Funding and Development Priorities Post-Orion, Post-SLS

kbd512 · 2015-03-20 18:47:06

I would like to know everyones' thoughts on what funding priorities should be in a post-Orion, post-SLS world. I think it's pretty clear that there's not enough funding to use either of these two systems and that both are monumental wastes of the tax payers' money. Moreover, it is precisely because Congress is forcing NASA to fund these two spending projects that there is no money left for the hardware required for space exploration.

If these two make-work projects can be de-funded, here's what I think the funding priorities should be:

1. Assist SpaceX with completing development of their flyback rockets to reduce the insane cost of getting to LEO

2. Initiate a deep space transit vehicle program that provides some measure of artificial gravity for extended duration missions

3. Properly fund closed loop life support development

4. Start work on a man rated SEP propulsion stage for the deep space transit vehicle

5. Properly fund development of EDL technologies required to land on Mars

If we are ever to extend our presence beyond Earth, I believe these technologies are required to achieve that goal.

RobS · 2015-03-20 20:34:59

I certainly would defund SLS, which is a colossal waste of money and a sad example of pork barrel spending by the US government. I'd start by having NASA purchase more inflatable modules for LEO, to stimulate Bigelow's efforts and make it easier for industry to buy them. I'd direct NASA to pay industry to build an inexpensive lunar lander that could be used by industry as well as governments, and inflatables suitable for lunar surface use. If Musk can build the Falcon 9, Falcon Heavy, and the unmanned Dragon cargo craft for about a billion dollars, it would not be difficult for him to develop a translunar injection stage launched by a Falcon Heavy and a lunar lander for a billion or two. The result of these two programs would be the following:

1. The beginning of commercial and industrial development in LEO. This would stimulate demand for launches and allow Space X to develop reusable rockets by itself (no need to subsidize the effort). Indeed, subsidizing any space development artificially strikes me as a bad idea. That's what has caused launches to be expensive in the first place. Stimulating demand and some competition is the better route.

2. Increased interest in non-governmental flights to the moon. This would stimulate the widespread use of the Falcon Heavy and open up a market for the bigger booster Space X wants to develop. It would take humans beyond LEO routinely. It would stimulate creation of more autonomous life support systems.

3. All this would stimulate competition with Space X. United Space Alliance and Europe would have to replace their Atlas, Delta, and Ariane families with new generation cheaper vehicles or go out of business. The same with the Russians and Chinese. We can already see this with Lockeed's proposal for the Jupiter tug and exoliner cargo module. Other companies than Bigelow would start producing inflatables.

From these developments, I think we would naturally see the creation of LEO fuel depots. Then what else do we need to go to Mars? A methane fueled Mars descent/ascent vehicle, ideally single stage and reusable. I can't see why Space X couldn't develop such a vehicle, 10 years from now, for a billion or two; they will have the experience by then in methane engines and in autonomous landing systems. An inflatable interplanetary transit vehicle could be derived from LEO inflatables, for which there would be considerable experience. Martian surface inflatables and vehicles would be able to build on the heritage of lunar equipment.

The trick to make this happen within the NASA budget is to develop all these things the same way the commercial cargo and crew transportation system to ISS was developed. Space X spent 1/12th as much money as NASA would have to build its Falcon and Dragon. The launch escape system for Orion alone cost more to develop than the Dragon capsule! The vertical assembly tower for the Ares 1 rocket--which was canceled--cost more to design and build than the Falcon rocket! NASA certainly can go to the moon AND to Mars with its existing budget if it utilizes the talent of American industry efficiently. And why shouldn't it? In the long run, the number of jobs created will be the same, but they will be jobs that actually produce a useful product.

SpaceNut · 2015-03-20 22:02:28

The free ride to do science onboard the ISS is an issue as its 3 billion a year plus, the question is who wants the science done needs to pay so as to move it off from NASA's books.

Second get others that want to go to space to foot there own passage up to orbit or beyond as that is the huge cost of using SLS for a taxi.

Nasa needs to coninue to spur on commercial developement for items that are needed for people to buy in order not only to go but to be able to stay.

RobertDyck · 2015-03-20 23:14:06

SpaceNut wrote:

The free ride to do science onboard the ISS is an issue as its 3 billion a year plus, the question is who wants the science done needs to pay so as to move it off from NASA's books.

That is exactly contradictory to the mandate of NASA. The issue is industry is not able to fundamental science. Fundamental research does not have an immediate application, so therefor has no commercial revenue stream. That means no one will pay for it if government & academia don't. And remember government strongly subsidizes academia, so again it all comes from tax dollars. NACA was created in 1915 to fund development of high-risk/high-payoff technologies for aeronautics. Without that, aeronautics would have developed *MUCH* slower. Industry is not able to fund research unless it is very low risk, and positive return on investment in extremely short time. Industry used to be able to invest in something that pays off in a couple decades, for example a steel foundry investing in a new furnace with lower operating cost, taking out a mortgage, with positive revenue stream while paying off the mortgage, and dividends to investors, but 25 years or more before the mortgage is paid off. Today, industry just can't think that way, they don't understand any investment unless it's paid off within 3 years. That means industry cannot invest in space technologies. NACA dramatically accelerated aircraft development. NACA was morphed into NASA, and that mandate for aircraft technology development remains part of NASA's reason for being. Fundamental research on ISS must be paid by a non-industry source. I agree that launch technology has matured so it should be off-loaded onto industry. Commercial launch services, as well as commercial crew transport and cargo to LEO. However, deep space technology is not mature, so fundamental technologies that are supposed to be developed on ISS are nowhere near ready to off-load onto industry. As for medical, pharmaceutical, materials, or other fundamental research: space station technology is not mature yet.

