It says here that the inner Van Allen radiation belt begins at 200km:http://en.wikipedia.org/wiki/Van_Allen_radiation_beltThat's above LEO,
The energy requirements to go intercontinental may be similar to what's required to achieve orbit. But the market demand for rapid intercontinental transport will likely outpace demands for orbital satellite launches for quite some time.
Optimized economics trumps optimized physics.
I'm assuming that a rocket-based intercontinental transport would be the most economical form of rapid intercontinental transport. Is that a reasonable assumption?
For example, a flight of about 10,000 kilometers would require a delta-V of over 7,300 meters/second, which is already about 80% of that required to reach low Earth orbit.
During my involvement with a hypersonic vehicle program in the late 1980s, the rule of thumb was that once you got over about 5,000 meters/second, the difference between that and an orbital reentry environment were small.
IIRC, the Saenger antipodal bomber skip-glide concept has been shown to be rather optimistic in its assumptions. Specifically in hypersonic L/D and re-entry thermal load.
But what if we don't want an airbreathing hypersonic solution? Why must we have one?What if you want to ballistically coast through the vacuum, to minimize your flight time?
It says here that the inner Van Allen radiation belt begins at 200km:http://en.wikipedia.org/wiki/Van_Allen_radiation_beltThat's above LEO, so why would a suborbital vehicle be in danger of traveling into the Van Allen belts? I don't think anybody worries about SpaceShipOne/Two hitting the Van Allen belts.
The idea behind this vehicle is that it should use rocket propulsion through the vacuum in order to achieve rapid intercontinental transit.
Because it would be used for commercial transport purposes, it should be designed to maximize payload capacity. Hopefully this would not necessarily balloon the size of the vehicle, since it only has to achieve a suborbital trajectory rather than achieving orbit.
Do a search on Philip Bono's Icarus/Pegasus VTOVL concepts for intercontinental sub-orbital transport. >>snip<< But they are interesting ideas... and I think suborbital transport could be the killer app for rocket transport.
Rapid intercontinental transport via a vertical takeoff rocket is largely oxymoronic because of the logistical overhead in placing payloads on top of vertical rockets and/or erecting vehicles from horizontal to vertical.
By the time you set up the rocket with its payload and have it tanked up for launch, you might as well have sent the payload via cargo jet. Explain to me a vertical launch system that can handle 10 or more launches per day from a single pad and then maybe we can begin to consider the practical economics.
Optimized economics trumps optimized physics. I'm assuming that a rocket-based intercontinental transport would be the most economical form of rapid intercontinental transport. Is that a reasonable assumption?
Hypersonic flight is still vapoware, but rockets have been carrying humans for over half a century. (I assume the X-15 rocketplanes were rockets and not jetplanes.)
Nothing says you HAVE to have an "airbreathing" solution, you can replace the external-burning ramjet with rocket engines and just fire them at the bottom of each "skip" to re-accelerte the vehicle and extend the next glide phase. However that would require more on-board storage as you're providing both fuel and oxidizer for the engines, and you also loose the L/D boost that external burning provides. So it's a trade off.
So...1) Rocket powered take off to around Mach-4 at an angle of around 70 or more degrees to exit the atmosphere. Maximum Altitude would be around 100km.2) Once "in-space" you apply the rockets to achieve horizontal velocity to around Mach-10. A bit more, a bit less depending on various factors but close enough for this example. Cut engines and coast.3) Re-fire engines occasionally to adjust trajectory to increase range and avoid falling back to Earth short of your goal.4) Reenter at around Mach-10 and slow to a glide and fly to destination to land.Does that sound about like what you're thinking?
It would depend on a huge amount of more specific information but no matter what your overall "payload" would be less than a similar capacity/range subsonic aircraft simply because of nature of a rocket powered suborbital vehicle.
IS suborbital point-to-point (P2P) high-speed/fast package-delivery (as it's listed currently) "THE" killer-ap for rocket transports? Opinions still differ on the idea with major questions over the "assumption" that the world is even ready for point-to-point delivery services.
YOU assume that current launch operations are "required" for any vertical take off and/or landing rocket vehicle but this is simply not true. Example launch facilty for high-flight rate launch and landings? The reinforced concrete pad(s) the DC-X flew from in New Mexico proved that the currently over-regulated and quite expensive launch facilities in current use are NOT required for a properly designed vehicle. However that same pad would have to have added equipment and facilites to handle any "normal" launch vehicle so it is quite clear the launch facilites are much less an issue than the vehicles themselves.The key is the questions of "practical-economics" and market for suborbital point-to-point versus current long range air transport.
