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Here is a mars mission concept based o Skylon orbital transport:
https://www.youtube.com/watch?v=Uj45Au3KCRg
It uses a GW-like orbital assembly facility
http://exrocketman.blogspot.it/2014/02/ … ility.html
and an artificial gravity long axis spinning spaceship-
Antimatter is a good choice for fuel to the stars, but it won't be ready in time for the first trips to Mars.
At the moment we just have a very good propulsion system that is easier to harness than antimatter: Orion drive. According to the guys who work at it, if optimized an Orion Drive can reach a specific impulse up to 20000 s. An Orion propelled spaceship can reach Saturn in one year and the Oort Cloud in less than five years. And we can have it now without inventing new technologies.
I was skeptical about Orion, but I was captured by this very cool short movie:
https://www.youtube.com/watch?v=uQCrPNEsQaY
after I read this old document,
http://www.projectrho.com/public_html/r … 09vIII.pdf
where every potential problem of Orion Drive is very well addressed, from thrust vectoring control to pusher plate protection and shock-adsorbers cooling...
It seems it can really works.
I find anything manned in the outer solar-system very speculative simply due to the duration of life-support and human-factors necessary to get their, it is not a propulsion problem alone, the radiation fields of the gas-giants make the GCR and solar-flares look mild.
That said the ability to brake cheaply at such locations would be great for any mission, Callisto though is not such a location, it's got practically no atmosphere so unless you were planning to brake in Jupiter's upper atmosphere and take a massive radiation dose I don't see the benefits. Titan is a very airo-brakable locations though and an unmanned probe using this tech to get into orbit their would be nice, though the savings may not be so huge because probes can do slow ballistic captures at almost no propellent cost. .
Callisto has very thin atmosphere, but the spaceship can use magnetoshell near Jupiter for hyperbolic capture then circularizing the orbit with rockets near Callisto. The spaceship need a command module shielded with 30-40 cm of water for crossing radiant belts, but probably we can use the same magnetoshell as mini-magnestosphere radiation shield.
Why is everyone so fixated on using aluminum? Thin aluminum sheeting is good for not only experiencing the direct effects of high energy ionized particles, but secondary effects from interaction between the ions and the atomic structure of the material they're being driven though.
More overwrap required.
Because it's lightweight, robust and cheep. You cannot have a passive shield against GCR even with polyethylene, unless you build a spaceship with two meters thick walls.
What you need is only a solar flare protected zone: a double aluminium wall filled with 20-25 cm of water ice is good. Ice it is also a very good heat sink for waste heat and a protection against meteorite puncture.
For CGR protection it will be better something like Boeing's 1500 kg superconductive mini-magnetosphere
The production and storage issues become much easier to overcome when you have more energy available to throw at it. That means making peace with fission, using more advanced forms of fission, and then moving on to fusion, before anti-matter becomes a truly viable option.
The attenuating matrix of this antimatter is solid, so this antimatter rocket, at the best, will have the same specific impulse of a good nuclear thermal rocket, with more and more troubles and costs in harvesting and confining positrons.
Instead of waste public money in this science fiction like spaceship, that will need almost a century of R&D to be developed (if it works), why not seriously invest in a almost ready and mature technology like nuclear thermal rocket spaceship, that can bring us to Mars in 10 years?
I found this very interesting work
http://www.dmzone.org/papers/Gourroncetal2014_VM.pdf
Valles Marineris may be an interesting site for the first manned mission.
What would be the point of a manned mission to Venus?
If the mission objective is surface exploration, then I would suggest that the best approach would be to establish a manned space station in Venus orbit and use nuclear/RTG powered telerobotics to explore the surface. You won't need to bring the robots back again and don't need to be concerned with the engineering difficulties of return from the surface or atmosphere, NTRs or floating balloon bases. The telerobots on the surface would consume a large portion of their power supply just keeping cool, but could use a mixture of bouyant and dynamic lift to float just above the surface. Ultimately, a VR type experience may be possible and much easier that trying to put people on the surface.