We aren't even ready to build a permanent, manned base on the Moon. Life support can't even work on ISS without continuous supplies. The urine processor clogged due to calcium deposits. The Russian life support system was nowhere near closed, it used electrolysis of water to generate oxygen. Water from the dehumidifier and urine filtration system was recycled, but absolutely no effort was made to recover anything from CO2. NASA noticed the Sabatier reactor from ISPP of Mars Direct, and used it to improve life support. That helped, but still has not fully closed the loop. We need that before we can build a base on the Moon. Or my preference, a human mission to Mars.

SpaceNut · 2015-03-21 12:39:46

I see that general science is most of what we are doing and not really the cutting edge, R&D stuff that we really need. Sure its nice to see if the corelation of micro gravity to health and aging can be slowed but at some point we need to get commercial industry to pay some of the bill and that happens by getting them access to the orbiting platform. It may even mean that Nasa pays to have them make the module for the station which will be later handed over to the public for use such as a space port shipyard dock to build stuff in.

Repost of thoughts;

Speaking of TV why is there no Nasa TV carried on any local public cable provider or over air free broadcast? You could do a news channel that gives up to date information on all of the missions that are ongoing and a seperate channel for life onboard the station. This way Nasa gets money coming in for what they are doing in the name of science.

SpaceNut · 2016-12-25 23:10:22

The recent methods of outing costs via twitter, rejection of Air force one replacements and pentagon behind close doors may yet yield the possibility of the costs being lowered or at least the tag line would raise...
The American people do need a more commercial space market venue from NASA and not more cost plus contract work. Unobtainium needs to go and we need to start being more cost concious with regards to what we build with.
SLS does have a space flight useage but it needs to be affordable.

GW Johnson · 2016-12-26 15:36:49

There are things that private enterprise does, which they nearly always do better than government. There are other things that they either will not, or cannot, do. Those are what government does best. It's why we invented governments, actually.

Applied research is what business likes to do, because it relates to revenue, and has a shorter time horizon. Basic research is not relatable to revenue, and has a much longer time horizon, so business will generally not do basic research. Even what the drug companies do is more applied than basic, although, of all the business types, they do the most basic.

Yet both applied and basic research are necessary. For one thing, the topics addressed in applied research come from, or are identified by, things previously addressed in basic research. NASA and the other government labs will always have key roles doing basic research.

Much of what is done on the ISS more-or-less falls in the basic research category. Only some is applied, although more could be. In both cases, ISS is the only game in town for doing zero-gee stuff over long times with close human observation. It would be egregiously stupid to ditch this capability. Once it becomes worn out, it would be smart to replace it, before the wear-out troubles kill a crew. Although, maybe in a better orbit for departures than the high-inclined one today.

What is needed for going to Mars (or anywhere else outside LEO) falls more in the applied category. The government labs hire contractors to do it for them, because applied is what business is really good at, better than government.

Several things are needed, although none are absolute prerequisites: prove out the inflatable habitat technology, learn how to transfer propellants in zero-gee/vacuum, including cryogenics, test and prove out new spacesuit ideas that include the MCP we know we will need at least part of the time, test and prove out the new inflatable and foldable heat shield ideas, test and prove out retropropulsive landing technology, test and prove out the newer ideas for life support that include more recycling, test and prove out spin artificial gravity, test and prove out LOX-LCH4 rocket technology, devise bigger electrical power supplies, scale up and prove out electric propulsion for moving big objects, test and prove out means for passive radiation shielding, get started on the R&D for active radiation shielding, and get some bigger launch rockets actually flying.

We could go with what we have right now (actually with what we had by 1995), but the more of these are fully ready to apply when we go, the better, and by far. Ditching SLS /Orion would free up plenty of money to do all of them. Just not the way that NASA and its favorite contractors have operated for the last few decades.

GW

Last edited by GW Johnson (2016-12-26 15:39:50)

kbd512 · 2016-12-27 01:48:20

I would like to see electric lift fans investigated to determine what role that technology could play in increasing delivered tonnage for a comparatively modest development investment and risk, in comparison to a supersonic retro-propulsion development program. I think we've already outlined what technology development is required in the Red Dragon Mars Lander / Habitat thread. Current primary battery and electric motor technology appears sufficient to deliver the performance required, as long as lift fans / compressors can be made to reliably operate in supersonic flows.

