Racescort666

What you describe is sort of how VTEC works, other manufacturers have different technology that does similar things but Honda had the patent on their system. VTEC is probably one of the less expensive methods to implement variable lift as well so that probably explains why it's stuck. StrandedonEarth does a pretty good rundown of engines below so there's a more detailed discussion down there. The main takeaway is volumetric efficiency. Most of the tricks to get air in and out of the cylinders is improvements to volumetric efficiency. With variable valve timing, it affects things like cylinder scavenging, the exhaust gas leaving the cylinder can pull the intake air into the cylinder as it leaves. The efficiency of this depends on engine RPM and the amount of valve overlap so they change valve overlap to adjust how much scavenging they get in a particular engine across the RPM range. There is a lot more going on than just scavenging though, valve timing can also affect how the air interacts with the plenum volume and intake runner length. Butterfly valves can be used to adjust both by blocking or adding another passageway/volume depending on engine RPM and load. Not all engine management is for performance though, sometimes they add VVT to help with low RPM emissions. It's hard to know without being involved in the development though. Do you mean overhead valve (OHV instead of OTV)? I've usually called them push rod motors since overhead cam (OHC or SOHC/DOHC) also have the valves over the head to avoid confusion. This is in contrast to a side-valve/flat head engine (images below). Yes, push rod engines have an advantage due to their compact arrangement. Theoretically, they should be worse at higher RPM because of having more reciprocating mass in the valvetrain but drag racers and NASCAR don't seem to have an issue revving them out to 9k-10k rpm. Side valve engine (exploded view): Regarding small blocks, if we're going to be pedantic... Only Chevrolet ever made Small Blocks. Ford retroactively started calling several of their engines "small blocks" since they compete with the Chevy engines. Since Ford Small Block refers to more than 1 engine family usually you have to be specific of which one. These would be the Windsor and Cleveland engines mostly but sometimes other ones get thrown in the mix as well. Chevrolet also had a line of Big Block engines which are distinct from the Small Block; namely, their bore spacing is 4.84" vs the SBC 4.4". By the nature of aftermarket, there is a bit of overlap in the displacements of big blocks and small blocks so displacement isn't really what determines if something is a big or small, it's really just a specific engine family. At this point, I should point out that Ford Big Block is a term that gets thrown around a bit too but that also refers to at least 3 different engine families of which, very few parts are interchangeable. The 60s-70s were weird times for the US auto manufacturers. The last thing I want to say is that I hate, HATE, HATE Engineering Explained. He's right on a few points but misses the mark by a wide margin and every time I watch his videos, it's like watching peak dunning-kruger effect in action. For example, every video he does on suspension: It's like listening to the cashier from Autozone who learned some buzzwords and can make a techy sounding presentation.

Since we're talking about intelligence agencies and not an autonomous vehicle start-up nor a village in Iran, I will ask who those organizations are? Maybe it puts me on some kind of list just for asking or the answer is "those who need to know, already know."

Bellcrank, although I would have called the quadrant you linked a bellcrank as well.

What is the transition speed/mach number from friction heating to compression heating in aircraft/spacecraft? @ARS, you should play World of Warships, excellent battleship duels. It is worth noting that historically, hitting the conning tower (bridge during combat) is bad but not totally fatal to a combat ship. Hitting the magazine on the other hand, well, HMS Hood went down in 3 minutes after the Bismark hit her in the magazine and only 3 men survived.

So a little bit of poking around regarding stainless steel, Alro sells 304 stainless that meets AMS 5513. "Aerospace grade" is vague at best so AMS 5513 is probably a good reference point but when it comes down to it, SpaceX is buying enough steel for this vehicle that a mill would probably make them their own grade. Anyway, Alro sells drops (left over pieces) that are around $5/pound. So maybe they're getting down to $3/kg but that's quite the jump. Also, the only thing that really makes it "aerospace grade" is inspection and certification. Hypothetically, without the inspections, a material is just as good but you can't guarantee that. @sevenperforce regarding the tank volumes, I screwed up the spherical cap volume. I didn't include the tube but my estimated dimensions are as follows: Spherical cap: a: 9 m, h: 1.71 m Upper tank cylinder length: 5.3 m Lower tank cylinder length: 4.1 m Fuel tank: 451 m3 Ox tank: 261 m3

Gotchu fam: Upper Tank (fuel right?): 778 m^3 Lower Tank (oxidizer): 261 m^3 I may have screwed this up but I used my tried and true scaling the picture in powerpoint technique.

