RCgothic

Found the tweet that made me think the engine bells were dented: Pretty sure now it's an optical illusion.

Yeah, there was a photo highlighting various dents. I thought I was sharing that one, but they're not as obvious as I thought. Now I can't find the original tweet I saw

They do look pretty in situ though. We don't get this view at 39A!

So, um, look at those raptor bells. Wonder what happened?

Boca Chica was just the southernmost East coast property they could get hold of. That's what a rocket launch site needs. That's it.

neat

My favourite alternate calendar is: 12 months of 5x 6-day weeks. 5-6 additional days attached to the end of December as a festive period. Months always begin on Monday 1st. Tuesdays dropped. Pros: 4 day working week. Only one irregular month. Weeks fit neatly into months. Calendar much more regular overall. There will always be 61 Mondays, Wednesdays, Thursdays, Fridays and Saturdays in a year, and 60-61 Sundays. Need to organise a meeting on the 7th? Know it will always be a Monday. Cons: Religious attachment to 7 day weeks. Birthdays on weekdays will never fall on weekends. I don't think there's much mileage in redefining the clock. For a start SI units are often defined in terms of seconds, so that'll alter so many constants for no real benefit. There is no universal clock and calendar that makes any kind of sense off-world. We'll probably do some sort of stardate with a basis of kiloseconds or something.

The FAA environmental assessment isn't due until Dec 31st. Then there's also FAA launch license. Assuming those both come through together Jan 1st is possibly the earliest opportunity. But I expect Superheavy B4 proving will take longer than 3 weeks from here anyway.

Check out this amazing piece of paper:

Also, when B1052.3 flies it will set a couple of new records: First FH side to be converted into an F9 instead of the other way around. First Falcon B5 core to be converted. Longest turnaround between flights - 907 days to Dec18th and counting

Turksat 5B will be B1052.3, first F9 flight of previous FH side booster recently pictured with a 2nd stage (Not on the Wikipedia list of Falcon cores - may have to make an edit). CRS-24 booster is as-yet unconfirmed. Doubt it'll be 1049.11. Could be 1069.1, but I'm leaning towards it being 1062.4. Edit: And I may have just set a precedent for how FH conversions to F9 are dealt with in the Wikipedia table. Nice. :-D

By the way, Starlink Group 2-3 is still slated for launch this month, would be flight 11 of B1051.

I'm not sure why it's 0.2deg. Also I see you managed to quote me as I was editing - it's a lot more than 925m/s.

It takes about 3.8km/s to plane change from the lattitude of Cape Kennedy to a 0.2deg inclination.

Balloons are also difficult. Jupiter is composed of hydrogen and helium. So you're going to displace the hydrogen and helium with what, hydrogen and helium? Zero density difference. Oh. So it'll need to be hot hydrogen and helium, but even then the difference you can get isn't huge. And because the difference isn't a lot, you need a relatively big and mass optimised envelope even to get a low payload. Then hydrogen has an excellent heat transfer coefficient and a mass-optimised envelope has poor insulation, so you'll be losing a lot of heat. So you need a lot of power to replace it. Basically, you get a low payload and high power requirement. And when the power runs out you sink.

Also note that a Mars Dragon would be doing very little independent flight. It could probably undock and re-enter on battery power alone.

That is a fair distinction. Jupiter's constituent gasses are less dense than Air, so at the 1bar pressure altitude there is less lift available than at the same pressure on Earth. There's also 2.4x the gravity, so the net effect is that 3x the power is required to maintain level flight. That's not impossible for a while, and the other gas giants a bit more benign than Jupiter, but a plane would still only survive as long as it's fuel lasted, and escape isn't really possible thereafter. A nuclear powered probe drone would probably be the best use case. Longest operational period followed by disposal to the depths.

XKCD's not wrong. It's just using a Cessna rather than a specifically designed exoplane. Here's the full article: https://what-if.xkcd.com/30/ Bsically, the problem is that gas giants have very deep gravity wells as well as having an atmosphere. Take Jupiter for example. Want to fly at a flight level where gravity =1G? That occurs at r=114000km. Jupiter's Radius? 70,000km. It's not happening. Want to fly at the 1bar level? Gravity is 2.5Gs and so it takes roughly 3 times more power to maintain level flight than on earth. A Cessna can't maintain level flight, but a plane with more power could. Briefly. (2.5G constantly would be extremely uncomfortable for the crew by the way.) 3x Earthly power consumption takes a toll. Want to refuel? There's nowhere to land and escaping to Low Jupiter Orbit takes 45km/s DV so basically you can't. Resume XKCD scenario now.

