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Archive for the ‘Models’ Category

id Software’s upcoming game Rage uses asteroid Apophis as the scene setter for a post apocalyptic world. (id is part of Zenimax now, which also owns Bethesda, who did Fallout, a similar scene but done with nuclear weapons…)

Is this even close to being realistic? No, because of multiple reasons.

You can check out the list of impact risks maintained by NASA here.

Apophis is zero on the Torino scale. The Torino scale is a balanced impact risk number, from zero to ten. There’s one one on the list at the time of writing. Apophis also has a 270 meter estimated diameter and not a very high velocity, 6 km/s.

We can use the impact effects calculator here for some gauging of what would happen. Even if we assumed it to be dense rock and the impact velocity to be 17 km/s, there wouldn’t be that huge effects (although they could be big locally).

Assuming it hits the ground, at 300 km distance from the impact site you would get a mild earthquake, and a sound as loud as heavy traffic. At 100 km you’d get a stronger earthquake, 6.7 on the Richer scale, and the fireball would be 4 times as bright as the sun. (Still probably no direct skin burns). You would get some sparse gravel ejecta at 100 km which means you wouldn’t want to be outside, but only very little dust ejecta at 300 km.

The main takeaway message is that since the asteroid is so small, the damage would not be widespread. You could not really destroy even two large cities with one. Hence no apocalypse.

If it hit the sea (likely), it could create a tsunami, and that could generate more damage to humans, depending on where it struck (this I don’t know very well), but the Atlantic, Indian Ocean and China Sea are probably very bad. The 2004 Tsunamis triggered by an undersea earthquake killed over 200,000 people.

It’s still very much worth observing and developing technology to prevent large asteroid strikes. It’s just that the public doesn’t seem to have any handle on what the effects are like.

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Assume a glacier that provides summer water for a billion people. What is its value, if it is destroyed by global warming? Since it currently provides services for free, it could be calculated as zero, according to some. Hence, a hypothetical economic activity by those people that gave them one dollar in total while destroying the glacier completely, would be worth doing? That’s suicide economics.

The word VALUE, it is to be observed, has two different meanings, and sometimes expresses the utility of some particular object, and sometimes the power of purchasing other goods which the possession of that object conveys. The one may be called “value in use”; the other, “value in exchange.” The things which have the greatest value in use have frequently little or no value in exchange; and on the contrary, those which have the greatest value in exchange have frequently little or no value in use. Nothing is more useful than water: but it will purchase scarce any thing; scarce any thing can be had in exchange for it. A diamond, on the contrary, has scarce any value in use; but a very great quantity of other goods may frequently be had in exchange for it.

Who’s the radical greenie who wrote the above? Mark Sagoff wrote an essay on stupid valuation of nature’s services back somewhen, where he made the above quote. Find out there, who said it…

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Experts on the Internet

A lot of internet discussion is ignorant speculation, rumor spreading, ranting and flaming. But that’s not all. The freedom and self-organizing nature of enables massive diversity. Newsgroups, mailing lists, IRC, forums, Twitter – and sometimes there’s something there.

Michael Tobis comments on his experience of reading about the Iranian riots on Twitter – way before anything was said in the printing press. Being his usual self, it acts as a motivation for a longer article about the resignation of reporting on important issues (global warming changing earth significantly being Michael’s issue because of his expertise in that).

I’ve long been saying related things  in relation to space issues.  Now, the traditional media defends its views and sheepish forwarding of NASA public facade material as the right way. Maybe some examples are necessary. The aerospace developments of national agencies are full of failures. All ventures have failures. It’s just that aerospace has so few successes – especially rocketry.

What if Nasaspaceflight.com had existed during X-33? NASP is moot here since it was a secretive military project – hence no insight possible there.

Would X-33:s failures and their reasons have been predicted much earlier? Ares I and V had their critics from before day one. Technical critics. Budgetary. Industrial ones.