Presuming there are no insurmountable obstacles in development, the combination of lift fans and inflatables or deployables maximizes what little utility the Martian atmosphere provides for EDL. The affordability of the alternatives, namely orbital assembly or super heavy lift rockets, seems to be a question that has already been answered- and neither are particularly affordable. Aerospace hardware is typically priced by the pound, and the cost curve is not linear. Therefore, the heavier the solution, the more it costs. If someone presents an alternative that is lighter than electric lift fans, you have my undivided attention. GW and I hashed out what the issues were with parachutes and balloon parachutes, and the more I looked into it the more intractable the problem appeared (to me, anyway).

I see LOX/LCH4 fueled rockets as yet another expensive diversion away from the problem of going there and coming back. Storable propellants are good enough to get the job done and have been getting the job done for many decades now. There is no need to reinvent the rocket, unless the result is a rocket that requires no propellant, in which case we should obviously determine the feasibility of that technology.

MegaFlex, BEAM, CAMRAS, IWP, MOXIE, HIAD, and ADEPT are the technologies that would benefit the most from accelerated development timelines associated with proper funding, as these technologies are nearest to initial operating capability. Thereafter, we must build and test a deep space habitat in space. At this point, I don't care if it's just attached to ISS with a hatch separating the mission crew from the rest of ISS. We need to put all the puzzle pieces together to determine how well they actually fit together.

In another four years, I would like all technology development halted so flight hardware can be assembled and flown to Mars and back (just a fly-by, no landing attempt), simply to prove to everyone that we can do it. Whatever we have at that point should be what we're using. If something fantastic comes along a bit later, then it can be incorporated whenever it's actually ready. In the mean time, I want to focus like a NIF laser on what is minimally required to get the job done, with no diversions for any other purpose. I'm only interested in running the ball down the field. How fast can we get to the end zone? I don't care if we have to fight for every inch. Progress is progress.

GW Johnson · 2016-12-27 13:46:37

I would do your lift fan explorations as part of the generalized category retropropulsion. I have doubts that the same configuration would work in both subsonic and supersonic slipstreams, and I have doubts about practical levels of disk loading in "air" that thin, even at the surface, much less 10 km+ up. Nevertheless, it needs a thorough look.

You only really need LOX-LCH4 rockets if you intend to make propellant while at Mars. That's the easiest combination to manufacture out of the local "air" and whatever ice you can find. Finding ice you can actually process is the weak point in that concept, which makes choosing the right site with massive ice deposits paramount. That's something most folks seem to ignore, but it could easily kill a crew if not done right.

But, LOX-LCH4 is not an untried item. It has been done by both Spacex and Xcor in the last decade. It was tried experimentally decades ago, or it would not show up in my 1969-vintage Pratt & Whitney Vest Pocket Handbook. (They didn't favor it back then because there wasn't yet the LNG technology needed for the support infrastructure. That came a decade or so later.)

We can do it today if we think we need it. The Raptor engine Spacex is testing 6 miles from my front porch seems to be working just fine. The version Xcor tested a few years ago was much smaller and piston-pumped for long life and safety. NASA need not be waited-on to do this. Those companies are already doing the work for their own reasons, and very far ahead of NASA in where they are with it.

The 1000 psia c* figures for the NTO-oxidized storables are hydrazine - 5860 fps, UDMH - 5680 fps, hydrazine-UDMH blend - 5560 fps. Those for LOX-oxidized combinations are ammonia - 5880 fps, UDMH - 6120 fps, hydrazine - 6220 fps, RP-1 kerosene - 6100 fps, LCH4 - 6120 fps, and LH2 - 7950 fps.

The performance potential of the storables and mild cryogens varies only about 9% from lowest to highest. That's the difference between 280 sec vs 310 sec of Isp, at ideal sea level expansion and 1000 psia. LH2 is around 32% higher performing than any of the storables or mild cryogens. But you incur difficulties with low density and harsh cryogen requirements to use it.

Basically, that says if you aren't going to make propellant on Mars, then NTO and a hydrazine blend are likely your best choice. But if you are going to make propellant on Mars, LOX-LH2 is your best choice. Performance is a tad better with the methane, but not by very much.

A better avenue for applied rocket research would be to gain experience with the Russian approach of running the turbopump assembly oxygen-rich, and dumping the entire turbopump stream into the combustion chamber. But we do not have to have that to go to Mars, the moon, or anywhere else outside LEO. What we have will work.

Applied technology development needs to end around a decade before you intend to fly. Otherwise very bad management decisions get made, decisions that bet on technologies which do not pan out in time. Both X-30 and X-33 died from these ills. So if you want to go in 2027, say, then you end the technology developments (or hand them off to some other separate entity) and basically freeze your designs in 2017.

GW

kbd512 · 2016-12-27 19:17:51

GW,

I have no issue with development of new engines if needed to service a requirement. I don't think LOX/LCH4 engines are required to go to Mars. It's just a funding diversion to give rocket scientists something to do. There's real work to do and the real work is making all of these enabling technologies run like Singer sewing machines. The storable propellants provide enough dV capability to get to and from the surface of Mars and that's all that's required for exploration. There's very little to gain from the complexity of long term storage of cryogenic propellants and a lot to loose if the propellants boil off or the propellant plant fails in operation. LoC and LoM don't sit very well with me and you already pointed out those possibilities.

