John Strickland makes the case against it over at The Space Review today. I don’t think this is right, though:
It is hard to imagine being able to quickly set up such a [lunar] base without a launch campaign of at least five HLV launches per year. To do this you will also need one or more cryogenic propellant depots in Earth orbit to assure that the propellant to support such a launch rate from LEO to the Moon or Mars is guaranteed to be available in LEO before the buildup begins. (Without the depots, the total cargo delivered to a base site for a given number of SLS launches would be cut about in half). The depots would also need to be launched by HLV boosters. Assuming a minimum of five SLS launches per year at $5 billion a launch, the total cost is $25 billion a year, far beyond NASA’s overall annual budget, let alone its human spaceflight budget. With a launch every two years, it would take a decade to provide the most minimal equipment for a surface base, and most of that would have been sitting there for many years and would thus likely be thermally damaged and unusable.
I really need to see the work here. On what is he basing the need for five launches per year? And how does the depot double the lunar payload? And why does the depot or depots require a heavy lifter? Is he assuming they will be launched full? The depot structure itself doesn’t weigh all that much and could easily go up on an Atlas or even a Falcon 9. And doesn’t that five billion per launch for the SLS assume a low flight rate? Presumably, if they really could do five a year, the per-flight cost would be much less. I’m not saying his numbers are wrong, but I’d need a lot more explanation to accept them. I do agree with this:
In addition to the political impasse over booster development, the nature of the current NASA planning system results in a vicious circle, seemingly created by deliberately not including advanced technology components into future mission plans. The reasoning behind these decisions are that the components do not yet exist, but the result is that the badly needed components are never developed, since there is never a specific mission designated where they will be used. Then when the mission is flown, its capabilities are greatly reduced due to the lack of the component. For example, NASA is currently budgeting money to develop cryogenic propellant depots in orbit, yet the depots are not included in or integrated into any plans for the BEO missions using the SLS. (This issue was the focus of a letter on September 27 to Administrator Bolden by Rep. Dana Rohrabacher.) Such delays and/or sapping of funds from technology programs for use by the SLS development by Congress allows mission planners to continue to exclude advanced technology solutions from future BEO mission plans.
This is the perennial institutional problem of technology development at the agency because, unlike its predecessor the NACA, technology development doesn’t seem to be viewed as NASA’s job, at least not enough to actually fund it. It’s always chicken and egg in that no one wants to put a new technology on the critical path for a mission, and because no mission requires it, the technology never gets the priority it needs for development. The solution to this is to refocus the agency on tech development, but that doesn’t provide enough pork in the right places.
I wondered if maybe he meant the equivalent of 5 SLS launches (650mT), but it doesn’t look that way. Neither the HLV nor the depot is required, you don’t even need one of the two, all you need is a lander that can accept propellant in space. And depots don’t require an HLV in any way shape or form. I like his conclusion, but not his logic.
Why on Earth would you want to focus NASA on tech development? They’ll ruin that too. They need to focus on missions, it’s the only thing they know how to do. As long as they get out of the launch business this will generate enough demand for the market to take care of R&D. Works best if NASA gets out of the R&D business itself.
Well, I want some agency focused on tech development, particularly that needed for settling and developing space. It’s what the NACA used to do before it became NASA. If not NASA, then who?
And what are “missions” and why should NASA be doing them? Serious question.
I want some agency focused on tech development
Whenever an agency is working on something there tends to be a problem of some sort. Department of Housing, Agriculture, Environment etc. The agency will claim they are from the government and they are here to help. I will suspect they are causing or at least prolonging the problem.
Why not leave it to the market? It works for many industries.
And what are “missions” and why should NASA be doing them? Serious question.
I can only answer that question assuming there is a NASA in the first place.
From the point of view of developing technology for settlement it doesn’t really matter what missions they do. Purely robotic science missions could be enough provided they generate enough traffic for launch vehicles of a minimum size no greater than ~5mT. That should give us cheap lift. After that the Bigelows and Bransons of the world can step in and take over. The Planetary Society, or the National Geographic Society could take over doing expeditions and NASA could be reduced to a funding agency. Or closed down.
Serious answer. The thing is, I thought I learned this argument from you among others…
Of course, we’d have to take baby steps to get there, but as long as we’re engaging in blue sky thinking, why not set this as our goal and try to achieve it as aggressively as possible, always bearing in mind that that still requires baby steps?
Looking back at NASA’s predecessor NACA, I see a pretty effective model of an agency doing tech development to advance the nation’s industrial base. NACA built many wind tunnels and did a lot of pioneering research on airfoils and drag reduction, among other things. Famous examples include the NACA Cowling that reduced the cooling drag of radial piston engines by a factor of three and the laminar flow airfoils used on the P-51 Mustang and many other planes. Dr. Richard Whitcomb came up with the area rule concept to reduce transsonic drag, a significant advance. Working for NASA, he also invented the winglets you see on many modern airliners and more efficient airfoils.
Those wind tunnels were used by more than just NACA researchers. Wind tunnels were expensive so NACA made them available to companies that couldn’t afford their own tunnels. They played an integral part in refining the designs of military and civilian airplanes for decades.*
NASA still does technology development. SpaceX adapted NASA’s PICA heat shield technology to create the PICA-X shield for the Dragon capsule. There are other areas where NASA can help such as materials technology that can lower rocket engine costs, lower cost propellant pumps such as the piston pump XCOR is developing along with ULA, alternative engine designs, etc. NASA can also contribute to technologies like long term life support systems and enhanced avionics technologies.
NACA was very helpful in advancing the US aviation industry from its terrible condition in 1917 to world leadership by 1945. At no time did NACA try to run its own airline or design its own airliners. They simply helped American companies build better planes.
*As a historical tidbit, I’ve read that America’s first jet airplane, the Bell XP-59A, wasn’t tested in a wind tunnel due to secrecy requirements. It showed in the results – the plane had pretty poor performance due to excessive drag.
It’s true that NACA did a better job than NASA. It’s also true that Samuel Langley’s efforts were a failure. And we don’t really know what would have happened without NACA, you can’t just assume the private sector wouldn’t have come up with its own solutions.
PICA was clearly a useful contribution, but was it cost-effective? What about the hypersonics work done at Glenn? Lots of interesting papers and proposals, but no flight hardware.
Let’s look at one of the more promising concepts:
Affordable Flight Demonstration of the GTX Air-Breathing SSTO Vehicle Concept
It is really very agile and New Space-ish for a NASA project. But do we really want to fund this sort of thing? Sure, it would be exciting but there are far easier things we could try first, namely precisely the things that our suborbital friends are working on.
And what are “missions” and why should NASA be doing them?
This one is easy.
http://www.nasa.gov/missions/current/index.html
Most of these are done and managed rather well, and are actually, IMO, good investment of public funds.