A Mars Direct hab could suffice as the orbital space habitat. And most transfers to and from the hab from LEO could be achieved by solar/nuclear electric ion propulsion ferry.
Here is a lot of hot stuff for a Venus robotic mission
That's a roughly factor 10 improvement in energy efficiency over ion rocket thrust. To provide a 0.1g acceleration for a 100t spacecraft would require about 100MW. Still requires a high R(P/W), but an achievable one. Would you need to be outside of Earths magnetic field before you switched it on?
I did a little research. The Saturn V engine power was 180GW at takeoff. That's impressive.
Yes, you need to be outside Earth magnetosphere to switch on your m2p2.
Another interesting option may be the MITEE hybrid electrothermal rocket: a low pressure high temperature NTR, that can reach 1700 s of Isp with an arc-jet afterburner:
This is what I am interested in for Venus_L2
About the Venus_Tail:
http://sci.esa.int/venus-express/50247- … gnetotail/
http://sci.esa.int/venus-express/50246- … s-express/
Lagrange Point:
http://en.wikipedia.org/wiki/Lagrangian_point
http://upload.wikimedia.org/wikipedia/c … s2.svg.pngI am interested in finding a way to mine the upper atmosphere of Venus from Venus_L2 if possible.
A suppose a more humble interest would be that a probe would study the magnetic activity at Venus_L2. It would be interesting to see if there could ever be a way to capture a magnetic loop using reconnection.
And having studied that, it might be supposed that a similar Mars_L2 exists. Lower temperatures there. If you could capture ions, and somehow convert them to gas, and then bottle it at the Mars_L2, maybe that could be of value. If you could lock onto a ejected magnetic loop with a spacecraft, perhaps you could somehow use that as a propulsion method outward in the solar system.
What you say is called "propulsive fluid accumulation": http://en.wikipedia.org/wiki/Propulsive … ccumulator
there are many interesting study on the topic.
The only difference is that on Venus you will also need a system to crack CO2 in CO and Oxygen.
Running the numbers gives an electric power input requirement of 2857MW [...] .
It's very difficult to cope with gigawatt range electrical power in space: conversion is so inefficient that you need a very huge and massive radiator to get rid of waste heat.
Instead of powering a ludicrous low thrust reaction electric thruster, a better to use electrical power may be to inflate a mini-magnetosphere for deflecting solar wind, like a sail: Robert Winglee's mini-magnetosphere plasma propulsion (if it really works as predicted) will give 1 Newton of thrust per KW of electrical power, so a 25 KW m2p2, you can easily obtain with a P&W Triton, will give you 25 N of thrust that can be used to rise the apogee of transfer orbit, shortening transit time.
m2p2 can be generated using every kind of propellant, even oxygen.
http://www.lpi.usra.edu/publications/re … wash01.pdf
Another good use of electrical power may be to power a magnetoshell for magnetoaerocapture, saving tons of propellant.
I have raised a new post to discuss nuclear ion propulsion and GW's proposal:
"OK, look. The dynamics of fast interplanetary travel demand propulsion that has at least a low-1000's of sec of Isp, and lots of vehicle acceleration capability: 0.1 to 5 gees. We have some technologies that have shortfalls, and we have those benchmarks. Not both! And we have some concepts we haven’t tried yet.
There are a bunch of electric propulsion schemes, some more mature than others. The best ones have the low-1000's of sec Isp, but all fall way short on vehicle acceleration: 0.001 gee or less. The most critical need is for a lighter-weight, more powerful electric power supply. That's what needs to be worked on. If the SLS budget were going toward that, we might have a solution in sight. But we do not.
Chemical and solid core nuclear thermal meet the thrust benchmark, but fall short on Isp. Many folks have objections to nuclear for any of a number of reasons, but we may just "have to get over it", and be careful how and where we employ it. Both technologies are essentially ready-to-use, especially the chemical. Here in the US, nobody is making LOX-kerosene engines but the newcomers like Spacex and XCOR. That needs to change. We also need to work on in-space cryogen transfers and long-term storage. The practicality for real interplanetary travel is not quite there yet, but could be.