I think our funding and time is better spent refining existing technologies in ways that make them more affordable and reliable. There's no serious argument to be made for switching to LOX/LCH4 to gain affordability or reliability. That means there's no readily discernible advantage to pursuit of less refined propulsion technologies when existing LOX/LH2 + solids and LOX/RP-1 technologies work so well. Every attempt at bleeding edge performance typically has serious cost and complexity issues, not to mention potentially lethal effects for crews if reliability or performance aren't up to par. On that note, I see no reason to take the Russian approach to rocket engine design when it's not required to do what we say we want to do.

I believe any feasible aerodynamic lift or drag system will be the most affordable and reliable system for soft landing on Mars. The requirements that retro-rockets have to achieve for that purpose is so high that reliability will invariably take a back seat to performance. It's an invitation to disaster and I don't want to risk it if it's not absolutely necessary.

In closing, let's push hard to get Falcon 9, Falcon Heavy, and SLS man-rated, put the rest of the puzzle pieces together to see what picture it paints, and move forward with the rest of the program. We haven't landed on anything in living memory and it's long past time to reprise our planetary exploration capabilities to prove, once again, that we have the right stuff.

Oldfart1939 · 2016-12-27 20:55:36

GW-
From my recollection, the new SpaceX Raptor engine is running O2 rich through the turbopump, same as the Russian engines. What really excites me is the possibility of upgrading the Falcon 9 with Raptor engines and CH4-LOX, which may give a significant performance boost; then on to the same upgrade for Falcon Heavy.

SpaceNut · 2016-12-27 23:11:41

The trouble with R&D from the contracts is that it does not care about repeatablility of others to make, costs controls to make it affordable to build and even a time line for commercial implimentation by others...
Just look at apollo manned missions versus space x as it has taken contract to commercial implimentation 50 years.....
Shuttle will never happen for commercial and the closest to one is the lifting body design of Dreamchaser.....
The modules of ISS to cargo was I would say 2 decades and thats only due to the same company which was contracting for them is the same that is still making them for ATK....and not Nasa...

kbd512 · 2016-12-28 00:31:19

Oldfart1939,

You're talking about redesigning the rocket. Even if the thrust level produced was the same, and it's not, there's no such thing as simply swapping out engines. If SpaceX wants to hit that 25t to LEO mark with Falcon 9, they'd be better off using composite tanks to reduce the empty mass of both stages. If even greater performance was still desired, then they should redesign Merlin to use a full-flow staged combustion cycle like Raptor uses. That'd likely defeat the purpose of Merlin as an inexpensive and reusable engine.

The full scale Raptors could simplify the plumbing and thrust structure a bit, but the thrust produced would not match the 9 Merlin-1D's without a third Raptor and there'd be no possibility of first stage recovery unless Raptor is capable of extraordinarily deep throttling. It may or may not be feasible to directly substitute the 1/3 scale technology demonstrator Raptor engines for Merlins. If substitution is possible, then switching to Raptor technology might be beneficial if the cost of the engines is roughly comparable and first stages will be routinely reused.

Oldfart1939 · 2016-12-28 00:51:53

kbd512-

My understanding of the Raptor engine recently tested IS a full scale engine with a significant thrust improvement over the Merlin, and an Isp of 383 seconds in the vacuum modification, and is based on Methylox propellants. Certainly there would be extensive redesign/increase of scale, but that's exactly what's needed for a more than 2 man mission to Mars. My ideal first mission crew size is 7 astronauts.

Last edited by Oldfart1939 (2016-12-28 00:53:31)

GW Johnson · 2016-12-28 12:33:28

My point about LOX-kerosene vs LOX-LCH4 is that there's just not hardly a dime's worth of difference in achievable performance. Look at the 1000 psia c* numbers: 6100 fps versus 6120. No real difference to the overall ballistics of designing engines.

The only reason you would switch to methane is for making propellant in situ on Mars. This is where mission objectives, not technical differences, drive hardware selections. But at the cost of a few percent performance, the long term storage problem is easily solved with NTO-hydrazine blend. That c* is between 5560 and 5860 fps, only around 10% lower.

However, once you have the methane rocket working, and Spacex is just about there with its Raptor engine, it then becomes just another tinkertoy in your bag of tricks. Once that happens next year (2017), the only difference between Merlin and Raptor is that one is smaller thrust and the other is larger thrust. And as I already pointed out, if you intend to make propellant on Mars, methane is the way to go.

So, for the all-storable option, where’s big NTO-MMH engine we need for the lander? Who is working on that? We’re talking about something a lot larger than Spacex’s Super Dracos for a 50-100 ton lander vehicle. Likely 60-70 tons. Metric tons. Even if the vehicle is powered by, say, half a dozen of them. If we are going in the 2020’s, that engine should be in verification testing right now.

The LOX-LCH4 engine is not going to delay anything, I don't believe. It will be habitats with artificial gravity and a radiation shelter, and supple spacesuits, a scaled-up electric thruster (maybe using something besides xenon), and propellant-making technologies (if we choose that path) that delay us. None of that is yet ready enough to go.

Arguments over how efficient the life support recycling is, is the real canard by which bureaucrats want to delay things. This mission could have been done with the 1956 concept of packed expendables only. You just need bigger vehicles to contain the larger weights and volumes.

