The IIS Express

[scottb50]

I doubt a 727 could see 700kts. A 727 is worthless above about 35,000 feet anyway because of the engines, not the wing. A lot of airplanes operate in the forties and 50's everyday. The Concorde flew in the low 60's. You could put more powerful engines on a 727 and fly it at 45,000 feet, but that's not what it was designed for. The same basic fusalage is flying at 41,000 in the 757 and 737 business jets, the wing is different, but the 727 airfoil is probably better than either of the others at high altitudes.<br /><br />That part of it isn't a problem, the problem is carrying enough mass to put something into orbit. An L-1011 puts about 1200 pounds into orbit Pegasus, though physically it could probably handle more weight, just not more bulk.<br /><br />A single stage to orbit, fully re-usable vehicle would have to be Shuttle scale. To orbit a comparative returnable vehicle would require a +1 million pound takeof weight version of White Knight, at least. <div class="Discussion_UserSignature"> </div>

 

[bobvanx]

<font color="yellow">To orbit a comparative returnable vehicle would require a +1 million pound takeof weight version of White Knight, at least.</font><br /><br />Yep.<br /><br />Any talk of rail-lunched, undercarriage ditching stacked flyback booster and orbital craft, when you start really getting the scale of the vehicle and comparing it to the number of flights you'd realistically have to have to support it, just seems silly.<br /><br />I mean to say, we can wish it were different, and keep going off on "gee, what if...?" but the facts of economics and physics make heavy lift airlaunch as likely as establishing an underwater research station on Europa.<br /><br />Which has been my point all along, that we're just never going to see an orbiter class lifting body get launched at 50k feet.

 

[bobvanx]

<font color="yellow"> I doubt a 727 could see 700kts. A 727 is worthless above about 35,000 feet anyway because of the engines, not the wing. A lot of airplanes operate in the forties and 50's everyday.</font><br /><br />That's part of what I was saying, that the engines just can't push the plane fast enough. And yes, I know planes fly higher, but I don't have any pilot friends who fly those. Lastly, I wonder if he's telling me the ground speed or the air speed?

 

[halman]

Scottb50,<br /><br />The L-1011 is a very poor example of airborne launching capability. It is an aircraft which was designed to carry people, in a pressurised cabin. The fuselage weighs more than the wing does, I'm sure, and creates far more drag than the wing does.<br /><br />Efficient airborne launching requires aircraft designed specifically for that purpose, which is why the White Knight looks so strange. It is the first aircraft that I am aware of which was designed from scratch to carry another vehicle to altitude. It is basically just a wing, with a small pod for the pilot.<br /><br />An aircraft usually has a service ceiling, which is the highest altitude which it can operate efficiently at. But the service ceiling is usually way below the absolute ceiling, which varies from day to day depending on the temperature, humidity, and how much the aircraft is carrying. An empty 727 can probably reach 700 knots air speed at 60,000 feet, but it would be straining.<br /><br />The RF-4 reconnisance bird frequently operated at 90,000 feet. However, a B-52 could turn inside the turn radius of a RF-4 at that altitude, because it has a greater proportion of wing area for its weight. The White Knight might be able to haul SpaceShip One up to 75,000 feet, but it would probably use more fuel gaining the last 25,000 feet than it did the first 50,000.<br /><br />Mass in and of itself is not going to get you into orbit. It is how the mass is ejected, and where it is ejected. You could eject all of the mass at ground level and never gain more than 100 meters altitude. The space shuttle ejects all of the mass of the Solid Rocket Booster propellant and about half the mass of the liquids in the External Tank getting to about 130,000 feet and 1 mile per second. The remaining half of the liquid propellants, about 800,000 pounds, are what give it the other 4 miles per second of velocity.<br /><br />And aerodynamic lift is never a factor in the shuttle's climb. It is all engine power <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[marcel_leonard]

