ChrisSpace

Would it really cost much to clean the soot out of a nozzle? I actually did my math the other way around. The current BFR plan uses 240 metric tons of Liquid Methane and 860 metric tons of Liquid Oxygen, giving a total propellant tank volume of 566.3 + 750.2 = 1316.5 m^3. If all that was filled with Liquid Methane you'd have a wet mass of 793 metric tons (assuming a dry mass of 235 metric tons). With an Isp of 644s that gives a total Dv of 7681 m/s. That's over a kilometer per second more than the current design, plus the lowered mass means the launch vehicle wouldn't need to be as large and expensive. But that doesn't even matter since SpaceX wouldn't be able to aquire the assets to mass-produce NTR thrusters anyway.

Woah, sorry I'm so late, let me just go over what's been said so far: "No clue. Nothing's changed that would make the Moon make any sense. It'd be great if it did, but it just doesn't work out." I'm pretty sure the moon does have some profitable... something. The low gravity makes large-scale colonization impractical, but there's probably tons of valuable minerals, plus the moon could be used as a halfway point between LEO and Mars (Dv to Mars is a lot lower from Lunart Orbit IIRC). "Shotwell confirmed that SpaceX is currently attempting to procure nuclear materials in order to conduct research and development of nuclear propulsion for spacecraft." NTRs with Methane propellant, perhaps? In any case, I doubt a corporation like SpaceX could acquire the required materials. "Aiming for 2022 cargo mission." This. This is the important bit. When I first heard that SpaceX had drastically changed their plans, at first I was worried that it was the beginning of the end for them, and that eventually they'd become the next NASA. But the two things that changed my mind about that were: - They haven't pushed back their schedule NASA-style - Out of the four SpaceX mars vehicle concepts the company has shown over the years, this is the first to break the trend of increasing size. For example: Falcon XX launch capability: 140 metric tons to LEO MCT BFR launch capability: 260 metric tons to LEO IIRC ITS launch capability: 300 metric tons to LEO when reusable Current BFR launch capability: 150 metric tons to LEO ...and the smaller the vehicles are, the less time, money and resources are needed for development. In other words, the current BFR is probably more likely to be a success than the ITS ever was. "Construction of BFR starts in "about 6-9 months". " I doubt that'll actually happen so soon, but I really hope it does. "I think a fair number of people would not really want to take the kind of g-loading involved in suborbital flight." Well it's obviously going to end up as a system for the super-rich only, not everyone. "Volume he said was like A380. In economy config, that can hold over 800 people." For multi-day trips to the moon or multi-week trips to Mars, I'd put the maximum at 100. "We can finally send those Flat Earthers to space soon?" We can't even send them to Antarctica right now. But yeah, it would be cool if we could send them into space. And leave them there. "Looks like Elon is bending to practicality again. And I don't mean that testing on the Moon first is NECESSARY (although it certainly is helpful- and cheaper than testing equipment on Mars), but that some people THINK it is needed. And sonetimes, perception is all that matters... " But as you said, it's cheaper than testing equipment on Mars. Also, if something goes horribly wrong, help is only about 3 days away. "Regardless of fuel cost, noise killed Concorde. A suborbital hypersonic projectile heading towards a major city center is not going to be very popular." If the landing site is several kilometers out to sea this may not be as big of a problem. "Yes, that's how he intends to fund the thing: by shifting all resources towards BFR. I suspect they will stockpile Merlin engines and second stages and reuse all 1st stages. Don't expect F9 launches to become any cheaper. Any savings through reusability are going into BFR development. It's a huge gamble IMO. He is literally betting the entire company on reusability and BFR." For a corporation like SpaceX, this is the kind of thing they have to do if they want to reach Mars. "And as for cost, wasn't it in the 10 billion range for the 12 m version? Think it's safe to say it'll be somewhere between 5-10 billion." Probably. I'd still estimate it at 10 billion. "I was wondering the same. For SpaceX, I guess it's a good test of the mission architecture close to home (propulsive landing and all