A cheap and easy way to space.

[Jazman1985]

"Clearly the key to low cost space delivery systems is Areospike/Scramjet engines "

This may be a key part of a long term space delivery system, but for now I think Halman has some great points that I agree on,

"Instead of trying to incorporate the latest technology, or the most powerful engines, I would rather take the approach of simple, proven rockets, operated at less-than-maximum power. By using multiple engines, we build in redundancy without increasing complexity. And the demands of the mission profile for airborne launching are much lower than for vertical launching, which requires thrust to weight ratios of greater than one to one. Even .75 thrust to weight ratio will work, because all that is required is to accelerate the vehicle, not to lift it."

Although I think having the capability of T/W ration of > 1/1 is important to have, it might not be necessary, as even an initial ratio of .75/1 will quickly have a ratio of 1/1 seconds after ignition. Personally, it's very exciting that there are so many new aerospace companies or people developing both Hybrid and Liquid rockets. Once these companies are producing products in excess of immediate needs,(once they can hand a buyer a rocket off the shelf instead of taking months to build one from scratch) I think we will begin to develop "A cheap and easy way to space". If someone can purchase a rocket and integrate it into an existing craft without having to build it themselves, we will begin to see many more people becoming interested in space travel and advancing rocket technology even faster. While I think that SpaceX has a great plan to reduce overall costs to access space, I see much more promise in things like the Rocket Racing League for driving public interesting and creating a quick turnaround time from engine and structure development to actual use. Learning how to safely launch a rocket powered vehicle(whether capture or under its own power) horizontally from the ground, which has recently been shown by Armadillo Aerospace, XCOR Aerospace and Scaled Composites will favor quick movement in this field, and I think will prove to be the safest and cheapest method to achieving orbit. The lack of and the fact that no launch abort system is necessary reduces the years required to build a rocket significantly, Elon Mush recently stated that it would take 2-3 years to develop this system, a significant portion of the total rocket development time. He has also delayed his Falcon 9 rocket launch significantly, if the vehicle was launched horizontally at altitude over the ocean, while the development time may be more to develop the carrier vehicle, a failure to launch would not be such a large deal, as one occurring in Florida on land.

 

[SteveMick]

Every scenario for space access starts with the problem of achieving the velocity and altitude for low Earth orbit.

Well, every one except for the tether or beanstalk idea, but the problem with that one is the huge scale of such a project, siting issues, and the fact that it doesn't make any money till its completed. It's a fantastic idea, but its hard to see it happening anytime soon IMO.

Well there is a middle path: electrodynamic tethers. These use miles long conductive cables or ribbon thru which an electric current of high voltage is discharged into the ionosphere. The current creates a magnetic field perpendicular to Earth's and since the tether can't easily rotate it gains or loses orbital altitude. At least that's my understanding.

With electrodynamic tethers, you can start small, use inclined orbits not just equatorial (but that's where the profit is), and begin making money fairly early in the process.

The scheme: 1. Launch a solar powered ED tether to LEO with a device to allow connection of another tether at its lower end
2. Launch another one and attach
3. Repeat 1&2 until a few hundred mile length is reached
4. Increase mass by adding space junk if possible and second stages from tether section deliveries
5. Launch and attach comsat or other payload for GEO
6. The payload will not need to reach orbital velocity for attachment since the tether is at the orbital velocity for its center of mass which is at a higher altitude which will be less. The tether will respond by losing altitude and will recover this altitude over time magnetically. The tether will continue to energize itself at low altitude only and work its way into an egg shaped GEO transfer orbit and release the comsat
7. Return to LEO and collect paycheck
8. Send up more tether sections to increase length and so reduce its orbital velocity further
9. Introduce climbers for future payloads
10. Launch first payload using climbers by slowly raising it along tether with climbers to the high end and releasing it
11. Increase length of tether until only first stage of a launcher is required to rendevous with the tether due to the tether's lower velocity. As tether mass increases altitude loss will go down and payloads up.
12. Continue to raise payloads and use profit to further increase tether mass and length.
13. Eventually bring the tether down to speeds achievable by a SR-71 type air breathing vehicle and lower the end so that the vehicle can fly an arch up out of the atmosphere and reach the tether.

No arguments over where to put the tether ground station or over flight issues and no need for too much money up front.