All of these would benefit from a separate focused space tech development agency though, i.e. these should serve as primary customers to the R&D and drive the roadmap.
“technology development doesn’t seem to be viewed as NASA’s job, at least not enough to actually fund it.”
There’s another slight wrinkle to this, but it doesn’t change the conclusion. NASA does have technology money, but it tends to be seed money to take brand new never before done ideas to the point where the researcher can coax them to work on his lab bench. If you want to take it from there to a bulletproof reusable solution that could be integrated into a mission there’s no money for that. The technology money won’t fund it because it’s not new technology, it’s been done by that researcher already. And missions won’t fund it because they rightly point out that it’s not mature enough to be relied upon.
You could say the problem is that NASA doesn’t fund R&D. It funds R, but no D.
So you are saying there is a gap to be covered between TRL 4 to TRL 7 ?
The new OCT Space Technology area is supposed to address this problem. It includes what they call “Early Stage Innovation” (NIAC, research grants, SBIR/STTR, a “Center Innovation Fund”, and Centennial Challenges), “Game Changing Technology” development for technologies that advance past the early stage, and “Technology Demonstration Missions” (general technology demonstration missions, small satellite technology demonstration missions, and flight opportunities on suborbital vehicles). There are also area-specific technology efforts like the ones for Exploration, Planetary Science, etc.
The following page lists the general space technology demonstration missions in development or planned (funding permitting) (small satellite missions are in a separate area):
http://www.nasa.gov/mission_pages/tdm/main/tdm_overview.html
The demos include Autonomous Landing Hazard Avoidance Technology, Cryogenic Propellant Storage and Transfer, Deep Space Atomic Clock, Human Exploration Telerobotics, Laser Communications Relay Demonstration, Low-Density Supersonic Decelerator, Mars Science Laboratory Entry, Descent and Landing Instrumentation, Materials ISS Experiment-X, and a Solar Sail Demonstration.
The area is not awash with money, but it’s recovering a bit from the days of Ares. To stretch funding, a lot of the demonstrations are hitching rides to space as secondary payloads, payloads hosted on spacecraft with other purposes, or using the ISS facilities. Some also include partner organizations.
As an example mission, here’s the page for the Cryogenic Propellant Storage and Transfer Technology Demonstration Mission:
http://www.nasa.gov/mission_pages/tdm/cpst/cpst_overview.html
All the numbers for SLS assume 4 launches a year.. as we already know, they more than likely won’t even get one launch a year from it.. that’s one reason why all the numbers are wrong.
I have seen the contention before that it would require heavy lift to get the depot up in the first place; some may be assuming a full depot, but others might be assuming a very large depot. Is anyone aware of any depot designs out there that take advantage of expandable structures such as Bigelow modules? I’m thinking of a very large depot capable of being launched on Atlas/Delta/Falcon.
This particular issue (of the short-term cost level of a base build-up launch blitz) is not one which has been covered by anyone else to my knowledge and is partly independent from the arguments about the technical merits of and the development costs of the SLS. The article is intended to extend the discussion of the merits of the SLS beyond those two latter items to include the operational costs and vehicle construction costs.
This is one of those arguments which cross what seem to people to be topic boundaries, such as Cheap launchers vs. SSP, and in this case, how you build a lunar or Mars base vs. the SLS launch price. You have to think of these issues as describing a system. What use would a heart-lung machine be if it only did one of the two functions? Also, one item may be totally dependent on the other.
Note that I would like to have a private, re-usable HLV to enable the launching of really large depots which could contain over 100 tons of cryogenic propellant. A wide HLV is also needed for putting wide based Mars landers with integral aeroshells into LEO before being used at Mars.
Some of the payloads that would need to be landed at a lunar base site before the crew arrives are: a spare lunar ferry insulated against the lunar extremes, a reactor to keep all the equipment warm via electric power, an excavator to dig holes and bury the crew habitat with lunar regolith, the crew habitat itself, which would probably come in more than one section. This is the bare minimum. We would not expect all bases to be at the poles, and the temperature extremes are severe there also.
The mere fact that no launch price estimates have been released should be raising a lot of questions. I did a lot of searching and found no NASA launch cost estimates for the SLS or its payloads. The launch cost estimates are based on the physical construction costs of the SLS vehicles more than on the purely operational (launch) costs as essentially nothing is re-used. Note that current dollar costs for a Saturn V with its payload are in the same range.
Having LEO depots would double the lunar payload that could be placed on a single launcher. since a lot of the mass on a fully fueled payload would be the fuel.
It is perfectly possible to launch usable depots without an HLV. The Falcon Heavy could launch a pretty large one by itself. The upper stage could be designed to use fuel from the depot to put the depot in orbit. A depot could be launched empty or with just enough fuel to put itself into orbit.
For use in Lunar orbit, I assume that any depot would have a series of docking ports which allow fuel transfer to and from Lunar ferries and Earth-Moon transit vehicles. The ports add to the mass and bulk of the depot. It would be harder to assemble such a structure in space due to all of the physical plumbing connections that would need to be made. Thus I would like to see an HLV available when we need one.
I hope this discussion will result in someone turning up launch and payload price estimates. There were some given during the Constelllation period, but they were ridiculously low.
John
Note that I would like to have a private, re-usable HLV to enable the launching of really large depots which could contain over 100 tons of cryogenic propellant
Such large depots are unnecessary.
A wide HLV is also needed for putting wide based Mars landers with integral aeroshells into LEO before being used at Mars.
Such large aeroshells are also unnecessary.
Perhaps these will one day be useful (I doubt it, but you never know), but you claimed they were necessary, even for a moon base.
Having LEO depots would double the lunar payload that could be placed on a single launcher. since a lot of the mass on a fully fueled payload would be the fuel.
True, but the payload capacity of a three-core EELV would be enough. We really don’t need anything bigger, not even without depots.
The Falcon Heavy could launch a pretty large one by itself.
So could a Falcon 9.
Some of the payloads that would need to be landed at a lunar base site before the crew arrives are: a spare lunar ferry insulated against the lunar extremes, a reactor to keep all the equipment warm via electric power, an excavator to dig holes and bury the crew habitat with lunar regolith, the crew habitat itself, which would probably come in more than one section. This is the bare minimum. We would not expect all bases to be at the poles, and the temperature extremes are severe there also.
Uh, a reactor is a non starter. Part of the attractiveness of the lunar polar region is that you can use solar power almost all the time with only tens to a hundred hours of darkness to get over.
We designed a power lander that can put 100 kW solar plant on the surface using a Delta IVH vehicle.
The thermal extremes at the poles are less than in the equatorial regions.
What can be done in a non SLS world is a build up of robotics capability on the surface using inexpensive launch vehicles such as light Delta/Atlas and Falcon 9’s. These robotic payloads, coupled with adequate power from a power lander, would allow almost everything to be put in place before a crew arrives.
