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I think you are missing the point.
You need to ship a load of life support to the Mars surface. For the return journey that doesn't apply. So why have one craft that serves as both lander and ascender...especially if you have some use for a multiple ascender?
EDL is Entry, Descent, and Landing Configuration..
Ascent only uses the EDL to get to the surface for use for a return to orbit and beyond dependant on design.
Current rover https://mars.nasa.gov/mer/mission/space … shell.html
https://mars.jpl.nasa.gov/msl/mission/spacecraft/https://upload.wikimedia.org/wikipedia/ … ematic.jpg
elderflower, the fuel LCO/LOX sure is easy to manufacture but its a poor fuel for a rocket to which there are no known engines to use it. The Mars hopper vehicle (with a specific impulse of approximately 250 s), was proposed principally because carbon monoxide and oxygen can be straightforwardly produced by Zirconia electrolysis from the Martian atmosphere without requiring use of any of the Martian water resources to obtain Hydrogen.
Here is another forum topic Carbon Monoxide for fuel on Mars
Which has the Experimental evaluation of the ignition process of carbon monoxide and oxygen in a rocket engine.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Unless you have built the ascent craft from scratch on the surface of mars..that said you need to land which is the EDL....entry, descent and landing as you have sent it there from Earth....
Now can you design the Ascent vehicle for recycling I am sure that you can and did suggest it is possible elsewhere with a scaled falcon 9 version for a mars lander with the use of retropropulsion landing meaning no use of a parachutes, heatshield but until we can do so here with the first stage via space x we can not say that we will ever do so with mars...
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Oldfart1939,
I don't think anyone here would suggest that we stop using chemical propellant rockets to get to orbit. We don't have any working alternative technologies for that purpose. However, the real "mass killer" for delivered tonnage is the continued use of chemical rockets in space once orbit has been achieved. Chemical rockets should only be used for achieving orbit, whereupon more efficient forms of propulsion take over.
We've already done this using SEP, but it's a very low thrust system that requires constant high electrical power input over mission durations spanning months to years. The Xenon propellant typically used in SEP is prohibitively expensive and rare. If Argon-based thrusters can deliver similar Isp, even if the electrical input requirement is a bit higher, then SEP may be viable for high power systems used for cargo delivery. The Xenon propellant systems are simply too expensive to scale up to the sizes required. Between the Xenon propellant and solar panels, in-space propulsion systems suitable for delivery of heavy cargo could easily cost more than the rocket that delivered it to orbit.
At this point in time any NTR is a high-risk, low-reward technology. Even advanced engines like the ground test demonstrators developed for Project Timberwind can, at most, double the specific impulse of LOX/LH2 powered chemical rockets. Although numerous start/stop cycles have been demonstrated, reusability has not. Let's face facts here. A solid core NTR will have a life cycle measured in hours, after which the rocket will be flown into the Sun to dispose of the core. That may fall within the realm of feasibility for exploration missions, but it'll always be an extraordinarily expensive endeavor, if only because the companies that would actually contract with NASA to design, test, and build the hardware would only undertake such projects on "cost plus" contracts. Cost-plus contracts provide no incentive for contractors to provide deliverables on-time and within budget. I fail to see how this would help NASA accomplish anything other than spending its budget.
The fusion driven rockets do not require elaborate multi-hundred million dollar facilities to capture and process radioactive exhaust products. Major universities with plasma physics laboratories can conduct all the experimentation required using existing laboratories that can also be repurposed for other research uses. There are no infrastructure projects required to develop or use this technology. The metal propellants, propellant storage vessels, super capacitors, electromagnets, and solar panels are already mass-produced for commercial purposes and/or used elsewhere in fusion or particle accelerator research. There's nothing overly-specialized about the technology, apart from test instruments, modeling software, and foil liner control process. This makes the technology affordable and available.
I would like to make the point clear that the basic process and its ability to initiate fusion was demonstrated four years ago. Whether or not the actual mechanics of the process work is not speculative at this point. Apart from systems integration, current work involves improving the output gain from fusion (more bang for every buck of propellant purchased). For clarity, fusion from this process was never intended to extract any electrical output from the input, although some of the electrical energy from the previous "shot" is recovered from the coils and stored in the super capacitors. The D-T pellet fusion merely superheats the Lithium foil liner. The liner absorbs most of the heat and radiation, the heat converts the foil to a plasma, and an electromagnetic nozzle expels the superheated plasma.