Steve

 

[scottb50]

Every scenario for space access starts with the problem of achieving the velocity and altitude for low Earth orbit.

Well, every one except for the tether or beanstalk idea, but the problem with that one is the huge scale of such a project, siting issues, and the fact that it doesn't make any money till its completed. It's a fantastic idea, but its hard to see it happening anytime soon IMO.

Well there is a middle path: electrodynamic tethers. These use miles long conductive cables or ribbon thru which an electric current of high voltage is discharged into the ionosphere. The current creates a magnetic field perpendicular to Earth's and since the tether can't easily rotate it gains or loses orbital altitude. At least that's my understanding.

With electrodynamic tethers, you can start small, use inclined orbits not just equatorial (but that's where the profit is), and begin making money fairly early in the process.

The scheme: 1. Launch a solar powered ED tether to LEO with a device to allow connection of another tether at its lower end
2. Launch another one and attach
3. Repeat 1&2 until a few hundred mile length is reached
4. Increase mass by adding space junk if possible and second stages from tether section deliveries
5. Launch and attach comsat or other payload for GEO
6. The payload will not need to reach orbital velocity for attachment since the tether is at the orbital velocity for its center of mass which is at a higher altitude which will be less. The tether will respond by losing altitude and will recover this altitude over time magnetically. The tether will continue to energize itself at low altitude only and work its way into an egg shaped GEO transfer orbit and release the comsat
7. Return to LEO and collect paycheck
8. Send up more tether sections to increase length and so reduce its orbital velocity further
9. Introduce climbers for future payloads
10. Launch first payload using climbers by slowly raising it along tether with climbers to the high end and releasing it
11. Increase length of tether until only first stage of a launcher is required to rendevous with the tether due to the tether's lower velocity. As tether mass increases altitude loss will go down and payloads up.
12. Continue to raise payloads and use profit to further increase tether mass and length.
13. Eventually bring the tether down to speeds achievable by a SR-71 type air breathing vehicle and lower the end so that the vehicle can fly an arch up out of the atmosphere and reach the tether.

No arguments over where to put the tether ground station or over flight issues and no need for too much money up front.

Steve

So now right back where we started. How do you get all this stuff to orbit? That is the primary problem.

On the other hand this particular idea has been around for a long time.

 

[SteveMick]

Hi Scottb50 I'm not sure exactly what you mean by your comment.
The tether is launched by conventional launchers, but as it becomes longer and more massive, the velocity required to achieve connection to the lower end goes down and hence the velocity required to achieve orbit. The tether will orbit at the velocity required for orbit at its center of mass which may be hundreds or thousands of miles up. The first big reduction in launch cost occurs as required speed drops to a speed such that only the launcher's first stage is required. Not only does this save the cost of a second stage, but its mass becomes extra payload mass. At first the entire tether can be used to raise payloads to GTO, but it will likely become far more efficient to use devices that will carry payloads up and down the tether so that more payloads can be delivered per unit time.

As the tether continues to grow, each section added requires less energy to place in orbit than the one before.
Once the tether reaches a length that allows air breathing vehicles to reach the speed needed to arch up out of the atmosphere to meet it; costs to reach orbit drop dramatically. Since the tether can use its electromotive force to overcome drag, it could even descend to the altitude and speed of jetliners. It could then lift air to increase its mass and to supply oxygen for propellent, etc. in space.

Since payloads are lifted to GTO or other high orbit destination or beyond for profit very early in the process, less financing is required, increasing the odds of its happening relative to some other ideas. The tether, if structurally redundant such as the HoyTether, should have a long lifetime and be repairable if hit by small pieces of space junk. Over its lifetime it should be able to lift many, many payloads for significant profit

You're correct that electrodynamic tethers are an old idea. One of my fellow paper presenters at the '85 Space Congress discussed ED tethers. Although they have been suggested for orbit altitude raising and/or maintenance and for deorbiting space junk, I haven't seen anything that grows to the scale I'm discussing or that uses climbers or reduces the velocity needed to place payloads in orbit.

Steve

 

[scottb50]

I think you misjudge how much it would take to put such a plan into action. You would not only have to develop the system you envision but the system to launch it into Space. Current vehicles ar pretty expensive.