I wouldn't delay things waiting for Raptor-re-engined versions of Falcon-9 and Falcon-Heavy. As exciting as that prospect is, you go with what you got. If the better thing is ready in time to use, then use it. Just don't count on it. That caution applies to all the tinkertoys, by the way.

What bothers me about the planned Mars missions I have seen since the 1980's is a fixation on Apollo-style mission objectives: just visit one site, plant the flag, pick up some rocks, and come home. And to compound the error, this is preceded by a flyby or orbit-only mission that is almost as expensive, or else a stupid survivalist stunt if kept small.

Columbus and Henry Hudson did not visit just one site on their first trips. Nor did anyone ever sail all the way to the New World, look over the rail without landing, and go home. That would have been an insane waste! And they knew that.

We should learn from that. The point of going is to find out what all is there and where exactly it is, so that later trips can plant bases or colonies that really can self-sustain. Key to this multi-site visit objective is the empirical knowledge that no two sites will ever be alike. They never, ever have been here. Why would Mars be any different?

It's as hard or harder for us to send people to Mars, as it was for them to cross the Atlantic half a millennium ago. If we choose to do this at all, why would we ever visit just one site? No two sites will be alike there, any more than they are here. Why would we ever do a fly-by or orbit-only mission? As hard as this is, those ideas are still totally insane, just as they were centuries ago!

Visiting (and evaluating) multiple sites requires a reusable landing boat vehicle if based out of orbit, or some sort of long-distance travel-and-habitat means if you land at one site. Period. End of issue. This drives your hardware selections and mission architecture, not some stupid throw weight limit, that is essentially arbitrary.

If you do not do in situ propellant production, it makes the most sense to base out of low Mars orbit and use an orbit-to-orbit transport for the manned vehicle (that you use both ways), and separate landers to visit multiple sites. Send return supplies and landing supplies ahead unmanned with electric propulsion. Build a reusable single-stage lander, and live in it while on the surface at these various sites. Bring more than one of them for redundancy and rescue capability. Simple as that.

See how mission objectives drive hardware selection and mission architecture?

It makes even more sense to recover and re-use that transport for subsequent missions to Mars or elsewhere. Why build this expensive thing many times, when once will do so many jobs? Build it big from the outset to accommodate future mission growth (that’s the beauty of orbital assembly, finished size is not an impediment).

That is the thinking behind the Mars 2016 mission outline I posted over at "exrocketman". It's the old 1956 mission concept updated to modern technologies, including rendezvous and docking, which we have had since Gemini half a century ago. And this mission architecture still makes a great deal of sense in that updated form.

If you choose to make in situ propellant, you get something that more resembles what Musk has in mind with his giant rocket/spaceship design. One site has to be pre-identified somehow (that’s the first big weak point!) as the “right” place to put your propellant plant, which I’m guessing stays inside one of the giant spaceships landed unmanned, one-way, ahead of the manned trip.

That site has to be previously verified as having massive buried ice deposits, that can be “mined” with steam down a drill pipe. How you do that with Red Dragons sent one-way, unmanned, by Falcon-Heavy has not been revealed yet. How you tie this source of water to the propellant plant in the belly of that big ship without a crew is also unrevealed as yet. Probably because none of this is fully thought-through yet. But still it could be done. Question: can it be done in time, or must we wait for the 2030’s or 2040’s? I do not know the answer.

You need to make enough propellant for the manned ship to return, and for the rovers or hoppers needed to visit other sites 100-1000 km away (that’s another weak point, those vehicles are missing). The third weakness is propellant manufacture: people die if the plant doesn’t work, or if the site isn’t “right”. That’s because the whole thing depends upon ice mining, as well as the “universal” Martian air.

I think Musk’s plan needs a lot more thinking-through of these issues, but I applaud him and his people for trying to think outside the box. He ditched the launch weight limit with a bigger rocket. Orbital assembly is the other way around that constraint. And Musk does some of that “orbital assembly” by orbital refueling of his giant spaceship.

The other mission plans with their severe weight limits imposed by straight shots to Mars, are just versions of the same Apollo flags-and-footprints nonsense we saw on the moon. Mars is not the moon, you simply must think far outside that box! Or else it is just not worth doing. It’s still too hard to get there at this time in history to waste the trip.

GW

kbd512 · 2016-12-28 15:14:55

GW,

I agree with most of the points you're making, but I still think the best way to visit multiple sites in a single mission is to figure out how to make aircraft fly on Mars. If it's possible to make practical electric aircraft work on Mars, then there's virtually no point on the planet that couldn't be accessed in a matter of hours. More importantly, the same technology that would make powered flight practical also makes soft landing substantial payload tonnages feasible without resorting to dumping truckloads of propellants through a rocket engine. Every kilogram of payload delivered to the surface of Mars has a substantial price tag attached to it, so there's a clear incentive to limit EDL mass to what is minimally required to soft land. I could be wrong, but I think the best way to do that is a two stage supersonic compressor combined with a conventional two or three stage lift fan.

