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The real problem with the ARM ("asteroid redirect mission") is that it's not an asteroid mission, it's a lunar mission. The plan (such as it is) is to use a small unmanned vehicle to go out and grab an NEO (not a main belt object) and bring it back to the vicinity of the moon. They think they can do this with something resembling the few probes sent out there, but they're wrong about that, and such vehicles are NOT being developed.
Once the NEO is near the moon, then a moon rocket with a reprise of Apollo's capsule is adequate to go and look at it. The mission is only a week or two long, you can do it with nothing but a moon rocket and capsule, and you don't need a lander to visit an NEO. SLS is what a Saturn 5 looks like if built from shuttle-era technology in the congressional districts where shuttle stuff was built. Orion is quite literally Apollo-on-steroids, an Apollo design scaled up for crews from 4 to 7.
I disagree that shuttle could have continued as a still-safe vehicle. Shuttle was never safe, it was always an accident-waiting-to-happen, driven there by arbitrary budget constraints. Every time they fixed something, they made it worse (SRB joints case in point: you NEVER EVER use multiple O-rings in a solid motor; if it leak checks OK at 5 psi, it'll hold at 5000 psi). Plus, the airframes were reaching fatigue end-of-life sooner than expected. Plus the avionics were so obsolete they were reduced to obtaining spares off Ebay.
You can easily recognize when an outfit is serious about manned travel in deep space from the crewed habitation design approach. It will have artificial gravity-by-spin, it will have a solar flare shelter (and they won't use cosmic ray exposure as an excuse not to go), and it will have plenty of properly-arranged space in which to stay sane. The ISS fails to fill the bill researching these issues, on all three counts. It comes the closest on space-to-stay-sane, but Skylab was the real "standard".
And no, you don't need a giant rocket to launch all this stuff at once. We have already learned how to assemble things on-orbit from docked modules. That's how we built ISS. The difference is, we can now launch those modules for $2000-3000/pound instead of the $30,000/pound we were paying with shuttle.
GW
This is an example of only one way (out of a gigantic plethora of ways) that ground truth can be so vastly different from expectations and remote sensing results. Sometimes we shoot ourselves in the foot out of ignorance, as described below. Other times, Mother Nature shoots us in the foot by refusing to conform to our expectations , measurements, and theories. Either way it happens all the time. The smart mission planner takes this into account as a failure he assumes will happen.
GW
Copied off MSNBC news on the internet, from their “Science” section:
Curiosity's experiments on Martian soil may be inadvertently eliminating traces of organics, British researchers reported this week. One of the compounds the rover is on the lookout for is jarosite, a mineral associated with conditions potentially suitable for life. Curiosity tests for jarosite and other interesting substances by flash-heating soil samples, watching for telltale signs of certain elements.
Tests conducted by a team at Imperial College London show that this heating process may cause the jarosite to break up and give off free oxygen — which can then destroy organic compounds in the soil. Essentially, the testing method could eliminate what it's looking for in the process.
I have no clues about calculating such things from first principles. I do know that zirconia makes a semi-practical material, good to about 4000 F (near 2500 K).
There are some rare-earth oxides and carbides that have been identified as "ultra-high-temperature-ceramics", or UHTC's. The best of these will go to around 7000 F (near 4000 K). These are heavy, have some structural strength in shear and compression, seem resistant to thermal shock, but conduct heat in copious quantities. They're nose tips, not insulators at all. You have a truly enormous backside heat removal problem with them.
Remember my alumino-silicate heat shield paper in Denver? I'm looking pretty closely at fibrous zirconia in porous forms now, for another combustor insulator job. The problem is structural: nobody makes a zirconia cloth as coarse as the alumino-silicate fire curtain cloth I used so long ago, which resembled boat cloth in fiberglass work. The problem is also porosity for low thermal conductivity, the antithesis of structure, unfortunately.
I am iterating toward a two-layer/two-material approach, trying to get the 4000 F temperature resistance of the zirconia next to the fire, and the structural strength of the alumino-silicate composite on its backside, where things are much cooler. What works as a low-conductivity combustor insulator might also work as a retro-radiating refractive heat shield, if surface-coated black.
GW
The best data I have on Titan says its atmosphere has a very tall scale height and a surface pressure greater than 1 atm. You should use that for aerodynamic deceleration all the way to a parachute landing. They did with Huygens probe. The velocities involved are quite low, because of the weak gravity that gives rise to the tall scale height. Heat protection isn't the governing issue the way it is here. There's a bit of drag loss on the ascent, but again, gravity is weak and orbital/escape velocities are quite low.
