Fresh nuclear fuel isn't very dangerous. It's only after it's been used for a bit that it gets full of nasty isotopes.

So the simple answer is to launch the reactor cold and only activate it once safely in orbit.

That incident was in 1958. NERVA didn't start seeing budget cuts until 1969 when Nixon got in, over a decade later. It seems unlikely there was any connection.

>Sure you can make one that's ⅓ of mass, but that doesn't help much if you will still end up needing 3 of them. You know

The three final engine designs in the SNTP program all had thrusts of ~45,500lbf - about 80% of NERVA's 55,500lbf, while weighing between 3000lb and 4200lb - only about a tenth of NERVA's 40,000lb.

The best all around design was probably the partial flow expander, which offered an isp of around 935s and weighed 3300lb for 45,700lb of thrust. Two of those would weigh 6600lb - only 1/6th as much as a single NERVA, while producing ~65% more thrust and ~11% better isp.

No, plenty of rockets have worked on the first try. What is much rarer is for a given agency (or company) to succeed on their first try.

For example, NASA's first attempt to launch one of their own rockets; Scout, failed - but the subsequent maiden flights of Saturn 1, Saturn V, Space Shuttle, and SLS all succeeded.

Ditto for SpaceX with Falcon 1 failing, and then Falcon 9 and Falcon Heavy succeeding. Fingers crossed for Starship.

Net positive energy is indeed kind of arbitrary. Hitting Q=1.1 is not substantially more difficult than hitting Q=0.9. There's no barrier or even minor bump to get over, it's a continuous scale of linearly increasing difficulty, and even that scale can vary a lot depending on the specifics.

A comparison I might make as an aircraft geek is that it's not substantially more difficult to make an engine that produces 1.1 tonnes of thrust than one that makes 0.9 tonnes of thrust. As it happens, that's pretty damn close to the thrust numbers of the first and second production models of the world's first fighter jet engine; the Jumo 004.

However, the reason it's significant is that if we suppose that the engine in question weighed exactly one tonne, then the first model would be incapable of lifting it's own weight off the ground, while the second model could. Increasing the thrust by that small amount is relatively trivial and mundane, but the consequences of crossing that 1:1 threshold are profound.

(As it happens the Jumo 004 actually only weighed about 0.75 tonnes, so both versions could in fact lift their own weight off the ground)

I mean it typically takes 5-10 years for a new rocket to come online, and methane only started getting popular circa 2016-17, so this is pretty on schedule.

>Loss of an entire payload of satellites.

That was a payload failure, not a launch failure, since the rocket delivered the satellites to exactly where it was supposed to. And they didn't lose the entire payload - 11 of those satellites are currently in operational orbits.

Starlink payload failures also aren't exactly rare - SpaceX have lost 321 to date over 64 launches, or about 5 per launch on average. If you want to consider losing some satellites to be a launch failure, then SpaceX have had 37 launch failures over the course of the Starlink program.

This would give Falcon 9 Block 5 an overall launch success rate of only 72%, making it by far the least reliable operational launch vehicle with a statistically significant number of launches - an obviously absurd claim.

You can use the aforementioned Starlink numbers to argue that SpaceX aren't very good at building reliable satellites, but by the standards used in the industry they're very good at building reliable rockets - Falcon 9 has had no launch failures in the last 6 years and 158 launches.

>For literally old fashioned satellite calls. SOS.

Limited data rate, yes. But not comparable to old fashion satphones in the sense that you need specialized hardware to talk to a geo sat, and not limited to SOS (though that's certainly one of the more useful aspects).

>T mobile can’t offer what AST doesT mobile can’t offer what AST does

The only difference I can see is bandwidth. And while an individual AST sat likely has a lot more throughput due to it's size, I can't see them getting anywhere near Starlinks numbers though so bandwith over a given area is probably comparable.

If they did reach some deal to integrate directly into the Starlink sats then they'd face the exact same limitations TMobile are.

>can’t be combined on a starlink satellite

That's literally what they're doing though.