With respect to the LOX/LCH4 rockets, if you have practical electric aircraft to fly around Mars with, then you don't need LOX/LCH4 unless you're trying to deliver a payload heavier than a Space Shuttle to orbit from the surface of Mars. That's exactly what Mr. Musk is trying to do. It's an interesting concept but, much like low yield nuclear explosion powered spaceships, not very practical.

The entire point of the precursor mission I proposed is to prove to everyone that we can, at the very least, send people to Mars and return them to Earth without killing anyone. It's merely a concession intended to alleviate fears that we're sending people on one-way missions with no possibility of return. You don't need to convince me that it's unnecessary and wasteful, but there are quite a few people who believe that sending people to Mars is a suicidal stunt rather than a serious attempt to explore our solar system.

With respect to flags-and-footprints, even with the mass constraints imposed by ordinary heavy lift launch vehicles, it doesn't have to be that way. Powered flight makes a lot of surface exploration not only possible, but practical- perhaps even more so than a crewed surface rover if the objective is to collect samples of whatever looks interesting and then return the samples to a proper lab for analysis.

GW Johnson · 2016-12-28 16:39:10

Well, let's just say I'm skeptical but intrigued by the notion of some sort of aircraft on Mars. Some sort of helicopter would really help, at least up to a few 100 km. But the density is so bloody low, I have to be very skeptical of any sort of airplane or helicopter projects for Mars. You still need very, very low landing speeds not to crash. Almost regardless of the scenario you are looking at.

With densities that low (fraction of a percent of that here), dynamic pressures are minute at such speeds, and you can only build so much area before the square-cube weight growth eats you up on Mars, even at the lower gravity. Aero coefficients are the same there as here, they have no density or pressure or velocity effects in them. Those went to dynamic pressure.

I know much less about helicopters, but small airplanes that land on dirt strips here need to touch down between about 30 and 60 mph to be reliably not crashed by your ordinary pilots. No one has built a large dirt-strip airplane in a lot of years now, but landing touchdown speeds on them (I'm thinking of the B-17) were under 100 mph, even with specifically-trained pilots.

At 60 mph here on Earth at sea level, dynamic pressure is around 9.2 psf, and not-quite-stalled lift coefficients on straight, subsonic wings are about 1.1 or thereabouts, with little or no flaps. (Not much higher with flaps.) Your wing loading W/S is then limited to just about 10 psf max at 60 mph touchdown. Significantly worse in thinner air at altitude or on a very hot day.

For the same touchdown speed on Mars (a simple kinematic requirement to avoid a rough field crash, nothing to do with actual aircraft design otherwise), CL is no different, and the density is about 0.7% that here. Dynamic pressure is then about 0.064 psf. That limits your wing loading to about 0.07 psf, those being Mars pounds at 38% of corresponding Earth pounds, of weight. 100 sq.ft can carry ~7 lb Mars weight, which is about 18-19 lb Earth weight.

Wing structure weight typically is the 0.58 power of aspect ratio. My C-170 has aspect ratio near 7, and its wings (without fuel) weight about 100 pounds (Earth) each. Their total of 200 lb here is about 76 lb there on Mars. Even if advanced carbon composite, they would still be about 30 lb there (2.5 times lighter). Higher aspect ratio might lower that ~10-20% before you push structural limits too far on the materials. Looks like a losing proposition to me. No payload, no fuselage, no power supply, no propulsion. Just the wing.

Why would a helicopter (or any other subsonic lift fan) be any different? They're not different here in any significant respect.

GW

Last edited by GW Johnson (2016-12-28 17:21:59)

SpaceNut · 2016-12-28 20:32:43

To no surprise a quick 1 word search on Airplane turned up these following topics and even helicopter....

Airplanes on Mars
The airplane surface area, angle of attack, forward speed for lift and overall mass air the factors in plane design...

Scouting Mars by Helicopter
The rotor does have the angle of attack, surface area but rather than forward lift being created its upward lift created by tip speed, or RPM.

One man one way suicide mission
This was one option for missions to mars as it cuts mission launch mass from earth and would shift it to cargo instead of a return plus would leave nothing in mars orbit as it would be all on the surface of mars.

GW Johnson · 2016-12-29 17:13:01

I probably should have based my numbers on ~150 sq.ft of wing area, not 100. But it makes no real difference to the conclusions.

GW

SpaceNut · 2016-12-29 17:55:34

Unless we find means to reduce parts used in the helicopter mass we will somehow need to find a way to create more lift.

GW Johnson · 2016-12-30 11:45:50

You cannot find more lift, unless you can tolerate supersonic blade speeds aerodynamically, structurally, and from a lethal noise standpoint. The blade tips on the Tu-95 Bear are just-supersonic at full power, and it can be heard from a shallowly-submerged sub if flying at low altitude. A supersonic prop was tried in the 1950's on an experimental variant of an F-84 Thunderjet. It was not found attractive at all. The Nazis also tried it, and abandoned it, during WW2.

You can add extra blades, but there's interference from blade-to-blade that starts robbing you of your improvements. Conventional wisdom says about 6 blades is max, but I really suspect that number is actually up around 13-15, for a rotational tip speed under 0.9 Mach, and a well-subsonic slipstream. Spin faster or fly faster, and it starts looking like ~6 blades max again.

