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  #1  
Old 10-05-2019, 12:23 AM
Yakamaniac is offline
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Is there a safer way to orbit?


Launching vertically has been the only option for most of the history of space flight, but new technologies are making possible a better way to put people into space. A two-stage to-orbit, totally reusable space plane is an important step in making space exploration a manned enterprise. Taking off straight up requires everything to work right, and gives very few opportunities to abort the lift off.

Right now, to rotate the crew on the International Space Station requires at least two launches, and that is just for six people. We need something which can carry at least a dozen passengers, safely and routinely, so that crew rotations on bigger space stations do not require lots of launches. And the concept I am advocating is only for people; cargo can, and should, launch straight up.

By using an air-breathing, horizontally launched first stage to carry the orbiter to altitude, many abort options become available. To begin with, a launch track would be required, instead of a runway, and the magnetic catapult would be able to stop the launch stack in event of a refused take-off. This catapult is only to accelerate the stack to about 500 kilometers per hour, which is how fast I figure the wing will have to go to be able to lift off. The catapult will reduce the length of the launch track considerably, as fan jets are very slow to accelerate.

Because the wing will have to lift a fully-fueled orbiter, plus its own fuel, I figure take-off weight will be around 1 million kilograms. To accomplish this, I visualize a bi-plane, with an upper wing which is inflatable, so that it can be deflated after the orbiter launches. Overcoming all that drag will require 10 or 12 of the biggest fan jets available, but at least there will not be much weight involved in an undercarriage, as the launch track will support the wing.

The orbiter will have to ride on the carrier wing's back, as it will be too large for the wing to straddle. Also, the orbiter will light its engines while still on the carrier wing, and then fly off. This way, no altitude is lost, and high g pull outs are avoided. Because the orbiter will not be a heavy lift launch vehicle, and it will not be taking off straight up, it will not require large, powerful engines. Exotic, difficult-to-handle fuels such as liquid hydrogen won't be needed. Everything about this spacecraft will be designed with robust safety margins.

Having the passengers suit up to transfer to the space station or ferry vehicle would be wasteful, and would require considerable extra weight. Instead, the passenger compartment can be lifted out of the payload bay with an arm, to be swapped with one containing passengers heading back to Earth. The passenger compartment would have built-in life support for the transfer, although I am not sure if it will have a zero-gravity toilet.

The orbiter would land on a runway at the launch site, using extendable wings to reduce stall speed. Sufficient cross-range capability would allow for alternate landing sites. Landing the carrier wing will be much more difficult, as the wing will be very difficult to handle in cross winds. I propose that the launch track be used as a means of allowing the wing to mate with a sled being moved by the magnets on the launch track. This would allow the wing to land at a higher speed, maintaining control even under severe crosswind conditions.

Turn around time on the carrier wing would be very short, probably under 24 hours, so only a few will be needed. Orbiters will have much longer turn around times, but a sufficient number will allow launches as often as necessary.
  #2  
Old 10-05-2019, 01:58 AM
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An inflatable wing? Made of what, now?
I'm not sure I understand exactly all the different steps in your proposed launch profile, but it sounds somewhat similar to what Virgin Galactic is currently working on with White Knight Two and SpaceShipTwo, but that is not capable of reaching orbit. They're working on a compatible spacecraft, LauncherOne, that is capable of reaching low Earth orbit, but it will only be capable of carrying a payload of about 500 lbs.
I think you have a lot more to work out than just whether or not to include toilets in your passenger compartment.

Last edited by Bear_Nenno; 10-05-2019 at 01:59 AM.
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Old 10-05-2019, 03:18 AM
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Stratolaunch was developed to launch large rockets from an aerial platform. It didn't have the OP's complicated launch track and so forth, just a humongous two-fuselage plane. However, since Paul Allen died, it's become the world's largest white elephant.
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Old 10-05-2019, 08:41 AM
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First, a reminder that space isn't far away, it's "fast away". Most of a rocket's fuel isn't used to go up, it's used to go fast.

With that in mind, how do you plan to get the orbiter from the 500 km/h speed of the wing up to the 28,000 km/h speed required for low earth orbit without using "exotic fuels"? Even if 500 km/h is just the takeoff speed of the wing, and the cruising speed is something closer to Mach 1, you're still looking at a required change in velocity of 26,000 or 27,000 km/h.
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Old 10-05-2019, 09:20 AM
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What MikeS said. Building a spaceplane that can reach an altitude of 400 kilometres (where the ISS orbits) in one or two reusable stages is probably feasible - the X-15 reached more than 100 kilometres (a widely used definition of the lower bounds of space) with 1950s technology. The problem is getting it to such an altitude and accelerating it to the ~28,000 kmph of orbital speed that it needs (going sideways, not upwards) to stay there.
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Old 10-05-2019, 09:52 AM
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Originally Posted by Schnitte View Post
What MikeS said. Building a spaceplane that can reach an altitude of 400 kilometres (where the ISS orbits) in one or two reusable stages is probably feasible - the X-15 reached more than 100 kilometres (a widely used definition of the lower bounds of space) with 1950s technology. The problem is getting it to such an altitude and accelerating it to the ~28,000 kmph of orbital speed that it needs (going sideways, not upwards) to stay there.
Once you are up that high and moving at what I recall might be 20% of orbital speed, the amount of fuel needed to accelerate into orbit is manageable with existing rocket technology. You've already done a lot of the hard work by reaching that altitude and velocity. Of course the X-15 wasn't launched from the ground, a two stage to orbit plane is getting pretty large when all factors are considered. One theoretical possibility is refueling in the air at high altitude to allow a space plane to take off horizontally like a conventional plane, but that just adds more complexity.
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Old 10-05-2019, 10:58 PM
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Originally Posted by MikeS View Post
First, a reminder that space isn't far away, it's "fast away". Most of a rocket's fuel isn't used to go up, it's used to go fast.

