will probably be the biggest construction project the world has ever seen to come to pass.<br /><br />Vertical launching is the simplest method of putting mass into orbit. It is also one of the least efficient. I strongly believe that the problems involved in the airborne launching of a vehicle capable of putting at least as much payload into orbit as the space shuttle can carry can be solved in the forseeable future. The first airborne launched vehicle will certainly be smaller than the space shuttle, but success builds upon success.<br /><br />When a carrier wing rides in a truck which rolls on rails, and is accelerated by ground power to a velocity adequate for the wing to acheive enough lift to fly out of the truck, s <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[marcel_leonard]

I the words of Sir Arthur C. Clark: "<font color="yellow">Science Fact is always stranger than Science Fiction!</font><br /><br />AeroSpike, ScramJet, Laser, Plasma, and Ion propulsion all show promise to provide a new means of propulsion... <div class="Discussion_UserSignature"> "A mind is a terrible thing to waste..." </div>

 

[bobvanx]

Those are promising technologies for various needs. But really, aerospike is the only orbital capable tek you've listed there.

 

[bobvanx]

Well halman, I guess we'll get to see, won't we!<br /><br />BTW I'm not swayed by your fallacy of transference: <i>since we've spent money and time on X, therefore money and time spent on Y will yield the same result/failure.</i><br /><br />Regarding efficiency of one surface-to-LEO method versus another, I take the whole enchilada approach, looking at hardware to infrastructure to range safety and abort recovery and on and on. Verticle launch is efficient enough.<br /><br />I really wish airlaunch methods all the best as the future unfolds, but as najaB pointed out, since you want the vehicle to be reusable, dumping it is not an option, and since your rail-launched giant craft is leaving its undercarraige behind it won't have a prayer of landing fully loaded.<br /><br />Or maybe dumping the craft and saving the payload/pilots is a reasonable abort method. That's not for me to figure.<br /><br />Here's an anology that follows more closely the rules of logic. Will we ever put a semi tractor-trailer engine and transmission into a sports car? It's super powerful, so why not? The answer is because it's optimized for a specific task: very high torque. Likewise, you'd never put a sports car engine and tranny into a tractor, because that system is optimized for high speed.<br /><br />It's not a question of success building on success. It's a question of optimization.<br /><br />Orbital access requires a speed of 17,000mph. You've got to get to that speed in just a few minutes so you don't reconnect with the earth partway around your first orbit. A large mass has large inertia, and so wherever it starts, it's going to have to build its speed up using whatever propulsion is onboard. Here's a fact: <b>For a really large payload, the cost of getting out of the atmosphere is trivial</b> compared with the cost of accelerating to orbital velocity. It's so small that designing for it is inefficient.<br /><br />Here's another anology that's closer to the mark: airlaunch heavy lift is like designin

 

[phaedrus]

Clearly chemical rockets have serious drawbacks, so I've been thinking about a maglev launcher for some time. <br /><br />First, there is no theoretical reason the launch rail / tube couldn't be hundreds of miles long. The longer the rail, the more gradual the acceleration.<br /><br />Second, a (spherical ?) payload or sabot could ride inside an evacuated tube augmented by pressure from behind. Kind of a giant pea-shooter (or "supergun").<br /><br />Third, there is no reason the launcher would have to be at sea level. It could be built up the side of Everest or K-2 where Tibetan lamas would place a giant Ovaltine seal over the muzzle prior to pumping down. <br /><br />I know these ideas seem "far-out" but they have all been considered, and never really rejected (or combined into a working system). I suspect the reasons are as much political as technological. <br /><br /><br />See <A HREF="http://www.fas.org/news/iraq/1998/05/980500-bull.htm" /> Space: Space Guns</A><br /><br /><br /><br /><br />

 

[nacnud]

The reason why these kind of things have not and probably will not be built is cost. They might be cheeper over lots of launches but the investment is just not worth it at the current launch rate. The closest you are likly to get is the sub-orbital hopper from esa.

 

[halman]

bobvanx,<br /><br />I guess that I bury my meaning with verbiage. The orbiter portion would be specially designed to land with a heavy payload, because one its primary purposes would be to bring goods manufactured outside the atmosphere to specific destinations. One serious drawback of capsules is the requirement for lots of open space when landing. Bringing a payload into a metropoliton area is why semi-tractor trailer rigs where developed, because rail was not available everywhere.<br /><br />An abort during launch means seperating the wing and the orbiter, and which ever one is in trouble lands at the nearest landing strip. The orbiter might have to burn its engines to gain enough altitude to line up on the runway, but there is no need to throw it away.<br /><br />Also, I am not implying that since we have spent money and time on a technology which has still not matured, that the same will happen with space elevator technology. I was merely trying to point out that just because one aspect of space elevator technology has shown promise in the laboratory does not mean that we will be building a space elevator in a few years.<br /><br />I am attempting to post an image which someone else posted in a thread several months ago. Unfortunately, I have lost the link, and several searches have not revealed it. It is of an unmanned variant of the launch system which I have been championing. If anyone can find the link, I would greatly appreciate it. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[bobvanx]

It's very true that anything you can do to increase the speed of the vehicle without on-board propellents results in a higher mass fraction delivered to orbit.<br /><br />I like your comment about why land on a runway, in terms of positioning. A reusable vehicle will get great savings by coming back to a processing facility all by itself, rather than requiring a retrieval squad. Still, even passenger jets have those little tugs that do the fine tuning.<br /><br />Launch abort at flight speeds, with low altitude separation and independent landings... not improbable. I read they're building another runway at Mojave. The orbiter might have to dump oxidant or propellant, but again, seems doable.

 

[bobvanx]

I have a friend who pilots 727s. He tells me that he can fly so high that the rarified air can't hold up the wing at the speed the engines can generate. So he can fly the plane at a 700kt stall, as it were. The plane is literally skimming along, from air that is too rare to hold it up and air that's just dense enough to keep it in the sky.<br /><br />And there's no throttle left.<br /><br />The reason this occurs to me, is that if he could fly faster, the plane could climb higher. You'd start getting heating on leading edges before very long, but I'm curious whether you could get up to a useful speed, for orbital air launch.<br /><br />I guess what I'm thinking is, I wonder if you left the wing and orbiter mated, and started skipping up the atmosphere, if that would help reduce inertial losses to gravity.