For an interim habitat an inflatable from Bigelow or ILC Dover would work just fine. A first order of business would be the ISRU to harvest the metal in the regolith, melt it, and then pour into slabs that would be used to assemble a far more robust habitat than anything that could ever be lofted.
As far as crew goes, an open cockpit lander such as was designed for Lunar Gemini could be used to get humans from Low Lunar Orbit to the surface can that lander could be put there by a Delta IVH vehicle as well. A cislunar cycler between ISS and Low Lunar Orbit could be easily put together with a couple of smaller launches.
The era of heavy lift in the Apollo style is history, let it stay buried there.
It’s always chicken and egg in that no one wants to put a new technology on the critical path for a mission, and because no mission requires it, the technology never gets the priority it needs for development.
Note that the suborbital VTVL startups deliberately don’t put new technologies – and even many existing technologies like turbopumps – on the critical path to RLVs. Also note that they don’t want NASA developing RLVs.
So New Space orthodoxy is no government agencies, no unproven technologies when it comes to cheap lift. Why should it be different for other applications? There may well be specific classes of technologies for which government R&D makes sense, but if so that would require an explanation.
Also note that the absence of cheap lift is the only real obstacle to making private spaceflight profitable. Once we have cheap lift, commercial funding for RLV will follow, just like RLV R&D would follow from an exploration program using commercially launched propellant.
The suborbital VTVL startups have not even flown above a few thousand feet yet. Carmack used to rant about how his vehicles would never have parachutes, but now they’re abandoning powered landing in favor of them. XCOR long since recognized the need for pump-fed engines but prefer piston over turbine for the industrial base. While I too hope that the upstarts will change the world, they’ve yet to do it.. they’d be the first to tell you that talking about cheap lift as a result of these efforts is premature.
I’m not sure I understand your point, but I just noticed I muddled my own by mentioning government R&D when I meant unproven technologies on the critical path.
Do we agree that the suborbitals are working towards cheap lift? And even if they revisit early decisions (as was always likely), they are still staying away from advanced existing technologies (piston pumps or pistonless pumps rather than turbopumps) let alone new ones. You might say that what Paul Breed and Microcosm are doing with composite noncryogenic tanks is new technology, but it is really applying existing technology to a new application.
I agree with your point that the suborbitals have not yet proved that their approach is the right one, but I thought Rand agreed with this approach and thus his preference for risky technologies and government involvement in R&D seemed inconsistent to me. And since he is typically very consistent in his thinking, both on space policy and libertarian leaning politics, that surprises me.
Yup, but until they prove that they were right you can’t say they are right. 🙂
Trying to answer some more of the commenters points:
– I support NASA funding for Tech development like Depots but it must be carefully focused, with a specific and practical goal or product that can then be actually used in real missions.
To MPM – you make unsupported statements that:
– Large depots are not needed. Have you seen the requirements for fueling either a “mars fleet” of smaller vehicles or a single giant “Battlestar-type mars vehicle?. The fuel masses are much more than 100 tons, and if the fleet is to leave during the same window, the fuel must already be in the depot. We also need such a large depot in Mars orbit to support initial landing operations.
– Large base mars landers are not needed. You may want to read
my presentation “Access to Mars” at
http://www.nss.org/settlement/mars/AccessToMars.pdf
You may not have heard about the Mars EDL problem, but you will.
Please provide some factual support for your statements.
I am boggled that you think that I think we need an aeroshell to land on the moon, wide or narrow !
To everyone: Some think all of the 130 ton payload of the SLS would be able to be landed on the Moon, so they are adding up the mass of the objects I mentioned and think they can all fit on it. How about the mass of the transit vehicle and fuel to reach lunar orbit, and the mass of the lunar ferry and its fuel to land the payload. With an Apolo-like lunar stack system like the SLS implies, you would be lucky to land 20 tons of usable equipement with each flight, and thus 5 SLS flights would provide only 100 tons of equipment per year on the surface.
If you accept the concept of re-usable Earth to Moon transit vehicles, and re-usable lunar landers, then a lunar program using the Falcon Heavy is quite feasible. I am strongly in favor of such design for a lunar program. We just need to know what we are going to do on the Moon before we build the equipment.
For Mars use, I would be very interested in hearing how you would land efficiently with a narrow base lander or ferry much less take off again wit h the same vehicle.
My position is that only private companies should build and operate Earth to Orbit transport. NASA should use privately designed and built vehicles for exploration. I am getting more pessimistic that NASA can ever design a manned in-space vehicle itself again in a timely and cost-effective manner.
I am obviously against any NASA development of an HLV. If a private company thinks it can sell launches on its own HLV, who wants to say no.
It is clear that SpaceX is making real progress toward reducing launch costs in the near term by its posted launch prices. See: http://www.nss.org/articles/falconheavy.html
There is less information about the progress of the other companies, but I support a variety of approaches, since we will not know which ones will work best or be most cost effective until they are all tried.
John
With Lagrange point staging and depots all the way to Mars you don’t need >100mT depots. This also makes it easy to include low energy trajectories and high Isp propulsion into the mix.
I’m well aware of Mars EDL issues, and no you don’t need large aeroshells, small aeroshells combined with retropropulsion outside the Martian atmosphere would do the trick – or retropropulsion alone if need be. I didn’t say you claimed aeroshells were necessary for the moon, but that you claimed HLVs are. I include FH in that category – we don’t even need that, although use of it would be fine if SpaceX develops it on their own dime.
I’m having a hard time visualizing depots “all the way to Mars.” Please elaborate.
You could put depots in LEO, at EML1/2, SML1 and LMO. Propellant to all depots could eventually be prepositioned by SEP as proposed by Huntress in his excellent IAS study. Only LEO to L1/L2 would need some new technology development (self-annealing solar panels) and that is likely to be considerably easier than cryogenic depots. The more often you refuel, the smaller your transfer stages can be and the more you can make use of high Isp propulsion like SEP.
The question in my mind is how much delta-v (and propelant) is required to rendezvous and dock with each one of those depots. For example, flying from LEO to EML1 requires a certain amount of delta-v. Once you take on additional propellant there, you have to accelerate and fly to SML1 and then match velocity to refuel there. Once that’s complete, you need additional delta-v to go to the next depot. Without running any numbers, it seems that requires a lot more infrastructure and propellant than simply refueling in LEO or EML1 and then flying a Hoffmann or higher energy transfer to Mars. A depot in Mars orbit would be very useful for the return trip but not absolutely necessary.
To elaborate on Larry’s complaint, how are you going to get the depots to line up with a mission which has a high velocity trajectory and how are you going to get propellant to these depots? Keep in mind that the only reason for having depots in between is because your mission is not on a normal energy-efficient trajectory (the “Hoffman orbit”). That means even more delta-v for any propellant sent to these depots.