What we need is a cheap way to position building materials, my idea uses spent tanks as building blocks and used engines as in orbital assets or cargo for return and overhaul.

 

[SteveMick]

Scottb50

I certainly agree that using spent tanks and anything else is wise, and I have long advocated the use of dead payloads in GEO since the energy required to gather them into one place in GEO is quite low as compared to objects in LEO which are frequently in orbits of different inclination and altitude. I have written about using telerobotic vehicles, along with solar thermal tech, to use this treasure trove for building materials and the aluminum into solar thermal rocket propellent. There are more than a couple of million pounds of this stuff best I can tell.

I think you still may not understand this idea. While it is true that the tether has to be launched; it becomes part of an expanding system that will eventually make space flight cost very little more than an airplane ride and a bridge toll (I like the name "Spacebridge" for this scheme). Space junk could greatly help increase the tether's mass. This is important because in the early phases especially, as a new payload attaches to the low end of the tether, it must use its potential energy to accelerate the payload to a new equillibrium at a lower altitude. It trades some of its potential energy for the kinetic energy needed to accelerate the payload. Alternately, it could grab a big piece of orbital debris and release it from the lower end to de-orbit it while the new payload is simultaneously attached. If the tether is sufficiently large relative to the payload, the altitude lost will keep the payload higher than a hundred miles or so. At that point, the electromotive force of the solar cell supplied electrical current flowing thru the tether slowly raises the assembly to a higher orbit. As the tether gets thousands of miles long, the payload attaching to the low end need only reach a few thousand mph or less, but the energy needed to accelerate it to the required velocity is much higher. At this stage however, the tether is quite massive and so should be easily able to handle a comsat size payload without large altitude loss.

At some point early in the process, devices capable of hauling payloads up and down the tether need to be launched.

Money can be made from the start by using the first tether section to take a comsat to GEO transfer orbit, release it and return to LEO. Sections may then be added to lengthen the tether and spent second stages from these launches glommed on to massify it. Convienient space junk as well may be gathered and added. Yes you do need to launch the tether sections but once you launch it and the crawlers, you build a resource that can make space travel quite cheap and routine.

Steve

 

[scottb50]

Money can be made from the start by using the first tether section to take a comsat to GEO transfer orbit, release it and return to LEO. Sections may then be added to lengthen the tether and spent second stages from these launches glommed on to massify it. Convienient space junk as well may be gathered and added. Yes you do need to launch the tether sections but once you launch it and the crawlers, you build a resource that can make space travel quite cheap and routine.

Steve[/quote]

For this to work you would need massive equipment and a way to orbit it, before you could be in operation. The cheapest I can think of is the Falcon 9 and how many of them would you need?

 

[EarthlingX]

This sky-hook/tether might is a good idea, just not for the first step. It is a branch on a tree, we have to learn how to climb again.
Let's get up there first, cheap, frequent, safe for people, and if possible, not too dirty, then we can start building bigger structures, finally.

 

[halman]

Perhaps I am wrong, but it seems to me that one of the biggest difficulties that space exploration faces today is the spectrum of ideas which various people are presenting as the 'best' method or goal. Should we go to Mars, or to the Moon? Should we use capsules or lifting bodies? Should we wait until we can develop space tethers? In some cases, the technology is not advanced enough, in the eyes of many people, to support these claims, but to those on the outside of the debate, they all seem to have worth. When asked to provide money for space exploration, these people want to know that they are supporting a reasonable, sustainable program, which will have long term benefits.

But the experts can't seem to agree, which leaves the average person thinking that space exploration is not a good place to put a lot of money right now. It is not like other science projects, which either people support or oppose, because we all want to go into space, there is no question of that, it is just that we all want to do it differently, and go different places.

SteveMick, your proposal seems logical, and is probably valid, just as the space elevator is a logical, valid proposal. But we have limited abilities, and the creation of a tether hundreds, no thousands, of miles in length is beyond us right now, as far as I know. As our materials science is able to work in the zero gravity environment for a while, things will probably change, but your concept requires the use of equipment and theories which are unproven and non-existent.

