Earth to LEO - discuss

GCNRevenger · 2006-07-02 20:07:19

Yeah, which is why it annoys me to no end that they called it "Space Ship" One, when it was nothing of the sort. Rubber rockets are simply not the answer, at least not as the primary means of propulsion, even oxygen/kerosene engines probably aren't efficient enough.

And whatever about Russian space tourists, they couldn't build enough R-7 rockets to launch enough tourists to do much of anything even if they did have an unlimited supply of willing millionaires. And they don't.

Austin Stanley · 2006-07-03 04:05:56

Oh, and then there are "political" issues with suborbital freight...
1: If you have to launch in a hurry, how does the destination country know that you are not a hypersonic ballistic missile reentry vehicle? With so little warning and all.

Diffently a problem, but maybe not totaly insolvable. The major nuclear powers (US, Russia, China, rest of NATO) are on pretty friendly terms right now. Some sort of agrement could be worked out. After all, the same worry takes place each and every time someone launches an orbital rocket, which could also very well be a nuclear missle.

2: If you crash at multiple mach numbers into a populated area, the explosion will be as big or larger then the USAF's "MOAB" superbomb. Who pays for that? And can you imagine the insurance?

I think you greatly overstate this. Certianly having your re-entery vehicle crash into a city would be a very bad thing, but it probably wouldn't be as bad as even the 9-11 attacks, much less the MOAB. The power of KE strikes is vastly overated, and a delivery vehicle would not deliver even that amount of power. As unlike a specialy designed KE penetrator, the big, draggy, delivery vehicle is not going to be slowed by friction to a much greater degree and so is not going to impact at those multiple mach numbers, it probably won't even be supersonic. It's not going to be designed for supersonic speeds in the lower-atmosphere which means if it did happen to enter it at supersonic speeds, it would most likely break up and disentigrate (as well as slow down).

Furthermore, after launch the delivery vehicle will be almost entirely balistic at this point, with big empty fuel tanks. Even if it did hit something, it won't have the power that even the 9-11 airplanes did, since it will likely mass less than a large airliner (at this point), and won't have lots of fuel to feed a resulting fire.

This is not to say that a crash would be a good thing (it most certianly wouldn't), but it wouldn't be the end of the world either.

-----

Another issue of course is what still demands fast transit, AND can withstand the journey. Modern telcomunications is making the transport of paper (a major fast transit payload for buisness and legal deals) increasingly obsolete. Other potential payloads (like virus/bacteria samples) might be to fragile to withstand the trip. And other time urgent goods might be to bulky to be transported this way (like medical supplies).

GCNRevenger · 2006-07-03 06:55:58

I still think that it would be pretty bad... if the vehicle broke up, now you've got a cluster bomb too. The issue remains that a landing failure into anything important would be ruinously expensive for the suborbital courier company.

I agree with you about the lack of business such a vehicle would have, since launch preparations would be pretty involved (plus getting landing clearance), does this really save any time versus a plain old subsonic business jet? And Unless the company wants to keep a vehicle fueled (with cryogenics?) and a pilot on scramble standby, all launches would have to be planned well in advance.

Oh, and unless the vehicle can fly with plain old jet fuel, how do you get it back from destinations?

publiusr · 2006-08-11 14:20:01

I agree, the hype over spaceshipone is a bit over done. It only needed 1300 m/s de;lta v and yet it was almost 66% fuel by weight. With good liquid fuel rockets only 25-30% would need to be fuel. Yet people don't seem to understand that suborbital is with a capital SUB.

Good points.

Yang Liwei Rocket · 2006-08-26 10:41:29

Russia plans to launch two laboratory modules that would orbit near the International Space Station beginning in 2012, the state news agency RIA Novosti reports.
http://www.newscientistspace.com/articl … -labs.html
The laboratories would dock to the Russian side of the ISS before departing for three to four months to run their experiments in an orbit near the ISS. They would then return to the host ship so cosmonauts could unload experiments for return to Earth.

Tom Kalbfus · 2006-08-28 14:04:50

There must be something you can do with suborbital flights. What about intercepting an object in orbit? What if the suborbital spaceship collides with an object in orbit and the object in orbit is small and it hits the suborbiter in a certain place so that the suborbiter survives the collision. you can transfer velocity from the object in orbit to the suborbital object. One way to insert an object into orbit is with a high velocity cannon. I heard that some cannons can fire projectiles ar orbital velocity. So a cannon fires a shell at a suborbiter and the suborbiter maneuvers in front of it.

