ment18

A SSTO isn't impossible. Since they are launching at a significant altitude you can use vacuum engines, without doing the stuff rs 25 had to do. Depending on how much Dv they save from high altitude launch and the small forward speed, a significant mass fraction would be possible with engines similar to rl 10s. At 9000dv to orbit, which is probably a bit high, you could get a payload fraction close to 5%. This only accounts for engine and tank mass, so other structural stuff will cut into that severely, and a reusable vehicle borders on impossible due to heatshield mass and wings/landing prop.

Warning: Mostly guesswork I think the main reason is to reduce the height of the rocket. The taller the rocket, the more mass you have to spend to prevent it from being destroyed by wind, so a shorter rocket can be a bit lighter from slightly reduced forces. If the r-7 was meant to launch from a silo, launch size would want to be reduced, so having a small core stage bottom reduces horizontal size and then the expanding top allows for a shorter rocket. In addition, it also allows for shorter additional stages. There might also be something about the force transmission from the booster to the core. With the slight overhang from the expansion, it might make the booster attachment force transmission easier.

I'm interested to see what the power requirements are. Since it will be using molecules much lighter than xenon, it will need a lot more power to produce the same amount of thrust as a xenon vehicle since it will have a higher Isp. Also strange that a vehicle that weighed about 1000kg only had 40kg of propellant, but lost 200kg over the course of the mission?

It is possible to land boosters at extremely high accelerations, just reduces margin for error greatly. The changes suggested are all extremely large, complicated, and expensive. You can't just stick a second engine on the bottom of a vehicle, it greatly changes all the forces going through the vehicle and the entire structure of the bottom of the vehicle such as plumbing. Secondly, the rocket would loose half its payload, meaning you can only launch 1 sat at a time, halving the cost target you need to reach. Restarting engines is extremely far from trivial. Until a few years ago, supersonic propulsion was a big deal, and SpaceX is a private company so it doesn't share stuff. SRBs have nothing to do with man rating (Atlas V, Shuttle). SpaceX said it cost them about a billion to develop retropulsive re-usability, so it would probably 2-5 billion for Europe, which is not remotely acceptable for them. Also no throttling means landing is basically impossible. Can't correct for anything.

Making long range lasers is not easy, you still have to focus the beam correctly, which takes significant hardware. The best time to target something is the booster phase by far, since the object is extremely bright, very large, very fragile, and the atmosphere is not a problem once the altitude is significant. The trajectory of a thrusting object is predictable, I have never heard of a vehicle that randomly adjusts its acceleration in flight. Once the war heads are deployed, they are going to be highly resistant to your laser, since they are designed to survive reentry.

Its not cheaper. BFR will cost 1-10 million, falcon family cost 60-100 million. It is chicken and egg. SpaceX is biting the bullet because their purpose it to develop humanity into a much more capable spaceflight species, not to make the most profit possible from the status quo. Yes, SpaceX will spend many billions of dollars to make BFR, but BFR will revolutionize spaceflight and that is what everyone at SpaceX is there to do.

No, because full re-usability. There is a huge difference between throwing away 10% of your rocket and 0%. A smaller fully reusable rocket is not that much cheaper than a large one, and the development costs are going to be very similar. Why would SpaceX spend billions of dollars to make a smaller BFR, when they will only save maybe a few million per launch, and their goal is to get people to make bigger payloads? Falcon family cannot remotely compete. They are not large enough to have an efficient 2nd stage reuse, and cannot land on their launch mounts. They require much more refurbishment than a larger rocket designed with their knowledge of re-usability and at least one booster needs to land on barges for significant payloads.

Nearly everytime a booster impacts the ocean, it breaks up. Even previous spacex tests that softlanded broke up when the rocket tipped over. Not only was this flight done with three landing engines, so more precision required than with 1 engine, it also managed to set down so softly in the ocean that the stage survived tipping over. look at 0:24 https://www.youtube-nocookie.com/embed/ambXDKFZhN8

Heres something that looks legit https://physics.illinois.edu/news/article/24114 Its far beyond me.