What I am proposing requires no major advances, no breakthroughs, no leaps in abilities. Someone pointed out in another thread that a rocket sled could accelerate the stack to high enough velocity for it to take off, instead of relying on a magnetic catapult, which is unproven. I am convinced that we need to drastically upgrade our ability to put people in orbit, both by reducing the cost, and by increasing the number of people who can fly at one time. I am convinced that the lack of this capability is the single greatest factor holding back space exploration right now, and that the economic growth that is possible in space will not occur until we have this capability.

I am also convinced that the system that I propose could be operational in about 7 years, possibly less, and that it could be built for less than 100 billion dollars. (That used to sound like a lot of money, until the last year or so.)

 

[SteveMick]

Halman
I really like the idea of an electromagnetic catapult launch system. I remember the old movie "When Worlds Collide" used a rocket sled to get the launcher going and that was considered conventional wisdom in the Fifties about how space flight would be done. Electromagnetic is way better.

I think that I have given you the wrong impression about my idea judging by your objections to its cost and scale. I want to reiterate that this is an incremental largely self financing scheme that makes money from the very inexpensive start, and construction can be stopped and started at will. At every stage a system is in place that can reduce the energy needed to reach orbit and make profit lofting payloads. HoyTether Inc. actually makes tethers, so its hardly new tech and although deployment issues have hampered early efforts at on-orbit demo; this is more a reflection of the tiny budgets they had to work with than any fundamental problem. The first tether section may only be a few tens of miles long and weigh only a few hundred pounds even with the requisite grappling/docking device at the low end. It could be launched with a Comsat and deliver it from LEO to GTO and return for profit. Further sections could be mass produced to lower costs.

None of this really requires winning a political battle but rather the formation of a start-up company.

Steve

 

[neilsox]

Suppose we build an ED = electrodynamic tether 4000 miles long. The top end is twice as fast at about 40 times the altitude of the bottom end. Near the middle the speed is about 13,000 miles per hour, about 9000 miles per hour at the bottom and 21,000 miles per hour at the top, which is fast enough to go to GEO orbit, the moon or Mars except the travel time to Mars is excessive = 5000? hours and considerable breaking energy is needed to make a soft landing on Mars or the moon. The 9000 miles per hour at the bottom at about 100 miles altitude is about the limit of single stage rockets, so we still have the most dangerous and perhaps the most expensive part of the system. Longer than 4000 miles helps, but suppose we rotate the 4000 mile tether end over end with a tip speed of about 4000 miles per hour? This reduces the bottom end speed to about 5000 miles per hour, which perhaps doubles the payload of the single stage rocket. Problems are attachment timing of the pay load is critical, a jerk occurs shortly after attachment that could snap the tether and/or damage the payload and the whole tether is moved to a lower altitude, and a slower tip speed by the pay load. Tether orbit, and tip speed needs to be corrected perhaps every other pay load, or more or less continuously.
Advantages are the tip speed adds to the release speed of the payload at the top, perhaps halving the travel time to Mars. Also the tether can be in semi polar orbit. so it serves most of the nations of Earth at least occasionally. Since the circumference of the tip path is 3.14 times 4000 = 12,560 at 2000 miles per hour, payloads can be lifted every 6.28 hours if fuel for the tether is lifted alternate tips. This gives a high though put even if payloads average 5 tons. Higher tip speed and/or heavier payloads are possible if the tether is strong enough to survive the increased jerk, and the payloads can tolerate the increased jerk. A tip motor can spread out the jerk so that the jerk is less likely to cause damage. Tip motors can also fine tune the attachment and release of the payload and recover the tip speed. The ED feature can restore the average altitude of the rotating tether. Both can suppress transients traveling on the tether. The tether should have a Doctor Edwards type climber to repair damage to the tether by space junk and micro meteors. Neil

 

[BrianBoru]

I don't believe I'd use the term "little", to describe the first concepts. http://www.astronautix.com/lvs/shuttle.htm

 

[Valcan]

Ok my favorite is the one that looks like a stardestroyer :lol:

I think the idea for a small shuttle is a great one. If it could launch the same amount of weight as a medium to small rocket like the atlas and such for less money faster then you'd be set.

 

[thomastechie]

Can we resurrect the sea dragon rocket design?