With that in mind, how do you plan to get the orbiter from the 500 km/h speed of the wing up to the 28,000 km/h speed required for low earth orbit without using "exotic fuels"? Even if 500 km/h is just the takeoff speed of the wing, and the cruising speed is something closer to Mach 1, you're still looking at a required change in velocity of 26,000 or 27,000 km/h.
Kerosene and liquid oxygen have put a lot of stuff into orbit. Exotic fuels are used to get every possible bit of performance, which is what this concept is trying to avoid. (Think of school bus.) By launching the orbiter above the majority of the atmosphere, most of the fuel will be used for acceleration, not fighting gravity going straight up.

A vehicle about the size and shape of the Space Shuttle, but without the massive payload bay and the huge engines, could carry enough propellant to reach orbit, if the payload is only about 7,000 kilograms, and the launch pad is 14 kilometers up.
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Old 10-05-2019, 11:14 PM
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Originally Posted by dtilque View Post
Stratolaunch was developed to launch large rockets from an aerial platform. It didn't have the OP's complicated launch track and so forth, just a humongous two-fuselage plane. However, since Paul Allen died, it's become the world's largest white elephant.
Stratolaunch requires a massive runway, and the undercarriage weighs several tons. What is a fuselage for? Carrying cargo and passengers. The cargo the carrier wing needs to carry must be able to separate from the wing without being dropped.

My idea does away with all the weight of an undercarriage, and the expense of several kilometers of concrete 3 meters thick. And, up until the moment of take-off, the launch can be aborted without damaging the vehicles. If a failure occurs after take-off, the orbiter can light its engines and fly off of the wing, to come around and land. And an abort is possible at every stage of the launch, up to and including an abort to orbit.

By using several engines, with at least on of them capable of being throttled, the thrust can be kept below two gravities. During landing, at least one of the engines would be capable of firing, so dead stick landings are avoided.
  #9  
Old 10-05-2019, 11:37 PM
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The enemy of reliability is complexity.

Current rockets are very reliable, and the number of crewed aborts very low compared to launches. As complexity increases, you may find all the complexity in the abort systems becoming the main reason you need to abort.

One notes that conventional rockets safely abort launches right up to the point of lift-off. Only the shuttle didn't have a pad thorough to to orbit abort mechanism. All the current and planned ones do.

There is a lovely recent interview with Elon Musk done by Tim Dodd (the everyday astronaut) where Elon talks about simplicity in design. I think anyone involved in engineering design should watch it.

https://www.youtube.com/watch?v=cIQ36Kt7UVg
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Old 10-06-2019, 06:57 AM
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Quote:
Originally Posted by Yakamaniac View Post
My idea does away with all the weight of an undercarriage, and the expense of several kilometers of concrete 3 meters thick.
What do you reckon your magnetic catapult will cost?

Note that a fair few of those expensive concrete runways already exist, and are in fact rather cheap to use.


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The orbiter would land on a runway at the launch site ...
So an expensive runway is required?
  #11  
Old 10-06-2019, 07:39 AM
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So the idea of a plane launched rocket has been around for quite some time. Virgin has one working now for sub-orbital flights right now. Test rockets have likewise been launched this way. But they have never been heavy, and IIRC never orbital. I do suspect that is a hint of a reason. It may not scale up, and the amount of configuring you add like a inflatable extra wing speaks to that as a real issue.

What the vertical launch is doing is getting the orbiter away from the dense lower atmosphere ASAP, where it can better accelerate against air. In a rocket it had power, but fuel is limited, so straight up makes sense, however in a plane, especially a very heavy plane, you will have limited power, but much more fuel, so a horizontal flight pattern using lift to gain altitude and taking quite a bit more time makes sense. However is a plane, and a very exotic plane for that matter, make sense over a slightly more powerful rocket and some extra fuel?

You also have the extra complication of the safe separation of the aircraft to the orbiter, which is moving the liftoff from ground to air, but still has much of the same complications - remember when the orbiter separates it's going to want to come down, while the plane unloading the weight will want to go up under lift . I don't think it's as easy as you state, and the craft still have have to go through the stressful acceleration engine light off stage, we can read about that in Virgin's accounts when the rocket motor engages.
  #12  
Old 10-06-2019, 12:37 PM
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Originally Posted by kanicbird View Post
So the idea of a plane launched rocket has been around for quite some time. Virgin has one working now for sub-orbital flights right now. Test rockets have likewise been launched this way. But they have never been heavy, and IIRC never orbital. I do suspect that is a hint of a reason. It may not scale up, and the amount of configuring you add like a inflatable extra wing speaks to that as a real issue.
The Pegasus rocket, which launches from an aircraft, has put payloads in orbit. Small ones though, so doubts about scaling it up are valid. Stratolaunch was planning on launching Pegasus, except as many as three at a time, as I understand it. Well, not three at exactly the same time, but three on a single Stratolaunch flight. However, something fell through on this (and I can't remember what), so Stratolaunch started to develop their own rocket to be launched. That was cancelled when Allen died.

The OP's plan for landing the carrier plane is questionable. Since the carrier doesn't have an undercarriage, the idea is to land it on the track it was launched from, mating it with the sled at a fairly high landing speed. Has this kind of landing ever been done before?
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Old 10-06-2019, 01:22 PM
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Originally Posted by Yakamaniac View Post
most of the fuel will be used for acceleration, not fighting gravity going straight up.
Again, this is not an issue. Rockets don't go "straight up" and objects in orbit still experience a large majority of surface gravity. Most of the rocket's fuel is already used to accelerate; the lost acceleration due to gravity is minuscule. It's not effective to develop a highly complex alternate system to further reduce it.

Last edited by Cleophus; 10-06-2019 at 01:23 PM.
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Old 10-06-2019, 01:45 PM
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Originally Posted by Yakamaniac View Post
Launching vertically has been the only option for most of the history of space flight,...
Except the Pegasus which launches horizontally from an airplane.

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A two-stage to-orbit, totally reusable space plane is an important step in making space exploration a manned enterprise.
Why this configuration in particular?

Quote:
Taking off straight up requires everything to work right, and gives very few opportunities to abort the lift off.
Not really. All human-rated rockets have redundancy and abort modes. Though of course some are worse than others (e.g. the Shuttle had very limited abort capability compared to newer rockets currently in development).