Biggest problem with Titan is Saturn's gravity well. And for men, the travel time just getting there.
GW
This ISRU thing also leads back to an orbit-based mission with multiple landers exploring multiple sites. If you do that the first half of your stay at Mars, you can find the site where your ISRU is most effective in terms of actual ground truth. Remember, ground truth has always been at variance with remote sensing, everywhere we have ever sent probes.
The second half of your stay is where you land everything and everybody at the "best" site (likely the one sitting on top of the buried glacier, where you can mine water with hot water down a simple well). Put your base complex there, where it can succeed, and either mothball it or leave it running on automatic when you leave. I say that, because I really do believe there will only be one government-sponsored mission to Mars. It'll get cut off just like Apollo. If the base is there, visionaries like Musk will go back sooner.
If you have an orbit-to-orbit vehicle that can keep a crew alive for the long transit, why throw it away for the return? That vehicle could take crews to any destination inside the main asteroid belt, including the NEO's. So, re-use it. Build and launch the one, use it to visit the many places.
We keep iterating back to that 1950's concept of a orbit-to-orbit ship(s) plus landers, when we look at these issues from first principles, unconstrained by who has been building what. Because it has made sense for half a century now.
I hope Musk builds his giant rocket. Think $500/lb to LEO in 100 ton modules. Not the $1000/lb with 50 ton modules to LEO with Falcon-Heavy. Not the $2500/lb with the current commercial launchers in the 10-20 ton class to LEO.
GW
I think I read somewhere that the barge was 370 miles downrange for the first attempt.
GW
The "bad guys" I was referring to were not our arguing friends. But that's a valid point you make.
That image of a Boeing lander model looks surprisingly (maybe not so surprisingly) similar to what I got for a single-stage lander concept. Except that I made mine conical for streamlining during ascent, and easy heat protection during descent.
Mine was one-stage, though. I had both pressurized and unpressurized spaces in it. The idea was to "camp out" in the lander during the surface stay. I did use a small self-landing capsule as a control cabin/bail-out lifeboat. Something like a Dragon.
Bail-out capability only makes sense if you have a back-up lander with which to attempt a rescue. But if you do have multiple landers, it becomes a moral imperative.
GW
There aren't any "real NASA NTR engineers", and never were. The actual smarts were (and still are, to whatever extent they haven't died, retired, or gone on to other jobs) in the contractors that NASA hires, in just about any topic area you wish to discuss. Talk to the guys who actually did Project Rover, culminating in NERVA. There's 3 left, all in their 80's now. I did. What you say about NTR simply isn't true. Yep, it has unresolved problems. But it is NO dead end.
As for engineering art in chemical rocket work, yep, it's still there. Still about 40%, even in production work, just like I said. Less to do with the rocket engines themselves now (although Orbital Sciences might disagree with that!!!!), and more to do with successfully flying supersonic vehicles that have to stage.
Ask Spacex; they had real troubles with Falcon-1, until they finally talked to some of us old guys about that. That was somewhat of a humbling experience for them, and it's still a subject they do not like to discuss in public. But they did learn, and well. So far, anyway. But, they do not like to hire anybody over 40-45 years of age. Sooner or later, that art thing will bite them again, precisely because they don't like old, experienced hands on staff.
GW
RobertDyck: it's probably not wise to post things like the last two sentences in the previous post. It gives all sorts of bad guys way too many ideas. But BTW, I actually do remember Davy Crockett. There was another version of the same thing that used a 75 mm gun mounted facing rearward on a speeding jeep. Same problem, too: range < fireball radius. I think it was called Mickey Mouse, but I'm not sure of that after so many decades.
Quaoar: to answer your earlier question to me, I only had in mind two broad categories of gas core thermal engines. Those are open cycle and closed cycle. I'm not familiar at all with something called "saltwater" somewhere just above. I've been outside the industry for 2 decades now (one of those industry "consolidations" got me, where they fire half the workers, keep all the upper level managers, and live off the backlog for about 3 years until they can bail-out with their "golden parachutes"), making it very hard to stay abreast of things.
The closed cycle idea had a "transparent" wall between the uranium plasma and the propellant flow, so it was often called "nuclear light bulb. The open cycle depended critically on some sort of flow scheme that would retain the uranium in preference to the propellant, with a uranium residence time just long enough to achieve effective nuclear burn-up.