Its been a half century since the sea dragon super heavy lifter was conceived , NASA said that the proposal was " technically uninteresting " (huh? i thought we just wanted a powerful low cost rocket?)
with advances in materials science and better production techniques the engineering problems should be a lot less daunting , so why haven't any of the space agencies looked into this concept ,with all the bickering going on about payload weight penalties for the planed manned missions? any suggestions or pointers would be helpful

 

[halman]

NASA had to scrub the first launch attempt of Endeavor on Sunday morning, Feb 7th, due to low clouds. This is the kind of delay that I believe the system that I am proposing would avoid, because the orbiter would be launched above the clouds. The stack could launch in weather like this, because photo coverage of the stack launching would not be critical. It is the possibility of foam strikes, Solid Rocket Booster malfunctions, and Space Shuttle Main Engine failures that necessitate the photographic coverage of the launch, I believe.

We have got to come up with a system that can operate in less than perfect weather if we are going to be able to keep launch costs down. Vertical launching leaves no margin for error, and, if a problem does occur, it must be fully documented to be able to figure out what went wrong, so that it can be fixed. A horizontal take-off does not require ultimate performance, so a failure would not be catastrophic. Worst case scenario for a failure of the carrier wing prior to orbiter separation is the orbiter lighting up its engines, flying off the back of the carrier wing, and turning around for a landing at the launch site.

By using at least five engines on the orbiter, loss of one, or even two, would not preclude reaching orbit, because nominally at least two engines would be shut down during the ascent, to keep the g forces at a minimum. We also need to build our vehicles tough enough to be able to land in rain and windy conditions, just like airliners do.

 

[halman]

By proposing to cancel the Constellation program, yet increasing NASA's budget, President Obama is opening the door to the development of an alternative style of access to space. By freeing NASA from the tethers of building a vertically launched crewed spacecraft, Obama is turning that enterprise over to those who are already building such systems. But vertically launched step-rockets are the most primitive means of reaching space. Instead of focusing on missions to other worlds, NASA should focus on the next generation of launch vehicles, the ones that will be in use when step rockets will only be carrying freight.

Investment in completely new technology is difficult to get from the private sector, because there is likely to be little, if any, return on the investment for a long time. This is where government programs are needed, to pioneer the technology. Developing a passenger-only type of spacecraft which is completely reusable will open the door to private investment, because once such a system has been proven, it can be duplicated or purchased, and operated at a profit. NASA does not belong in the space transportation business, it should be working to improve space transportation, by developing more advanced methods of reaching orbit.

It is obvious to me that our technology is still too primitive to warrant large-scale investment in space access. Reusable, safe, reliable, cheap ways of getting into space still do not exist. There is little doubt that they are feasible, but a large investment is going to be required to make them a reality. It is the government's responsibility to make those kinds of investments, to pave the way for the private sector.

The space shuttle has been operating flawlessly the last couple of years, but it is still too complex, requires perfect conditions for launch, and demands hundreds of specialists be on the job for each launch. By taking the basic shuttle design, and modifying it to a passenger-only vehicle, we could reduce it in size to where it could carry the fuel needed to reach orbit internally IF we launch from 50,000 feet.

I am no engineer, but I suppose that the life support requirements for one person for a week come out to less than 1,000 pounds. If we have a crew of two, and a dozen passengers, that means a payload of 14,000 pounds. If we restrict the operation of this vehicle to orbits below 180 miles, we reduce the amount of fuel needed, and the size of the engines. If we could bring the weight of the fully fueled and equipped orbiter, manned, to under 1,000,000 pounds, there is absolutely no doubt that it could be carried aloft by a specially designed aircraft.

We don't need a space craft that can take people all the way to the Moon.

We don't need a spacecraft which can carry several tons to a 600 mile orbit.

We need a space craft which can carry a dozen people to the very edge of space, where they can transfer to a space station or another space craft. A highly specialized, dedicated passenger vehicle, with no compromises which make it unworkable.

We need to provide access to space for those companies which want to get out there and start making money.

 

[halman]

I have been trying to figure out what is the best way to deal with orbit requirements. We want to keep the maximum orbital altitude for the shuttle at the lowest possible level, but the best orbit for a space station is going to be much higher. It seems ridiculous to design the orbiter to reach any higher than necessary, because that has so much impact on how much propellant is needed for each kilogram of weight. So building it to travel to space stations hundreds of miles up just doesn't seem right. Some day, when we have learned more, maybe that will be possible, but I think that an Orbital Transfer Vehicle is going to be an essential tool in developing space.