Gas core nuclear thermal is absolutely immature, but holds the promise of meeting both the thrust and Isp benchmarks simultaneously. So, we ought to be working on it, too. That technology could enable travel if the search for a practical electric propulsion power supply fails. It's stupid to put all your eggs in one basket, as we all already know. If that word "nuclear" offends, well tough. Life ain't fair. Neither is physics. The electric power supply we seek for electric might well be nuclear. So, get over it.
BTW, my candidate power supply concept would be a nuclear thermal rocket device feeding an MHD generator. None of that heavy steam loop nonsense. Use it as a rocket for getaways and captures, use it for MHD electric on the transits between to raise midpoint speeds. Get thrust from the electrics and the released plume. Same rocket hardware does both, which saves vehicle weight. That might really start looking good if gas core nuclear was the rocket device. Then we could start looking at excess electricity to use for processing propellants while electric-thrusting on the transits. It pays to dream big. Tells you what you really need to be working on, too.
At the moment this engine is the best candidate for a NTR/NEP hybrid spaceship:
http://www.alternatewars.com/BBOW/Space … TRITON.pdf
When the ship is coasting, the rocket enter in idle mode, producing 25-100 KW of electrical power, using a closed cycle Brayton turbine and a little radiator, that ca be used to feed an electric thruster.
There are also very promising study about high efficiency (up to 42% termionic converter)
http://www.fkf.mpg.de/1253832/Highly-Ef … -Power.pdf
So in a future the NTR can be equipped with a very lightweight no moving parts powerful generator.
OK, that being said, now return to electric propulsion. The problem is power supply, as I said just above. The thrusters themselves are also a bit short on basic device thrust/weight, even when you don't count the power supply, so that's another area we ought to be working on, as well.
But, a good power supply could make the simple arc jet feasible, which could use just about anything as propellant, at least in principle. To use oxygen-containing materials as electric propellants, will require solving the reactive-oxygen problem, so we should just belly up to the bar and get on with solving that issue. That solution makes in-situ electric propellants a lot more feasible-looking.
Here is an interesting 1500s Isp hi-power arc-jet using hydrogen
http://erps.spacegrant.org/uploads/imag … 91-072.pdf
hydrogen has the highest specific impulse and may be simpler using the same propellant for NTR and for NTP. Hydrogen arc-jet may also be used for RCS.
Other promising technology is the nested channel Hall thruster
http://pepl.engin.umich.edu/pdf/IEPC-2011-246.pdf
It has an higher specific impulse (4000 s) and no grids, so theoretically it can use oxygen or any other kind of propellant (N2, CO2, NH3, H2O), but probably it has to be optimized.
Some (few?) parts of Mars have big buried glaciers, we think, so there is massive ice we could mine, just not at every site where we'd like to base. Maybe not very many at all. Who yet knows? The atmosphere there is mostly CO2, which at those temperatures is not all that hard to freeze for easy storage. How about CO2 as an electric propellant? Could we make that work? Venus also has CO2, but it has hellish conditions and big gravity well, which make it not so attractive at this time in history.
Titan has a largely-nitrogen atmosphere and a very weak gravity well, although Saturn's is considerable. Could we use Titanian nitrogen as an electric propellant to support activities in the outer solar system? The surface "rocks" seem to be water ice, so you have that as well. Plus, methane and ethane in liquid form in the lakes. Could any of these work as electric propellants?
There's the ices on the surfaces of 3 of Jupiter's big moons. Water, CO2, perhaps ammonia, and some other things. Could these be used? The moons have weak gravity wells, but Jupiter's is enormous, as is its radiation hazard. Not sure how soon we might be capable of safely recovering those resources, but somebody ought to be looking at it.
Callisto is far from radiation belt, but still inside the strong Jupiter's magnetic field and is protected from GCR. On Callisto surface radiation dose is very low, so Callisto's ice can be easy accessible.