GCNRevenger · 2006-08-28 17:03:08

Uhhhh no... when you are talking impacts on order of orbital velocity, nothing that you could possibly launch could survive it. Not to mention that G-forces involved would pulverise the vehicle.

Suborbital trips are for tourists. Burt Rutan is selling snake oil if he says different.

Tom Kalbfus · 2006-08-28 23:44:45

I was thinking more on this. Seems to me, the projectiles don't have to hit the ship directly. What if the suborbiter ejected a stream of smaller projectiles behind it and they were positioned so as to intercept the incoming stream of larger projectiles. the collision of the two objects would vaporize them both producing a cloud of gas headed toward the suborbiter. The gas cloud would hit the suborbiter before it had a chance to spread to much and it would accelerate the suborbiter forward and upward. The suborbiter would have a supply of these little pellets, they wouldn't have to be accelerated too much, just enough so that they get in the way of the incoming pellet stream.

Later on, a more advanced transportation system can develop from this basic idea. A Spaceship can land on the Moon, load up with lunar rock and dust, and then liftoff taking the lunar material to L1, from L1 it would eject a stream of lunar material on an intercept course with a suborbiter whose lift off is timed to intercept that incoming stream. The lunar materials fall toward Earth would accelerate it to almost the local escape velocity. Same deal as before, the suborbiter ejects a smaller stream of its own pellets to intercept the incoming stream of lunar pellets and the momentum of the resultant gas stream pushes the suborbiter into orbit.

Later on as a third stage, as Mass Driver is assembled on the Moon's surface, it accelerates a stream of lunar material past escape velocity and opposite the Moon's orbital motion around the Earth, this causes a stream of lunar material to fall toward Earth, all that kinetic energy gathered by that fall is transfered to the suborbiter by the same method I mentioned before boosting it into orbit. In this way, the Moon could really be a stepping stone on the way to colonizing Mars, and best of all, this plan does not rely on space elevators.

cjchandler · 2006-09-02 05:34:20

See magnetic mass driver page for a similar idea.

Tom Kalbfus · 2006-09-02 08:10:21

An idea like this was proposed in the Starflight Handbook by Eugene Mallove and Gregory Matloff for accelerating starships. The main idea was to avoid having the ship carry its own reaction mass. If you have the ship interact with exteror incoming reaction mass, you get a way from having a rocket carry its own reaction mass supply and thus the acceleration is limited only by the velocity of the incoming pellet stream. I see no reason why this idea could not work on a small scale just to get a ship from suborbital to orbital velocity.

The basic idea is to make pellets out of moon rock, accelerate them against the Moons orbital velocity so they fall towards Earth and Earth's own gravity will accelerate these pellets to near escape velocity but not quite. If the pellets are not intercepted they will go into an elliptical orbit around the earth witht he low point just above the atmosphere. Since the pellets will be accelerated one after another in the same direction, they will encounter similar gravitational forces and folow the same path towards the Earth. As this occurs in a vacuum their paths should be quite predictable. Perhaps transmitters will be accelerated with the stream of pellets so they can more easily be detected by the suborbiter so that it can position itself in front of them.

GCNRevenger · 2006-09-02 08:14:12

No, this is a completely dumb idea. Particles aren't going to vaporize in much quantity, they'll mainly just shred into shrapnel, and since Sir Isaac Newton is still mostly right, you would have to throw vastly larger masses of particles out the back in order for there to be much momentum transfer, otherwise the projectiles would just sail right through the cloud. And again, you are talking about hitting a VERY small target with extreme precision again and again within a narrow time frame, before the ship goes over the horizon away from the launcher. Not happening.

Today's materials could make a Lunar space elevator too, no magical carbon nanofiber composite cable required, why is anybody even bothering to talk about other options? There is already a solution to mass Lunar launch.

Tom Kalbfus · 2006-09-19 14:49:10

If only we lived on the Moon, a Lunar Space Elevator would be just the thing, but then the LEM had no trouble reaching Lunar orbit without one. I don't know how a Lunar elevator would help a suborbital reach orbit unless it dangles all the way to the fringes of Earth's upper atmosphere.