Being able to collect payloads at the edge of the atmosphere would have a tremendous impact on the size of the orbiter, because, the higher the orbit, the more fuel needed to reach it. So we need to design to carry maximum payload to about 300 kilometers, and no higher. I am certain that, once this system of carrier wing and orbiter is proven, it will grow in size and capability, until it may displace step-rockets for all but the heaviest launches. For really big rockets are much more efficient than small rockets. But I also think that we will only be sending large payloads into space for a few years, maybe 20 or 30, and then we will be able to make the big stuff up there.

The small stuff, the computers, instrumentation, and such will probably be manufactured on Earth for a long time, though.

 

[halman]

Ok my favorite is the one that looks like a stardestroyer :lol:

I think the idea for a small shuttle is a great one. If it could launch the same amount of weight as a medium to small rocket like the atlas and such for less money faster then you'd be set.

This is not about launching freight. People are the most expensive cargo there is, because the requirements for man-rating a vehicle are so stringent. Toss in the fact that the vehicle takes off straight up, and the requirements go through the roof. The consequences of failure of any component are so severe that the component must be backed up, and if it is really critical, it must be backed up twice. When you are going straight up, you can't bring it around for an emergency landing. You have to make sure that you can get the people far enough away from the rocket that they will be safe if it fails. All of this adds expense and weight.

If, instead, we take off like an airplane, ON an airplane, and wait until we can fly off the back of the that plane and accelerate at full throttle, heading just a little above the horizon, we don't have to have all kinds of redundancy. We can abort and fly back and land. Our engines don't have to produce huge amounts of power to lift us straight up, they just have to be able to accelerate us at about 2 gravities, and we will get there.

There are plenty of rockets around for carrying freight. But we are about to retire the only system that the US has to put people in orbit. Using one of the existing rockets would require extensive modification, added weight, and minimal capabilities. The Falcon 9 might be worth of man rating, but they are going to have to fly it, and fly it again, and again, to prove it. I hope that NASA is giving them plenty of money to get ready to fly.

But what is NASA going to put its engineers to work on? Another step-rocket? Isn't it time we built upon what we have learned from the shuttle program, and take the next step, the step that NASA wanted to take back in the late 1960's, but couldn't afford? Borrowing money from China to rebuild the automobile industry is not going to turn this country around, or even lower the unemployment rate. We need to capitalize upon what we do better than anyone else, which is getting to be a pretty short list, if you keep it to the good stuff.

Aerospace is our last area of leadership, the application of advanced aerodynamic engineering, engine technology, materials science, composite construction. The technology involved in horizontal launching will be used for generations, as it becomes the standard way of leaving for space. Carrier wings will get larger, orbiters will grow, and, someday, they will become the freighters hauling stuff to Low Earth Orbit. But right now, we need a spacecraft to get our butts out there, that can land where it takes off, can fly in poor weather, and doesn't rest on a razor edge of performance.

 

[halman]

I don't believe I'd use the term "little", to describe the first concepts. http://www.astronautix.com/lvs/shuttle.htm

I had not seen this page before. Thank you for pointing it out. I was basing my statement on what I had read back in 1969, when the first concepts were being worked out. It states in that astronautix article that the Air Force requested the payload be increased to 22,680 kilograms in May of 1970. I know that the design concept that I saw did not have a drop tank, and it took of horizontally.

 

[Valcan]

"Lockheed Martin announced that a C-5M test flight on 13 September 2009, set 41 new records. The flight's data have been submitted to the National Aeronautic Association for formal acceptance. The C-5M carried a payload of 176,610 lb (80,110 kg) to over 41,100 ft (12,500 m) in 23 minutes, 59 seconds. The flight set 33 time to climb records at various payload classes, and broke the world record for greatest payload to 6,562 feet (2,000 meters). The aircraft used for this flight had a takeoff weight of 649,680 lb (294,690 kg), which included payload, fuel and crew.[70]"

That means an existing aircraft can carry almost 85 short tons to 41,000 feet.

So why cant we get something as described above to 50,000ft. On a converted C5 or some similar aircraft.

http://en.wikipedia.org/wiki/Boeing_X-37#X-37A.2FB

It says (bottom of the page) the weight of the X-37B is only 12,000lbs. 6 short tons. So even if it gets scaled up 10 times that weight you've still got a carrier vehicle.