There were a great many variations on both ideas. In all of them, greater reactor power levels correspond to both higher and higher Isp, and to greater and greater difficulty dealing with the high temperatures.
The most mature technology available for a Mars mission to be built "today" would be chemical propulsion, although I think you could now add solar electric to that, for speeding up the long transits and sending unmanned cargo. No doubt about the chemical, and solar electric is starting to get used in real probes now. It's ready, too.
I think the real obstacles to having sent a Mars mission as long ago as two decades are institutional, not technical. One that most folks don't think about is the handoff of engineering art from one generation to the next "on the job". It doesn't happen anymore, now that jobs are so fleeting, and employees are like grapes ("a dime a dozen"). That's why we as a people keep reinventing the same wheels over and over (the lousy aluminum tires on Curiosity are but one single example).
This sort of "rocket science" stuff really isn't all science, no matter how loudly management types in and out of government and industry giants claim that it is. It's about 40% science (actually written down somewhere, but often lost anyway during all the "consolidations"), 50% art (never written down because management didn't want to pay for that), and 10% blind dumb luck.
And that's in production work. R&D projects are worse: more art and dumb luck, even less science. Mounting a manned Mars mission is most definitely NOT production work, precisely because we have never done it before. The moon trips just were not in the same league.
GW
NASA was founded to develop new technologies. So obsessing about TRL is contra-productive.
I quite agree with Robert about that. When NASA was formed in 1958, it had a front-burner reason-to-be of manned spaceflight (what became the Mercury program), plus technology development issues to address for both spaceflight and aeronautics. Most of the stuff that went into Mercury was not technology development, which is why they were able to pull it off in 3 years. Not much development was needed to fly Gemini, but a fair amount was required for Apollo. And that doesn't even count the launch rocket work.
That being said, technology readiness is quite important, whether or not you use that TRL scale to assess it. If you actually intend to fly something, then all the major bits had better be ready-to-apply technologies. History says if you try to develop a major technology during your vehicle development program, your vehicle will never fly.
The argument I see above about SEP vs nuke stuff seems (1) too vitriolic, and (2) kind of pointless. There are at least two versions of electric thrusters already flying successfully. VASIMR is nowhere near that ready. Neither are the other electric concepts, like arcjet.
There are some new versions of solar electric power that are essentially ready-to-apply. Those combined with the fully-ready electric thrusters are ready enough to fly right now, and we should use them for anything appropriate. The sooner the better. The other concepts need technology development work, which we should be doing.
In contrast, "gas core nuclear thermal" is nowhere near ready for much of anything yet, because almost none of the work was ever done on it. It could have been, and still could be. And I say it should be. There's at least two wildly-different versions of gas core, too.
The nuclear explosion drive was essentially frozen by neglect at its 1959-1965 state of the art. That was essentially ready for its first experimental flights, and so it still is today, if we elect to use obsolete fission device technologies. Better devices could be built, but that's necessary technology development work first. It could have been done, but wasn't. It should be done.
The solid core thermal includes NERVA and several variations of it that were identified as improvements, some experimentally at one level or another. All this died in 1973, with just a snit of work (by CIA I think it was), circa 1990. Basic NERVA was, and still is, about a year away from first experimental flight. The variations that would improve it, are a handful of years away from flying, given normal technology development efforts. These should be happening, but are not.
Biggest problem with any of the nuclear stuff is not technological readiness (which varies considerably), but suitable test sites. Plume capture with any rocket is difficult, this stuff is far worse. So, why don't we test them on the moon, in the open? No neighbors to bother. And you don't need nuclear to take it there for test. We really could bootstrap our way into this.
The electrics as we know them inherently involve high Isp but at extremely low thrust: a few newtons for a ton of hardware to be installed in many tons of vehicle. Accelerations are inherently very low (typically 10^-3 to 10^-5 gee), requiring the slow spiral-out/spiral-in flight plans, if only electric is to be used. And there's the Oberth thing: really that's just gravity loss accumulated over extremely-long burn times.
For cargo long flights and radiation exposures are not objectionable, generally. I think what we have learned says those really are objectionable with human crews. Which in turn says the manned vehicles need high-thrust rockets for arrival and departure burns, and electrics to speed up the long transits. Or, you ferry the crew out to the electric vehicle after it gets clear of the Van Allen belts, which means more launches.