They are simpler than conventional rocket and use pressure feeding, avoiding turbo-pumps.
http://arc.uta.edu/publications/cp_file … ISSW24.pdf
In the article above it is claimed they can have up to 40% more specific impulse than a same propelled conventional chemical rocket. So an high efficient LOX-LH2 pulse detonation rocket can reach 600-650 s of specific impulse. Can it be real?
This novel new idea for capturing into Mars (or other planetary) orbits looks to have huge potential for reducing IMLEO and for making reusable spacecraft viable.
http://msnwllc.com/Papers/Kirtley_MSNW_ … _final.pdf SLIDE SHOW
http://www.nasa.gov/sites/default/files … apture.pdf In-depth Paper
System masses are tiny, less then 1 ton for a system that can capture 60 ton vehicle at Mars in only a weeks time, because the system is electric and able to modulate drag in real-time it should be able to compensate for atmospheric fluctuations (conventional rigid shields have a narrow window to either burn-up or skip off and go hyperbolic) and brake faster and or safer, sufficiently safe that humans as well as cargo can use it.
The TRL is still low and it will need a few demo missions, but if this is on the table it significantly moves the needle in favor of a SEMI-DIRECT architecture over that of a DIRECT. In semi-direct you normally take a large mass penalty in braking the ERV into Mars orbit, the direct approach skips this by doing as it's name suggests and doing direct atmospheric entry. With nearly free MOI the semi-direct style ERV becomes much simpler as it no longer needs heat-shields or most of the propellent it is normally allocated, it just needs to arrive with the return propellent. Conducting Mars EDL from orbital speed rather then transfer orbit speed considerably simplifies the heat-shield necessary on any lander as well yielding yet more savings and opens the potential of multiple surface sorties from an orbital base.
In fact the ERV can start to become a real space-ship that would be re-used. If it is using a sufficiently high ISP propulsion system that it is not forced to drop stages then a complete trip to and from Mars could consist of just two propulsive events and two airo-captures around Mars and Earth respectively. An Ion engine is the most likely system to be able to do this, half the mass estimates for the magneto-shell are electrical systems that would be redundant with the engine and it's power supply so a simple shunting of power between the engine and shell further reduces mass.
The magneto-capture should be sufficiently low stress on the vehicle that deployed solar panels will survive so the vehicle will not undergoing any change in configuration and will be ready to simply spiral out from Mars and return to Earth. This saves both propellent and time compared to the standard flight plan with Ion propulsion which would have the vehicle spend on the order of 100 days spiraling down to a LMO after initially capturing into a high elliptical orbit as the standard Airo-capture is destructive of delicate solar arrays and can't be combined with SEP. To avoid keeping the crew in near deep-space during this spiral the crew lander is expected to separate before capture and to perform a direct entry. Again the magneto-capture would eliminate the separation event and allow all assets to be kept in reserve for rescue or multiple landings. Landing site options are likely to be massively more flexible with a parking in orbit as well.
Magnetoshell may also be very useful in a robotic mission to Titan: we can use it to directly capture the spacecraft from hyperbolic entry to Titan orbit, avoiding the risk of passing between the rings, like Cassini did, using the big antenna as a shield against debris.
If we put a magnetoshell on the tail of a manned nuclear spaceship like NTR Copernicus, we will have a huge propellant saving that enable even a manned mission to Callisto.
I have raised this post to explore the advantages and disadvantages of a Phobos-First approach for Mars exploration and colonisation.
I believe a Phobos First approach offers numerous advantages. Most significantly, it allows manned exploration of the Mars system to begin at lower state of technological readiness and with smaller initial investment than would be required for manned Mars surface missions and with more rapid returns of investment. As the Phobos regolith likely contains a high percentage of ejected Martian material, a Phobos scientific base would also allow the existence of Martian microbial life to be determined.
Sorry but I found 3 problems in your planned mission:
1) Phobos has no atmosphere, so astronaut will be exposed at an higher dose of cosmic ray during stay.
2) Phobos has no gravity, so astronauts have to spend more than 2 years in micro-gravity, risking blinding for optical nerve damage, hearth failure at reentry for hearth hypotrophy, and multiple bone fracture due to severe osteoporosis (entry velocity for a Mars-Earth transfer orbit is almost 14 km/s). Probably astronauts will not survive a high gee atmospheric entry after 2 years in micro-gravity.