Northrop Grumman and Scale Composites have the right idea about air to orbit delivery. I think we've been to busy playing rocket scientist to make any really progress since the 60s....<br /><br />Northrop Orbital Sciences<br />Scaled Composites<br />Virgin Galactic<br />X Prize<br /> <div class="Discussion_UserSignature"> "A mind is a terrible thing to waste..." </div>

 

[scottb50]

<<The L-1011 is a very poor example of airborne launching capability.>><br /><br />I was just using it as an example of what it takes to lift the required mass to put something in orbit from an air launch. Obviously there is no need for the fuselage for a true carrier aircraft. I would think, though it would save a lot of time and expense using 747 or even MD11 wings attached to a center section similar to the White Knight. If you look at the old Skycrane helicopter various module could be carried to accomodate passengers or cargo or it can be used without any modules to haul heavy loads on a sling, for logging and such.<br /><br /><<An empty 727 can probably reach 700 knots air speed at 60,000 feet, but it would be straining. />><br /><br />A 727 couldn't come close to 60,000 feet or 700kt period, even empty. <br /><br />The RF-4 reconnisance bird frequently operated at 90,000 feet. However, a B-52 could turn inside the turn radius of a RF-4 at that altitude, because it has a greater proportion of wing area for its weight.<br /><br />The SR-71 operated at those altitudes, but I don't think an F-4 was capable of much more than 60,000. A B-52 has a fairly high aspect ratio wing and could probably reach higher altitudes, but with the engines available mid 40's are probably a stretch, though I haven't looked up the capability. <br /><br />Very possibly a White Knight could reach 75,000 feet, but I doubt there would be much advantage in doing so and it would take other engines. The CJ-610 is certified to 51,000 on the older Lears and was tested much higher, the WK uses the military version of that engine that powers the T-37.<br /><br /><<Mass in and of itself is not going to get you into orbit. />><br /><br />You have to have the propellant mass to provide the thrust to achieve orbit and you have to have a way of containing it. Less propellant, less mass. Like you say the SRB's and half the propellant are used to get to 1 mile per second and you have t <div class="Discussion_UserSignature"> </div>

 

[halman]

Scottb50,<br /><br />The SR-71 routinely operated at altitudes in excess of 100,000 feet. Although its service ceiling was (and still is, I believe,) classified, I read several accounts of missions above that altitude. The RF-4 was typically operated between 80,000 and 90,000 feet, according to Air Force information in 1975. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[bobvanx]

<font color="yellow">Like you say the SRB's and half the propellant are used to get to 1 mile per second and you have to get to 5mps.</font><br /><br />halman and m_l, look at that statement very closely. This is the point of divergence, from where those of us who are creatively thinking about your ideas and trying to help you see where the unworkable parts are, and where your continued "yes, but what if?" is getting to be pointless.<br /><br />For a big payload with lots of inertia, it's the speed, not the altitude.<br /><br /><font color="yellow">the SRB's and half the propellant are used to get to 1 mile per second and you have to get to 5mps.</font><br /><br />All this propellant is getting used to accelerate a big load. <i>Not</i> to fly it to 50,000 feet. Until you modify your idea to take this basic, basic fact into consideration (I can already feel you saying, "Yes, but what you've got to undesrtand/see/realize--") then From where I am, you look like an ostrich with its head in the sand.<br /><br />So, what is your plan to accelerate your heavy-lift air launch vehicle to 1mps?

 

[halman]