Accuracy can be aided in several ways with regards to the pellet stream. For one, the pellets can be aimed very carefully, two, they could have a transmitter and GPS system in each leading pellet and the other pellets would automatically follow. The Suborbital ship would also have a GPS system, would be able to detect the incomming stream of pellets and place itself in front of them. And then a laser would focus in on each pellet varorising each ahead of impact with the suborbital. The energy of the impact would then be spread all over the entire surface of the impact shield rather than a tiny little spot. What hits the ship would be an incoming stream of gas, actually the reverse of a rocket if you think about it. The GPS would tell the laser where the pellets are, so it knows where to aim, it would also tell the Suborbital where the pellets are so it knows where to place itself, and the pellets would have little reaction thrusters so that it knows where to place themselves. If you like, they could simply be hollow shells filled with gas. Either the laser destroys the containers or the pellets empty themselves of their contents and move out of the way so that only their contents impact with the ship.

cjchandler · 2006-09-19 18:51:17

That sounds VERY expensive, and therese pellets are being shot from the moon? That's a lot of infrastructure and will need quite the industrial base on the moon. I don't think this is any where near a short term option, though I really like the concept of the rocket in reverse. I'd use it for interplanetary missions first though, were it's easier to aim. The craft uses some external power source to acellerate the pellets/gas like nucelar electric and external MHD thrusters?

Tom Kalbfus · 2006-09-20 08:33:59

I would think interplanetary missions with pellets would be harder, as planets move substantially more in relation to each other than does the Moon in relation to the Earth. Besides the problem that needs solving is that of getting the launch vehicle into orbit. Unlike in interplanetary space, you can't use ion drives, or solar sails to get into orbit, but once you are in orbit more options become available. What you need to get into orbit is something that's high thrust that will rapidly accelerate your vehicle to orbital velocity, if its too slow then it falls back to Earth.

As for the pellet stream being too expensive, what's more expensive building a car by hand or building a factory that makes cars? The factory is more expensive of course, but the per unit cost of each car it produces is lower than the cost of a hand built car. What we need to do is reduce the per unit coat of each trip into space, if we keep using the Shuttle or expendible boosters produced essentially by hand one at a time, we're not going to do that. It is much easier to mass produce reusable suborbital vehicles like Space Ship One, and we just need some extra outside infrastructure to get those into orbit.

cjchandler · 2006-09-20 09:24:10

I know infrastructure can reduce costs, but disposible pellets with extremely acuret GPS recivers and thrusters sound like a waste to me. Either you are going to have to build a huge mass driver on the moon with real human workers, plus import a hefty nuculer reactor or solar power plant, plus import all the electronics and thrusters for each individual pellet, I'm not sure you'd come out ahead unitl you had an automated factory for the chips and thrusters and an automated minning base to get the raw materials, since you can only use each pellet once. You are probably right that it can't compete with other interorbital methods like solar/nuculer thermal. The best use for suborbital flights is to make a bundle from tourism and use that money to get to orbit.

Tom Kalbfus · 2006-09-20 10:38:45

And there you throw up your hands and say it can't be done, while you yourself provide no solutions to solving this Earth to LEO problem. Staying the course doesn't solve the problem, building Ares rockets doesn't solve the problem either. The problem is we can only send a few astronauts into space. Space travel is a spectator sport because we haven't provided space travel to the masses. The suborbital space busness is essentially an expensive zero-gee ride with a momentary view of the Earth from space, where the sorts of people who roll up thousand dollar bills and smoke them, pay top dollar for a few moments of thrills. I'd like to turn these suborbitals into something more useful.

