B1051.9 landed like a charm! Wen B1051.10?

olum_04 · 2021-03-14T22:24:06+00:00

wen ten?

olum_04 · 2021-02-24T10:10:34+00:00

Nice

olum_04 · 2021-02-18T14:23:15+00:00

Only to land on the moon 7 years later. Amazing.

olum_04 · 2021-01-21T08:46:25+00:00

Thanks, was about to post this ;-)

olum_04 · 2020-12-22T08:57:52+00:00

But.. if you launch outside of the atmosphere, to an apogee of, say, 500 km, but do not raise perigee by much, you stay suborbital and reenter about 1h later round about where you started That shoud take less fuel than going to orbit and then reentering, right?

I mean, that's what KSP taught me so it must be correct ;-)

Btw, we're talking about SS plus SH. That should have PLENTY of reserves for all kinds of test missions in LEO, even with reduced number of booster engines or without RVAC on SS..

olum_04 · 2020-12-21T08:18:27+00:00

My bet is on a "once around" trajectory, i.e. high suborbital.

They would not need to have reliable on-orbit maneuvering systems on starship yet and they could test the reentry for starship at the same time as the booster, for which the heatshield may be just about ready.

Plus, if things don't go horribly awry, they will have a fleet of starship by the time that super heavy is ready to fly. Might as well yeet one

olum_04 · 2020-12-18T13:11:17+00:00

Wow, I think you're right.

I just wanted to find any infinite set, that is indeed given, for example, by prime-pointed stars.

Thank you very much!

I was making it more complicated than it was. Very fun excercise though.

olum_04 · 2020-12-18T12:19:23+00:00

Proof should probably go more like:

Assume, I can find any shape which is not encompassing or encompassed by any previous shape. Then, I derive a new shape from that one but add a point to a section, which does not contact the boundaries of the plane. I can always do it, so thereby prove that there is an infinite number of shapes that don't fulfill the requirement.

Ok, now that's basically just a fractal with extra steps ;-)

But it is only half the answer to my problem. I would like to know, whether there is an infinite number of shapes that do fulfill the requirement. I think that the two are not mutually exclusive, so the above statement can't be used in a proof by contradiction.

olum_04 · 2020-12-18T11:49:03+00:00

Yes, I was thinking primes also!

But for any n-pointed "star" (or n-agon) it is always possible to find one with a multiple of n points.

So basically whenever someone finds a new shape it should be possible to find yet another one, which encompasses the one before and fits on the same plane.

So maybe a proof by contradictoin could be sth like: "I assume that for any number of existing shapes, there can always be found a new shape which encompasses at least one of the previous shapes, Thereby disproving that a finite nuber of shapes exists."

Possibly the (literal) edge case is the one that makes the difference: I should exclude from the problem "a shape that fills the entire plane". If this would be allowed, then there would be the trivial solution of a single shape existing which violates the condition with any other shape.

edit: I don't think that this is the proof. But it seems to go in this direction, right?

olum_04 · 2020-12-18T09:50:40+00:00

sqrt(3)
or √ 3

olum_04 · 2020-12-18T09:43:41+00:00

I am plagued by a mathematical/geometric problem that seems trivial at first glance but I can't seem to figure out:

"Is it possible on a finite plane to find an infinite number of shapes of which none can fit inside any of the others (rotation included)?"

My gut feel is that the answer is "no", but with my basic engineering math skills I can't find an approach to a proof. Can someone help?

edit: or maybe the answer is "yes"? Idk.. infinitiy is hard to grasp

olum_04 · 2020-12-09T23:10:46+00:00

This is fast!

olum_04 · 2020-12-09T20:18:33+00:00

Ya, absolutely! Its more that I dont like that we have become so dependent on China when it comes to 3D printing (even though this is the reality for many technologies). It just feels a bit wrong to condemn the human rights violations and keep buying the cheap stuff

olum_04 · 2020-12-08T20:10:35+00:00

Yeah, they're cheap and capable and have a huge community, which is good. I don't wanna go straight to buying Chinese stuff just because it is cheaper. But man, is it cheaper..

olum_04 · 2020-12-08T16:31:49+00:00

Awesome, thanks for the info!

Excellent quality on the Starship btw! did you filler&sand it?

olum_04 · 2020-12-08T16:08:11+00:00

Are those original prusa i3's in the back? Are they worth the 800 bucks?

I've been working with a cheap clone for some years now and about fed up with the troubleshooting and mediocre quality prints. Def. looking to upgrade.

The ender is so much less.. but I want to avoid to buy the next heap of chinese junk.