3)Phobos is very little and will be very difficult to spend there 600 days waiting the launch window in good metal health.
Using the rocket equation for an ISP of 4190s and delta-V of 6200m/s, reveals that a 10 tonne vehicle travelling from LEO to Phobos Lagrange 1 (2.5km above Stickney) would consume just 1.6tonnes of propellant. If ten ion thrusters are used and supplied with 100kWe of power from solar panels with a specific power of 0.2kW/kg, then the total propulsion system mass is 830kg with 1600kg of propellant. Throwing in another 500kg for reaction control, computer, Earth communication, payload faring and Phobos landing thrusters, still allows a total payload of 7 tonnes, for each 10 tonnes delivered to LEO.
You cannot apply the deltaV tables for Hohmann transfer to non impulsive transfer: a Hohmann transfer orbit require a short and strong burn, with a very powerful rocket (chemical or nuclear thermal). With a low thrust slow spirally electric thruster gravity losses are high, so the Earth-Mars deltaV will be more than double.
Energy costs are very low, masses are 1-2% of entry and far less the heat-shields, read at least the slideshow before you comment.
Gravitational capture is slow and time spent doing it is effectively added to Transit time for radiation/consumables etc, it is likely to be a good interim solution for unmanned cargo and robotic missions though.
500 Gauss is only 0.05 Tesla and is not a huge field: probably the whole machine will have a mass of 100-200 kg (Boeing's mini-magnetosphere projected to shield the crew from SEP an CGR during Earth-Mars and Mars-Earth voyage has 0.75 Tesla and a mass of 3000 Kg cryocooler included).
A 100-200 kg magnetoshell weight less than an aerocapture thermal shield and less and less than the huge amount of propellant you save avoiding an all-propulsive insertion maneuver. With this device an Earth-Mars trip and return will have almost 7 km/s of delta-V instead of 14 km/s.
If magnetoshell works, it will be better a chemical propelled spaceship with magnetoshell than a nuclear propelled spaceship without it.
This novel new idea for capturing into Mars (or other planetary) orbits looks to have huge potential for reducing IMLEO and for making reusable spacecraft viable.
http://msnwllc.com/Papers/Kirtley_MSNW_ … _final.pdf SLIDE SHOW
http://www.nasa.gov/sites/default/files … apture.pdf In-depth Paper
System masses are tiny, less then 1 ton for a system that can capture 60 ton vehicle at Mars in only a weeks time, because the system is electric and able to modulate drag in real-time it should be able to compensate for atmospheric fluctuations (conventional rigid shields have a narrow window to either burn-up or skip off and go hyperbolic) and brake faster and or safer, sufficiently safe that humans as well as cargo can use it.
The TRL is still low and it will need a few demo missions, but if this is on the table it significantly moves the needle in favor of a SEMI-DIRECT architecture over that of a DIRECT. In semi-direct you normally take a large mass penalty in braking the ERV into Mars orbit, the direct approach skips this by doing as it's name suggests and doing direct atmospheric entry. With nearly free MOI the semi-direct style ERV becomes much simpler as it no longer needs heat-shields or most of the propellent it is normally allocated, it just needs to arrive with the return propellent. Conducting Mars EDL from orbital speed rather then transfer orbit speed considerably simplifies the heat-shield necessary on any lander as well yielding yet more savings and opens the potential of multiple surface sorties from an orbital base.
In fact the ERV can start to become a real space-ship that would be re-used. If it is using a sufficiently high ISP propulsion system that it is not forced to drop stages then a complete trip to and from Mars could consist of just two propulsive events and two airo-captures around Mars and Earth respectively. An Ion engine is the most likely system to be able to do this, half the mass estimates for the magneto-shell are electrical systems that would be redundant with the engine and it's power supply so a simple shunting of power between the engine and shell further reduces mass.