What is important and makes things different from mere ranting, or “armchair generals”, is that the NASA and ULA engineers provide, on their free time, insight into engineering matters. Instead of the public affairs that the rest of the media reports on. They have a passion for what they do and want to succeed and advance. If they see hopeless technical incompetence at the top level, they will voice their objections – it is practically their duty as citizens.

X-33 – Marching Towards Certain Failure

X-33:s first failure was trying to use very unproven technology (composite multi-lobed cryogenic tanks) in a billion dollar magnitude program. The technology could have easily been proven on a much smaller scale, very cheaply and fast, before starting the whole X-33 project. Competent engineers should have seen that one as a real high risk with easy reduction possibilities. You don’t risk billions just for fun, if you can easily avoid it! You risk it for politics though.

x33_tanksampletests

The table above is from NASA’s tank report (pdf in references), with tests done on tank samples done after the failure, revealing the gross inadequacy of the material for the intended purpose

If, on the other hand, the composite tank was seen as a high risk but not necessary technology for reaching X-33:s goals, then X-33 should have proceeded with the metal tank. In other words, if the composite tank was an optional “nice to have” component. But NASA:s Ivan Bekey testified otherwise – that X-33 had no use without the carbon fiber tank.

All around the X-33 seemed quite big and hugely ambitious on multiple fronts for an experimental vehicle anyway. What were the other objectives besides composite tanks? Could they have been tested in a faster and less expensive vehicle? The metal TPS comes to mind as one. Did it have even the inadequate bench background of the tank? There were military programs from the fifties to the eighties that had developed such things in labs – maybe there was something there.

What about the lifting body shape? The successing Venturestar kept changing shape constantly in simulations and grew big wings. It could very well be that Lockheed Martin and NASA simply didn’t know what they were doing, on any level really, and should not have started building X-33 in the first place. The knowledge base was not at the level to justify going that far yet. The close to existing J-2 derived aerospike engine was perhaps the biggest justification for the size and shape of X-33. But the potential reward of finally getting an aerospike engine flight tested just made the fall that much heavier – the large vehicle necessitated by this turned out to be unworkable. A failure on a lesser scale would not have been as hard. Close to ten years later, no aerospike has yet flown. There have been spike nozzles in hybrids and solids but no aerospikes, where the physical spike is cut off and replaced by a gas jet.

What should have been done to enable the X-33 building?

  • Bench tests of composite tanks (basic, room temp, progressing to multi-lobe, cryogenic). Test cryopumping as well (this has been done somewhat since).
  • Possibly aerodynamic tests with a much smaller vehicle (or generations) as a glider, first released from a helicopter, then an airplane and finally with a sounding rocket. Alternatively with conventional engines. Possibly horizontal takeoff to reduce test costs.
  • Aerospike engine small scale tests. Perhaps contract a smaller company for that, like Armadillo and XCOR have done tests cheaply for NASA methane engines.

If any of these solutions proved unfeasible, then no reason to build the Lockeed style X-33.

The Competitors

Rockwell had a shuttle shaped cylindrical tank vehicle with wings, which seemed pretty simple on the outside. McD had the DC-X growth model. At least both had some heritage in working hardware. There is very little engineering information available about the competitors so if anyone wants to help, drop me a note. Would they have succeeded?

Probably both would have failed as well, in the role of traditional X vehicles of developing new capabilities, mainly because of being too large. Both of the other potential X-33:s would have had a composite hydrogen tank as well (though possibly axisymmetric, even conical or cylindrical), so they could have had similar failure possibilities, though perhaps they would have had a different (sensible) development approach. As is evident from lab tests in the references, cryogenics and composites are hard to fit together.

The Shuttle thermal protection system  is notoriously work intensive, and as far as I know, the Rockwell proposal had quite similar tiles in its proposal. On the other hand, surface loading could have been less since the vehicle had its own tanks and high mass ratio. Also the SSME:s are very work intensive when reused. It was partly more of a rehash of existing technologies, which would perhaps have had moderate chance of success. If it worked, maybe one could try different technologies in it, if it was cheap to fly and could do incremental envelope expansion, while still having high enough performance to really stress test things like TPS or vacuum test less maintenance intensive engines. Heat loads on the composite structure would have been an interesting problem area as well.