So, limited to subsonic tip speeds, it is well-known that you want as much of your blade length operating as near to best L/D as you can achieve. That gets you the most disk thrust for the power required to spin it, something very important to a practical design. Best L/D speed is not fastest-feasible speed, it's usually in the lower third of the feasible speed band with more wing-like airfoils, with the exception being the very thin-section (easily-stalled) airfoils out at the tip.

And absolutely none of that known propeller technology is compatible with more than about a 0.8 Mach slipstream speed. Remember, we've had dive experience to just-supersonic speeds with propeller airplanes since the P-38 just before WW2. Props that work sbsonically simply quit working at all as effective thrusters as you hit the sound barrier, because you are spinning subsonic airfoils at vector-addition supersonic speeds, even if the rotational component is still subsonic.

As far as I know, there is no way around that. That "barrier" is precisely why jet engines were invented. They make supersonic flight possible, not some "trick" propeller design.

GW

Last edited by GW Johnson (2016-12-30 11:56:25)

RobertDyck · 2016-12-30 12:54:42

The objective here appears to be bringing the vision from the TV show to life. NatGeo showed a swarm of drones covering vast area quickly to look for resources. If helicopter blades don't work on Mars, could a jet engine? If there's an issue with the CO2 atmosphere of Mars, could a ducted fan?

GW Johnson · 2016-12-30 13:51:54

The lift fan or helicopter problem looks an awful lot like the static performance problem for the propeller. The stream tube is very wide at low speed from which the disk draws air, trending from wide to disk size at the disk plane, to about half the disk diameter at the achieved final exit jet velocity, several disk diameters downstream. That's from actuator-disk theory. Interrupt that exit jet (as with the surface, and you get less thrust.

There's some, but not a lot, of stream velocity at the disk plane. This stream velocity adds vectorially to the rotational tip speed, for an absolute tip velocity that really needs to stay subsonic. You can get away with up to about 0.9 or 0.95 Mach, because the sections there are so very thin. This thinness delays the transonic drag rise to such high speeds.

None of that depends on anything but speed, and speed of sound. The lift and drag forces per unit blade area depend upon dynamic pressure, and the lift and drag coefficients. These get integrated root-to-tip along with the chord length and twist distributions to get the net blade lift and drag. Thrust comes from the axial component of lift. Torque comes from the vector addition of the other lift component, and both components of the blade drag. It's just the geometry, but it gets a bit complicated to book-keep. That's blade element theory.

Technically, you need to simultaneously solve the blade-element and actuator-disk models, to get a reliable solution.

Ignoring any blade-to-blade interference problems, you just add this up for your total number of blades. That thrust, distributed over the circular disk area, is the "disk loading". (Disk loading is what you converge to make the two models solve together.) At max feasible pitch, that's all the lift there is, and it's usually associated with a lot of power (torque), because the max-thrust aerodynamics are not the most efficient. Murphy's Law, but a very real effect. Your efficient disk loading is less; that's where you usually want to fly.

Disk loading will be proportional to some reference dynamic pressure. That means for Mars, at the same speeds otherwise, disk loading is proportional to density, which on Mars is around 0.7% that here on Earth. For a given disk diameter, area x disk loading is all the Mars weight you can hold up. That's Mars weight units, which would be a larger number of Earth weight units, due to the 38% gravity. Earth weight is weight on Mars / 0.38.

What that really means is a disk design that would load to "X" weight/area disk loading here on Earth, will only load to 0.007 "X" /0.38 weight/area on Mars. The low density factor greatly overwhelms the reduced gravity factor. The resulting reduction in disk loading is about 0.02 that on Earth, or about factor 50 times less. That's just way out of the ballpark for what you can compensate with high strength/weight composite materials, which is nearer 2.5:1.

The 48 foot diameter 2-blade rotor on a Bell model 205 helicopter picks up a max gross weight of 9500 lb here on Earth. The same rotor could only hold up about 190 lb on Mars. If you can design around that kind of lowered disk loading (and you'll need a lot bigger rotor diameter and more blades), then helicopters on Mars are feasible.

People looking at little drones flying around here on Earth, then at how similar the landscapes look on Mars to some here on Earth, and then just make the leap to thinking that those same kinds of drones could easily fly around on Mars. They know about the lower gravity making things easier. But few realize just how close to vacuum that "air" really is. It only has significant dynamic pressures at supersonic and hypersonic speeds.

To get the same dynamic pressures we use here, wind speeds have to be just about factor 12 larger there. A 60 mph speed that produces 9.2 psf here at sea level, requires a 720 mph wind speed there. And THAT's the problem with helicopters, airplanes, or lift fans, on Mars. And parachutes.

GW

Last edited by GW Johnson (2016-12-30 13:55:54)

kbd512 · 2016-12-30 14:56:21

GW,

From a review of several modern turbofans and the Rolls Royce lift fan system, the fan blade tip speeds are definitely supersonic. The Rolls Royce F-35 lift fan isn't simply operating near the speed of sound, it's operating well above Mach 1. So, perhaps this isn't as much of a problem as we're making it out to be.