I think a properly-balanced space program would be spending at least something on all of these things, trying to get a wider variety of technologies mature enough to apply to each mission. I haven't really seen that done since the early 1960's.
GW
Didn't I see a news release yesterday that IVX flew successfully out of Guiana?
GW
It looks to me that the lease of the old USAF pads at Canaveral means Spacex really does mean to pay the propellant load penalty for launch site fly-back in Florida. That will reduce payload a bit, unless they already "built that into" their rockets.
Meanwhile, they are building a privately-owned commercial launch site at the southern tip of Texas, right on the Gulf coast, also for eastward launch like Canaveral. There are islands in the Gulf and Caribbean that could serve as real dry-land recovery sites, with min recovery propellant cutting into payload.
As far as I can tell, any polar stuff will go out of Vandenburg in California. Not sure what they intend to do there for any recovery (no islands southward of Vandenburg, that's abyssal plain Pacific floor out there, 2.5 miles down), but as far as I know, their polar stuff is only Falcon-Heavy stuff for USAF. Pricing benefits from recovery may not be that much of an issue for USAF. I think Spacex has a pad already built for Falcon-Heavy at Vandenburg, but I'm not sure about that.
They are building Falcon-Heavy facilities at Canaveral, and from what read, the South Texas facility will handle both Falcon-9 and Falcon-Heavy. I'm guessing that a bit extra payload for otherwise the same cost will be their "draw" for the Texas commercial launch site.
The only other thing I heard was that the new future giant rocket that some call the "Mars Colonial Transporter" will fly out of the Texas site. If so, it will have to be built in Texas, probably on site, as its stages will be far too big to ship across country.
GW
I don't know the escape trajectory payloads for the big version of SLS and for Falcon-Heavy. But the LEO payload ratio ought to be similar. SLS is around 100 to 130 tons, Falcon-Heavy 53 tons, to LEO. That's about 2 or 2.5:1.
If you just price the direct launch costs for your mission's tonnage on a unit payload mass, assuming you are flying full, Falcon-Heavy is unit priced around $1000/lb. What that says is SLS unit costs should be no more $2500/lb to launch the same tonnage for an equal total launch price, same total tonnage.
I don't believe anything published about SLS says the cost will ever be that low, in any of the configurations. And NASA's history has been to underestimate costs. Some of things I saw suggested $4000+/lb at about 100 tons to LEO. So why fly that launcher unless there is some really, really-compelling reason to launch individual payload units that massive?
That being said, why not break the Mars mission payloads into smaller modules that Falcon Heavy could fling, and do it that way for less launch cost money? 2 SLS launches would equate in tonnage flung to 4 or 5 Falcon-Heavy launches, depending upon whether the flung tonnage ratio was 2 or 2.5.
The key to actually achieving the savings with the smaller but way-cheaper commercial launcher is being able to break your payload items into the 53 ton increments. (That's a different technical design constraint, which may lead to a different design approach.)
Do that, and your direct launch costs will go down. But it does require that you think modular during the design processes, and it may mean orbital assembly instead of a direct shot to Mars. Hard to say, until one is actually doing a real design.
Why is the smaller commercial launcher so much more cost-efficient than NASA's Congress-mandated SLS? Because the supporting infrastructure (mostly the human headcount) is about 10 times smaller, and (also very important) the development schedule was a lot shorter. That comes from having to be competitive in the commercial launch business.
All mission designs are inevitably "sub-optimal", being entirely constraint-driven. That's just life. Inappropriate constraints lead to untenable results, though. That's also life.
I recommend we take off the constraint of political pork driving mission architectures and hardware selections, and just look at what you can do with what you already have in the way of launch rockets, within the lower cost constraint that commercial cost efficiency allows. I think the results will pleasantly surprise anyone who actually looks.
When the launch business needs a 100+ ton launcher, the participants in that business will come up with them. That's future, and probably 20 years out. Why let that delay going to Mars? We're flying up to 20 tons to LEO right now at $2500/lb, and soon up to 53 tons at costs as low as $1000/lb to LEO.
We built ISS out of items in the 10-15 ton class, and mostly at $30,000+/lb to LEO in the shuttle. We don't have to suffer costs like that anymore. Why should we take a step back toward a more expensive launcher? Just because it flings more tons? We don't have to do that.