Use of Lagrange point orbits (or perhaps other high energy staging orbits) deals with the alignment issue. Nodal regression is only an issue in low orbits and you still have frequent opportunities to get to a Lagrange point. Once you are in a high energy orbit you have long departure windows. Use of Lagrange points actually makes things easier than with large depots in LEO and no staging orbits, not harder. Lagrange points are really very strategically located crossroads, for a surprisingly long list of reasons.
That’s not the only reason, or not even a reason at all. What makes you say it is?
You may not have heard about the Mars EDL problem
What problem ? The fact that you can’t land much more than a few metric tons at once on the surface ? I don’t see what exactly is the problem ?
Or, so you dont misread me, lets flip the question around : assume, that forever and ever after you can ONLY land 1 ton pieces on Martian surface at a time. Say a hundred of them over a few years period.
How would you design your manned mars reference architecture then ?
@Larry J:
Using multiple depots actually saves propellant, in multiple ways. Your massive MTV now only travels between Lagrange points, so it only travels between the edges of gravity wells instead repeatedly ascending and descending them. Lighter and smaller craft are used between low and high orbits. Propulsive insertion into such high orbits is also much cheaper than with low orbits. Use of SEP for the propellant gives a major boost to Isp. Huntress and Farquhar even add aerobraking to their plan.
BTW, you can still do a Hohmann-type transfer to Mars this way.
You want a propulsive mars lander because the same vehicle is an ascent vehicle to mars orbit once refueled. We need this because although most supplies will go separately straight to the mars surface much will go unused with the crew vehicle (only used to go from orbit to orbit.) It also gives the wimps that aren’t colonists a way home.
No other solution saves as much money as a one way trip.
There are really only two overriding issues. Fuel transportation cost and economic justification. The good news is the economic justification pays for any fuel transportation cost (fuel cost itself is essentially zero.)
Focus on settling a new world and all other issues are irrelevant.
I’ll buy shares in a settlement charter today. That would finance everything.
I just love todays CAN’T DO attitude. /sarc.
More responses:
to MPM:
You cannot leave depots in a transfer orbit “all along the way to Mars” since:
– it makes no sense, since you do not need fuel along the way, only when you reach Mars.
– The depots once placed would move along the orbit past Mars and Earth and be deflected into new useless orbits.
Maybe I am totally misunderstanding the question!
I have a copy of the paper where an alternate method of deceleration is accomplished – by propulsion outside the atmosphere, and refer to it in my Access to Mars paper, which (hopefully) is in the process of being published. This wastes the ability of the vehicle with a relatively light PICA-X heat shield to get rid of most of the entry velocity via passive drag. It also uses a vast amount of propellant whjich has a much larger mass than the heat shield and you get a lot less payload. I can post the reference if you want.
to Larry J:
The point of placing a full cryogenic depot in Mars orbit is to support the initial “bootstrapping” phase of base construction before the propellant plant is operating. It is actually easier to move a depot along a transfer orbit away from Earth than to leave it in Earth Orbit, since the large “Hot” Earth is hitting the depot with infrared radiation and makes it harder to keep cold. If you can achieve ZBO (Zero Boil Off) in LEO, you can do it almost anywhere. The depot is just one of a number of payloads needed for the sytem to work.
The depot placed in Low Mars Orbit (400 km) would be re-filled by cargo Ferries (5 tons with every trip up) and can serve as a reserve for the Earth Return vehicle. The ERV would not keep fuel in its own tanks until just before the return since the fuel would boil off. Of the 20 tons brought to orbit from the surface by the Ferry, 15 would be used for the trip down and 5 used to refill the depot. 20 trips would re-fill it from the empty state.
MPM is exactly right in that the same Depot design can be used in a variety of locations.
High energy fuels like LOX and LH2 weigh less than low Energy fuels per unit of delta-V so you get more payload or cargo.
I am sure that MPM did not mean to confuse the issue with his “depots all the way to Mars” comment but obviously some people assumed that that is what he and I meant. It is not of course. The depots would be placed in orbits around Earth and Mars where they would stay.
Yes, Earth-Moon Largrange points 1 and 2 may also have Depots placed at them, and could be as useful as one in Lunar orbit, since the lunar orbit depot has to have its orbit re-adjusted all the time or it will impact the surface.
To Reader: Yes, THE EDL PROBLEM:
The Earths atmosphere slows things down to about Mach 1 at 25 miles high or they are toast. With Mars, the surface is at the same atmospheric density as the Earths at 36 miles high. You lose about 3/4 of your speed as you enter the Mars atmosphere, but it is too thin near the surface to slow you down the rest of the way so you can use a chute. The Curiosity Rover has a 15 foot in diameter heat shield for about a 1.3 ton entry probe. If you want to do the same velocity reduction for a 70 ton manned or cargo lander, you would need a chute with about 54 times the AREA of the Curiosity heat shield. Such a large chute could not be built and it would not open. The only way may be to start braking via rocket thrust DURING the late stages of entry. this is called Supersonic Retro Propulsion. We need physical tests to prove that this method works. Look at my presentation on the NSS web site for the details.
To Ken:
Yes, exactly right. You cannot build more parachutes, hypercones, ballutes, etc at Mars, since you do not have a factory there. Your propellant plant does not need a crew to operate, and so the fuel can be made at Mars using Mars ice, so it is not an expendable and finite resource like the chutes.
I would advocate that two fully fueled depots would be sent to Mars to support any manned expedition, in case one was damaged.
I addressed your points in my other posts. Specifically depots at moon and Mars Lagrange points and in LMO and exo-atmospheric retropropulsion backed by aerodynamic deceleration and propellant prepositioning by SEP.
See Huntress’ report for details of something very similar. I keep using the wrong name for the sponsoring organisation, it’s IAA, not IAS:
The Next Steps In Exploring Deep Space
It’s a wonderful, visionary report, much better than the Augustine report – which isn’t saying much, since it was awful – and I recommend it to everybody here. It focuses on the scientific aspects, leaving commercialisation to other minds, but calling for engagement with proponents of commercial manned spaceflight.
Another very interesting report came from the OASIS people, which has many good ideas, but is focused on government led infrastructure and suffers from the usual Big Government NASA mega project mentality we all know and love.
Orbital Aggregation & Space Infrastructure Systems (OASIS) PowerPoint presentation
Orbital Aggregation & Space Infrastructure Systems (OASIS) PDF paper
If you combine this with Dennis Wingo’s ideas on use of lunar resources, New Space ideas on the importance of market forces and demand pull, and the sort of incremental thinking people like David Masten and Jeff Greason have applied in their own work (and which sadly made it into the Augustine report only in a debased form) and which is common in my own field of agile software development, then I believe you have the major pieces for a comprehensive vision for space exploration, development and settlement.
Back to your points. The terminology all the way to Mars may have misled people, but I think it is in fact correct if you do in fact stop at each node. I’d be happy to hear of a better way of describing it.