I really don't know whether the pellets need to be self-guided, I only presented that as a wose case scenario. It may be possible to take all the gravitational forces into account with a super computer and aim the pellet stream very precisely with a super computer so that the pellets come out at exactly the right speed and in the right direction so that they are in the right place at the right time to propel the space craft into orbit. The suborbiter may have on onboard radar system to detect the incoming stream of dumb pellets and relay information of the pellets position relative to itself, and the suborbiter's GPS system will tell its exact position, such that the ground lasers know exactly where the pellets are in order to vaporise them. The lasw of gravity and motion are extremely predictable, so maybe the pellets themselves don't need to self-correct their course. You just have to make sure the suborbiter is positioned right and the laser is targeted right. The pellets could be hollow aluminum spheres filled with oxygen, the laser wil ignite them turning each one into an expanding cloud of aluminum oxide gas. I believe a clever solution will get us into space, not a stay the course with expendibles or infrequently used shuttles. Its best if the suborbiters don't have to use liquified cryogenic fuels, we need a simple rocket engine thats easy to reuse and is capable of getting above the atmosphere, then the pellets and laser can do the rest. There is also the matter of putting a Mass Driver on the Moon, pointing it in the right direction and sighting it right, the velocity of the pellets should be variable. As we are planning on building a Moon base anyway, I figure a Mass drive would be just the sort of thing to build. Yes it is a one time big expense, but if we can lift alot of suborbiters into orbit with that thing, we can amortize its cost.

cjchandler · 2006-09-20 17:05:42

Ah, but I have suplied an alternative, look on page nine of this topic. Giant balloon/mirrors and solar thermal to orbit. That may not work either, I put teh chances at 1 in 25 but the development costs and infrastructure would be dirt cheap, if you see the end of the disscusion the numbers for a 3 metric ton capsule are not unreasonable. The problem of aiming the mirrors could be dealt with by using a ground facility with a huge mirror area, possibly one of ones already build could be used and then the balloon could be small with just one smalish very good mirror for aiming. Don't like that one? Here's another idea along the lines of the airship to orbit but mor reasonable. Using carbon fiber, mylar and thin film solar panels build a large star shaped waverider that can change it's shape for different speeds. Then use the elctricity from the panels to drive propellers, whihc can run in the super thin air and supersonic flow because the blades are waveridershaped.

Tom Kalbfus · 2006-09-20 23:35:31

Sorry that this is at the end, I just joined, but here's my two cents. Any craft that must use megawatts of stored energy per second is inherently dangerous and ineffecent. Since failure must be kept to a minimum this adds cost and voila- 10,000 dollar per Kg. While conventional ideas like adding an air breathing first stage, reusablitiy, and small workforces can help, they are not going to provide the cost savings looked for. Rockets don't seem too complex at first glance but the exhaust velocities that are limited nessesitate all the smallest effeny increases possible, light weght tanks and so on to keep the rocket a reasonable size. This is what makes small rockets expensive. As for big dumb boosters, they may be a bit of an improvment, but the specail facilities needed to make them and launch them, along with the cost of raw materials and labour drive the cost up. Therefore what is needed is way of providing those raw megawatts safelly and cheap enough so that it can get by with a 20% effentcy. Chemical rockets are not going to provide that kind of power, though not expensive in themselves, the tanks and engines are. The only possiblity I see that is reasonable is beamed power, or accelorating slowly so you don't need megawatts a second. My views on slow acceloration are posted on "airship to orbit" thread, but here I'll discuss beamed power. Microwaves spread out too much and are expensive and inneficent to genorate. Lasers are way too expensive, however there is no reason one has to use a laser to beam light. Given a resonably large reciver, ordinary light from the sun should be able to be focused on spacecraft. I advocate building stationary large variable focus mirrors and using cheap (read free) solar power. How might this be done economically? Baloons, 30 km up with clear tops and reflective bottoms filled with hydrogen could collect large amouts of light given a large enough diamiter and a hard ring. If the baloon material was streachy the foucus could be ajusted by changing the internal pressure. It could be aimed with small electric propellers. Maybe this is radicall enough to be cheap. At least there is low start up costs. The spacecraft it's self could use the light to heat hydrogen to nuculer rocket temperatures.

The hydrogen kind of has to be outside the ship for you to focus the Sun's light on it with the baloon's mirror. Also hydrogen is a clear, colorless glass, the concentrated sunlight would mostly pass right through it without heating it. Also the ship would be moving rapidly, the baloon would have to track it, it would have to be pointed halfway between the Sun and the ship at all times, which means it would have to rotate as the ship moves farther and farther away, and with increasing distance, it would have to change its focal length quiet rapidly especially as the ship accelerates faster and faster to orbital velocities. Another complicating factor is that the air the baloon is in, is not likely to be still, the baloon will likely be blowing around with the air currents. So the baloon will have to constantly be changing its focal length, be tracking the receeding spaceship all the while it is taking the air currents in to account. At least the Mass drive on the Moon does not move, it stays precisely on the spot on the moon where it is place. The Moon itself moves along a predicatble path around the Earth, governed almost entirely by its motion and gravity, the pellets also move in a predictable path courtesy of Sir Isaac Newton, there are no random air currents blowing the pellets around.