McD’s precursor for their X-33 design, the small flying DC-XA program was cut prematurely (after having survived agency changes and funding problems) after a crash from a trivial easily avoidable failure, an unsecured hose. It could have made sense to do DC-XA again, to try the high speed properties, flying at different angles of attack and test the turnaround maneuver that it should perform after re-entry for landing. It would also have made sense to keep in the DC-XA scale and try lots of other solutions in the same vehicle (or fleet). It’s cheaper to test when at small scale. Only when the low capabilities of the vehicle would have been exhausted and good enough solutions found, would it have made sense to move to a bigger vehicle.

Conclusions

All  in all, space is no different from other fields, that rationality is the most effective way to reach sustained progress. It is obvious to any engineer worth their salt that one should retire as much risk as possible, as cheaply and as fast as possible before moving to the big bucks and long development time game.

Sadly, aerospace seems like a hopelessly irrational field in this regard. There are historical reasons for that attitude. Crash programs like Apollo or military ones have left their mark too deep – the field is unable to grow to a rational mature one. It is evident when looking at NASA’s troubled history with manned spaceflight. Since Mercury, Gemini and Apollo, it has not been able to build much incremental progress. STS was a partial success in capability – but it has stifled progress. Everything must always be started over, and at giant scale – making the unavoidable multiple tries very costly, both in time and money, and even utterly shameful in case of failures. A gigaprogram with failure as no option is a recipe, not for sustained progress, but for either a great disaster, or stagnation. A gigaprogram with failure inevitable is waste incredible.

So, the media of today should examine the world in such a perspective. Simplistic “against NASA / for NASA” analysis serves no one. There have been such incredibly farces lately that I’ve had to double check I wasn’t reading the Onion.

I speak for many, when I say, we don’t want delusional Programs, we want rational Progress!

Some sources:

1 Final Report of the X-33 Liquid Hydrogen Tank Test Investigation Team, NASA Marshall

2 Cryopumping in Cryogenic insulations for a Reusable Launch Vehicle, Johnson et al., NASA Langley

3 Proceedings of the RAND Project AIR FORCE Workshop on Transatmospheric Vehicles, Chapter 3: Design Option and Issues, containing X-33 general overview and info about the competitors, Gonzales et al, RAND Corporation

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I think it’s Doug Cooke, presenting NASA things to the panel:

Key exploration objectives slide:

vlcsnap-50143

2. To ensure sustainability, development and operations costs must be minimized

Oh my.

Next thing: [these things] “drives you to heavy lift”. Excuse me?

EDIT:

Of all these goals in the slide, Ares I goes directly AGAINST each, except maybe for point 6, separate crew from cargo. It is mind boggling.

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Ongoing.

Norm AugustineNorm Augustine

You can stream NASA TV with VLC, just paste this link into it:

http://www.nasa.gov/55644main_NASATV_Windows.asx

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2009-06-01 Air France flight 447 crashed with over 200 passengers on board in the Central Atlantic.

At this early point it seems the failure was initiated by severe turbulence. Wings have been known to snap off because of very strong up- and downdrafts. In this case it might not have been so severe, but a failure cascade might have started. Anyway, breakup was high in the air as the debris is scattered so widely.

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This is something I’ve been toying with for a while. A homebuilt single seater. Must be under 300 kg and stall under 20 m/s to enter ultralight regulations in Finland. A HKS 700 engine with 44 kW power would be nice (it’s modern, which is rare in aero engines), though it is quite big and the design struggles to keep the requirements with it.

Modeling with Blender (no landing gear in these models, it will be fixed and tricycle)

Light Version

Light Version

Cruise Version

Cruise Version

One of the design goals is very basic construction. Another is STOL performance. Yet another is that a 190+ cm tall pilot should have comfortable seating.