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Right now, to rotate the crew on the International Space Station requires at least two launches, and that is just for six people.
And why is it a problem that it takes two launches to send a full crew? Seems like a good practice to replace only half the crew at a time, to provide continuity.

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We need something which can carry at least a dozen passengers, safely and routinely, so that crew rotations on bigger space stations do not require lots of launches. And the concept I am advocating is only for people; cargo can, and should, launch straight up.
Are you conceding from the start that it's more expensive than launching straight up?

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By using an air-breathing, horizontally launched first stage to carry the orbiter to altitude, many abort options become available. To begin with, a launch track would be required, instead of a runway, and the magnetic catapult would be able to stop the launch stack in event of a refused take-off. This catapult is only to accelerate the stack to about 500 kilometers per hour, which is how fast I figure the wing will have to go to be able to lift off. The catapult will reduce the length of the launch track considerably, as fan jets are very slow to accelerate.
Yes, the catapult could stop the spacecraft, but only if there was enough track left to slow down and stop. So really, this abort mode is only useful if something fails during the first few seconds - e.g. engine failure. Then again, on a conventional (vertical liftoff) rocket, if the engine fails immediately upon ignition, before the rocket leaves the pad, it can shut down all engines and abort. Some (e.g. Soyuz) have clamps that holds the rocket down until the engines are started up.

Also, what if the rocket catches fire and explodes right after ignition? On a conventional rocket, the escape rocket ejects the crew capsule away from the exploding rocket. This doesn't sound like an option for your spaceplane.



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Because the wing will have to lift a fully-fueled orbiter, plus its own fuel, I figure take-off weight will be around 1 million kilograms.
How did you come up with this number?

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To accomplish this, I visualize a bi-plane, with an upper wing which is inflatable, so that it can be deflated after the orbiter launches. Overcoming all that drag will require 10 or 12 of the biggest fan jets available, but at least there will not be much weight involved in an undercarriage, as the launch track will support the wing.
Not sure where to start. The wings need to be strong enough to lift the weight of the entire aircraft/spacecraft, because that's what wings are for. So you can't have wings that are supported by the launch track. And how would inflatable wings support that much weight?

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The orbiter will have to ride on the carrier wing's back, as it will be too large for the wing to straddle. Also, the orbiter will light its engines while still on the carrier wing, and then fly off. This way, no altitude is lost, and high g pull outs are avoided. Because the orbiter will not be a heavy lift launch vehicle, and it will not be taking off straight up, it will not require large, powerful engines. Exotic, difficult-to-handle fuels such as liquid hydrogen won't be needed. Everything about this spacecraft will be designed with robust safety margins.
Why would a horizontal launch require less powerful engines than a vertical lift? Whatever the orientation, the purpose of the engines is to (1) overcome air resistance, and (2) accelerate to orbital speed. If anything, horizontal launch would require more power because it would take longer to get out of the atmosphere.



Quote:
Having the passengers suit up to transfer to the space station or ferry vehicle would be wasteful, and would require considerable extra weight.
Which is why no spacecraft in history has used that method of transferring to a space station or another spacecraft. You just connect the docking ports and float in through it.

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The orbiter would land on a runway at the launch site, using extendable wings to reduce stall speed.
Why extendable??

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Sufficient cross-range capability would allow for alternate landing sites.
Is there any abort mode for a failed landing (e.g. not lining up correctly with the runway)?

Quote:
Landing the carrier wing will be much more difficult, as the wing will be very difficult to handle in cross winds. I propose that the launch track be used as a means of allowing the wing to mate with a sled being moved by the magnets on the launch track. This would allow the wing to land at a higher speed, maintaining control even under severe crosswind conditions.
You say cross-wind would be a problem, yet you propose using the launching track for landing, which means you can't choose which direction to land??
  #15  
Old 10-06-2019, 03:36 PM
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There may be a safer way to orbit, but this Rube Goldberg contraption isn't it. This is more like, "Hey, what if we took rocket launch and made it much more complex, with a whole bunch of new critical failure points?" It's hard to imagine a mode of launch more dangerous than trying to launch an airplane down a track with a fully loaded orbital rocket on its back. And if that rocket goes boom at any time, there's no escape system for the astronauts or the flight crew. And that moment of separation would be a doozy. What is the plane below going to do? Release the clamps and then go into a high speed dive to avoid the multi-hundred thousand pound bomb falling above it? Or does it just sit there while the rocket lights its massive engines and attempts to roar away without a collision or frying the plane? And this is a safer solution than just launching a rocket from a pad?

Aerolaunch was never about safety - it was an attempt to lower the cost to orbit. But it was comparing itself to the outrageous launch coats of the traditional aerospace companies, and compared to them a case could be made that small payloads might be cheaper to launch this way.

The era of reusable rockets is going to make air launch obsolete. In fact, a mature reusable rocket industry could make the concept of a space elevator obsolete, as reusable rockets can theoretically be cheaper.

There may be one safer way to get to orbit - by balloon. The concept is that you ride one balloon to a much larger, floating platform at 140,000 ft, and from there you get into a gigantic, mile-long balloon that rises to 180,000 on lift, until the air is too thin to support the balloon. Then the balloon fires ion engines to accelerate it horizontally. As it accelerates it gets aerodynamic lift from the sparse molecules of near space, but drag is so low that it can keep on accelerating and surfing on air molecules until it is in orbit. The process would be slow and careful and very low stress.

To come down, you reverse the process, descending over days or weeks by very slowly braking with ion engines until you can start getting aerodynamic lift from the atmosphere. then you just slowly brake until you descend back to the stratosphere station, then you get back into your smaller balloon and make a peaceful, quiet slow return to Earth. No significant atmospheric heating, no heat shield required, and the whole system could be solar powered.

In theory, the math appears to work. The devil, as in all big engineering projects, lives in the details. But if we could make it work, it could be made extremely safe in time.

Last edited by Sam Stone; 10-06-2019 at 03:36 PM.
  #16  
Old 10-07-2019, 02:07 AM
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Originally Posted by kanicbird View Post
...