cjchandler · 2006-09-21 15:23:29

Please keep reading on page nine, the rocket moves in a long arc around the balloon/station. To heat the hydrogen coal dust is mixed with it so it will absorb the sunlight very well, it is inside an fussed quartz regenerative cooled nozzle. At 30 km up there are no winds, it is perfectly calm. The aiming is a problem, but I think it can be solved by putting the balloons on the ground or lower and using a smaller secondary mirror for aiming. It may not work, but requires less costly infrastructure than the moon pellets idea. What it really comes down to on each others designs is how accurately your mirror/rail-gun can be aimed. While 1400 km is a long distance, it is no where near the distance between the earth and the moon. To hit a meter sized target my mirror must be accurate to 0.040926 degrees in the x and y axis. Hard, but not undo-able. The distance from the moon to the earth is 360,000 to 405, 000 km. There is the first problem that must be dealt with by careful timing as being off by 45 000 km could leave the pellets in a drastically different orbit, or miss orbit all together by hitting the earth or flying past it. Secondly, the since the distance is so small if you want to be accurate to one meter (having the pellets spread out over thousands of square meters is not going to be good no mater how much your sub orbiter can adjust), you need to have a rail-gun accurate to 1.592x10^-4 degrees, and be able to accelerate your pellets to 2800 m/s. I can't think off any way you are going to be able to get that kind of accuracy. if one end of the rail-gun assuming 500 meter length is off just 0.2 millimetres you will miss the target, if the pellet has no other forces to disturb it like a slightly less polished rail on one side that but the time it reached earth would have been amplified into a huge difference, or some other slight change. Then there is the laser that is supposed to explode these pellets at just the right time which is going to add a good bit of cost and complexity. Just because theoretically we can determine the path of a particle because of the laws of physics doesn't mean that we can be perfectly accurate because our machines all involve a certain level of ambiguity. I don't see how this is going to save money without some changes.

Tom Kalbfus · 2006-09-21 15:42:15

The Railgun is not aiming for the ship because the ship it not there yet when it fires the pellets off. The pellets have to be aimed for above the Earth's atmosphere, and its the ships worry to get in front of them as they pass above the Earth, much like the way a surfer gets in front of a wave. The wave doesn't aim for the surfer. Where ever the pellets end up, the suborbiter has to be in front of. All that is required is for the suborbiter to detect the incoming stream of pellets. There is no question of the mass driver aiming for something that isn't there yet. Your sunbeam on the other hand has to be aimed. The suborbiter has to get into orbit, doesn't matter which particular orbit, any orbit will do and from their it fine adjust to the right orbit, but the main push into orbit is achieved by the pellets.

cjchandler · 2006-09-21 16:18:16

No, the acuraccy of the rail gun is paramount. If the pellets are shot "dumb" from a stationary rail-run, besides the gun only able to shoot pellets durring a short time of the moon's orbit, even if you are not worried about accuracy because of being able to correct for it on the other end, your precision needs to be very good, that is the reapeatablity of the shot as if the pelets are in the same general area in orbit around earth, but average 10 -100 meters away from each other, it's useless, unless your ship is gigantic, which I supose could work. I'm thinking Space ship one with a massive umbrella like structure that unfolds at the highest point. Still, the time required for this to eventually break even finacially is enourmous, I'd rather go for a more near term solution. Like it or not, we can test the fesiblity of the solarthermal to orbit today without a huge investment or scientific break thoughs in rail-gun tech. Optical tracking systems shouldn't be as hard as pellets, those telescopes looking at other galxays don't seem to have too much trouble tracking them.

