RCgothic

We're on track for a serious rise in average global temperatures. Whilst no-one here is suggesting the effects will be immediate, we could easily beach +3 deg C within my lifetime (twice that at the poles), and much more within our children's. The immediate effects of 3deg will be extremely servere storms, extremely severe droughts, and extremely severe heat waves. As temperatures and humidity rises, Wet bulb temperatures exceeding 35deg (currently exceedingly rare) will be experienced in more places, effectively rendering anywhere this could occur lethally uninhabitable to humans and animals without AC. Given that North America is already experiencing the worst drought on record, Canada is experiencing a crippling heat wave, we've had some of the most active hurricane seasons ever in recent years, and land temperature in the Arctic circle recently exceeded 48 degC, note that we're just getting started and then recalibrate your definition of "extremely". The last time global temperatures were that high, there was no ice cap and sea levels were 20m higher than today. Ok, we've acknowledged that temperature change won't happen overnight, and sea level rises will lag temperature rises. But 20m is enough to inundate almost every major city on earth, and the most productive farming lands are low lying. Over a billion people in South Asia alone would be displaced. Plant and animal life can't adapt to changes this fast. There will be mass extinctions and many food chains will completely collapse with unpredictable results. Even if not, the flora and fauna of regions will change drastically. With reduced land area, reduced farmlands, billions of people displaced, the socioeconomic pressure will be extreme. National borders will be re-written, with associated wars. Nuclear powers could collapse or become belligerent in defence or to secure resources. This comes with heightened risk of nuclear exchange. Honestly, I genuinely don't know if it's possible to be too alarmist on this subject. Anyone under 40 stands a strong chance of living to see a large portion of all of the above coming to pass. We are already seeing it come to pass. We're well past the point of evidence where we go "even if we clean up our act and it was all for nothing" - no, it genuinely is not for nothing. Every mitigation will slow and delay the coming changes, buying more time to adapt. But even so, the WHO estimates air pollution kills seven million people a year worldwide. Addressing that alone would be worth it even without the climate effects. As is, I think we're going to have to do some *serious* geo-engineering to get out of this one. Personally think we need immediate nuclear and renewable-powered carbon capture and sequestration starting yesterday, together with a complete ban on burning any fossil product as soon as practicably possible. Unmitigated climate change is most likely survivable as a species, barring some Venusian runaway. But there are a great many survivable things that we shouldn't want to experience.

Wow, that's a very bleak outlook and it sounds like I wouldn't want to work there.

Agreed they need a reusable upper stage, but maybe get New Glenn flying first, eh?

Ultimately the build site is much too far away from the launch site. They're not going to roll back and forth between each launch.

Certainly if all Superheavy/Starship stacking had to happen away from the launch site and SpaceX still wanted to pursue their aggressive flight cadence they'd need something as tall as the VAB with at least 4 bays. Probably a good reason for doing the stacking on the launch pad. I'm curious though as to what the payload integration facility for Starship will look like.

Extra-big bay details:

I'd go with additional processing space. Current high bay can basically manage one complete vehicle at once (Starship+Superheavy). Honestly, the spending SpaceX is doing on Starship and Starlink is unprecedented. I really hope they survive.

True, but the header tank's not *that* big.

It's not photo parallax, or the bottom one would be smaller still (but it's not).

Hope this helps Hope this helps Hope this helps. Edit: I don't know how that happened. I thought it wasn't posting. >.<

I'm pretty sure there will be a deluge, given the water tank.

More bits for the OLIT, probably part of a roof section.

Scoping of thruster power: A constant power of ~8kw required at an exhaust efficiency of 70% to add an energy of 84.5 billion joules in a six month burn. The current MMRTG produces 110W. The space station's new ROSA solar arrays produce 20kW from ~82m2. At 11AU instead of 1AU they'd produce just 165W each. So power would definitely be a challenge for an ion powered craft.

I've re-run my calcs for a trajectory similar to the originally proposed mission, and it broadly agrees. C3 of 120km2/s2 for earth departure (11km/sDV) and DV of 13km/s at rendezvous at the ascending node in ~2032. Uses the full advantage of earth's velocity, makes such a huge difference. I think the DV of 13km/s at ~11AU is going to be the difficult bit. Limited power for ion thrusters from RTG/solar and high-ish TWR required. A flyby would definitely be easier

The engine ignition at T=0 and clamp release at T+7 feels extremely weird. A very long hold down period.

I found the error in my maths, I was out by a factor of 2pi on my conversion between time elapsed and mean anomaly, so that all makes sense now. So, getting to the comet 1y before periapsis assuming a launch in early 2026 (big ask) requires a departure velocity of 41.2km/s, and it will arrive with an orbital velocity of 9.1km/s. At arrival, the comet has an orbital velocity of 12.8km/s and the angle to the intercept orbit is 87.3deg. The DV for rendezvous is therefore 15.4km/s. Ouch. Departure is at 53.0 deg to earth's velocity, which is 29.8km/s. Therefore need an excess departure velocity from earth of 33.3km/s. Earth's escape velocity is 11.2km/s, so that's 44.5km/s in LEO, or a DV of 36.7km/s. C3 of 1110km2/s2. Oh, and that'd probably need to be from a polar parking orbit. OUCH. Ok, so that's definitely the reason they're not attempting an interception before periapsis!

I'd be surprised if they did 9 on a suborbital pad, but who knows. Orbital launch pad will be able to take the full 33.

I'm not hugely familiar with ion thrusters, but I would have thought that what worked well for Dawn wouldn't work as well for this application? I think Krypton thrusters certainly have a high enough ISP, however this application may require a lot of point impulse at rendezvous and krypton thrusters have even less thrust than xenons. How long would it take to alter trajectory by 12.5km/s (or more, given the inefficient long burn)? The other concern I have is power. At 11AU the solar power available is 1/10th of that available to Dawn at 3AU, and RTGs don't provide very much power either. Starship + Centaur would definitely have enough power for the initial trajectory for a spacecraft 3t wet. A science package equivalent to Dawn, 750kg ish dry seems reasonable for a rendezvous. Might want more for a flyby trajectory to maximise data collected in a short encounter.

My current issue is that I'm struggling to reconcile the stated period with current position, semi-major axis and eccentricity. With a time until periapsis of ~9.5 years and a period of 3 million years, the mean anomaly (M) should be basically 360 deg. Eccentricity is almost 1, therefore the eccentric anomaly M= E - e*sin(E) should give E of basically 360deg as well. This would put the comet well inside the stated position of 19-21AU. Also I can't get true anomaly and eccentric anomaly to agree for the given values. @sevenperforce interested in your thoughts.

Yes, it's thought be be a large Oort cloud object, ~60km in diameter, that we've spotted in good enough time to *potentially* go and have a look. But we probably won't. It'd be a major mission launching in about 7 years and as nothing has yet been prepared chances are slim to none. It just caught my interest, so I'm seeing if I can calculate a hypothetical mission, and I'm interested in what other people come up with. Short period comets are not, at least as far as I'm aware. Long period comets (from out by the Oort cloud) are hard to get a good look at because they can't be predicted from historical observations. They have to be spotted in enough time to plan a mission.

Calculating intercepts is tricky. My first thought is that 2014 UN271 is super-inclined relative to earth's orbit. This basically proscribes taking full advantage of earth's velocity around the sun unless aiming for the ascending or descending node. At a current solar radius of 19-21AU UN271 is already inside the descending node (~79.6AU), and the ascending node at ~10.9AU occurs after perihelion. I wonder if this is why they're targeting 2033 for a rendezvous (after perihelion). There must be easier comets to visit. Nevertheless, I will persist.