I'm writing a textbook on Space Systems Engineering. Check the "view history" tab on any page to see who wrote it.

>according to your claim 18x more H2 coming out the ass, is that true?

That's your number, not mine, and it is wrong.

Electric arc furnaces are for remelting scrap iron to make new steel. About half of US steel production is remelted scrap. The other half has to come from a "reduction" furnace that removes oxygen from iron ore. Historically this was a blast furnace, but Boston Metal has a different process.

If the question was "how can I get really expensive electricity in 14 years", then yes nuclear is the answer. 14 years is the Vogtle 3 & 4 reactors in Georgia, approved in 2009, supposed to be operational this year.

The energy of formation of Iron III Oxide is 5.16 MJ/kg or 1433 kWh/ton. Actual energy needed depends on the efficiency of the process, including heat losses.

Wholesale solar and wind range from $26-50/MWh x 1.433 MWh/ton = $37-72/ton. Since steel goes for ~$750/ton these days, power cost is not a show-stopper at reasonable efficiency.

Gasoline used in my car's life (215,000 miles so far) - 25,000 kg. Lithium used in a full electric EV - 10 kg. One is much less than the other. Steel in both kinds of cars - about a ton each.

Electricity for EV to drive 215,000 miles in 22 years (my car's age) - about 72,000 kWh. US solar capacity factor - 24.4% (actual average output divided by rated panel capacity). Average power needed to produce that much power in 22 years: 372 Watts. Rated panel capacity needed: 1.52 KW.

Output per panel: 550W from largest US manufacturer rated at 585W but allowing for power loss as the panel ages. So you need about 3 panels. Panel Mass 34.4 kg x 3 = 103.2 kg. Much less than the car, and 250 times less than ICE gasoline needed.

So there aren't zero side effects, but a lot less.

> (nobody wants a dirty bomb going off in the sky)

Before you start up a reactor for the first time, the core is low radiation. Reactors produce short-life fission products, which is what makes nuclear waste dangerous.

Rocket mass is in kg, not moles. Exhaust velocity is ~9 km/s for hydrogen, vs ~4.5 km for H2-O2 engines.

I'm a space systems engineer, who has worked on nuclear rocket designs. My opinion is the time for nuclear-thermal propulsion is past. Solar-thermal can get the same performance - both heat H2 to the limits of the materials. But solar doesn't have all the nuclear baggage to deal with.

Nuclear-electric has much higher performance (3-20 times), though like all electric systems it has longer burn times. The reactor can be much smaller (1 MW rather than 1 GW), making radiators and such easier to do.

It would require significant renovation. Office buildings don't generally have private bathrooms and kitchens, and large ones don't have many windows per person.

There are more guns than people in the US (not evenly distributed though). That's the highest rate in the world, 4 times as many as Canada, 8 times Australia, and 24 times the United Kingdom.

> Bakugo's Howitzer Impact

Not familiar enough with manga physics to answer your question. I only do physics for this world :-).

> What is the point of adding the danger of a nuclear energy source

Because a nuclear-thermal engine can use pure hydrogen rather than a hydrogen-oxygen mix. Lighter molecules go faster at a given temperature, and H2 is much lighter than H2O. So you get roughly twice the exhaust velocity/specific impulse.

Nope. This test was a proof of concept engine. The next version will be a fully functional engine that they can measure specific impulse, thrust, and engine life for.

Nuclear rockets use pure hydrogen as propellant. Lighter molecules move faster, and H2 is much lighter than H2O.

> You can't just heat up water and shoot it out the back,

That's exactly what the third stage of the Artemis I rocket did on Nov 16th. Except the water was carried as separate hydrogen and oxygen tanks, and burning them is what produces the heat. What comes out the nozzle is superheated steam.

That's not how rockets work. Vehicle speed changes as your run the engine and produce thrust (push). Earth and Mars already are in orbit around the Sun. To get to Mars, you have to change your orbit so the other end crosses Mars' orbit at the same time Mars is at that point.

In theory the RDRE would improve chemical rocket efficiency by about 10%. There is a finite amount of energy in any fuel/oxidizer combination set by the chemistry. Regular rocket engines use a turbopump to push the ingredients into a combustion chamber at high pressure. The expansion of the resulting hot gas is what turns into thrust.

The RDRE feeds the ingredients at lower pressure, and uses a detonation to create the high pressure for expansion. The energy otherwise used to run the turbopumps is then directly used for thrust. Turbopumps generally tap off some of the fuel and oxidizer flow to power themselves.

There are other subreddits for astrophotography, so this one limits photos to 1 day a week to allow more room for general space news.

> Replacing coal plants will happen

For the US, it has already mostly happened. Coal has dropped 60% since 2008. By the time Boston Metal gets a full size steel plant built (about 5 years) coal will mostly be gone.