So far, I have NOT seen the really, really-compelling need to only fling 100+ (to LEO) ton items (or whatever the numbers are for a direct trajectory).
GW
Oil platforms require a bottom to rest upon and be anchored too. If you go far enough offshore, past the edge of the continental shelf, the bottom is unreachable at over 2 miles down. In deep water, a self-positioning barge is the only answer.
To return the stage all the way to launch site requires a lot more propellants. They're already burning off a load just to ease the atmospheric entry speed (that's the 3-engine apogee deceleration burn) and control the fall (that's the long 1-engine burn) with supersonic retro propulsion now.
Stage recovery propellant cuts into payload, but not as much as my first intuition would have suggested. The powered landings they want to do just might be survivable at their low inert mass fractions. Chute landings in the ocean not.
GW
My point is that none of that is yet known, and must be explored thoroughly, before lives and fortunes get bet on this stuff. Promising as it seems to be.
Recent history: the beta-phase formable titanium alloys ultimately did not pan out well. Turns out they age at room temperature. Not so very useful after all.
GW
"America is not the world" -- true enough. But stereotypes don't work either. America is a huge and diverse place. Not all Americans live in cities of various sizes. While a small percentage, a huge number of us live rural.
As I do, on an operating small cattle ranch. And further from "average", this is Texas, which really once was a whole 'nother country. And yet most of you by now know I have a heavy-duty aerospace engineering background with 2 decades industry experience.
For me living out here on the ranch, the nearest town is 5,000 people. The "big city" a bit further away is 200,000. If you count all the incorporated suburbs. It's a hundred miles (160 km) to any really big city areas. And yet that tiny town of 5000 is where Spacex does its testing.
So, how non-stereotypical is that?
GW
What that article really says is that they solved a fundamental science problem with adding aluminum to a steel melt (controlling where the iron-aluminum mix crystals form). What they have not yet done is solve the other practical problems with a new material. In fact, the article only identifies one such practical problem: some way to prevent the contamination that ruins the properties. They have no solution yet for this.
And, you can bet there will be a whole host of other practical problems, apparently yet to be identified. There always has been a plethora of practical problems with new materials, so there always will be. Things like how does it respond to heat? How does it respond to repeated loads? Does it change properties with time and / or low heat? Is it heat-treatable for properties control, or not? Is it hot- or cold-workable for properties control, or not? How does it respond to extreme cold?
Don't look for this stuff in Mil Handbook 5 any time soon. There's an enormous amount of work to do yet.
GW
I'm thinking a solid rocket to near-circularize, plus a small hydrazine thruster to "fine-tune" the circularization. Both technologies can be adapted to very high gee. I personally have worked on solids for 5000 gee+.
The launcher is a tube floating semi-submerged in the mid-Pacific. You "fuel" it with hydrogen and oxygen gases.
GW
Unconventional ways to LEO: what about that light gas gun launch of gee-hardened stuff? Last time I saw anybody talk about it, they were talking under $100/lb to LEO.
GW
If harvesting CO2 is the goal, you can do this better on Mars (or even from smokestacks here on Earth). On Mars, the environment is nowhere near as harsh, and the gravity well is not as deep. On Earth, the environment is benign, and the gravity well is not an issue. So, I echo Quaoar's question: why go to Venus? What is there to do at Venus that cannot be done elsewhere and easier?
The only answer I currently have is satellites looking outward from about the orbit of Venus, with infrared, to far more efficiently find asteroid threats to Earth. We don't need the planet to do that.
GW
Arguing about this vs that is not a good thing, as vitriolic as this conversation became. All those propulsion ideas deserve serious attention in a balanced program. Some are readier-to-use than others, in some cases by enormous margins.
I rather like electric propulsion for unmanned cargo, in spite of the flight times. Spiraling is a real problem there, that and the gravity-loss penalties. But cargo doesn't care. Doesn't get radiation-sick, doesn't go psycho from confined boredom, doesn't eat or breathe.
You simply can't leave Earth that way with men, because you spend weeks in the Van Allen belts, when days will kill you.
To utilize the advantages of electric with men, you need to put both electrics and conventional engines on the craft, and use both. You simply have to do impulsive dV's at Earth departure and arrival to limit radiation exposure times crossing the belts. At Mars, you could spiral in and out, iff you can afford the extra flight time. ("iff" = "if and only if")
The real advantage using electric with men is faster transit times between parking orbits. You can build up speed efficiently to midpoint, and then efficiently slow yourself back down. That cuts transit time very significantly. 1 month's thrusting at 0.001 gee adds up to around 25 km/s. Whether that's realistic at all for a mission I do not know. But numbers anywhere near that class are very impressive.