>AST does not require any special equipment or software. T mobile does.

SpaceX and TMobile both say otherwise. They say it will be compatible with existing 5G capable phones, and that as far as the phone will be able to tell a Starlink sat will appear indistinguishable from a cell tower.

AFAIK AST are using the exact same approach, just with a larger antenna.

SpaceX are already collaborating with TMobile for mobile.

SpaceX aren't the only ones. OneWeb and Iridium are also advocating for better regulation of low earth orbit.

>Why do they have to be orbital

Because suborbital satellites tend to have lifespans on the order of minutes. Having to replace your entire satellite fleet on a bi-hourly basis is a very, very poor business case.

>And you charge people for use of your internet service just like every business ever.

That works if you have a monopoly, but not in a world in which competition exists.

If it costs you ten times as much to launch a comparable satellite constellation to your competitor, then you need to charge each person ten times as much, or subscribe ten times as many users which means 1/10th the bandwidth per user, or some combination thereof.

Either way, the consumer gets a worse deal, so why would they purchase your service as opposed to your cheaper and faster competitor's?

Virgin Galactic will never reach orbit. Virgin Orbit however have already done so, and as a sister company I think it's fair to lump them together for the purposes of comparing to Blue Origin.

Falcon Heavy in expendable configuration is still an order of magnitude cheaper than SLS. Though even then you'd need some extra development to get it to work - propellant crossfeed, or sticking the ICPS on top of S2.

Starship-derived is definitely the better solution.

>Falcón heavy is not human rated, and will never be.

It could be if the desire was there. SpaceX originally planned to do it when they had a customer who wanted to fly on it, but after the customer changed their mind SpaceX no longer had any reason to do it.

If NASA asked SpaceX to crew-rate Falcon Heavy, it would be done. It would hardly the first time SpaceX changed their minds in order to meet NASA's requirements.

Also, the fact that Falcon 9 is crew rated, currently flying on a regular basis, and arguably the most reliable launch vehicle in history means Falcon Heavy is starting from a good basis, moreso than SLS I'd argue.

>SLS is 80% more powerful

In terms of raw thrust, sure. But it's also very inefficient, such that in terms of payload capability it's only around 25% more capable to TLI, and most of that is from the high efficiency upper stage. If you put a similar high efficiency stage on top of Falcon Heavy (traditionally the SLS's ICPS is proposed, but Centaur V would be even better) it actually gets pretty damn close. With propellant crossfeed in the mix you'd all but match it.

Such developments would take time and money, but would still likely be cheaper than SLS in the long run. However much like with crew-rating SpaceX would prefer to focus on Starship, and NASA currently show no interest in developing such capabilities, though the previous administrator did raise the possibility.

>This is comparing a heavy lift manned-capable rocket to the falcon 9

Technically speaking, Falcon 9 is both heavy lift and 'manned capable' - though NASA prefers 'human rated' or 'crew rated' as they're gender neutral.

So to be more accurate, this is comparing a super heavy lift lunar-crew-rated rocket to Falcon 9.

>The payload must either be super small or it’s gonna take a looooong time to get there with a falcon 9 right?

This particular lander is small because it's a secondary rideshare payload, but Falcon 9 should be capable of sending somewhere in the range of 5-6 tonnes to TLI, which I wouldn't call 'super small'.

I'd also like to note that sending payloads to the moon slowly often takes more energy, rather than less.

For example, SpaceX's recent launch of KPLO/Danuri to the moon via a ballistic transfer, which is expected to take ~4 months required accelerating to 10,521m/s, while Artemis 1 will only accelerate to about 10,100m/s and will get there in ~5 days.

If you look at this animation of Danuri's trajectory, the reason why will become obvious - it starts by going out about 4 times further than the moon (Indeed, with a max altitude of 1.56 million km it has even gone past the L1 point), then targeting the moon as it falls back down.

This approach takes a lot less fuel for the spacecraft to brake into lunar orbit than going directly there - essentially you're making the launch vehicle do more initial work so the spacecraft has to do less.