How would using a giant rail gun to propel a rocket into space fare?
This would be equivalent to taking the best thing about conventional rockets and replacing it with the worst possible alternative!It isn’t a bad idea at all to have a Rail-gun like launch system, wherein the entire setup providing the energy to the rocket is external and doesn’t need to be dragged along or compromised at any point. You impart gigantic amounts of kinetic energy to your rocket and launch it like a bullet into the air.But the problem lies in the air! The closer you are to the ground, the denser air is, the more drag it will generate.Consider swimming for instance. The faster you move your hands, the more resistance you face. Air is also quite similar, only worse, when you are at very high speeds.But air density is only significant for first ten kilometres or so.Conventional rockets build up speed as they go up, passing through the atmosphere at lower speeds, and facing less resistance as they further speed up at higher altitudes. Rail launch will do the exact opposite, higher speeds at low altitudes.Suppose you need to shoot your rocket straight up till Low Earth Orbit (200 km altitude). Using the ideal gravitational energy relation:[math]GmM(1/{r_1}-1/{r_2}) = 1/2mV^2[/math]we get a required launch velocity of 1950.89 m/s, roughly Mach 5.8. The structural and thermal loads on the rocket will be immense.Here’s a missile (highly aerodynamic compared to a rocket!) simulation at Mach 3 at Sea level for comparison:Shock formations, a pressure of 10 atm at nose and temperatures in excess of 830 K on the surface. Compared to this, a rocket at Mach 6 will definitely have to go through hell. Even if the structure somehow, miraculously survives, the shocks and temperature rise will dissipate most of its energy into atmosphere, and the rocket will not make it much far.Also, Everyone Dies!
If a gun of a mass of 40kg fires a bullet of a mass of 0.01kg, with a velocity of 400m/s, then what is the recoil velocity of the gun?
The momentum is equal for both. SoM(gun) * V(gun) = M(bullet) * V(bullet)SoV(gun)=M(bullet) / M(gun) * V(bullet)= .01 / 40 * 400 = 1/10 m/s = 0.1 m/sA 1 m (39 inch) barrel length implies an acceleration of 80,000 m/s2D=V^2 / (2*a) → a = V^2 / (2*D)= 160,000 / 2 = 80,000 m/s2V = a*t → t = V / a= 400 / 80,000 = 1 / 200 second = 0.005 sThis means the gun is accelerated atV = a * t → a = V / t= 0.1 / 0.005 = 20 m/s2And is displaced byD = 1/2 * a * t^2 = 0.5 * 20 * 0.005^2= 0.00025 m = 0.25 mm
What is your favorite gadget of 2018?
Hands down, the Apple Watch 4.Quoted directly from Apple’s website:Series 4 represents a fundamental redesign and re‑engineering of Apple Watch. From the curved corners of the larger, all‑new display to the architecture of the S4 chip, every detail has been thoughtfully considered. Apple Watch has always been a uniquely personal product. And now it’s even more powerful.The display. It’s one of the most elegant looking displays you can find on a smartwatch. It uses a technology on the top of the OLED called LTPO which improves the power efficiency of the device, allowing you to get 18 hours of usage on a single charge despite a smaller battery in a thinner chassis.Digital Crown. This small tiny crown has been made 30 percent smaller than previous generation yet includes 21 more components.ECG feature.This is my favourite feature of the Apple Watch 4. The ECG(Electrocardiogram) feature isn’t just there for kicks and giggles. It actually works as intended and is accurate!S4 chip. A groundbreaking, revolutionary chip with a 64 bit architecture and dual cores, it provides 2x faster performance to it’s predecessor, the S3. Let me show you something.Ok we may not have an Apple Watch benchmark, but holy shit I can do 60fps physically-based Metal rendering and realtime physics on the Series 4 ? pic.twitter.com/GXza08pgIP— Steve Troughton-Smith (@stroughtonsmith) October 2, 2018Even after performing the above CPU-intensive task, it uses only 64% of the CPU itself!The developer also mentioned to get such performance, he needs an iPhone 6S or newer which just blows my mind to even think how fast the S4 SiP(System in package) is!Overall, this was my favourite Apple and tech gadget of 2018. There were many other that did blow me away like the Oppo Find X, the Vivo Nex, OnePlus 6T, Mate 20 Pro and as such but no other device had me as fascinated as this.Hope that answers your question. If not, I am a message/comment away.Signing off,~Waleed~Links: Apple Watch 4 User Discovers A-Fib Heart Issue Through ECG FeatureApple Watch Series 4's processing power will blow you away | Cult of Mac
What is the Hyperloop? How does it work?
Elon Musk's revolutionary hyperloop is proving to be the future of travel.But what is a hyperloop?In Musk’s words, a hyperloop is a system to “build a tube over or under the ground that contains a special environment.” Cars would basically be propelled in this tube. One example could be a huge sort of pneumatic tube where high-speed fans would compress and push the air — although the friction implications make Musk skeptical that it would work. Another option is having a vacuum in the tube and using electromagnetic suspension instead. Musk acknowledges it is hard to maintain a vacuum (one small leak in hundreds of miles of tubing, and the system shuts down), but there are pumping solutions to overcome this. He favors the second solution.What Is Elon Musk’s Hyperloop, And Why Is It Important?How does it work?Hyperloop has four key features.1) The passenger capsules aren't propelled by air pressure like in vaccuum tubes, but by two electromagnetic motors. It is aimed to travel at a top speed of 760 miles per hour.2) The tube tracks do have a vaccuum, but not completely free of air. Instead, they have low pressure air inside of them.Most things moving through airtubes will end up compressing the air in the front thus, providing a cushion of air that slows the object down. But the hyperloop will feature a compressor fan in the front of the capsule. The compressor fan can redirect air to the back of the capsule, but mostly air will be sent to the air bearings.3) Air bearings are ski like paddles that levitate the capsules above the surface of the tube to reduce friction.4) The tube track is designed to be immune to weather and earthquakes. They are also designed to be self-powering and unobsrtuctive. The pillars that rise the tube abobe the ground have a small foot-print that can sway in the case of an earthquake. Each of the tube sections can move around flexibly of the train ships because there isn't a constant track that capsules rely on.And solar panels on the top the track supply power to the periodic motors.With these innovations and completely automated departure system, Elon Musk dreams of the hyperloop being the fastest, safest and the most convenient form of travel in the world.Source: Tech InsiderScience of the Hyperloop