You also have the extra complication of the safe separation of the aircraft to the orbiter, which is moving the liftoff from ground to air, but still has much of the same complications - remember when the orbiter separates it's going to want to come down, while the plane unloading the weight will want to go up under lift . I don't think it's as easy as you state, and the craft still have have to go through the stressful acceleration engine light off stage, we can read about that in Virgin's accounts when the rocket motor engages.
This is the key point - For a decent sized orbiter, you still have some powerful rocket engines on a massive load. We can see from vertical launches what this means - a huge flame shooting out the back of the orbiter.


This means that the launcher has to get the hell out of the way before the engine fires; meaning some serious maneuvering while the orbiter is just an unpowered projectile, losing speed or height (or both) waiting for the launcher to get out of the way.

Plus, there's the problem of creating an aerodynamic launcher. the logical configuration is the orbiter is under the launcher, since when the load is dropped, the launcher will rise. An orbiter on top (like the Shuttle/747 transport configuration) means more complex maneuvering to separate, and the orbiter needs sufficient aerodynamic lift to rise above the launcher without power - and this is a very risky maneuver compared to dropping. If you light the engines before decently separated, you are basically blowtorching the launcher during separation- not the best technique for a thin-skinned aluminum structure carrying jet fuel... or humans.

Also, what do you gain? A flying body unless incredibly powerful will be subsonic, and probably only fly to 50,000 feet or so at most. How long after liftoff is a vertical rocket going 500mph? How long before it's at 50,000 feet? It's probably simpler to strap on some solid boosters than build a complicated air launch system.

You don't want to make a launcher go much faster, since who knows what happens when you drastically change aerodynamics at, say, Mach 5? The 600mph is almost nothing compared to the 18,000mph or so needed to orbit. The only real gain is getting out of the thicker air.

There's a reason that big aircraft (bigger than a fighter) don't use variable geometry wings. The size of the pivot hinges, the strength of motors to extend wings against drag at almost mach1 - not going to happen for an airliner-sized craft. Inflatable, even worse. Not feasible with current technology.

The trouble with catapult tech is that it adds speed in short distance using high acceleration. Modern rockets pull a few Gee's; but most aircraft (the launcher) are not designed for that. adding the strength to handle it means adding weight. Plus, it does not account for safety issues. You are carrying an orbiter craft fully loaded with humans and flammable fuel - what if the separation process fails? Having an escape tunnel back to the launcher is not feasible. An escape rocket like the ones on capsules means the left-over craft is a lot less aerodynamic, possibly unstable. You have to allow the possibility of landing without separation.

landing in crosswinds is typically handled for airliners with a simple rule... don't. If the crosswind exceeds the limit, use a cross runway instead. There are two ways of dealing with crosswinds - bank to stay straight, or crab. The B52's apparently had all steerable wheels, so it could land crabbed. Banking risks the wingtip striking.

Hooking up with the landing magnetic receiver is an unnecessary complication, adding the issue of more weight to put any magnets into the launch craft. You also underestimate the ease of mating two devices precisely travelling 500mph; and what then? It decelerates at a hard rate, what stops the launcher from sliding off the front of the sled?

A sled braking hard with a large load on top will tend to rotate forward, causing nose strike.. Some serious engineering is required to prevent nose tipping. tailwheel aircraft always risked nose-over with heavy braking.

Most aircraft landing are going nose up to reduce speed. coming in hot has its own risks. Nose up, the craft will take several seconds to level off down once the read makes contact with the sled, eating up precious runway ; plus, how do you get the sled up to speed to match the incoming aircraft - it takes some serious distance to get up to 500mph even if it is capable of serious acceleration. 600mph is 10mi/minute or a mile every 6 seconds. the window to match speed, contact, lock and start to decelerate is pretty short. The shuttle allegedly had the aerodynamic qualities of a brick, and needed a 3 mile runway and a drag chute to stop.

All in all, vertical launch is the way to go. The Shuttle's fatal flaw was mounting the shuttle on the side of the tank where it was susceptible to ice debris, instead of on top. IIRC, there has not been a case where the rocket failing killed the crew during any other vertical launches.


One suggested tech I saw (Heinlein? Clarke? Niven?) was to put a magnetic launcher running up a mountainside. The (unmanned) sled would be aerodynamic enough to glide down after the launch or use parachutes, the rocket would fire at the end of the run, you might get a few thousand mph and a few thousand feet of altitude to kickstart. Being just a sled, the launcher would not need fancy engines, or any maneuvering to avoid being blasted, or anything fancy like that - it would just drop away like the Shuttle solid fuel boosters, maybe a small perpendicular rocket blast from the sled to ensure separation. the only question would be how expensive a 30-mile track would be, how to build it on a tall mountain, and how much speed you could get out of it. Allegedly toward the end you would curve it toward vertical if you could to increase the effective launch profile.
  #17  
Old 10-07-2019, 07:50 AM
joema is offline
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Originally Posted by Yakamaniac View Post
...the concept I am advocating is only for people...By using an air-breathing, horizontally launched first stage to carry the orbiter to altitude, many abort options become available. To begin with, a launch track would be required, instead of a runway, and the magnetic catapult would be able to stop the launch stack in event of a refused take-off. This catapult is only to accelerate the stack to about 500 kilometers per hour, which is how fast I figure the wing will have to go to be able to lift off. The catapult will reduce the length of the launch track considerably, as fan jets are very slow to accelerate....I visualize a bi-plane, with an upper wing which is inflatable, so that it can be deflated after the orbiter launches. Overcoming all that drag will require 10 or 12 of the biggest fan jets available, but at least there will not be much weight involved in an undercarriage, as the launch track will support the wing....The orbiter will have to ride on the carrier wing's back, as it will be too large for the wing to straddle....
This and similar concepts and issues have been discussed before many times on this and other forums. Some of these have been very detailed with lots of references. See below.