As for the inefficiency of fully propulsive descent:
1) It was a limit case, I actually suggested “small” (<8m which is actually quite large) aeroshells (not necessarily conical) and enough propulsive deceleration to make them workable
2) It saves the expense of an HLV which is substantial
3) It doesn't matter too much if you have ISRU, cheap lift or SEP. We have SEP, we'll need ISRU anyway and a propulsive approach will contribute greatly towards development of cheap lift.
Yes, THE EDL PROBLEM
You just reiterated what everyone here knows. Why ?
If you want to do the same velocity reduction for a 70 ton manned or cargo lander
Thats what i tried to question, but you chose to ignore it. Why do you keep thinking in terms of 70 ton landers ? Whats wrong with 140 1-ton landers instead ?
The Huntress report has a lot of good ideas in it but since it is dated to 2004, 8 more years of thinking has happened since then, such as the ideas of Dr. Paul Spudis, the discovery of the EDL problem, the recent focus on depots, etc.
The report does support an orbital base at Mars, use of aerobraking (no mention of aerocapture), a lander that can take off again, use of ISRU propellants for return, etc. However, it goes into almost no detail on how the Mars orbit to Surface transport system would work. It does not mention Depots in Mars orbit or use of cryogenic fuels. This is not to fault the report, but to show how much good and new thinking has happened just since 2004. I also agree strongly with the ideas of Greason and Wingo.
I think we both agree that the purpose and type of mission should influence the booster design, not the other way around.
To be clear about the use of the Depots: I assume a Large depot (or several) is in LEO in the best orbit plane and inclination for frequent Mars orbit departures.
A Ferry (or other Mars-bound vehicle) would be at least partly fueled and place itself, acting as its own second stage, into LEO and rendevous with the Depot, where it would take on enough fuel for Earth departure. The ferry must be able to carry enough fuel for 4.1 km/sec of Delta-V (for the Mars surface to orbit trip), so it should be able to act as its own second stage to reach LEO and also to reach escape velocity from LEO to a Mars transfer (interplanetary) orbit once refueled. The cryogenic fuel would all be expended during the escape burn.
I see no need to move the Ferry to a high Earth orbit or other node for final departure. This might take even more fuel than a direct departure from LEO and orbit plane alignment problems could cause complications.
The Mars-bound vehicle: (Ferry, depot, crew vehicle, cargo vehicle or even a depot), would use aerocapture and orbit trim on approach to Mars to reduce propellant mass to a minimum, using hypergolic or non-cryogenic propellants. (The depot with its prime mover would use part of its own cryogenic fuel for the trim maneuver.)
Here is the reference for the so-called “fully propusive” paper (means they use thrusting as the main way of decelerating out of orbit before landing) , a very wasteful method.
[Marsh, C. 2009] Marsh, C. L. and Braun, R., “Fully-Propulsive Mars Atmospheric Transit Strategies for High-Mass Payload Missions,” IEEEAC 1219, 2009 IEEE Aerospace Conference, Big Sky, MT, March 2009. URL:
http://www.ssdl.gatech.edu/papers/conferencePapers/IEEE-2009-1219.pdf
Note that the authors did NOT acvocate use of this method – they were just exploring possible avenues to see if they were dead ends or not. That one was. The extra mass of fuel for the lander would require MORE fuel to slow down the extra mass of fuel ! This is a self-defeating proposition!
One of the expendable designs I use for comparison to the Ferry has a 10 Meter by 30 Meter aeroshell with its own attitude control, all of which is expended before landing. Where does it crash? Hopefully not near or on the base!
Using the reusable Ferry system with Mars derived fuel saves over 50% of all mass needed from Earth.
John
John, I appreciate your efforts, but you are making some glaring errors.
There is no EDL problem, there really isn’t. Yes, mostly aerodynamic deceleration is difficult. So don’t do that. Exo-atmospheric retropropulsion followed by aerodynamic deceleration followed by propulsive final descent and landing solves all problems. Rand had a post on that the other day, you may want to look at the comments.
The focus on depots isn’t new and Huntress makes use of them in a way because his proposed spacecraft are reusable. He set out to demonstrate NTR isn’t necessary and said so explicitly. He must have realised his proposal also demonstrated you don’t need HLVs, and I imagine he deliberately didn’t mention that to avoid controversy.
Also, you don’t appreciate the advantages of using Lagrange points.
– It *saves* propellant by better managing energy and by using high Isp propulsion where possible. This is one of Farquhar’s great contributions. Study them before you dismiss them out of hand.
– It needs smaller stages with lower thrust and Isp requirements
– It facilitates reuse of the MTV
– It has much longer departure windows because there are no issues with nodal regression
– The thermal environment is better for depots
– The environment is better for SEP because you have continuous sunlight
The list goes on and on. Your solution by comparison is crude and primitive by comparison. Read what Farquhar has to say. Check out the OASIS work on a Lagrange point gateway station. Check out Kirk Sorensen’s thread on use of Lagrange points over on nasaspaceflight.com. Departing straight from LEO is a *really stupid* idea.
As for fully propulsive being wasteful, didn’t you read what I wrote in my earlier post? Braun is analysing a strawman and proposing something that will require major R&D. We have more pressing issues to solve than paying Mr Braun to do his preferred type of research.
I wish that you would respond to my arguments instead of misrepresenting them and restating your positions.
I think we both agree that the purpose and type of mission should influence the booster design, not the other way around.
No, there should be no influence of the mission on the booster unless there is some really pressing reason, which there isn’t in this case. Spacecraft are designed to boosters, not the other way round. Of course whenever a *new* booster is designed it is designed around both existing and hypothetical future spacecraft, but that’s begging the question. You shouldn’t spend money on booster development for the heck of it. We’ll never get cheap lift as long as NASA is involved. SLS needs to die and exploration needs to be decoupled from the “need” for an HLV. I know this may sound extreme, but it is the bitter truth and it has been explained on this blog many times by many posters including our gracious host.
I am sorry that we are not communicating effectively. Everyone has had access to a different set of sources and ideas, and if we all had access to all the sources and ideas, we would all be geniuses.
I went back to the “fully propulsive” 2009 paper and checked out the values. The mission still requires S.R.P. during the peak of entry which is stretched out to reduce heating, and uses no real heat shield or other deceleration device aside from the vehicle’s own passive drag and rocket thrust. Therfore the S.R.P. research that Braun supports is still needed for that vheicle. As the authors point out:
“As expected, the “fully propulsive descent system sees a significant increase in needed propellant. The added propellant requires larger propellant tanks resulting in growth of the propulsion system mass. In this case, the mass benefit of eliminating the heatshield is overshadowed by the increase in propellant and propulsion system mass, resulting in a drastically lower payload mass.”
