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Exhaust velocity is inversely proportional to the molecular weight of the exhaust gas, which is also true for Isp.
We've now had another "Lunar Distraction" from the far more important goal of Mars. I really believe that putting together a complete inventory of available space vehicles, not only the ones made here in the USA, would allow us to conceptually select some of the other modules for building a Mars mission system.
About the only type of structures achievable in these early visits will undoubtedly be inflatables. Maybe a lightweight but very strong polymeric dome could be assembled there, but the abrasiveness of lunar dust will definitely degrade cloth fiber type materials. The problem of building radiation shelters is more extreme on the Moon than on Mars, minus any atmosphere.
The problem plaguing NASA is a long "logistical tail." "Old Space" is too deeply beholden to "cost plus" financing and that form of contract to be competitive. If NASA is involved, figure on it costing at least double or triple the figure you've quoted. Of course all the hardware will be "Old Space," and prohibitively expensive. My solution: put it up to a competitive bidding process with SpaceX, Orbital ATK, and Blue Origins as the bidders, along with "Old Space." Maybe get top 2 competitive contractors with a bonus prize of $1 Billion for the first to achieve the surface of the Moon?
It appears to me, that given the $$$ required to revisit the Moon for more than another "Flag & Footprints" excursion, we could actually have a viable mission to Mars for an 18 month research expedition. Dr. Zubrin admonishes us for being "seduced" by the nearness of the Moon. It will be many generations before a viable Lunar civilization will arise, simply due to lack of useable in-situ resources.
I'm definitely in the Mars-next camp, not a Back-to-the-Moon supporter.
We need to develop a compact and lightweight100-250 kWe Thorium-based nuclear reactor for off-Earth use. Could be used for both Moon and Mars.
For me, the Moon is something of a depressing place; work on the surface is limited to 14 days out of the Lunar cycle. Yes, there is something there for a Planetary Geologist to study, and the establishment of Astronomical observatories would also be worthwhile. Tourism? Yes, but getting there is more than half the fun! I'd go for the rocket ride myself, but one can get enough magnificent desolation in a day or two. "It's a nice place to visit, but I wouldn't want to live there." Mars on the other hand is a place for a chemist/biochemist/biologist to have some real fun.
Somehow, I simply cannot comprehend the enthusiasm for returning to the Moon. We have a bunch of rocks picked up 45 years ago, with little scientific revelations as a result. Mining? Resource extraction? The Moon is a desolate environment and at the present, has little to offer either scientifically or economically. About the only possibilities are, as GW suggested, a Nuclear Propulsion Test Facility, and a base for a monster radio telescope. For me, as a scientist (retired!) the return isn't there for the economic outlay. The only positive: it's NOT in LEO!
Martian Mist, the original, made and triple distilled from synthesis of ethylene followed by addition of water across the double bond. Right from the Martian atmosphere! One of the first colonial products anywhere & everywhere: Booze!
It would appear that a real decision needs to be made in regards to the type of lunar mission we are seeing in our projection, and whether it's merely a sidestep on the way to Mars or not. I really believe it's time to move on beyond the concept of a small throwaway lunar lander--just to reprise Apollo. We now have orbital assembly capabilities that were lacking in the late 1960s and early 1970s. We no longer have the monster Saturn V booster, but emerging reusable booster first stages such as Falcon Heavy. The comments coming out of Hawthorne, regarding another Falcon 9 upgrade with more thrust, should translate to the Falcon Heavy at some point, too. A redesign of the Dragon cargo trunk into a fuelled and strongly powered descent/ascent stage, to and from the lunar surface should be relatively straightforward engineering project. NASA has allowed use of the Russian built RD-180 engines on the Atlas series of rockets; why not consider incorporation of Russian MMH/NTO engine from the Proton M "Briz" upper stage into the trunk? This is the S5.98 engine developing 19.62 kN of thrust, with a specific impulse, Isp = 328.6 sec. This could be augmented using the Super Draco engines in a parallel application for lunar landing and takeoff, if the entire vehicle mass is still to large due to unconsumed fuel onboard. having this engine available should allow something of a reverse engineered total vehicle mass to be calculated. TLI should be carried out by a Falcon Heavy second stage. For the engineers among us: the engine specifics are Mass; 95 kg. Engine diameter: 0.98 meters; engine length: 1.15 meters. The actual "Briz" stage carries 19,800 kg of propellant/oxidizer, allowing a total burn time of 3,200 seconds. Engine is rated for up to 8 restarts.
I suggest this engine, or a suitably similar one manufactured to U.S. specifications for the simple desire to keep from having to reinvent the wheel.