Presuming no show-stopping technical issues are encountered, and there have been none up to this point, an aluminum foil fueled cargo delivery propulsion unit could very well be the most economical way to quickly deliver heavy cargo to Mars, especially if the transit duration is increased to 180 days. Aluminum is heavier than Lithium, but the cost of the fuel is negligible and reusable rockets make shipping heavier payloads to low Earth orbit less of an issue than it would be with expendable rockets.
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kbd512-
The downside to the current concept of fusion utilizing the Deuterium-Tritium couple for ignition is the ejection of a neutron in the process, which either (a) requires a LOT of shielding mass, or (b) it's entirely robotic/unmanned. If that method is used, a lot of the cargo will be glowing in the dark from induced radioactivity at time of delivery. (Tongue-in-cheek statement). The one valid excuse for developing the Moon is to harvest the He-3 from the regolith, since He-3 and D do NOT eject a neutron upon fusion.
None of this discussion is really all that new, since Robert Zubrin examined a lot of these possibilities in "Entering Space."
In the near term, resurrection of the NTR concept is within our technical grasp through an upgraded NERVA program. If we use it as simply a deep space power module until the core is exhausted, the glowing remains may be disposed of as you suggested by flight into the Sun. The core will undoubtedly be reusable for several missions by swapping out fuel modules robotically.
As you stated, in the immediate foreseeable future, we're stuck with chemical propulsion--which isn't that bad. We CAN go to mars and return. We can also initiate colonization. Venturing further out in the Solar System requires more innovation.
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Oldfart1939,
I've made no attempt to misrepresent what happens. You do get neutron and gamma radiation. Between the two, my understanding is that the gamma radiation is the primary emission source in this particular system because the low-Z Lithium liner absorbs most of the neutrons and subsequently emits gamma rays. Like neutrons, gamma rays are also very difficult to shield against. I would like to point out just how much Lithium is between the crew and the location in the propulsion unit where the neutrons are created. There are multiple meters of low-Z Lithium to absorb the neutrons produced by D-T fusion in the propellant tanks. Even so, the gamma radiation is a problem and shadow shielding is part of the overall concept.
If you think the neutrons from fusion are difficult to shield against, then wait until you start operating fission reactors at gigawatt output levels and let me know how much of a problem you think the neutron and gamma radiation from fusion is in comparison to fission. The smallest Timberwind demonstrator reactor was 1GWt. There are various other concepts for using NTR that involve output levels up to 25GWt.
The 1000s specific impulse of the particle bed NTR systems is slightly more than double that of our best chemical rockets. Admittedly, that's a dramatic improvement. However, the specific impulse of the FDR systems is more than 5000s and the thrust produced by the plasma jet is in the range of tens of megawatts. Shipping aluminum foil propellant to space is no problem whatsoever. Lithium is somewhat more problematic, but still doable. There is no requirement for LH2 storage, as would be the case with NTR-based in-space propulsion systems.
The most dramatic performance improvement NTR systems would provide is in the upper stages of conventional chemical rockets. A Falcon Heavy booster stage combined with a PBR-NTR upper stage should provide lift capability equivalent to initial variants of SLS. I think an appropriate time to consider development of NTR upper stages would be after SpaceX demonstrates second / upper stage recovery. If SpaceX can reliably recover upper stages intact over the course of a couple years, then a PBR-NTR upper stage makes a lot of sense. This presumes that the fuel elements remain intact and no radiation leakage occurs.
I would like to see an advanced Falcon 9 variant with a PBR-NTR upper stage providing 50t to LEO performance. Rockets with this lift capability would be part of a modular Mars exploration mission architecture combined with FDR in-space propulsion units. The same rockets could deliver Mars Ascent Vehicles, rovers, consumables, or a Mars orbital space station using FDR propulsion units. The fuel requirement for 6 month duration cargo flights is low enough that there'd be no individual mission architecture components requiring Falcon Heavy rockets, never mind SLS or ITS.
I think that the funding wasted on SLS could easily have produced PBR-NTR upper stages for Falcon, Vulcan, and New Glenn reusable rockets. Even without PBR-NTR, those commercial rockets vividly illustrate just how bad an idea our expendable $500M SLS rockets were and are.