The magneto-capture should be sufficiently low stress on the vehicle that deployed solar panels will survive so the vehicle will not undergoing any change in configuration and will be ready to simply spiral out from Mars and return to Earth. This saves both propellent and time compared to the standard flight plan with Ion propulsion which would have the vehicle spend on the order of 100 days spiraling down to a LMO after initially capturing into a high elliptical orbit as the standard Airo-capture is destructive of delicate solar arrays and can't be combined with SEP. To avoid keeping the crew in near deep-space during this spiral the crew lander is expected to separate before capture and to perform a direct entry. Again the magneto-capture would eliminate the separation event and allow all assets to be kept in reserve for rescue or multiple landings. Landing site options are likely to be massively more flexible with a parking in orbit as well.
I'have read about it. If it works, it will cut by an half the deltaV budget of a mars mission, so it will be very easy to build a complete reusable orbit to orbit spaceship (something like GW's design) and perform magnetoarocapture at Mars and Earth arrive. Evan a mission to Saturn with a solid core NTR will be easier with this device: we can use it at Earth return and reuse the whole spaceship.
There is a never addressed issue about cloud cities: start up. We cannot build a floating colony, using CO2 for synthesizing carbon composite, without a big base with industrial machinery and we cannot build a big base with industrial machinery without using local materials. So how to start-up?
The only way may be to build a modular floating base in Earth's Lagrange points using asteroids or Moon's resources, then send it to Venus, perform an atmospheric entry for every module (that can be inflated at the opening of the aeroshell) and dock them.
Very very expensive and risky: build a base on Mars is almost three order of magnitude easier and cheep.
I think that maybe there's something we're all missing here, which is the fact that there seems to be no reason at all to build this rocket engine. An open cycle gas core design could have an Isp of 5000 s, but with the mixture radios being proposed chemical would be probably choose to 200 s. Don't bother with the chemical, just use the gas core.
The idea was a very simple rocket: gas-core has a lot of trouble in avoiding the contact between core and chamber wall: having the core confined outside in the plume will result in a simpler and lighter engine, with less problem of cooling that can run all regeneratively cooled, avoiding heavy radiators.
The chemical rockets are cheep and are used without afterheater in low delta-V maneuver(2-4 km/s for change plane, course correction and low energy orbital transfer) to not waste very expensive uranium. Chemical rockets plus AH will be used only in high delta-V maneuver, like orbital ascend from a cloud city of Venus or Uranus, or to insert the ship in high energetic monotangent orbit to outer planets.
An alternative may be a solid core NTR with a gas core afterheater: solid core will have something like 10.5 km/s of exhaust velocity and can be used alone in high energetic orbit from inner to outer planets, with a magnetoshell for capture (all the planets has space habitats where it is possible to refuel, so spaceships don't need to bring propellant for the return trip) and the spike core afterheater will be used only to ascend orbit from a gas giant cloud city.
I'm still skeptical that you could get the heat transfer to work out properly, but I haven't done the calculations. If you want to do some and they show otherwise, then I suppose it's possible.
I'm not able to do the calculation, but the problem of heat transfer was addressed by a group of Lewis Research Center in the 50-60. They know hydrogen is almost transparent to UV radiation up to 10000°K, as you correctly said, but they solved the problem using a mixture of solid particle seeded hydrogen.
Are rotor-rockets able to do anything for that mission profile that a regular one can't? I'm not really familiar with what the concept can offer, only that it was experimented with and their seems to have been no follow up.
rotor-rocket can fly in the atmosphere like a spaceplane with atmospheric engines, without the mass penalty of wings an engines (actually we have no jet engines able to burn fuel using CO2 as an oxidizer). Rotor blades with tip rockets are very light, can function in every kind of atmosphere and during ascent augment the rockets exhaust with atmospheric gasses, resulting less propellant consumption
Probably, from what we can build now, a LOX-RP1 SSTO Rotary Rocket will be the best suited vehicle for Venus atmosphere.