Immature things like gas core ought to be worked on, with an eye to making them mature. Those need not be huge money-pit projects, either. Wise outfits always invest in longer-term R&D as well as the short-term stuff. Only the foolish outfits insist on funding only near-term-payoff R&D. Too bad the fools outnumber the wise by such huge margins, in and out of government.
I don't know if VASIMR will ever pay off. No one does. But you have to try to find out. That's just life. VASIMR is no further along than it is because of poor funding, like so many other things. I agree completely that there are at least two other electric schemes that are readier-to-apply. And it sounds like the solar power thing to power them is just about ready, too. That's a good thing, and I'd like to see it used ASAP.
Beyond the asteroid belt, we're going to need nuke electricity for our electric propulsion schemes. Today those are still kinda heavy for the power. Sounds like some R&D needed there.
If nuke propulsion is objectionable to test here on Earth, then do it on the moon. Good reason to go back: build a testing base. There's solid core NTR, gas core NTR, and explosion propulsion, that I know of. Explosion is probably the closest-to-ready, followed by a decent solid core scheme. All need work to make them ready for when we do need them. And eventually we will.
We need to do some more supersonic-hypersonic retro-propulsion work, too. What Spacex has done so far (Dragon and Falcon 1st stages) is marvelous, but there is more to do before we fully understand how to really do this reliably. We're going to need it for practical Mars landing boats.
GW
Interesting. I had forgotten about this one.
I've seen a lot of things like this over the years. That's an awfully-detailed WBS and cost model for nothing but a speculative concept study, and at that a concept never tried before. That's why most of those things died on the vine: too much accounting and not enough engineering, too early in the process.
All space capsules have the aerodynamics of a brick. A refrigerator isn't mass-coupled enough. That's OK, a capsule doesn't have to lift much, just slow down. The propulsive landing approach has since been vindicated by Spacex, of course.
GW
I like RobertDyck's mission plan. That's about the minimum mission that makes any sense at all. Anything less is flags-and-footprints nonsense.
I think all 4 could have paramedic training, which sort of makes up for sending only one biologist/doctor, enabling us to send the geologist. It makes no sense not to send a geologist.
Here's my concern, and it is based on a gut-feel assessment of government behavior over the last 4+ decades. I think there will be one (and only one) government-sponsored/funded mission to Mars. No followups at all. Not ever! That's where Robert and I differ fundamentally.
Any subsequent missions will be funded almost entirely by visionary private/commercial entities (and there are precious few of these). If the base ain't there, I doubt they go, anytime soon. Even Musk.
That means you do absolutely as much as you possibly can, in that one first government mission. Period. Not worth going otherwise. And that extends to precursor missions to Mars orbit. Do that, or land. Not both. Never happen.
My other concern is picking exactly the right site for the base before we go and get some ground truth. Ground truth has always been different from expectations and remote sensing, since the very first probes. That's just history. Expecting different is foolish.
That ground truth effect is why I'd like to see multiple sites visited before we build a base. But that's inherently not a minimal mission! You have to base from orbit to do that for the first part of the stay, until you select your "best" base site.
"Best" is defined in terms of the ISRU techniques that work most productively, and every site will differ in that measure. "Every site is different". That's been another truth we have known since the dawn of time, even here at home. To ignore that is also foolish.
Somewhere between those extremes is the (one-and-only) mission we can really afford.
GW
Pencils, plain or mechanical, always break off pieces of the lead. These are smaller, harder-to-see-and-recover items with mechanical pencils, even here on Earth. In space in zero gee, they float about the cabin, not noticed. Until it gets in your eye!
Even in a spacecraft with artificial gravity this will be a problem, because every so often, you have to go back to zero-gee. All the debris becomes a hazard at that point, including pencil lead bits.
So, all-in-all, today the modern zero-gee pen is a better, safer solution. Early on, the pencil (risks and all) was OK, because that's all there was available.
That being said, I still admire "KISS" thinking (keep it simple, stupid).
GW
I guess in the sense that if it develops lift at all, you could call it a "space plane", wings or not. Most lifting bodies have terribly-poor lift characteristics once subsonic, though. That really needs real wings.
GW