bobvanx,<br /><br />Please understand that this is *not* my idea. (See Northrup Grumman concept vehicle image above.) Arthur C. Clarke described airborne launching in his 1954 novel "Prelude To Space."<br /><br />As I understand the mission profile, the orbiter starts its engines after the carrier wing has reached aproximately 50,000 feet, the wing pulls up, the orbiter seperates, the wing dives away, and the orbiter continues in a shallow climb. As the orbiter's velocity increases, it is thrown higher in altitude by centrifigul force. <br /><br />The amount of propellant needed to reach orbital velocity in this manner is considerably less than for the same vehicle and payload launched from the surface vertically. The savings result from the increased efficiancy of using aerodynamic lift to gain the first 50,000 feet of altitude, as well as using atmospheric oxygen to combust the fuel during this part af the ascent.<br /><br />As far as losing altitude after seperation, consider the Blue Angel demonstration maneuver where the aircraft is slowed to stall speed, the nose is pitched up, and the engines switched to 'afterburner.' The thrust keeps the aircraft from losing altitude as the velocity increases to the wing's stall velocity.<br /><br />I think that it is kind of like moving the launch pad to 50,000 feet, and tipping it over to about 10 degrees above the horizontal. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[bobvanx]

<font color="yellow">The amount of propellant needed to reach orbital velocity in this manner is <i>considerably less</i> than for the same vehicle and payload launched from the surface vertically.</font> <i>(italics added by bobvanx)</i><br /><br />No, it's <i>not</i> considerably less at the scale of a heavy-lift vehicle (which is where you keep drawing the thread to). It <i>is</i> considerably less for a vehicle flying the SS1 class mission.<br /><br />But when you're looking at getting a large payload up to orbital velocities, launching from sea level or 50k feet makes very little difference.<br /><br />Here's the last time I feel like saying it:<br /><br /><b>It's not the altitude, it's the velocity.</b><br /><br />I might check back to this thread someday, to see if you've incorporated this fact into your exploration. But for now, I'm bored with seeing the same arguments and propostions which have been hashed through coming up, clearly without regard to the new information that gets presented.

 

[scottb50]

http://www.wvi.com/%7Esr71webmaster/srqt%7E1.htm<br /><br />http://www.highironillustrations.com/aviation_specification/spec_f4.html <div class="Discussion_UserSignature"> </div>

 

[scottb50]

It's always speed to get to orbit, altitude can be corrected relatively easily once in an orbit. To replace the SRB's would take a pretty big wing.<br /><br />I also think we have to think to at least Shuttle payload capability as a minimum to get anywhere in Space. Everything to do anything has to be taken up, so the more capacity the better. <br /><br />Using SRB's or wings accomplishes the same thing; getting a payload above the bulk of the atmosphere were they release an upper stage that continues to orbit. The fact SRB's can impart a lot more momentum, and reduce propellant requirements for the upper stage. to make up the velocity difference at release of the stage, 1mps with the SRB's and .1mps with a wing. the altutude difference is of much less importance.<br /><br /><<So, what is your plan to accelerate your heavy-lift air launch vehicle to 1mps? />> <br /><br />I think the only real alternative is a flyback, Shuttle SRB based, first stage and a flyback second stage that reaches a minimal, once around orbit and returns for re-use. <br /><br />Orbitally bases upper stages rendevous and transfer payloads, sending a descending payload back and taking the ascending payload to higher orbits. <div class="Discussion_UserSignature"> </div>

 

[halman]

Scottb50,<br /><br />Okay, I was wrong. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[halman]

Scottb50,<br /><br />If the shuttle weighs 4.5 million pounds at launch, and the vehicle weighs about 160,000 pounds, and carries about 50,000 pounds of payload, then the Solid Rocket Boosters and the External Tank weigh about 4.25 million pounds. By the time the SRB's seperate, there is about 800,000 pounds of propellant left in the external tank, which is what is used to gain 4 miles per second of velocity. So it takes about 3 million pounds to acheive the first mile per second, and 800,000 pounds to acheive the last 4 mps. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[craigmac]

The future of LEO Delivery ....