+Z is up in the construction orientation, not the flight orientation. Kinda makes sense to me. Although -X is usually the direction of travel for me.

Hopefully the select "control from here" on the command module before hitting space bar.

He's making a fusion bomb.

Considering that Oxygen and Methane are liquid at approximately the same temperature, I'd say it improves simplicity.

Back when I was playing KSP every day I would confuse KSP view controls with Solidworks/NX view controls

They fall because they make poor decisions:

This sounds awfully heavy, unless you're building a... oh...

Well, I didn't think I would come across a paper like this but here we are: https://www.diva-portal.org/smash/get/diva2:893827/FULLTEXT01.pdf I seem to remember Travis Pastrana and/or Ken Block talking about using the brakes/gas to control attitude of a car in the air but I can't for the life of me find the video. The short version: it absolutely is a thing; although, as stated, it's much more pronounced with motorcycles (like in motocross/dirt bikes).

I just read that and immediately thought of this thread.

Yeah, I remember Kazaa and Napster...

I use the phrase “the difference between screwing around and science is writing it down” pretty regularly at work. So I figure it’s fitting that the origin of that phrase be shared here: https://www.tested.com/art/makers/557288-origin-only-difference-between-screwing-around-and-science-writing-it-down/?sf204908632=1 Testing can certainly be tedious but it can also be rewarding and fun. Most importantly, professionally, it’s for a purpose and if you do a poor job collecting data, it’s just a waste of time and money.

Bummer, I will be busy tomorrow during the launch window. "non-optional social event" that won't have tvs or laptops.

Well, that makes the decision on which launch to watch easy.

I could see the drive away from using hypergolics though. Partial insertion/circularization is done after a 6-ish hour coast, which isn't that long considering. According to this paper ULA experiences 1.0%-2.6% O2 boiloff per day. So I don't think that carrying the extra 0.5%ish of LOX would be as big of a performance hit as using a solid or hypergolic kick stage. Not to mention the added complexity of another staging event and hardware. Even the fact that the second stage is way overpowered at that point, carrying a little extra fuel (if the tanks are big enough) for partial insertion/circularization would be worth it.

Sounds like the dude is straight up BA. He must be Jeb’s cousin or something.

@tater that was very interesting. I love hearing Tory Bruno talk about rockets, that dude know his stuff. I know Elon is a bit of a favorite around this forum but Tory knows his product line backwards and forwards. He's also under no illusions that SpaceX does certain things better than ULA but I think they are in a good spot for delivering a lower risk launch vehicle.

You have a typo there, the SSME is the RS-25 which was developed from the HG-3 which was supposed to be a performance improvement over the J-2. The RS-68 was developed as a cost effective engine to be used in expendable launch vehicles thus its use in the DIV. It doesn't really have much in common with the RS-25 other than fuel. Construction is different (channel wall of the RS-68 vs tube wall of the RS-25), the RS-25 is completely regeneration cooled while the RS-68 has an ablatively cooled nozzle, RS-25 is staged combustion while the RS-68 is gas-generator. They maybe incorporated some "lessons learned" from the RS-25 but I wouldn't call that derived from.

I see this frequently as well. It will be fiberglass -> plastic (piece part cost save, yay!) then plastic -> fiberglass (warranty cost save, yay!). Sometimes cost save ideas are really good and/or confusing and sometimes they're not well thought out and end up costing more in the long run. And you're right, sometimes vendor contracts dictate why designs end up being a certain way. I can think of several parts off the top of my head that haven't changed in many years because they're locked in at a contract price that's favorable.

Something I found interesting from that article: For reference, the Atlas V 411 that OSIRIS-REx launched on was around 55 m tall.