Re safety, when describing the forces and dynamics on the shuttle during initial powered ascent, astronaut Story Musgrave likened it to a "butterfly bolted onto a bullet". It could withstand that -- but only in a narrow range of attack angles. This was not unique to the shuttle -- by necessity all launch vehicles must be extremely thin and light. They are only strong in the load paths required. This is why you rarely see partial launch vehicle failures -- with buckled skin, trailing smoke like a WWII bomber as it limps into orbit. They either work near perfectly or the failures rapidly cascade to total destruction. This would be the case with any design, whether horizontal or vertical launch, mag-rail assisted, airbreathing or not.

In general the problem is an efficient two-stage fully reusable launcher must achieve a very high staging velocity (roughly around Mach 10), otherwise the upper stage is huge and combined vehicle weight is high. See graphs:

https://photos.smugmug.com/photos/i-.../i-nKLmZSR.jpg

https://photos.smugmug.com/photos/i-...-SZXsshF-L.jpg

Prior similar discussions:

http://boards.straightdope.com/sdmb/...5#post20114485

http://boards.straightdope.com/sdmb/...2#post19506732

https://boards.straightdope.com/sdmb...1#post21889103

https://forum.nasaspaceflight.com/in...?topic=47164.0

https://forum.cosmoquest.org/showthr...aceship-design

Last edited by joema; 10-07-2019 at 07:54 AM.
  #18  
Old 10-07-2019, 09:07 AM
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Originally Posted by md2000 View Post
Also, what do you gain? A flying body unless incredibly powerful will be subsonic, and probably only fly to 50,000 feet or so at most. How long after liftoff is a vertical rocket going 500mph? How long before it's at 50,000 feet? It's probably simpler to strap on some solid boosters than build a complicated air launch system.
That's really the telling thing here. In your scheme, you'll have a very complicated system to basically get yourself to about 50,000 feet and probably a few hundred knots before you launch, and it probably takes a good long while to get to that altitude, etc...

It's probably a lot easier to just use solid rocket boosters- I'm willing to bet that by the time a more conventional rocket gets to 50,000 feet (~15 km), it's going a whole lot faster than a few hundred knots.
  #19  
Old 10-07-2019, 02:33 PM
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Anyone interested in this might want to read https://en.wikipedia.org/wiki/Project_HARP. The High Altitude Research Project was an attempt to put objects in orbit using a great big gun. It got objects up as high as 180 km, but with only a quarter of the delta V needed for escape Of course, it could never have been used to put humans in space (deadly acceleration).
  #20  
Old 10-07-2019, 03:27 PM
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...you'll have a very complicated system to basically get yourself to about 50,000 feet and probably a few hundred knots before you launch, and it probably takes a good long while to get to that altitude, etc...It's probably a lot easier to just use solid rocket boosters-
That is correct. The two main losses are "gravity loss" and "drag loss". These are known for various launch systems and while significant, are not dominant.

E.g, LEO orbital velocity is about 8,000 meters per sec. Gravity loss on the space shuttle was about 1,222 m/s and drag loss was about 107 m/s, or about 16.7% total.

However raising the launch vehicle to 50,000 ft at a few hundred mph would not totally eliminate these, only reduce them. Even at 50k ft a launch vehicle is not totally horizontal, so it's still accumulating gravity losses. Likewise there is still air drag at 50,000 ft, in fact that is close to the "Max Q" or greatest aerodynamic pressure for many ascent profiles.

As a wild guess if we assume the gravity and drag losses were cut by 1/2 or 2/3, that gigantic effort (and development expense) to lift a huge vehicle to that altitude by mother ship or magnetic rail would only save about 8-11% of the total delta V.
  #21  
Old 10-09-2019, 11:59 AM
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What do you reckon your magnetic catapult will cost?

Note that a fair few of those expensive concrete runways already exist, and are in fact rather cheap to use.



So an expensive runway is required?
The orbiter would not be heavy enough to require the three-meter thick (or more) runway the carrier wing and orbiter stack would require, nor would the orbiter need a 4 or 5 kilometer long runway, which a large, heavily loaded aircraft requires.
  #22  
Old 10-09-2019, 12:19 PM
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What the vertical launch is doing is getting the orbiter away from the dense lower atmosphere ASAP, where it can better accelerate against air. In a rocket it had power, but fuel is limited, so straight up makes sense, however in a plane, especially a very heavy plane, you will have limited power, but much more fuel, so a horizontal flight pattern using lift to gain altitude and taking quite a bit more time makes sense. However is a plane, and a very exotic plane for that matter, make sense over a slightly more powerful rocket and some extra fuel?

You also have the extra complication of the safe separation of the aircraft to the orbiter, which is moving the liftoff from ground to air, but still has much of the same complications - remember when the orbiter separates it's going to want to come down, while the plane unloading the weight will want to go up under lift . I don't think it's as easy as you state, and the craft still have have to go through the stressful acceleration engine light off stage, we can read about that in Virgin's accounts when the rocket motor engages.
My goal with this idea is to use the atmosphere instead of fighting it, by using air-breathing engines and aerodynamic lift to gain as much altitude as possible, providing as many ways as possible to recover the entire launch vehicle in case of a failure, and to make a space plane the default mode of transport for people.

Of course, if we never develop large space stations, interplanetary manned spacecraft, or other projects requiring lots of people in space, than all of this is moot. But I want to believe that someday there will be hundreds of people working in space, and getting them there and back will be a big deal.
  #23  
Old 10-09-2019, 12:25 PM
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The OP's plan for landing the carrier plane is questionable. Since the carrier doesn't have an undercarriage, the idea is to land it on the track it was launched from, mating it with the sled at a fairly high landing speed. Has this kind of landing ever been done before?
No, the recovery concept I am proposing is untried. But I can't think of another way of getting a large aircraft back on the ground safely when it has lots of lift and large amounts of surface area. The stall speed will be very low, but the vehicle will be easily pushed around by the wind.
  #24  
Old 10-09-2019, 12:32 PM
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Again, this is not an issue. Rockets don't go "straight up" and objects in orbit still experience a large majority of surface gravity. Most of the rocket's fuel is already used to accelerate; the lost acceleration due to gravity is minuscule. It's not effective to develop a highly complex alternate system to further reduce it.
At the time of the Solid Rocked Booster separation, the space shuttle was going about one mile per second. Half of the fuel in the external tank had already been used, which means that the other half provided enough acceleration to reach 5 miles per second.
  #25  
Old 10-10-2019, 07:54 AM
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My goal with this idea is to use the atmosphere instead of fighting it, by using air-breathing engines and aerodynamic lift to gain as much altitude as possible, providing as many ways as possible to recover the entire launch vehicle in case of a failure, and to make a space plane the default mode of transport for people...
Several factors prevent air launch of large vehicles from being worth the tremendous development cost and risk:

(1)The kinetic energy required for orbit is a squared term (KE = 1/2*m*v2), so a booster (whether mother ship, mag rail, etc) achieving subsonic speed doesn't help much.