Aero analysis (just basics, mostly the wings, not the Blender models) with XFLR5:

wdetail

Wing Streamlines Near Flap End

I’ve also toyed with a basic glider “airchair” idea as a starter project and looked at new foils for it to minimize wing size (XFLR5 has inverse foil design which is nice):

Very High Lift Foil for A Low Speed Glider

Very High Lift Foil for A Low Speed Glider

I’ve been exchanging info with Karoliina. Mini-Sytky, KR-1, Cri-Cri, Luciole and MAG-01 serve as the closest examples of similar designs, though there are marked differences.

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I wrote this architecture proposal, FLEX, a few years ago. It analyzes NASA’s approach that the ESAS study picked and notices how most of the mass in a lunar exploration stack in LEO is actually liquid oxygen. By using a propellant depot, the LOX can be lifted with tankers and any launchers imaginable (I wouldn’t use a Pegasus though). The rest of the stack is also naturally divided into about 20 ton chunks: EDS with its hydrogen, the CEV crew vehicle (Orion) and the LSAM lander (Altair).

No new heavy lifters need to be developed, there is enough US, nevermind world launch capability to support a moon exploration program. Launchers can also be improved on the run, because they are not tied to the single use, nor is the use dependant on the single launcher, and because they can fly often, hence improvements are worth the investment. This all could be achieved much sooner and cheaper than the current approach, and is much more robust for the future.

Go read it if you haven’t.

There are some comments at an old Nasaspaceflight.com thread that deal with a lot of the common questions about it.

I really don’t have the faintest idea of the background knowledge level of the readership here so I don’t know how much basics I should give, so feel free to ask in the comments if anything is unclear.

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Pump Power

There’s been some discussion of pump power. It is extremely easy to calculate it when using SI units.

A flow front in a tube has a power:

W=Fv

W power, F force, v speed.

The force is

F=AP

Where A is cross sectional area and P the pressure.

Also,

\dot{V}=Av

Where V is volume so its time derivative is the volume flow.

Thus we can combine these and get

W=Fv=APv=P\dot{V}.

1 kg/s at water density is a volume flow of 1E-3 m^3/s. If pressure is 10 bars, that’s 1 MPa (Megapascal, 1 Pascal is 1 N/m^2) in SI, and thus the power is 1000 W or 1 kW.

1 kW for 90 seconds means 25 Watt hours (I know, I know, this is a horrible unit of energy). With modern LiFe batteries that have 100 Wh/kg energy densities (J/kg could often be more useful measure), a quarter of a kg battery could power the rocket for 90 seconds. With an exhaust velocity of 2 km/s, 1 kg/s gives a thrust of 2 kN. Thus the rocket could be in the 200 kg mass category. The battery mass seems negligible.

Of course, in real life the pump efficiency is a small number and thus plays a big factor, and the pump times are longer too.

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Spacetransportnews has a link to another in the long list of nontechnical space dreams.

Earth’s radius is about 7000 km. The Van Allen belts start somewhat above 500 km from Earth’s surface. Hence, ballistic arcs have to be either very short or then very shallow. And shallow arcs mean high speed. Close to orbital. New York to Paris is about 6000 km. That’s roughly one seventh of the great circle. It is very clear that to travel such a distance ballistically and at low altitude, you need most of orbital velocity. ICBM:s have very high apogees because of this.

The corridor between the atmosphere’s top and the Van Allen belts is so narrow, just a couple hundred kilometers, compared to the horizontal distances, a couple thousand kilometers, that ballistic point to point travel for humans does not make sense.

Nobody seems to recognize this fact. We get vague dreamy projections by even the normally technically hard nosed engineer people in the alt space circles. Wake up. Orbital mechanics wins. Transatlantic point to point is harder than orbital.  Never mind transpacific.

Grumpy mode off…

Word coin: Narrow suborbital ballistic corridor.

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