The increase in descent propellant mass (as used in a reusable ferry) would make it impossible to return to the surface with fuel brought up from the surface, and the payload could be cut from 30% to as much as 90%, depending on the design, which makes it much less useful as a re-usable system.
Do not confuse their reference vehicle’s parameters for those of the fully propusive version. My Ferry provides a 36% payload (25 metric tons) on descent (out of a 70 ton descent configuration), the Fully Propulsive provides at best 15% (equivalent mass would be 10.5 metric tons. Their system is using Methane-LOX instead of LH2-LOX so this comparison is not fair.
I know that Zubrin also is a EDL denier, but he to will have to face the numbers some day soon.
Depots were known in 2004, but very little attention was paid to the possibilities they offered. I could point out that I was pushing Depots in 2005 such as in:
“The Mega-Module Path to Space Exploration” – Space.com Oct 7, 2005
http://www.space.com/adastra/adastra_mega-modules_051007.html
It would help if you would present specific links to the relevant Farquhar documents. I can at least agree that the thermal environment is better at EM L1 since it is much further from the warm Earth.
I did check the delta-V values for Earth to Mars departure and found that LEO to Mars approach is about 3.7 km/sec and LEO To E-M L1 then E-M L1 to Mars Approach is about 3.77 km.sec, a 70 meters/sec difference. The direct departure avoids a 5 degree plane change which would use some delta-V.
This data is from the detailed delta-V chart on page 87 of the IAA report on Space Solar Power, which can be downloaded from their web site. The values I quote have the deceleration burn of about 2.5 km/sec eliminated from the total delta-V since in my system all approaching vehicles use aerocapture and an orbit trim of about 100 m/sec.
If the propellant was created on the Moon and brought to E-M L1 then the system would make a lot more sense. You may have access to information that suggests other reasons to fill the departure vehicles at the E-M L1 point, which I do not have yet. However, many sources point to the advantages of thrusting close in in a gravity well vs thrusting far away from it, as in flyby thrusting to gain speed for an outer planet mission.
Maybe the only thing we can agree on for sure is that we oppose the SLS and in general any government designed and operated launcher.
John
Hi John,
I hope we agree on rather more than that and more still after some more discussion, probably not all in this thread. It’s obvious to me that you’re one of the good guys and that your enthusiasm for some sort of a commercial HLV is sincere.
But what triggered my criticism was your claim that an HLV is necessary for Mars EDL and because we need large depots. I’m not saying these couldn’t be useful eventually, merely that they’re not necessary right now. And the crucial point of course is that I want to create a large and fiercely competitive propellant launch market as soon as possible, because I subscribe to the New Space philosophy that that is a very promising approach to cheap lift, which itself looks like an absolute prerequisite for commercial manned spaceflight, let alone settlement. Designing exploration missions around an HLV, even a smallish commercial one like FH would hurt that cause.
As for your specific points:
Clearly mostly propulsive descent would use considerably more propellant than mostly aerodynamic deceleration, but the aim was not to reduce propellant use or even IMLEO, but to prevent the need for large aeroshells and thus an HLV. Also note that Braun’s paper (with which I was familiar but to which I wasn’t referring) doesn’t deal with the possibility of refueling in Mars orbit, which makes a big difference. It lets you preposition propellant to Mars orbit with SEP (similar to what Huntress proposes), which reduces IMLEO significantly, perhaps even below that of an aeroshell! If you used ISRU you would definitely get below that and with RLVs you would still end up cheaper even with much higher IMLEO.
If you enter after coming a dead stop, you reach a terminal velocity of less than about 750 m/s, for which you shouldn’t even need a heatshield. This is a limit case of course, there’s no need to avoid aeroshells, just to avoid very large ones. These intermediate cases are much harder to analyse of course, which is why I can’t give numbers here.
All this is not to say that aeroshell research wouldn’t be useful, merely to show that an HLV isn’t necessary for the reasons you mentioned.
I agree that being able to land with enough propellant to take off again would be nice, but I’m not convinced you could make that work even with huge aeroshells. More importantly, I think we are going to need surface nuclear power and ISRU for Mars surface operations anyway. As far as I know this is conventional thinking. Not that that proves anything, but it’s not just some loony theory I came up with.
As for Lagrange points: they’re absolutely crucial even if you do have an HLV, if you do have large depots and do use aerobraking with large aeroshells. I’ve mentioned most of the arguments already, but perhaps I can improve on that in the light of your comments.
Delta-v from LEO to L1/L2 can be done for only 3.2km/s if you use efficient but slow (100 days) three body trajectories. The whole network of such trajectories is known as the “Interplanetary Superhighway”. Fascinating stuff, based on modern insights from the theory of dynamical systems and differential equations. Such trajectories are mostly useful for cargo and propellant, not crew, but that makes up most of the IMLEO.
You are correct that you want to apply thrust as low in the Earth’s gravity field as possible to make maximum use of the Oberth effect. That is why Farquhar proposes using an Earth flyby. This costs you only ~600m/s for the initial perigee lowering burn, but if your MTV only travels between Lagrange points that lops an impressive 3.2km/s off your total mission delta-v, which saves a lot of propellant! It is also much easier to use aerobraking back to a Lagrange point than back to LEO, or to do the same propulsively. Only your crew and propellant needs to be lifted to L1/L2, and not even the propellant once you start using ISRU, although that is likely far in the future. Similarly impressive savings can be had on the Mars end.
Huntress and Farquhar propose an elaboration of this, with use of Earth Lagrange points as well as moon Lagrange points, and with flybys of both Earth and moon. Aerobraking is a standard part of their plan, with use of Mars Lagrange points being optional.
Use of SEP to preposition propellant to any of the forward nodes (Earth, moon or Mars Lagrange points and low Mars orbit) would give another massive improvement.
Going back to your original arguments, you argued that not using Lagrange point staging approach would use less propellant and would have less problems with orbital mechanics and launch windows. I’ve argued that the exact opposite is the case on both points. In addition you would have much lower thrust, Isp and stage size requirements.
But the main reason is that I want to see a large and fiercely competitive propellant launch market as soon as possible. Doing things the way I described would lower the minimum required size for a launch vehicle to compete in this market, which will aid the development of small RLVs which are all we need.
Here’s a link to Kirk Sorensen’s thread I mentioned earlier. It explains some of the orbital mechanics issues better than I could. The Huntress paper contains more details.
An Alternative Lunar Architecture
The entire idea that anyone will be landing 70mt payloads on mars is plain ridiculous.
Just for some perspective, 18-wheelers take 25 tons max payload.
And I still have no idea why you would want to land more than a regular small truck size at once.
Most of the Manned Mars Landers in existing mission studies are from 60-80 tons, with some as low as 20 and some above 100. The deciding factors are the fuel mix, the minumum payload size (the object you want to use on the surface), the landing method and the structural mass of the lander/ferry.