Learn your history! Especially if you are planning on using it to bolster your argument! Point of fact: The X-15 rocket PLANES were in fact built to fly and study the hypersonic (above-Mach-5) flight regime and did so extensivly. They proved out the techniques, materials, and issues with flying for extended times at hypersonic speeds. It should be noted that almost all "manned" rockets have traveled routinly at hypersonic speeds both going into space and returning from space. Hypersonic speeds above Mach-6 have proved mostly probematical due to high aerodynamic stress and heating which is why a lot of the study for hypersonic transport systems include some means of active cooling (using the assume cryogenic fuel) or a "skip-glide" type flight to allow radiative cooling.Hypersonic flight is NOT "vaporware" and neither is hypersonic Air-Breathing flight, but then again "intercontinental" rocket flight is on the same level being quite possible, just not proven to be economical or practical.
I don't understand how a fraction of an orbit is different from a purely ballistic trajectory - both involve unpowered coasting. I don't see why every ballistic trajectory has to go thousands of miles into space, when you can have a shallow ballistic trajectory.
Or what about even the Roton concept? Couldn't that likewise be adapted for sub-orbital point-to-point? I haven't heard anybody propose that yet. Roton ultimately could not be made workable as an SSTO, but its design could probably be adapted to achieve suborbital point-to-point.At least Roton's overhead rotor design could be a robust way to address that "last-mile" leg of the journey (and even the "first mile" as well).
Or for a more practical solution, mag-lev trains running in vacuum tunnels at hypersonic speeds. Very expensive to build, but massive throughput of passengers.
Fair enough - it's understood that rockets have to carry the extra LOX weight, since they're not burning in air. On the other hand, scramjets have to withstand the prolonged atmospheric frictional heating, which probably entails its own weight penalty. Plus, even scramjets have inferior power-to-weight than rockets, right? (I'm talking about the apparatus, not the fuel+LOX)
Well, the world should be ready to move on, since commercial air travel hasn't evolved for a long time. It's still being done the same way as it was during the 1960s. >snip good stuff<With commercial air travel now increasingly a commoditized business dominated by price-wars, there should be room to compete in a differentiated and much higher-margin space, where currently no competition exists.
My point in saying that, is that it's more logical to try to develop a suborbital point-to-point vehicle based on the more mature and proven rocket technology, as compared to the as yet unproven, expensive and precariously complex scramjet technology.
'Couple of points out front:1) Scramjets aren't neccessarily needed as a standard subsonic-combustion ramjet can be effective up to speeds of Mach-8.2) Ramjets or in fact most Air-Breathing engines can have higher Thrust-To-Weight ratios if you really need them, but the economics aren't usually there for them to be in general use. (Military engines for example)3) Air-Breathing engines are "accellerator" and "cruise" type engines in that they steadly and efficently continue to accellerate the vehicle to the limits of their performance. This is not as much of an issue if the vehicle is using the atmosphere as a 'support' medium as well, (think "lifting-trajectory" using wing/body lift) however rockets are very inefficent at any sort of "cruise" mode and are pretty much just straight accelleration engines. They tend to require very high T/W ratios simply because they demand Vertical Take Off, high angle trajectories in order to get up and out of the atmosphere as soon as possible.3) Thrust-To-Weight isn't as important in the type of suborbital flight we're discussing.Drag and such for a ramjet is pretty low overall, better the more you "intergrate" the intake/exhaust system into the vehicle. An "external-burning" ramjet uses the body of the vehicle and the shockwaves generated by hypersonic speeds as the "walls" of the engine. By injecting fuel into a specific point the body/shockwave dynamics are used to compress the fuel air mixture which then uses the body/shockwave dynamics to allow optimum expansion of the exhaust.You CAN do a skip-glide with rocket burns instead of air-breathing, but as I noted you lose some of the advantages available.
Step 1, not so much. Step one pretty much covers all types of "take-offs" that are possible. It only concerns itself with the portion of the flight from where you decide to start the suborbital run through the speed needed to get above most of the atmosphere.Step 4 you just shorten the "flying" portion with a terminal velocity fall into range to restart your propulsion system for landing.In the end the overall flight mechanix are the same.
One would think. Proving it however is the issue
Actually? The original "two-person" (no cargo) ROTON was designed from the start as an SSTO vehicle. It was only when it grew bigger that it lost the SSTO ability and started having heavier issues.I don't see any reason it wouldn't work.
Don't get stuck on "hypersonic" meaning "scramjet" because you don't NEED scramjets to fly at hypersonic speeds. Just saying...Randy