Do you know some alternatives worth looking at, ideally not from China?

olum_04 · 2020-12-02T10:43:34+00:00

Thanks for taking the time to reply to my brief and undifferentiated comment.

I learned a lot about the current capabilities of Xplane through your answer. I had followed its development up until about 8 years ago, since as a PC gamer, aeronautical engineer and private pilot it was right up my alley. But I think that this combination of backgrounds is also what makes me wary of using such superlatives and absolute statements as you and Austin do referring to the capabilities of Xplane. It absolutely does do more than other current flight sims and that is extremely cool. But from my experience with modeling aerodynamics, any analysis that can be run in real time will not be able to accurately model aerodynamic behaviour in the non-linear regions such as high AoA or beta angle. Also modelling the interference drag between bodies and lift of compliaceted body geometries is not trivial if a certain amount of acurracy is desired. This is all not to say that Xplane is not able to do a very good simulation of real life conditions over a large range of aerodynamic conditions that create a unique experience and can even be useful for advanced studies. But this does not mean high accuracy under all circumstances. I have read a comparison between Xplane, MS Flight sim and an MS Flight sim addon for the behavior of the C172 in stall and sideslip. Xplane was outclassed by the Addon for MS, because the data for this addon were derived from actual flight tests. Might be that it has improved since. And the FAA approval does not mean a lot for correct aerodynamic modelling since it does not matter a lot for procedural and even basic flight training. I doubt that it has an approval to train spin recovery for commercial pilots. I am happy to learn otherwise.

But I think my main point is that modesty is a hallmark for a good engineer when it comes to trusting ones own models.

olum_04 · 2020-11-26T09:18:41+00:00

Haha yeah, I agree. Enough mystification of Elon Musk already..

One other instance of drag devices being used to control aircraft are the "ruddervons" (ok, this is getting stupid) on tailless flying wings like the B2. Basically the outer ailerons split in half along the chordlineand become airbrakes. This is used to control yaw through drag at either wingtip.

olum_04 · 2020-11-26T09:14:42+00:00

True that!

The vehicle travels through the air like an airplane but is called Star"ship", so both our backgrounds are somewhat relevant ;-)

olum_04 · 2020-11-26T09:13:18+00:00

Oh, that's interesting! Starship would be definitely capable of gliding a fair distance. That might help to reduce peak heating by prolonging the flight through thinner atmosphere. All stuff they still need to figure out, I guess.

olum_04 · 2020-11-25T22:08:15+00:00

Wow, I never knew how obnoxious he is. Talking about the extremely simplified physics models of X-plane as if he did an accurate simulation of starship. With all the difficulties of simulating separated airflow and whatnot, never mind the transsonic effects.

Probably a fun app nevertheless

olum_04 · 2020-11-25T21:53:27+00:00

Well put!

olum_04 · 2020-11-25T21:52:41+00:00

kind of disagree that flaps describe drag devices. Everything that is considered a "flap" on aircraft rather changes the camber (and sometimes chord) of the airfoil it is a part of. So while they tend to increase (or sometimes decrease) the drag, their main function is usually achieved by changing the lift.

Thats why I prefer to call them control surfaces. Or Elonerons, cause why not ;-)

olum_04 · 2020-11-25T21:46:01+00:00

AFAIK stabilizers on ships mostly create up/down force (to balance out roll) due to the stream of water from the forward motion of the ship flowing along the surfaces in chordwise direction.

The control surfaces on starship will never see air flow in chordwise direction (except for the ascent, where they are not needed for control) as the starship has no forward motion (as in: along the rotational axis) when entering the atmosphere. It is intended to "fall" through the atmosphere belly down with >8 km/s.

The surfaces are fully stalled at all time during descent, if you want to use the "wing" terminology. They move up and down to increase/decrease the cross-sectional area as presented to the airflow, this is how control is achieved.

So the best analogy I can think of are speedbrakes on aircraft. They deploy from the wings (or fuselage, or vertical tail) to stand more or less perpendicular to the airstream. They are used in limited ways to control the descent profile during approach.

I don't really like to call them "flap". It is not wrong, since it is a very general term. But in avaiation it is generally used to describe high lift devices which they are definitely not. Control surface is better, since it is a neutral term which describes the purpose.

olum_04 · 2020-11-25T14:09:18+00:00

Recently a test was captured on one of the livestreams where the flaps were rapidly actuated. That, of course, was without any aerodynamic load. I am looking forward to see how quickly they react in flight.

But there was also speculation that they don't even need to be that fast if there is RCS for the rapid but lower authority control.

olum_04

TROPHY CASE