GW-
Back when I was still in engineering school, I simply loved both Statics and Dynamics--and all units were in Feet-Pounds-Seconds. I don't really have any problems making the conversions, but as you said--it's easier to refer to absolute measurements in familiar units. Units which were new to me were Pascals, Newtons, etc. I also have a private pilot certificate, so measurement of altitude is still in mm HG or inches, Hg. Conversion of units was always how the professors made people look stupid.
rbd512-
I'd like to second your appreciation for the input of GW on this forum. It takes me some time and effort to get a full understanding of some of the things discussed here, only because a lot of my math and physics is very rusty--vintage 1957-1961. My chemistry, on the other hand is pretty up to date. Part of my struggle is not conceptual, but dealing with the changes in units utilized; I have a relatively recent copy of Sears and Zemansky, as well as pulling out a copy of Thomas for the math. But--I'm getting there.
What was in essence demonstrated is the Photosynthetic Reactions converting CO2 and H2O to carbohydrates can still work under extreme conditions. There are bacteria, notably Halobacterium Holobium that exist under pretty saline conditions. A simple reminder that bacteria are Plants!
As the OP of this topic, the cubesat experiment was done to show that zero gravity had no adverse effects, and the Atacama desert data was to indicate the soil type and salinity. Not that potatoes could be grown outside a pressurized greenhouse. Just making a case that crops could be grown there in greenhouses without too much chemical soil modification.
Just comment, not aimed at anyone in particular: too many acronyms can make an article virtually unreadable to most.
According to the article below--Mark Watney was right. Potatoes CAN grow on Mars, verified by a CubeSat experiment.
I am a strong supporter of Thorium nuclear reactors.
For any treaty to have true legal standing, it must be enforceable by the signatories. As a political pragmatist, I simply ignore such a blatant Socialist pile of cow manure as the Moon Treaty, especially since the U.S. never signed on to it. I'm just not a starry eyed idealist; sooner than later, we'll need to get over the treaty prohibiting the introduction of fissionable materials in space. We realistically need Nuclear Reactors for several applications: Nuclear Thermal Rockets, power for ISPP on Mars, and energy for maintenance of a colony; power for lunar exploration/exploitation, and development of the Asteroid belt objects. What NEEDS to happen WILL happen, and no scrap of unenforceable paper will have any bearing on the outcome. Sure---there will be "outcry from those left out."
The FP of RP-1 may be -76 F, but it undergoes a massive increase in viscosity prior to freezing, rendering it incapable of flow. The Falcon 9 uses RP-1 chilled to -7 C because of this undesirable feature. In Diesels, it's called "gelling."
If other large-mass payloads can be landed on the Moon, I'd say the roof structure for support of a good quantity of regolith--at LEAST a meter thickness-needs to be made from something besides an inflatable material. the walls--just pile regolith against them but have a structure that's not going to collapse under many tons of rocks and fines. Maybe excavate a crater-like hole in the ground, then push regolith back against it and have a strong polymeric hard roof structure. Bury the whole thing except for the entrance to the airlock. Sort of like the bomb shelters that were popular back in the 1950s? I for one, wouldn't want to live that way, though. I'd go absolutely bonkers during the 14 day lunar night.
I personally have no issues with either methylox or hypergolic combinations involving N2H3CH3 and NTO. The hydrazines can be a mixture, which subsequently lowers the melting (freezing) point. This has an excellent Isp = 325s. Musk talks about the new Raptor engine using CH4/LOX with Isp = 383 +/-. Granted, that's SpaceX, not Blue Origin.
SpaceNut-
The BE-3 is a hydrolox system, and has it's own problems/limitations, being cryogenic.
Blue Origin today announced the first customer, Eutelsat, for it's New Glenn Rocket satellite operations beginning in 2021. Photos of the first BE-4 rocket motor were also released for public viewing.
http://spaceflight101.com/wp-content/up … 7x1024.jpg
The announced payload capacity to LEO is 45 metric tons, with a 13 metric ton payload to GTO.
GW-
It's my position that an orbiting lunar satellite is not anything we really should spend money on... Even a permanent base on the lunar surface is of questionable utility--other than for military purposes or a huge astronomical telescope. The folks who question the sanity of colonizing Mars should have apoplexy when discussing a permanent presence on our own satellite. They think that Mars is worse than Antarctica, but conditions on Mars are benign when compared with the Moon.
In my mind, there's really no justification for having a continuously manned space station in orbit around the Moon. The overall health hazard level is just too high for long term occupancy. Unfortunately, the lunar surface isn't much better, but a Bigelow habitat on the surface could be covered with regolith for some shielding against not just Solar flare protons, but also attenuates the GCR background.
Final comment: On to Mars!