The original reasons for large mass landers were to land a habitat module with the crew, and also to land a return to orbit vehicle near where the crew will land, as in Mars Direct. 20 tons is comparable to a space station module or shuttle payload of 14 feet diameter by 45 -60 feet long. In my Access to Mars presentation, there is a good list of all of the heavy stuff you would want to use at a Mars base, unless all you want to do is take a few pictures and go home. The other issue is that you do not want the crew to have to do a lot of assembly from small parts into large objects. They will not have the time.
Even though Mars has less gravity, 25 tons is close to the minimum mass to return to orbit with a crew. You do need 4.1 km/sec to reach low Mars orbit. In my re-usable Ferry, the crew is in a 5 ton crew cabin/capsule on top of a vehicle otherwise massing 120 tons, but it also carries a payload of 20 tons of fuel up to orbit in its oversize tanks, of which it uses 15 tons to land again with another cargo item. With just a crew cabin (an expendable vehicle), and no other payload, the ascent vehicle could be small as 25 -30 tons, but you still have to land it first! On Mars, the 125 ton Ferry ready to take off weighs only 47.5 tons (38% gravity).
The deciding factors are the fuel mix, the minumum payload size (the object you want to use on the surface), the landing method and the structural mass of the lander/ferry.
No, the only deciding factor is the flight rate. If you want to get anywhere anytime soon, you probably need to design a Mars reference architecture that does not land more than 5 tons at a time on surface, and thats an absolute maximum.
That means that any passengers will never get home.
This is a totally unrealistic limitation.
Right now we could not do this even for an unmanned mission such as a sample return mission.
We still need basic technology development, and it is being starved due to the SLS and other wastefull efforts.
John
That means that any passengers will never get home.
No, it absolutely does not.
Think about it for a while, play with different on surface staging strategies, supplemented by Mars orbit and various Lagrange point staging strategies. The limitation of being able to land only a few ton chunks on the surface at a time does absolutely not mean that you cannot get back home.
TO MPM:
I am not sure which time period you mean by “right now’, but surely with no budget for payloads, we do not need one right now (in the next few years). In the best of all possible worlds, payloads and boosters would be funded simultaneously, so that the booster was available when it was needed.
However, I suspect that Musk or someone will create one anyway, and that once it is created, we will be able to take advantage of it. The only question is how long will the SLS continue to steal money from the ccdev and other time-critical programs?
In fact the Marsh-Braun 2009 paper DOES cover a depot:
“An in-situ supplied propellant depot in Mars orbit would allow a mission architecture in which the spacecraft refuels after insertion into Mars orbit. In this approach, the vehicle would travel to Mars, use its Earth-based propellant to insert into Mars orbit, and then refill its tanks at the Mars propellant depot before initiating the fully-propulsive descent to the Mars surface.”
My approach for the initial series of landings is exactly the same. However, the first landings carry down the ISRU equipement and a reactor to power the system, which starts turning Mars ice into propellant. As soon as there is enough propellant, a cargo ferry returns to orbit for another payload. When a crew hab is buried, a crew Ferry comes down the crew starts work.
The ISRU component is critical to the system working.
I fully agree that we “want to see a large and fiercely competitive propellant launch market as soon as possible.” Note that the cargo vehicles to take the propellant to the L1 point would need to be have depot-level insulation. I will read up on some of the orbital mechanics tricks that you are describing. It is more complex, but with a “pipeline” of fuel being supplied to the depot at L1, such a system could work and save mass an delta-V. I am not sure if there are counter-tradeoffs that would make it an even choice or not.
The Ferry architecture is designed to land sufficiently large objects so that they can be used without significant assembly , except for the fuel plant which would be a package plant able to be connected together by robots. The system is optomized to reduce cost, propellant and delta-V. Methane-LOX will not do the job, nor will narrow based expendable landers. To afford to continue to operate the SYSTEM, you need a reusable lander. The wide-based lander also allows long cargo items to be carried close to the base of the lander where they can be off-loaded easily by robots. The work to define this system began in June 2010 and got input from a bunch of others including some well known rocket scientists and engineers, who I will not mention on-line.
The use of the no-heat shield, narrow based, expendable lander negates all of the work and thinking that went into the Ferry design and would result in a flags and footprints only Mars program, specificaly the scenario we want to avoid by creating the Ferry as an example system. With a structural engineer and a professional trajectory simulator, the design could be improved considerably.
I am confident that by the time we are ready to design Mars landers a wide HLV will exist that can boost them into orbit. the HLV can boost a payload roughly 50% wider than itself, so an 8 meter HLV could launch a 12 meter base vehicle.
We want a wide base Ferry and wide aeroshells for the other vehicles going to Mars to allow them to use aerocapture. Otherwise, as March and Braun (2009) note:
“the burn to transfer the vehicle from the hyperbolic approach to the 400 km altitude circular orbit requires approximately 2.5 km/sec of V. This results in a propellant mass fraction on the order of 50% for the orbit insertion burn. If all of the needed propellant is to be transported from Earth, the baseline vehicle with a mass of 60 mT in Mars orbit grows to over 350 mT at Earth departure.”
This would drive the cost sky high and prevent an on-going Mars exploration program.
Hopefully when my technical paper on the Ferry comes out a link to it will be posted in my blurb on the NSS web site: http://www.nss.org/about/bios/strickland.html
John
Hi John,
I really like our conversation. Do you guys have some sort of forum where we could discuss these things?
I am not sure which time period you mean by “right now’, but surely with no budget for payloads, we do not need one right now (in the next few years).
I meant not even for Mars missions with reusable landers.
Note that the cargo vehicles to take the propellant to the L1 point would need to be have depot-level insulation.
Not necessarily, the propellant can be launched straight to an L1/L2 depot or even delivered directly to the MTV, as Huntress proposes.
The Ferry architecture is designed to land sufficiently large objects so that they can be used without significant assembly , except for the fuel plant which would be a package plant able to be connected together by robots.
I agree with this goal, and I think you are saying 20mT (or 3.2 fully grown elephants as NASA likes to call it) payloads would be enough. If so, I agree. I still don’t think this requires a lander with a dry mass over 20mT itself, nor that the lander should be capable of landing its return propellant. A reusable lander with 4.1 km/s delta-v should be able to land itself propulsively without needing a wide aeroshell. Refueling can take place both in LMO and on the surface.
Methane-LOX will not do the job
Probably not the way you are imagining it to be used, but it could if you refueled both at the surface and in LMO.
The use of the no-heat shield, narrow based, expendable lander negates all of the work and thinking that went into the Ferry design and would result in a flags and footprints only Mars program
But that’s not what I’m suggesting. My goal is to have both a meaningful long term exploration program and commercial development of space, and I don’t see that happening without RLVs and I do see an HLV getting in the way of RLVs. If the HLV is a commercially developed FH or EELV Phase 1 it could be less bad, but I still think it’s unnecessary and it would be good to know for sure either way.