Tom Kalbfus · 2006-09-22 10:35:35

Except your proposal requires the launch vehicle to carry enough reaction mass to reach orbit, mine doesn't. The reaction mass to reach orbit in my case comes from the Moon and that reaction mass comes with its own kinetic energy from falling toward Earth, you reaction mass must be heated by a beam of light to have the necessary kinetic energy to reach orbit. Also my pellet beam would put us on a track for reaching the stars, since the limiting factor for reacing reletavistic velocity is the limitations on reaction mass that can be carried on a starship. Besides I'm not convinced that smart pellets would be all that hideously expensive. The smart part of the pellets guidance system could be but a small fraction of the pellets entire mass and it might thus be economically transported to the Moon. What we need are microthrusters on each pellet. Most of the umph that goes into the pellet's trajectory would come from the mass driver. But perhaps if each pellet were heated to a plasma, then the ship could use a magsail to intercept the resulting pellets. Although magsails are pretty far out technology right now, so it might be easier to have a guidance system on each target so it can be vaporized and hit a solid target on the spaceship.

cjchandler · 2006-09-22 16:36:03

Why does using reaction mass damn a proposal? Your plan uses reaction mass to get up to 100 km. As for leading the way to intersteller travel, I don't think so. even if you could move at the speed of light most interesting systems are too far away besides the fact that you wouldn't be able to slow down. Those pellets aren't going to get all the way to where you want to slow down for centuries. The same aregument could have been made about chemical rockets, "lets wait until we have fusion powered rockets, then we can use the same technology to reach other stars." Lucky we didn't or we wounld have anything in space today. I also cannot see how throwing away hundreds of gps computers and thrusters each flight is going to reduce the costs significatly below those of expendable rockets. This is not a personal attack by the way, I think your plan is ingenious and the kind of out of the box thinking that's nessisary, but it just isn't going to work, for practical reasons.

Tom Kalbfus · 2006-09-23 01:24:26

Pellets can't slow you down, but the interstellar medium and stellar winds can!
Ever hear of a magsail? A magsail is a magnetic field which contains plasma and can be pushed by the Solar wind. A magsail craft is limited to the speed of the solar wind that pushes it, so it can't get very close the the speed of light, but their is nothing that says pellets can't push faster, the relative speed of the solar wind would then be as fast a the ship that moves through it, and can thus slow it down from relativistic velocities.

cjchandler · 2006-09-23 07:41:05

I have no personal intrest in traveling at reletevistic velocities, holding out for FTL , so I leave you on your own to figure out the magsail. One thing that does intrest me about them is that once I read an article somewhere that claimed besides their thurst they provided excellent radiation shielding. Wish I remembered where that was...

New Mars Forums

Announcement

#176 2006-07-02 20:07:19

Re: Earth to LEO - discuss

#177 2006-07-03 04:05:56

Re: Earth to LEO - discuss

#178 2006-07-03 06:55:58

Re: Earth to LEO - discuss

#179 2006-08-11 14:20:01

Re: Earth to LEO - discuss

#180 2006-08-26 10:41:29

Re: Earth to LEO - discuss

#181 2006-08-28 14:04:50

Re: Earth to LEO - discuss

#182 2006-08-28 17:03:08

Re: Earth to LEO - discuss

#183 2006-08-28 23:44:45

Re: Earth to LEO - discuss

#184 2006-09-02 05:34:20

Re: Earth to LEO - discuss

#185 2006-09-02 08:10:21

Re: Earth to LEO - discuss

#186 2006-09-02 08:14:12

Re: Earth to LEO - discuss

#187 2006-09-19 14:49:10

Re: Earth to LEO - discuss

#188 2006-09-19 18:51:17

Re: Earth to LEO - discuss

#189 2006-09-20 08:33:59

Re: Earth to LEO - discuss

#190 2006-09-20 09:24:10

Re: Earth to LEO - discuss

#191 2006-09-20 10:38:45

Re: Earth to LEO - discuss

#192 2006-09-20 17:05:42

Re: Earth to LEO - discuss

#193 2006-09-20 23:35:31

Re: Earth to LEO - discuss

#194 2006-09-21 15:23:29

Re: Earth to LEO - discuss

#195 2006-09-21 15:42:15

Re: Earth to LEO - discuss

#196 2006-09-21 16:18:16

Re: Earth to LEO - discuss

#197 2006-09-22 10:35:35

Re: Earth to LEO - discuss

#198 2006-09-22 16:36:03

Re: Earth to LEO - discuss

#199 2006-09-23 01:24:26

Re: Earth to LEO - discuss

#200 2006-09-23 07:41:05

Re: Earth to LEO - discuss

Board footer