that), but that's about it. Tourism as well, maybe. However, SpaceX could haul cargo to the moon for other moon-interested companies/countries (NASA, JAXA, Russia even) and make some money with that (essentially a lunar delivery service). Other than a quick moneymaker and testing bed for SpaceX, the moon seems to be a dead end. Their real goal is and always will be Mars, and IMO they're using the moon as a stepping-stone." So long as it's profitable enough to assist development of the Mars programme, it's worth it. "Well, being a multiplanetary species is more than just "cool". It can save us from some cataclysmic event. Or overpopulation." Overpopulation? Just to keep the world's population growth still you'd need to shoot hundreds of thousands of people off the planet every day. Although I guess it would be possible if you take the words "off the planet" out of that sentence... "What event would make Earth less habitable than Mars though?" I can think of a few scenarios, however they all fall into two categories: A: Things that would kill everyone on Mars too (Alien superintelligence extremination, the Singularity, etc). B: Things so unlikely I doubt any sapient species in the Local Group has ever had to deal with it (collision with a dwarf planet or relativistic comet from interstellar space, exoplanet encounter changing Earth's orbit, pandemic that gets everyone, etc). "I just got a great idea how a Moon colony can be profitable. Set up a top-security prison there and send world's most dangerous criminals there. Governments would pay to keep them hundreds of thousands of kilometers away from Earth, where there's literally nowhere to run." The bottom of the ocean. Exact same result. "Regarding BFR Earth-to-Earth concept... So, how do we differ a BFR from an ICBM, again?" The same way we differ sounding rockets and other suborbital rocket launches from ICBMs. On a side note, a BFR-based ICBM could easily deliver 5 Tsar Bombas, 136 B83 bombs or 416 W88 warheads at once. "P2P is more useful to the military than it will be for travel. Redefines "rapid response."" Moving 800 soldiers from anywhere to anywhere else in under an hour? Launching an entire network of orbital kinetic bombardment satelites at once? I imagine the military could think of all kinds of uses for this. "I would expect they DON'T make their 2022 launch date for the first cargo (with humans by 2024). In fact I don't expect any humans of Mars until 2032." I'm actually having a bit of difficulty trying to figure out how much time they actually HAVE to establish a basic self-sufficient colony. Estimates for the "due date" are currently varying from the 2040s to 2090s in my calculations. "By contrast, with Musk's plans to perfect Falcon Heavy reusability first, it's probably not by until at least *2052* that the first human colonists would set foot on Mars" Well, in that case we're probably [REDACTED]. "But now it doesn't look like SpaceX has any realistic competitors for the position of cheapest traditional launch service to LEO or GTO" But they DO have multiple groups, factions and individuals who may try to sabotage them. "If there would be any visits or tourists on Mars then airlocks are going to be guarded by armed men just like we guard borders." Or you could, y'know, lock them. "I think that people living on a suitable large torus habitat would have far better lives. They'd have an outside to walk around in shirtsleeves, they'd still be able to do "space" stuff, best of both worlds. Mars would be interesting to visit, but not to live." What benefit would the "outside" inside a habitat have compared to the "outside" inside a dome on Mars? "Ok, so, assuming 4 million a launch, divided up by 100, is $40,000 a person. Minimum (But that's grossly unrealistic)." Last year Elon put the goal at $200,000 per person IIRC. If that hasn't changed, the cost per launch to Mars would be around $20 million. "How long does it take to develop a rocket with new technologies ? 10-20 years?" In the space race, less than half a decade for some systems. "It needs to be said that until good studies are done on mammals at 0.38g, including a few generations of offspring, we don't know at all if Mars is someplace for people long term." If the surface gravity of Mars is too low for large-scale colonization, that would just leave Earth and Venus. And colonizing Venus is just... possible, with floating colonies in the upper atmosphere, but... "No. Surviving on an island requires timber, metal, and high ground to protect against storms" I think you underestimate the storm's power.