(2) In a baseline surface launch at sea level, total air drag losses aren't that high. For the space shuttle it was 1% of delta V. So it doesn't save much drag loss to lift the 2nd stage to, say, 50,000 ft.

(3) Gravity losses from the vertical component of ascent are higher than air drag losses, but still relatively modest.

(4) The cost and technical risk of developing an air-breathing mothership capable of replacing the 1st stage of a conventional reusable booster (e.g, SpaceX) is huge. We already have reusable conventional first stages and they work fine. THAT is what a mag rail or airbreathing booster is competing against.

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...At the time of the Solid Rocked Booster separation, the space shuttle was going about one mile per second. Half of the fuel in the external tank had already been used, which means that the other half provided enough acceleration to reach 5 miles per second.
The total ET propellant (LOX+LH2) is about 735600 kg. The SSMEs on average burn 1440 kg/sec over the 8.5 min ascent. So by SRB separation at 120 sec, about 1440*120 or 172,200 kg of ET propellant has been used, which is 172200/735600 or 23.4%. About 76.6% or 563,400 kg of ET propellant remains at SRB sep, which is at about 130,000 ft altitude (24 miles) at about 5,000 ft/sec.

The shuttle stack mass just after SRB sep is about 563,000 kb of ET propellant, 26,500 kg for the ET, and 109,000 kg for the orbiter, or a total of 698,500 kg or 1.54 million pounds.

So the question is what kind of air-breathing mother ship would be required to lift an orbiter the same size and mass as the shuttle stack at SRB sep to an altitude of 50,000-100,000 ft at either subsonic speed or the shuttle's 5,000 ft/sec speed?

That stack weighs 1.54 million pounds. The largest and heaviest aircraft ever to fly was the AN-225 which could lift a single internal payload of about 416,000 pounds. It could lift the empty Buran shuttle which weighed about 130,000 pounds but not very high: https://upload.wikimedia.org/wikiped..._Manteufel.jpg

So you'd need something vastly larger than the AN-225, and which could lift a 1.5 million pound *external* payload to over 50,000 ft, and the faster the better. Picture something 10 times the size and weight of an XB-70. The development cost and technical risk would be incredibly high, and you'd still have to separately develop the orbiter.

This issue was discussed in this AIAA paper which said: "a typical straight and level subsonic horizontal air launch such as used by the X-15 research rocketplane does not
result in any significant changes in the delta V requirement".
"A Study of Air Launch Methods for RLVs" (Sarigul-Klijn, 2001): http://mae.engr.ucdavis.edu/faculty/...a2001-4619.pdf

Last edited by joema; 10-10-2019 at 07:56 AM.
  #26  
Old 10-12-2019, 07:05 PM
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Anybody wanting to know more about why hypersonic air-breathing launch vehicles have thus far been unsuccessful should read these three documents:

The Hypersonic Revolution, Volume III by Dr. Larry Schweikart: https://www.google.com/url?sa=t&rct=...2Q4CCT9NhWUhx9

Facing the Heat Barrier: A History of Hypersonics by T.A. Heppenheimer: https://history.nasa.gov/sp4232.pdf

Single Stage to Orbit: Politics, Space Technology, and the Quest for Reusable Rocketry by Andrew J. Butrica. This book is available free if logged into Scribd.com (Amazon link shown here): https://www.amazon.com/dp/B002CZP1TQ/
  #27  
Old 10-12-2019, 10:02 PM
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The stall speed will be very low, but the vehicle will be easily pushed around by the wind.
A constant wind pushes all airborne vehicles around equally.
  #28  
Old 10-14-2019, 05:01 PM
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Except the Pegasus which launches horizontally from an airplane.


Why this configuration in particular?


Not really. All human-rated rockets have redundancy and abort modes. Though of course some are worse than others (e.g. the Shuttle had very limited abort capability compared to newer rockets currently in development).


And why is it a problem that it takes two launches to send a full crew? Seems like a good practice to replace only half the crew at a time, to provide continuity.


Are you conceding from the start that it's more expensive than launching straight up?



Yes, the catapult could stop the spacecraft, but only if there was enough track left to slow down and stop. So really, this abort mode is only useful if something fails during the first few seconds - e.g. engine failure. Then again, on a conventional (vertical liftoff) rocket, if the engine fails immediately upon ignition, before the rocket leaves the pad, it can shut down all engines and abort. Some (e.g. Soyuz) have clamps that holds the rocket down until the engines are started up.

Also, what if the rocket catches fire and explodes right after ignition? On a conventional rocket, the escape rocket ejects the crew capsule away from the exploding rocket. This doesn't sound like an option for your spaceplane.




How did you come up with this number?


Not sure where to start. The wings need to be strong enough to lift the weight of the entire aircraft/spacecraft, because that's what wings are for. So you can't have wings that are supported by the launch track. And how would inflatable wings support that much weight?


Why would a horizontal launch require less powerful engines than a vertical lift? Whatever the orientation, the purpose of the engines is to (1) overcome air resistance, and (2) accelerate to orbital speed. If anything, horizontal launch would require more power because it would take longer to get out of the atmosphere.





Which is why no spacecraft in history has used that method of transferring to a space station or another spacecraft. You just connect the docking ports and float in through it.