There is absolutely no reason why a human-based Mars exploration mission must deliver all the components required to Mars aboard the same vehicle. That's just a mission disabler. If using chemical propulsion, then ISS had a similar IMLEO tonnage requirement to a Mars exploration mission and we didn't try to deliver the entire station to orbit on a single rocket, so why would we ever try to do a Mars mission that way? The lunar missions were done that way because it was within the realm of feasibility to do so, there was very little experience with orbital assembly, and we were working with primitive computational and rocketry technology at that time.
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kbd512-
I'm not arguing with you at all; just pointing out that we HAD the capability to utilize NTR 40 years ago, and didn't. That technology MUST be buried somewhere around NASA in the musty archives. My comments were aimed at making some RAPID progress, and not waiting around for some esoteric new development to provide a magic wand transformation to the space program. A PBR with a lot higher Isp sounds attractive. What irritates me is the stop-start nature of lots of these programs--ultimately wasting tons of money--then throwing away the results.
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Oldfart1939,
Some rocket scientist, and I use that term pejoratively in this instance, either lost or forgot to write down how to fabricate the fuel elements. Of all the possible things that we could lose or forget over several decades of inactivity, why on Earth did it have to be the fuel elements? It's such a fundamental thing for any fission reactor. We have the neutronics analyses and other important and difficult to predict data, we have far better manufacturing methods available for the reactor vessel, turbo pumps, and control systems, but no fuel elements. In any event, NASA is busy re-creating this "lost" technology.
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Here's what NASA produced for their PR on NTR and the NERVA program. In addition to "losing" the plans and details for production of the nuclear core fuel elements, they also managed to "lose" the plans for Saturn V. Government (in)efficiency?
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Its called reverse engineering from what you have inputing it back into the modern 3d electronic system we use today. But this is where the art skills come in when trying to make it work from the newly made items from these efforts. This is what has been done with the J2 engine from the apollo era.
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For GW Johnson #11 ...
A search request for aqueous and ammonia, submitted to FluxBB, came up with your interesting post about "real" propulsion methods. I decided to post the link below here, in part because it refreshes the topic in the forum.
The purpose of my search was to follow up on a post by kbd512, about use of (and more importantly, shipment and storage of) ammonia.
https://www.cfindustries.com/globalasse … _na_v3.pdf
The pdf at the link above appears (at first glance) to contain information anyone thinking of using ammonia in a campaign to replace hydrocarbon fuels would want to study.
I came away from a scan of the pdf thinking that 19% solution of aqueous ammonia is plenty dangerous enough for the average person.
(th)
Last edited by tahanson43206 (2019-04-19 13:01:07)
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Hi Tahanson43206:
Household ammonia solution can kill you if the exposure is such that those fumes concentrated in limited air volume is all there is to breathe. That's 5% ammonia in water, from the bottle in the grocery store.
I've used 5% and 10% diluted to 5% for environmental cleanup work, for spilled battery acid. Inside a big rig truck trailer, that was quite lethal without breathing gear.
What they used developing the old blue-line prints from the paper drawing days was 40% aqueous ammonia. If you spilled that inside an ordinary room, you had 5 to 10 seconds to escape before being overcome. If overcome, you died.
Farmers use anhydrous ammonia as fertilizer, but they have to be very careful how they do it, as the vapors are immediately lethal.
Ammonia as rocket propellant must be essentially anhydrous.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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For GW Johnson re #61
Thank you for your reply! I apologize for intruding on this topic (humans or robots) but hope bringing the topic back to Active will inspire others to continue the discussion!
(th)
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There were many miracles in the fire of Notre Dame but the reason for machines were very evidant in how to fight the fire.
A robotic 1100-pound fire fighting robot Colossus of the Paris Fire Department was in the fire fighting it when men could not go.
https://www.independent.co.uk/news/worl … 77526.html
Shark Robotics says the Colossus – which is 2.5 feet wide and 5.25 feet long – can carry 1,200 pounds and be operated from almost 1,000 feet away. Controlled using a joystick, the machine is waterproof, fireproof and can even withstand thermal radiation, according to the company. It can crawl up stairs. The machine’s lithium ion batteries can last for up to eight hours, and the robot can be equipped with cameras, sensors and a smoke extracting fan.
The point is when you design the machine for what it must do and test its design you get what you require when you need it the most.
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Meet a robot that could crawl through extraterrestrial caves
https://www.albanyherald.com/news/meet- … 937de.html
Why not both?
or older discussion
Humanoid Robots Could Build Martian Settlements
https://newmars.com/forums/viewtopic.php?id=10281
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