I too have thought about this long and hard and I believe I’ve come up with a scheme that does not require an HLV. You could even make do without aerobraking, dedicated depots or even without any cryogenic propellant transfer, although the latter stretching it for Mars surface operations, though not for Phobos / Deimos. Still useful as a reference scenario te help you assess the value of various technologies.
If all of the needed propellant is to be transported from Earth, the baseline vehicle with a mass of 60 mT in Mars orbit grows to over 350 mT at Earth departure.
This still ignores SEP and ISRU as well as RLVs. And remember that the whole idea is that if you have enormous launch costs initially that will lead to quicker development of RLVs which will allow substantially lower cost even at substantially higher IMLEO. The argument is not so much that Mars needs RLVs, but that commercial development of space requires them and a Mars exploration program can provide them. Not all that different from using a Mars exploration program to fund HLVs if you think about it, but RLVs are enormously useful to commercial development of space while HLVs aren’t useful at all, at least not for the foreseeable future.
The NSS site has no reader column for posting replies to articles since it would require a site moderator and our volunteers are already stretched thin. One result of such work is the revison of our web site header as you may notice. The NSS Directors have their own discussion listserver, but a lot of the discussion does go on right on the sites that actually publish original articles or create links to them like this one. This site does make it very easy to reply to other poster, facilitiating a conversation.
The NSS blog has postings but no response post capacity.
http://blog.nss.org/?Referrer=http%3A//nss.org/
Some of my articles on the NSS site are under Space Transportation.
Links to more can be found under my blurb under (about).
It is too bad it is hard to trade email addresses on a public site.
(No Insulation) Even for a fast liquid fueled transit from LEO, this means at least 3-5 days of boil-off during the transit. The mass of the insulation would be much less than the mass of the fuel that boils off.
Remember that some of the landed objects will be BULKY rather than just heavy. We need a good sized cargo bay that can carry insulated propellant storage tanks for the depot at the surface base, pressurized rovers, habitats, etc. Since the Ferry has oversize tanks for taking its descent propellant UP, it is less dense coming down than other designs and therefor slows down more from passive drag. This is a synergistic design.
“I still don’t think this requires a lander with a dry mass over 20mT itself, nor that the lander should be capable of landing its return propellant. A reusable lander with 4.1 km/s delta-v should be able to land itself propulsively without needing a wide aeroshell. Refueling can take place both in LMO and on the surface.”
Dry mass = 30 tons (24% of dry mass on liftoff ascent)
Fuel mass (descent – 15 tons) (ascent – 75 tons)
payload (descent – 25 tons of cargo) (ascent – 20 tons of fuel)
NOTE: the ferry could not land its own ascent propellant, as the payload is 25 tons and the ascent fuel requirement is 75 tons. The reverse IS possible, as the 20 tons of propellants carried as payload on ascent are used 15 for descent and 5 to refill the depot in orbit. No ferry can take off again until the surface fuel production is running and has produced at least 75 tons of fuel. Ferries must be able to withstand the Mars surface environment, but they do have an aeroshell and hull around their internal components, unlike the rovers.
“Probably not the way you are imagining it to be used, but it could if you refueled both at the surface and in LMO.”
If you refuel in LMO, this means you are using fuel brought from Earth. This would only occur during the bootstrap phase before the surface fuel was available. The whole point of the design is to become independent of any fuel brought from the Earth at great expense.
The smaller boosters would be used in a great number of flights to bring up smaller cargo, crews an propellant to store in the depots in various locations. Having a private HLV should not detract much from the launch volume for the medium sized boosters. One poster here wants to use 1 ton capsules. This means we would be sending astronauts to orbit in chunks. We do not have nanotech yet that can re-assemble a person from chunks!. The same is true of the lack of cheap manpower in space to assemble integral vehicles from chunks.
Note that I do not want an HLV unless it is a reusable HLV !
We do need some kind of HLV for Space Solar, large telescopes, work areas in orbit to service vehicles in a pressurized envioronment, etc. These all take a wide airlock/mirror/transmitter element array, etc which cannot be easily assembled from chunks in orbit.
I have backed the idea of an electric drive tug to move cargoes from LEO to GEO and other cis-lunar locations for years. Howver, we would need a much lighter energy source to use electric for fast Mars transit missions.
It would also make aerocapture very tricky – as any solar array would need to re-fold itself behind a large aeroshell Otherwise the system would need to spend more months spiraling in to LMO.
John
It looks as if our goals while not identical are perfectly compatible. If you ever have the time I’d love to discuss this on the new SpaceRef forum, but we all have to choose what to do with our limited free time, so I’ll understand if you have no time for that.
If you refuel in LMO, this means you are using fuel brought from Earth.
If so, probably by SEP and perhaps by SEP + RLV. But it could also be from Phobos / Deimos. Or eventually from the moon or Ceres. All of these would be perfectly acceptable, even in the long run. Not that you’d have to stick with them forever, it’s just good to know it wouldn’t be a dead end. And it’s an approach that is designed to rely on as little new technology as possible and delegating as much of the transport infrastructure and R&D to the market.
Note that I do not want an HLV unless it is a reusable HLV !
Same here, but it’s a much more ambitious target and unnecessarily so, with propellant making up the bulk of IMLEO, especially if you deliberately design things that way.
We do need some kind of HLV for Space Solar, large telescopes, work areas in orbit to service vehicles in a pressurized envioronment, etc.
You overstate the case, this can all be worked around. A servicing area could easily be unpressurised using inflatable sidewalls (like a bouncy castle), in fact an unpressurised hangar would likely be more useful. Telescopes can be folded or assembled.
Howver, we would need a much lighter energy source to use electric for fast Mars transit missions.
True, but only using SEP for propellant initially and eventually including dry cargo would be good enough. And more than good enough once we have RLVs. I agree it would make aerocapture trickier, but I’m trying to avoid relying on that. Note that this differs from avoiding it completely. It would like to leave all infrastructure and R&D issues to the market. If aerobraking propellant is more cost-effective than using SEP, then that would be fine with me.
I will check out the Spaceref forum. I have had several articles published there.
The big point of the surface production of propellant is that you can use essentially existing equipment, as all the steps are already being done on Earth every day. You just have to modify the steps to operate in 38% gravity and a much colder environment. If you use fuel from Phobos, you first have to develop all of the microgravity equipment to convert the water in the rock into LOX and LH2. This could take decades to perfect. Turning ice into it in a gravity field is much easier.
Until communities exist on Mars, exploration will primarily be funded (if at all) by governments, but the vehicles should be designed and built by private companies. There are no minerals on Mars known that would be profitable to ship back to Earth so there is no profit motive.
Making everything collapseable is partly what has made the Webb telescope so expensive and so risky since it has to deploy all of the folded up parts. There are cost trade-offs every time you try to reduce the mass and size of a payload.
John