Why extendable??


Is there any abort mode for a failed landing (e.g. not lining up correctly with the runway)?



You say cross-wind would be a problem, yet you propose using the launching track for landing, which means you can't choose which direction to land??
Given that space-based industry will become common, people will be needed in space in numbers far larger then six. Partial crew rotations will involve carrying at least ten people, plus shuttle craft crew. Think of an off-shore oil rig. And I find it hard to believe that capsules are the ultimate technology for carrying people to and from space.

Yes, my concept would be more expensive than conventional vertical launching.

A refused take-off can occur for a variety of reasons. The launch track would be able to stop the stack from take-off speed without destroying either vehicle. This will require a longer track, but that is acceptable.

I use the term 'wing' to refer to the carrier wing, which would be supported at its center by the launch track.

Launching straight up with a large payload requires a thrust-to-weight ratio of greater than 1 to 1. Accelerating horizontally is possible with thrust-to-weight ratios of less than 1 to 1.

Large wings are a problem during launch and ascent, because of turbulence, but landing with small wings requires very high speed. So wings that can be extended to reduce landing speed are desirable.

Having one engine that can be restarted during landing would allow a go-around.


Unless you have a dry lake bed which allows landing in any direction, cross wind landings will happen. A large, very light plane will have a lot of problems landing in a cross wind. A retrieval system which allows for recovery of the aircraft at speeds of 500 kph would make cross wind landings easier, I believe.

This whole concept is based upon a perceived need many years in the future. We may end up not needing people in space, or only very small numbers, in which case this concept is worthless.
  #29  
Old 10-14-2019, 05:21 PM
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Originally Posted by Yakamaniac View Post
Given that space-based industry will become common, people will be needed in space in numbers far larger then six. Partial crew rotations will involve carrying at least ten people, plus shuttle craft crew. Think of an off-shore oil rig. And I find it hard to believe that capsules are the ultimate technology for carrying people to and from space.

Yes, my concept would be more expensive than conventional vertical launching.

A refused take-off can occur for a variety of reasons. The launch track would be able to stop the stack from take-off speed without destroying either vehicle. This will require a longer track, but that is acceptable.

I use the term 'wing' to refer to the carrier wing, which would be supported at its center by the launch track.

Launching straight up with a large payload requires a thrust-to-weight ratio of greater than 1 to 1. Accelerating horizontally is possible with thrust-to-weight ratios of less than 1 to 1.

Large wings are a problem during launch and ascent, because of turbulence, but landing with small wings requires very high speed. So wings that can be extended to reduce landing speed are desirable.

Having one engine that can be restarted during landing would allow a go-around.


Unless you have a dry lake bed which allows landing in any direction, cross wind landings will happen. A large, very light plane will have a lot of problems landing in a cross wind. A retrieval system which allows for recovery of the aircraft at speeds of 500 kph would make cross wind landings easier, I believe.

This whole concept is based upon a perceived need many years in the future. We may end up not needing people in space, or only very small numbers, in which case this concept is worthless.
Put the end of your track high up, outside of most of the atmosphere, and forget the wing, now you have a magnetic launch system.

Capsules kinda are the best thing for getting people to and from space. Anything else increases complexity, and complexity is more stuff to go wrong. If you have infrastructure already there, then all you need is life support for the time to rendezvous, and a robust craft that can handle re-entry.

The Space Shuttle was somewhat useful before we had a space station to go to. It provided many of the amenities that are needed for survival in space for up to two weeks at a time. It also weighed about a third of what the ISS weighs. For every three shuttle missions, we basically launched the entirety of the ISS. Now that there is somewhere to go, there is no need for such a complicated human transport system.
  #30  
Old 10-14-2019, 05:23 PM
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I don't understand what this would do that Starship and Super Heavy don't have well coverered. I assume you are familiar with Starship and Super Heavy from SpaceX? They are fully reusable and will enable huge payloads to LEO and beyond.
  #31  
Old 10-15-2019, 09:46 AM
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Now what *might* be handy for putting stuff into orbit at low cost might be some sort of ground-based linear accelerator (mass driver) set up in some kind of mountainous region that could get your payloads going pretty fast and fairly high before their own rockets kick in.

The whole trick to getting into orbit after all, is going fast enough to basically fall past the Earth. Your orbital height is determined by your speed- the faster you go, the larger circle you describe as you fall around the earth and vice-versa. Deorbiting and re-entry is basically slowing down such that you quit falling past the earth and start falling into it.

So anything you could do that would get you going faster without actually having to burn onboard fuel would probably be a good thing.
  #32  
Old 10-15-2019, 10:36 AM
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Now what *might* be handy for putting stuff into orbit at low cost might be some sort of ground-based linear accelerator (mass driver) set up in some kind of mountainous region that could get your payloads going pretty fast and fairly high before their own rockets kick in.
Where earth orbit is concerned, a ground based accelerator is going to have to impart a lot of energy to be useful.

For reference, an aircraft carrier catapult can fling a 40,000-pound aircraft off of a level deck at 150 MPH - provided that aircraft is already operating at something close to max thrust.

The Soyuz rocket weighs in at 672,000 pounds, and 150 MPH is a flea fart compared to the 17,000+ MPH needed for low earth orbit. If you want to justify the cost of your accelerator program, you had better substantially reduce the cost of the vehicle, which means you had better give that vehicle a lot of takeoff speed.

Except you can't, not at ground level. The space shuttle hit max Q at about 35,000 feet altitude, at a speed of 1000 MPH. If you try to go 1000 MPH at ground level - even assuming ground level is up in the mountains at 10,000 feet - you'll shred your vehicle unless you toughen it up, i.e. make it heavier. But if you can't even impart 1000 MPH of speed from your ground-based accelerator, then you can't make your rocket much smaller than the Soyuz. Your rocket won't be cheaper.