It really shouldnt be that hard.

 

[Valcan]

I remember on another forum here someone said the wrong part of the spaceshuttle is reusable. Wouldnt the above help?

How big and how much would a launch vehicle have to weight if its whole job was simply to get a load into space. Not renter?

 

[csmyth3025]

"Lockheed Martin announced that a C-5M test flight on 13 September 2009, set 41 new records. The flight's data have been submitted to the National Aeronautic Association for formal acceptance. The C-5M carried a payload of 176,610 lb (80,110 kg) to over 41,100 ft (12,500 m) in 23 minutes, 59 seconds...

I think the technology for air launching crew and resupply spacecraft to the ISS already exists. The C5-M, as you point out, is capable of taking 176,610 lbs to 41,000 ft. The Russian AN-225 has a reported payload capacity of 550,000 lb and a service ceiling of 36,000 ft (per Wikipedia). It seems likely that a purpose-built air launch aircraft could surpass these capabilities.

Now that NASA has accepted the idea that the heavy lift of large payloads should be handled separately from crew exchanges and routine resupply, I wonder why NASA seems to be stuck on the idea of ground launched rockets for both roles. Are there technical reasons why air launch would be considered infeasible or undesirable for launching "light" spacecraft to LEO?

Chris

 

[StarRider1701]

If, instead, we take off like an airplane, ON an airplane, and wait until we can fly off the back of the that plane and accelerate at full throttle, heading just a little above the horizon, we don't have to have all kinds of redundancy. We can abort and fly back and land. Our engines don't have to produce huge amounts of power to lift us straight up, they just have to be able to accelerate us at about 2 gravities, and we will get there.

Halman, the only problems I see with your 2 vehicle system is that your space plane starts out too low and too slow. Your carrier vehicle can only get to 50,000 feet and is probably not going much faster than 500 mph.

For your same 100 billion why not build one ship that is a cross between an SR-71 and a shuttle. With SR-71s engines (1960's tech, nothing new there!) the craft can fly to at least 120,000 feet and be travelling two or even three times as fast before firing the rocket engine. Logically speaking, the higher and faster you can be prior to firing your rocket, the better off you are.
The craft would probably look more like an SR-71 with a re-entry shield than a shuttle, but since you were specifically speaking of carrying people only, not cargo, this should work for what you want, and be relatively easy to build since the tech is old hat. If fact, I'm guessing new tech could even improve the jet engines capabilities, allowing you to go faster and higher on less fuel.

Not sure why NASA hasn't tried something like this, theyve owned 3 SR-71s since the Air Force quit using them.

 

[Jazman1985]

Starrider, I think the main idea is to keep it as low-tech and simple(therefore cheap) as possible. While we have proven capable as a country of building a craft like the SR-71, and there's obviously no technological stopping point to prevent us from doing it again, it has been shown that maintaining and using a supersonic aircraft is expensive. (granted, it would probably be cheaper if we kept getting more experience at it.) While the carrier craft itself may not be relatively difficult to build, seperation of the first and second stage at super-sonic speeds will prove very challenging, and considering it has never been done before, may take some trial and error. Although, if the second stage was to sit in front of the first stage carrier wing in a horizontal configuration it "could" eliminate that problem. For now though, I think super-sonic seperation AND an carrier launched orbiting spaceship may be too much to ask to be developed at once.

 

[StarRider1701]

You've missed my point, Jazzman. NOT two ships, two are too inefficient because they cannot get high enough or fast enough to do much good. Although you are right, if you could get the carrier ship to go that fast, seperation would be scary! Not to mention very dangerous.

One ship, perhaps based in part on the SR-71 with an internal rocket added to get it into orbit. Capable of re-entry and landing, to be reused over and over again. The 71 sure had one great glide path and as I understand it, it was capable of safe, unpowered landings. That means you would only need to carry enough fuel to get to the rocket ignition point, plus a small safety margin of course.
I'm not sure what you mean by hi-tech or low-tech - the SR-71 was designed and built in the early 1960's, in other words 50 years ago! Are you telling me that its still considered high-tech these days?!? Although, it can fly higher and faster than any other aircraft even today, so maybe it still is high-tech...