I think they want to use the manuevering thrusters, since the methane thrusters will be pretty powerful, but I haven't done the math so that could be unreasonable. I think the BFR has serious lift in the front, Elon said during the presentation that the wings were required to keep the vehicle stable during reentry, which suggests that they only pull the center of lift to approximately the center of mass of the vehicle.

I think it is something similar to MISTY, though operated by someone else since I think the NRO has said it isn't theirs. The launch was successful, everything worked but noone will say anything because its classified. There have been no substantiated claims that it failed, and SpaceX says the rocket operated as expected. https://en.wikipedia.org/wiki/Misty_(satellite)

It is actually dozens of photos stuck together. The arm that the camera is mounted on is just edited out, since it is confusing since it was in many different positions for different parts of the picture and only small parts of it were visible. https://www.universetoday.com/122883/why-dont-we-see-the-curiosity-rovers-arm-when-it-takes-a-selfie/

NASA is a organization with budgets assigned by congress, for the purpose of (1st) jobs and (2nd, by a lot) research. In order to get any significant space travel, we need to go private, or have a near dictatorial space travel thing. Luckily, we are going in this direction with Musk and Bezos. And like what, it takes a few weeks or months to recover from a year of 0g?

We have no experience with long term human health at low G enviroments. There is probably a very large difference between human operation in 0.2g and 0g, as one has a significant acceleration to help settle fluids and do stuff, while the other had none. Most things vary off % difference, not absolute. We, as a species need something to do with our resources, besides blow each other up, a goal. The only goal I can think of is expansion through the universe (has evolutionary backing!!!), so maybe cost won't be an issue since it is the ultimate goal, it is why we generate resources.

The M-1 engines might be good, it was a proposed super large hydrolox engine for a rocket that would have otherwise used 12 j-2s. 6.67MN 428s Vac https://en.wikipedia.org/wiki/M-1_(rocket_engine)

The new BFR was specifically sized so that it's development could take place in existing facilities (they are acquiring new ones for more long term manufacture I think). The cost of refurbishing the BFB might be smaller than the F9 booster because it is much better optimized and fuel cost are less than 1 million for BFR. You loose the reliability component of the BFS with only one raptor vs 7. SFS would use two different propellants, a major annoyance based on the locations of current landing prop tanks, landing prop would freeze. You now have a rocket with 2 or 3 different propellants, wouldn't fit with current launch facilities for F9 anyway. SFS would be really useful from an aerodynamic testing and reentry dynamics. The payloads for BFR won't appear until BFR flies, so SX just needs to bite the bullet and fix the chicken/egg problem.

If it stays in the 1st stage insterstage it has to push the entire 2nd stage right? Over 100t on F9

The right leg also looks bent a bit oddly, so I don't think either of them sustained any permanent damage.

You said infinite, so anti matter. Antimatter costs an absurd amount of money, but it is no matter. Could build millions of particle accelerators powered by a Dyson swarm to generate it at a reasonable rate and make physicists really happy. Building the swarm could easily be done using Orion or NSWR.

How important is wind? I would think that it doesn't really matter considering the size of airliners and their high speed and that we currently use straight runways in only a few directions. It seems much more useful as a way to put a much larger number of runways in a smaller space, at which point it might be much easier to use an octagon instead of a circle. Don't have to curve the edges of the runway or do any turning.

New Shepard is going almost strait up, while F9 has significant horizontal velocity, which is much harder.

The article I saw was that the capsule would be autonomous with the passengers trained for some emergency situations.

In SpaceX's defense, most of those things are overlapping. In addition, there are limits on how fast they can do things that are not based on the abilities of SpaceX's engineers. They are limited to how fast they can launch by how fast they can fix launch pads from normal flights, test rockets, get all the politics out of the way for a launch, etc. Might as well plan and work on other things that can be done mostly internal (like making new vehicles) while they are waiting for other things to be done. It is possible for a group to work on multiple things simultaneously. Also, everyone has failures early in their history.

What is the difference between a slave and subsistence wages with long hours? @Bill Phil You were referring to WW2 Germany, correct? N A Z I goes to pedant?

Just out of curiosity, what are you using these things for?