All of this is without considering the g-loading imparted by the accelerator. Orbital launch vehicles typically don't exceed 3 g. If you want to avoid adding additional mass to your rocket to have it tolerate higher g loads, then your accelerator can't exceed 3 g. Want to achieve 1000 MPH takeoff speed? You'll need 16 seconds and 11,250 feet of rail. Not including additional length to allow for decel of whatever will remain attached to the accelerator rail.

This is not practical.

Last edited by Machine Elf; 10-15-2019 at 10:38 AM.
  #33  
Old 10-16-2019, 04:12 PM
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A two-stage to-orbit, totally reusable space plane is an important step in making space exploration a manned enterprise...
This overall concept was discussed in a video posted yesterday by Fraser Cain, publisher of Universe Today. It is called AstroClipper. There is an actual company behind this, albeit a tiny one: https://youtu.be/qWfkW2y-hAQ

The problem is very few details are given. It is easy to make a compelling graphic, e.g: https://photos.smugmug.com/photos/i-.../i-2tBk3CN.jpg

But it's not too different than a child making a crayon drawing of a rocket and saying "this part goes here". When you ask the actual engineers and managers tasked with implementing that in the real world, reaching affordable, workable solutions is a lot harder.

E.g, NASP, which initially looked very promising based on Tony Du Pont's original design. Further engineering scrutiny using real-world numbers and margins and more detailed modeling indicated it was just not possible. Neither AstroClipper or other similar paper designs have yet been subjected to that.

The additional problem all novel launch systems face is -- if they ever fly -- they will be competing with SpaceX's super-low prices. This was known years ago: http://theconversation.com/spaceplan...will-win-51938

SpaceX projects the price per kg to LEO for Starship and Super Heavy will be less than a fully recoverable Falcon 9, so the task for airbreathing, magnetic rail or other novel launch systems is more difficult than ever.
  #34  
Old 10-18-2019, 12:06 AM
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As several people have pointed out, getting into orbit is all about going fast. Accelerating in a horizontal direction. Getting above the bulk of the atmosphere is necessary because turbulence will destroy a vehicle traveling at high speed. Max-Q is the region in a launch trajectory where speed and atmospheric density combine in their most destructive potential. As long as aerodynamic lift is possible, turbulence can be encountered, but max-Q speeds go into the hypersonic range before lift disappears.

A space craft launched at 15 kilometers can accelerate horizontally while using aerodynamic lift to gain altitude. As the speed increases, the vehicle will ascend as the Earth curves away beneath it. A space craft capable of landing horizontally will have sufficient lift to fly off of a carrier vehicle that is traveling at twice the stall speed of the space craft. Putting the carrier wing in a slight dive would assist with separation, as well as reducing chances of a collision. The carrier wing would have shielding to deflect the exhaust of the space craft.

The amount of engine power needed to accelerate a given mass horizontally is less than the amount of engine power needed to lift that same mass vertically, so a vehicle launched horizontally at high altitude will not require engines as large as would be needed for a vertical launch.

Much of what I propose is based upon an orbiter that would resemble the space shuttle orbiter, but would be considerably lighter. The space shuttle was a heavy lift launch vehicle, which launched vertically. This meant that the engines had to be extremely powerful, which means using lots of fuel. Reducing the payload requirements to a value around 6,000 kilograms would mean that the orbiter could be as much as half the weight of the space shuttle, given that composite materials are available now.

Providing a way for the spacecraft to land horizontally reduces the danger of a vertical landing, while increasing the number of potential landing sites. Much less fuel is needed for a horizontal landing as well. There has been no demand for an extremely large aircraft to carry weight to altitude. Aircraft design has focused on carrying payload internally for long distances, with the most common payload being passengers. Designing an aircraft to lift weight to altitude means using a straight wing, perhaps two, and lots of engines.

Complexity is never desirable, but safety often demands it. Multiple redundancy, abort options, and robust construction will factor into passenger space craft design, more so than payload capacity. Every fatal accident brings about questions of whether space flight is needed, and how safe it should be. Accelerating a human being to orbital velocity will never be totally safe, but every attempt should be made to try.
  #35  
Old Yesterday, 01:18 PM
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A space craft launched at 15 kilometers can accelerate horizontally while using aerodynamic lift to gain altitude. As the speed increases, the vehicle will ascend as the Earth curves away beneath it.
And as the Earth curves away underneath your accelerating vehicle, the angle of attack of that vehicle will increase. Up to the point of stalling.
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  #36  
Old Yesterday, 07:59 PM
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And as the Earth curves away underneath your accelerating vehicle, the angle of attack of that vehicle will increase. Up to the point of stalling.
Aerodynamic lift would taper off around 35 to 40 kilometers, so a stall is unlikely. The engines would be gimballed for vector control as well.
  #37  
Old Yesterday, 11:48 PM
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Yakamanic: the trouble with your idea is that it's not any safer, and it's not efficient.

In summary, you're talking about a complex aircraft launching a rocket. Propelled by kerosene.

If you have to build a rocket, why not use the same rocket engines, but optimize the nozzles for sea level thrust, and have one rocket carry another? This is a more straightforward approach and it means less components to design.

What are you saving with the aircraft? The only savings I see is the aircraft uses less fuel, but costs a lot more maintenance since it's a huge and complex aircraft.

It's also not especially safe, the aircraft is carrying a rocket fully loaded with fuel.

So, each flight, you burn kerosene and aircraft components, or instead you can just burn kerosene and rocket components.

As it turns out the latter is cheaper. Also, methane is cheaper than kerosene. So the next logical thing is to build your 2 stage rocket a bit bigger, for the economies of scale, and to burn methane instead, because it costs less. (not sure how much the methane SpaceX is using actually costs, tbh - the problem is it's not actually natural gas, it has to be purified in a gas separation plant)

SpaceX has the right idea. The biggest tweak I would make to their plans, as an armchair rocket scientist, is to go smaller. The BFR, I suspect, is too big to be cost effective. Instead, use the same Raptor methane burning engines, but use about 3-7 for the lower stage and 1 for the upper stage. Same rocket, just scaled down, and build more of these rockets. Rely on docking in orbit to put together an interplanetary mission.

Last edited by SamuelA; Yesterday at 11:50 PM.
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