The first manned mission can be performed in this way:
1) atmospheric entry with the base
2) slow descend using free wheel rotor and hovering in the atmosphere collecting samples
3) fire tip rotor rockets and start ascent in high atmosphere
4) fire main rocket engines and rendez-vous with the ERV in low orbit.
If we want a more long stay in the atmosphere, we have to add a balloon on the nose of the Rotary Rocket:
1) atmospheric entry with the base and the rotor blades folded
2) inflate balloon and atmospheric floating in the currents and collecting samples
3) unfold rotor blades, detach balloon
4) fire main rocket engines and rendez-vous with the ERV in low orbit.
Sounds like there would be a problem in terms of transferring the heat from the UF6 to the Hydrogen. Plus the UF6 would still probably fall into the atmosphere.
The presence of water from oxygen in the exhaust gas can enhance heat transfer, if it not enough the plume can be seeded with carbon nanoparticles injected in the nozzle.
A layer of gas from gas generator turbines flows radially under the truncated cone base, avoiding direct contact with the plug core (it can be carbon seeded if necessary) and protecting it from melting.
Contamination is not a problem, because, in the story, Earth has space elevators and the rocket is supposed to connect Venus and Uranus cloud cities to orbit.
If it works, this rocket will be very good for coming back from Venus atmosphere to orbit: http://www.newmars.com/forums/viewtopic.php?id=7168
Hi, happy new year to all!
I would like to use this very simple chemical-nuke hybrid rocket to power the spaceships of may next novel: I beg the engineers of this forum to tell me if it may work or not.
The engine is composed of many LOX-LH2 rockets, disposed around the rim of a truncated cone aerospike nozzle, which may also act as an entry shield, as a moderator/reflector and as a shadow shield, with an outer layer of tungsten, a layer of beryllium hydride and a beryllium neutron reflector, all LH2 regenaratively cooled.
The gas core is uranium exafluoride, stored in a gadolinium shielded tank.
During atmospheric operation the engine works like a normal LOX-LH2 rocket with a 6:1-5:1 oxidizer/fuel ratio.
When the spaceship is in space, the LOX/LH2 ratio is lowered to 1 or 0.5. Uranium exafluoride is puffed out from the truncated cone plug, become critical, reach 5000-7000°K and expands, forming a long spike that heat the plume like an afterburner, giving an exhaust velocity of 16 km/s or more.
During the burn, the core is confined by the plume. When the burn is finished, the core will flow out in the space, without contaminating the engine.
It may be very cheap because it has the simplicity of a chemical rocket, without the complexity of solid-core NTR control machinery.
May it be work?
Alcubierre Drive works by stretching the "fabric" of space. (Or dimensions of space.) It stretches, then compresses, so the small bubble of space the ship resides within moves relative to the universe. That means the ship does not experience acceleration. So it does not experience change of velocity. So yes, it will continue to move at the same speed and direction as before "warp drive" engaged.
If you build a "warp ring" in Earth orbit to carry a DreamChaser to Mars orbit, then be very careful about orbit before departing. Because Earth has greater gravity, an orbit with the same velocity will be much lower altitude. And to go from circular orbit to circular orbit, you have to depart Earth when a direct line from Earth to Mars is pendicular to Earth. And arrival will be will be perpendicular to Mars. That means you better steer correctly. Failure to stop will pass Mars without impact, but if you're aim is off then you could impact Mars. If you aim directly at Mars instead of Mars orbit, then warp drive will disengage when the ship is within the planet. That means impact at warp speed.
I suppose you could disengage warp drive a little early. That would result in falling into an eliptical orbit. But apoapsis will be higher from Mars than that point. Velocity will be toward Mars, so periapsis will be much lower altitude, but velocity will have to fall to stop before coming around, so apoapsis will be higher.
May be interesting to note that there is a new theory, the Scale Symmetry, that expected some kind of primordial negative energy particles called "ghosts".
http://www.wired.com/2014/08/multiverse/
Many theorists consider ghosts a big flaw of Scale Symmetry, but even antimatter, initially, was considered a big flaw of Dirac's Quantum Field Theory. Dirac took it seriously and later antimatter was discovered.