Over the last 12 months, renewables provided more electricity than coal or nuclear individually (not together).

Somebody call the [Pinkertons](https://en.wikipedia.org/wiki/Pinkerton_(detective_agency)#Homestead_strike)!

(an awful event in union history)

> There are very few buyers that have the capabilities of using material produced in space, ... There's no manufacturing in space yet. ... build said manufacturing capabilities

Well, I'm working on that. Check the "view history" tab on any page of that book to see who wrote it.

All your words that I quoted above are correct. Aside from robot arms and a 3D printer on the ISS, there is essentially no industrial capacity in space yet. Factories of the kind we build on Earth are too heavy to launch into space. So how do you get started?

A "seed factory", as I describe in that unfinished book, is a starter set of machines and tools that are used to make more machines to expand itself. This is where asteroid metal and carbon come in. Iron is by far the most important industrial metal, and 98% goes into making steel (iron with added carbon). Metallic asteroids are already in native form. They don't have to have the oxygen removed like iron ore on Earth.

The added machines are first to increase scale from the starter set, and second to make machines that work with other materials (glass, aluminum, etc.). You will still have to deliver some materials and parts from Earth while you bootstrap, but a lot less than if you tried to bring everything from Earth.

The starter machines can be as light as 20 kg, so certainly a single 100 ton Starship payload should be able to deliver a functioning machine shop with usable capacity.

You wouldn't jump into this without doing some R&D. We need to fly some asteroid retrieval missions in the ton rather than ~1 kg range coming back on the Osiris-REX mission. Ideally you want several different asteroid type samples. Then you feed those materials into pilot-scale processing machines and figure out what works and what doesn't.

NASA is like 1/16th of the space market. It is much more diverse than most people realize, and most of it is services, not launch and building satellites.

I used the steel as an example, because it is the same place you would extract the Platinum Group Metals. The first space-mined products are likely to be (a) bulk rock for shielding, and (b) water and carbon compounds for propellants and life support.

> She sticks to the "SpaceX is a transportation company" line.

Thousands of Starlink internet satellites are making them an Internet provider more than a rocket company. I expect them to chase any business that their launch cost advantage makes profitable.

If you can show there is a market for the products, existing mining companies have more than enough funds to finance such projects.

There is no need to send people to mine asteroids, it is not like they are going to be wielding a pick-axe. The two sample missions we sent to nearby asteroids Bennu and Ryugu found they were "rubble piles" rather than a solid chunk of rock or metal. Just a big pile of rocks loosely held by gravity.

So "mining" consists of sending a robotic probe to an asteroid of this type, slipping a sturdy bag around a suitable sized rock, pulling the drawstring tight, and flying away. The bag is to prevent loose bits from falling off and possibly damaging the probe.

My math shows a 10 ton probe with 26 tons of propellant can haul 1000 tons back from a nearby asteroid. Since some asteroid types have up to 20% carbon compounds and water, which can be turned into more propellant, the mining process can be self-fueling after the first trip.

Aside from collectibles and science, the point of asteroid mining isn't to bring stuff back to Earth. It is to replace the high cost of launching stuff from Earth.

Let's say the Starship rocket works as intended and can fly for $20 million a launch. It takes about five tanker flights plus the cargo launch to get ~120 tons to the Moon's neighborhood. So $120 million for 120 tons is $1 million per ton. If you can mine usable products from asteroids for less than this, you come out ahead.

Metallic asteroids contain about 15-50 parts per million of the "Platinum group metals" (the ones below iron, cobalt, and nickel on the Periodic Table). Parts per million is the same as grams per ton, so 15-50 grams per ton. Average PGM price is around $50/gram, so market value is $750-2500/ton.

They are alloyed with the three base metals as ~90% iron, 1% cobalt, and 9% nickel (the proportions vary by sample). So first, you have to extract the PGMs from a chunk of iron alloy, and second a little added carbon turns the iron alloy into a decent steel alloy. There are other asteroid types (the carbonaceous ones) with carbon, so that's not hard.

Now your ton of metallic asteroid is worth $1 million for structural steel in space, because that's the launch cost you avoid for not launching structural parts from Earth. The value as structural metal is worth way way more than the small amount of precious metals in it.

You can try to separate out the PGMs before leaving the asteroid, or afterwards so you can use both the iron alloy and the PGMs, but I highly doubt you can process it in space for the $750-2500/ton market value. For comparison, the price of hot-rolled ordinary steel on Earth is $775/ton right now.

Parts from 83 shuttle flights were used on Artemis 1 mission. When the Shuttle program ended, the Orbiters and parts inventory didn't vanish into thin air. Whatever was still usable, they used.