 

[marcel_leonard]

<font color="yellow">A 727 couldn't come close to 60,000 feet or 700kt period, even empty.</font><br /><br />Don't think that 700 series of Boeing planes is the route you want to take into LEO. If we are going to succeed with affordable Orbital Delivery Systems we will have to re-think, and re-engineer our avionics. Rocket, Jet, ScramJet, AeroSpike, and Ion propulsion alone won't do it. However may be a combination of some of these technologies may be the ticket. <div class="Discussion_UserSignature"> "A mind is a terrible thing to waste..." </div>

 

[scottb50]

Rocket and jet maybe, the rest are irrelevent. <div class="Discussion_UserSignature"> </div>

 

[marcel_leonard]

You didn't read the the statement; before you automatically disagreed w/ me. Why; could it be force of habit....? <div class="Discussion_UserSignature"> "A mind is a terrible thing to waste..." </div>

 

[scottb50]

I did read it, I also went back and reviewed the links provided.<br /><br />I stand by my response. <div class="Discussion_UserSignature"> </div>

 

[marcel_leonard]

<font color="yellow">Rocket and jet maybe, the rest are irrelevent. </font><br /><br />Could you please elaborate? <div class="Discussion_UserSignature"> "A mind is a terrible thing to waste..." </div>

 

[marcel_leonard]

<font color="yellow">Ion Engines CAN NOT BE USED TO DELIVER ANYTHING TO LEO FROM THE EARTH. Their thrust to weigh ratio is not great enough to move even itself out of the gravity well. </font><br /><br />Correction current ion drives; which are used on satillies can not reach low earth orbit. That doesn't mean that furture ion propulsion technology won't provide greater trust. <div class="Discussion_UserSignature"> "A mind is a terrible thing to waste..." </div>

 

[mrmorris]

<font color="yellow">"Correction current ion drives; which are used on satillies can not reach low earth orbit. That doesn't mean that furture ion propulsion technology won't provide greater trust. "</font><br /><br />True. A future generation of ion drives, advanced beyond anything that current scientific minds can even conceive at this time might be able to achieve a thrust-to-weight ratio of greater than one. <br /><br />It also possible that aliens will land next Tuesday and give mankind the plans to their antigravity drive.<br /><br />With only modest amounts of hallucinogenic substances -- <b>anyone</b> can be a visionary.

 

[marcel_leonard]

<font color="yellow">With only modest amounts of hallucinagenic substances -- anyone can be a visionary. </font><br /><br />Obviously not!!! The point being that you seem to spend quite a bit of time discussing current Jet, and Rocket technologies; which you fail to realize that 100 years ago these technologies were <font color="orange">advanced beyond anything that the current scientific minds could even conceive at that time</font> <div class="Discussion_UserSignature"> "A mind is a terrible thing to waste..." </div>

 

[scottb50]

The aerospike does hold a lot of promise, but it's simply a different type of nozzle for a rocket engine. As for the scramjet it can help get a vehicle up to mach 8-10 but it has to be in the atmosphere, it is also dead weight leaving the ground and only useful to 100,000 feet. <div class="Discussion_UserSignature"> </div>

 

[mrmorris]

<font color="yellow">"...100 years ago these technologies were advanced beyond anything ..."</font><br /><br />Yep -- and no one at that time was speculating that they'd exist, either. In the fifties, people widely believed that in the year 2000, hovercraft would have replaced the automobile. In the early sixties -- people thought mainframes were the only computers that would ever exist. In the eighties -- Bill Gates thought 640K was more memory than a PC would ever need. No one predicted the Internet would become the force it has.<br /><br />You can't predict with any degree of accuracy more than a few years into the future which technologies will make revlutionary advances, and which ones will stagnate and largely disappear. You <b>certainly</b> can't predict which new technologies will be invented because invention is, by definition, the creation of something no one has ever thought of before.<br /><br />You persist in pointless speculation about events and technologies that won't see the light of day for decades (if ever). The most likely thing to cause a revolution in spaceflight is not evolutionary advances in known technologies, but the development of a currently unknown propulsion method, or a revolutionary advancement in existing ones due to the creation of some enabling technology (for example room-temperature superconductors). Once again -- such a development is not subject to prediction -- you can't determine at this time what the enabling technology will be or when it will become available. Ergo -- you're simply releasing hydrostatic pressure into the perceptible movement of air parallel to the ground.<br />