I don't know what the ultimate feasibility of shock compression is and no one will know for sure without experimentation. It's entirely dependent upon whether or not the input power requirements remain within the realm of feasibility. I'm not trying to make something fly in the conventional sense of the word. I'm trying to generate enough thrust to soft land 3,800kg. Is that achievable with supersonic compression and expansion alone, an electrically operated and CO2 powered rocket engine to use a crude analogy, or is some combination of compression and lift from a lift fan stage required?

As I've stated several times before, I'm not an engineer of any kind and I don't know all the formulas related to compressor power, mass flow, head, and efficiency. In the last few days, to the best of my ability, I've taught myself how to calculate these things using online resources. In the same way that I created a little tool to calculate the mass of HIAD, I need to create a little tool to calculate compressor performance. I'll try to do that this weekend. Although I think I know what I need to know now, it would really help to have input from a real engineer, such as yourself. I realize that since I was the one who proposed this, I need to know and be able to calculate these things for myself but assistance would be greatly appreciated.

I try not to post without first having conducted a modicum of research to have some basic understanding of the subject matter. I realize now that I should've done that first, with respect to gas compressors and power requirements, and then posted my findings for everyone else to pick apart.

I have three concepts I want to explore and welcome any input that other posters here can provide.

1. Two-stage lift fan

As the F-35 lift fan system and modern turbofans demonstrate, supersonic blade velocities are not an insurmountable problem. This is the preferred method for generation of lift, as it is the most well-developed solution to the problem. The fan must spin much faster on Mars, but the fan speeds are well within the capability of electric motors to deliver. Lift fans are actually fairly inefficient in terms of power expended to produce a given mass flow.

2. Two-stage supersonic compression and subsequent expansion

In this configuration, a two stage 10:1 supersonic compressor compresses the 6mb atmosphere (at Mars SL) to 600mb (corresponds to a pressure altitude between 10,000m and 15,000m here on Earth), and expansion nozzles exhaust the hot gas at supersonic velocities to provide thrust. This is the least mechanically complicated configuration, but seems to require the most input power.

3. Single-stage supersonic compression and two-stage lift fan

In this configuration, a single stage 15:1 supersonic compressor first compresses the 6mb atmosphere (at Mars SL) to 90mb (corresponds to a pressure altitude of 55,000m here on Earth), reduces the velocity of the gas in the outlet to subsonic velocities in an expansion chamber ahead of the lift fan, and then two contra-rotating lift fans use the compressed gas to generate aerodynamic lift. This is the most mechanically complicated configuration, but seems to require less input power.

The design goals for this project are to generate 46.5kN of thrust, which corresponds to 1.25 * 3800kg. I have also recently reviewed some patents by Babcock and Murray that permit exceptionally efficient use of electrical power. The 1MWe input power limitation I initially imposed does not appear to be a hard limitation, but the primary batteries still have current draw limitations that cannot be exceeded.

Side Bar:

I contacted NASA yesterday to obtain information on their unsolicited proposals process and have also attempted to contact Ramgen. I've been reading NASA's documentation for unsolicited proposals to try to determine whether or not any existing research grants or projects have investigated the use of supersonic compression technology for the purpose I intend to use it for. NASA has done some flow modeling work for Ramgen several years back, but so far as I can determine that seems to be the extent of NASA's interaction with Ramgen.

SpaceNut · 2016-12-30 18:22:36

Please take the lift fan and helicopter to the .. Scouting Mars by Helicopter .. as this is really far of the topic in the initial post....

kbd512 wrote:

I would like to know everyones' thoughts on what funding priorities should be in a post-Orion, post-SLS world. I think it's pretty clear that there's not enough funding to use either of these two systems and that both are monumental wastes of the tax payers' money. Moreover, it is precisely because Congress is forcing NASA to fund these two spending projects that there is no money left for the hardware required for space exploration.
If these two make-work projects can be de-funded, here's what I think the funding priorities should be:
1. Assist SpaceX with completing development of their flyback rockets to reduce the insane cost of getting to LEO

This will happen when space x flies the heavy version with the triple barrel which will mean a new nose for the falcon 9 will be needed and I am sure software tweeks....

2. Initiate a deep space transit vehicle program that provides some measure of artificial gravity for extended duration missions

This is either a tether design, baton spin or something large but in either case its not just a demonstrator of the technology but one with humans onboard for a long duration in order to prove it works

3. Properly fund closed loop life support development

Congression wim, presidential direction change aside it sure would be great to see a strong space program but I do not believe Nasa needs to be totally directing what does get build or done.

4. Start work on a man rated SEP propulsion stage for the deep space transit vehicle

Power sources seems to be the stumbling block after the thruster unit for quick transit.

5. Properly fund development of EDL technologies required to land on Mars

Nasa is working on HIAD, Adept but the other commercial providers need to also step up to the plate for the R&D as well just simply not pay a fee for technology which they may not be able to duplicate.

If we are ever to extend our presence beyond Earth, I believe these technologies are required to achieve that goal.

I do hope that we can go beyond LEO soon and to have something other than the ISS for a destination in LEO to go to.

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