I'm aiming to see if I can get something that can hypothetically reach the lunar surface using avaiable resources with a budget of just a few million dollars. I'm aiming for... 6, maybe? First I'll see if it's possible for 1.

Well, from what I have lying around the house, and from a bit of internetting, here are some options I have found: Solid chemical rockets (model rocket motors are already easy to acquire, but the exhaust velocity is really low) Liquid chemical rockets (much harder to build, higher exhaust velocity) Solar thermal rockets (similar to solar sails but more expensive and produces more thrust) Laser sails/Laser thermal rockets (similar to their "Solar" counterparts, however they'd need a powerful laser and the most powerful civilian-made one I know of had an output of 200W from 1kW of input energy) Some kind of "Orion" using conventional explsives? (I have no idea what the thrust or exhaust velocity for this would be) Personally I think a combination of methods would be most practical. Liquid chemical rockets to boost into orbit (helped by Solid chemical rockets that detach during ascent STS- or SLS-style), then one of the more efficient low-thrust options to travel between planets. I might do some math on this later. Edit: Okay, after looking around on the internet, here's some links that should help give a rough idea of what kinds of propulsion systems should be available through various means of aquisition: http://www.watzlavick.com/robert/rocket/regenChamber/index.html http://www.watzlavick.com/robert/rocket/regenChamber3/index.html http://aeroconsystems.com/cart/liquid-motors/rocketdyne-lr64-rocket-motor/ http://pages.total.net/~launch/ss67b3.htm http://www.maxentropy.net/rocketry/liquidproject/design/design.htm http://www.dailymail.co.uk/sciencetech/article-2068224/Up-sale-online-A-NASA-rocket-engine-used-build-missiles.html http://www.rocket.com/files/aerojet/documents/Capabilities/PDFs/Monopropellant Data Sheets.pdf http://www.rocket.com/files/aerojet/documents/Capabilities/PDFs/Bipropellant Data Sheets.pdf http://www.rocket.com/files/aerojet/documents/Capabilities/PDFs/GPIM AF-M315E Propulsion System.pdf http://aeroconsystems.com/cart/liquid-motors/rocketdyne-lr101-bipropellant-rocket-motor/ As an example, if one of the types of 1000lbf engines is used and they're arranged in the same way as the engines on the bottom stage of the ITS, that should provide 186.8kN of thrust. If we give the main vessel's chemical propulsion an initial TWR requirement of 1.0, that gives it a mass of 19048kg.

Death Is mayonaise an instrument?

In Isaac Arthur's "Dead Aliens" video, he described a scenario in which multiple alien individuals intentionally froze themselves in a crater of permanent darkness so their bodies could be brought back to life in the distant future. In the scenario, humans showed up 2-4 million years later, but given the circumstances described in the video, what's the longest the bodies could've stayed sufficiently intact? Also, I once heard that one possible solution to the Fermi Paradox is that aliens could be contacting Earth, but their thoughts and actions are so slow that it takes months for them to say a single word, and as such it's indistinguishable from background noise. While I highly doubt this is common enough to be relevant to the FP, or that it would take MONTHS to hold a single conversation, I'm still wondering: What's the slowest speed at which thoughts and actions can occur in a complex biological organism? One-quarter of a human's? One-tenth? One-thousandth?

The closest we've ever had so far to someone who literally saved the world. Truly a respectable and admirable individual.

I was doing these calculations when I saw that you replied. For slightly more accurate data: Solar escape velocity from 1AU orbit: 42.13km/s Earth's current orbital speed: 29.65km/s Relative velocity: 12.48km/s AOA is negligible over such large distances 12.48km/s for 5 days = 5.39 million km Angular size from Earth (assuming P9-sized object): a bit over 0.4 degrees

As of September 2017 there are about 180000 forum members. Feel free to use that information however you want to in your calculations.

Alien technology/materials that can't be reproduced by humans? Small portable wormholes connecting different points in the galaxy?

After certain events that have been hapenning in the news I was expecting this thread to be very different.

But it's 90% other stuff and also has some very unscientific elements (demons, telepathy, alternate realities, etc.) so...

"Bill wurtz memes"

Granted. It's cold, you're tired and there's nothing to do. I wish I could see into and travel through 4-dimensional space.

I'm getting some really mixed messages here.

The writing and visuals are all mostly "homemade".

Here's a fun scenario I thought up. Let's say I go back in time 65 million years and a few days, swat the Chixulub impactor out of the way, and in it's place I put a large tank of antimatter with an amount of antimatter with a mass-energy equal to one half of the impact energy of the Chixulub impact (surrounding matter should account for the other half, I think). If the antimatter all stays in the tank until it hits the seafloor in the Yucutan peninsula, how would the resulting explosion be different from the impact that took place in real life? Would the fireball, tsunami, EMP, earthquakes etc etc be the same size and strength or not?

"[squeaking noises]" - Desert rain frog

I'm writing an anime fanfiction which will have lots of sci-fi elements later on (wormholes, lasers, battles in LEO, etc), so does that technically make me a sci-fi writer?

Earth has Pizza. And chocolate. As for dwarf planets, Ceres, because it's the closest and probably the only one that could have any strategic value in the next few centuries.

Not sure what that is, but I'm pretty sure this little [insert descriptive words here] should be able to take care of them:

Fallout

You didn't see the stellar-mass black hole that the solar system is now moving straight towards. I launch a "Project Thor"-style kinetic bombardment satelite network.