None of Energia, Saturn V, SLS or N1 were/will be capable of anything other than a flyby. A couple hundred tonnes a year to LEO is nowhere near sufficient. And a Mars mission at Opposion has a duration of 1.5y, not 3y.

Perhaps the use of the word instantaneous is not correct. I didn't mean it got up to speed instantaneously, I understand how centrifuges accelerate slowly. The centripetal acceleration experienced by the payload at 2222m/s at 100m diameter is ~100000m/s/s or ~10000Gs. In the earth's coordinate frame the acceleration vector is constantly changing direction. Take any instant just before launch. The acceleration is 10,000Gs. I then compare with a linear accelerator, where the acceleration to 2km/s over 100m is basically instantaneous, even if applied as a constant further impulse with constant acceleration. Yes, none of this is really instantaneous. Over 8km the acceleration would last around 7s. Imprecise language, sorry.

Dragon was originally going to be used for moon missions. Obviously I'm assuming that upgrade path still exists, because otherwise we're designing a new capsule from scratch. Don't like that? Fine. Then there are no suitable capsules for current rockets. Boring answer, sorry. Want a bigger hab with more space? Fine. Add additional modules and then more fuel. Or count both SLS and Superheavy as current rockets, ignore SLS, and build something with Superheavy. But I think that breaks the rules of the topic. And again, yes, I know it's a lot of dockings between modules full of hypergolic fuel. If you don't like dockings, add another launch to add a CanadaArm to perform the berthings. Don't like that many modules? Fine. I've already agreed it's the high end of infeasible. Enjoy the boring answer. Still don't like it? Well then it just can't be done with current rockets. They all lack the payload, flight rate, and a low enough cost point to raise enough storeable propellant for a Mars mission. Enjoy the boring answer. Ultimately, Starship is absolutely the way to do this properly. It's definitely not being done by any other current rocket, or by SLS.

No, I don't think it would be easier. Compared to spin launch the vacuum chamber would have to be a lot larger - probably 400mx100m across instead of 100m diameter. The tension members need to be in vacuum or they'd contribute very significant drag. The acceleration would probably be similar to Spin Launch around 5000G falling to 0G, averaging 2500G. The tension element would have to hold enough force to accelerate a multiple ton rocket at 5000G. See how thick the rotor is on Spin Launch? Except a crossbow needs flexible elements. Worse, the angle means the tension is a multiple of the force needed for acceleration. Very implausible. Also when the tension elements reach the end of their travel 2000m/s is very close to being a hypervelocity impact where materials behave like liquids. Significant issues.

Re-entry element selection: Ok, so Orion is totally the wrong capsule to take along for this ride. For every 1t that makes the round trip though TMI, MI and then TEI, that requires about 30t of storable propellant. Orion is enormously overweight. The combined Orion ESM weighs 26.5t. On this mission it will never fly free. The only thing it's needed for is is heat shield. Ideally we'd come up with something like Soyuz descent element, but that's a bit small for a crew of 5-6 and I suspect a conical capsule is better for re-entry from interplanetary speeds. That leaves Dragon 2, which weighs 12t wet. It has previously been mooted with an uprated heat shield, so that's if not quite ideal, probably the best we've got without designing a bespoke ultra-lightweight re-entry vehicle. At 14.5t lighter than Orion, that's something like 435t saved on the round trip. Launch Vehicle Selection: Similarly, SLS will not be useful in this mission (even if it were a currently operational rocket, which it's not). The amount of mass to Mars is well over 1000t. EUS can't push that much out of Earth's gravity well even with refuelling, which it doesn't support. We're going to have to use storable hypergolics and do orbital construction. That's going to take a *lot* of missions, and a lot of missions will cost a lot. What's the most cost effective launcher with the highest flight rate? Falcon 9. Falcon 9 can do about 15.6t reusably, so that's the module limit. 5m class fairing isn't ideal, but payload will be mostly propellant drop tanks. Note: all current DIVH, Atlas and Arianne 5 launches are spoken for and Vulcan, New Glenn and Arianne6 aren't current launchers either. That really doesn't leave much choice in the medium-heavy lift categories. There's Falcon Heavy, of course, but most of its payload is propellant residuals that won't be useful as storeables and we really don't know at this point that any member of the Falcon family can lift more than 15.6t actual payload to LEO. There's the Russian Angara or Proton of you want to throw the Russians a bone politically. Or there's the Chinese Long March series, for a properly international mission. Martian Hab: A Mars mission is going to be in the surface a while, probably over a month. It makes sense to pre-position a hab. A 15.6t module on the way to Mars would have about 11t mass budget not counting propellant That really isn't much for a longish duration stay, but it's probably the minimum baseline. It would take about 6x 15.6t propulsion modules to send the Hab to Mars, or 7x F9 flights. Crew Module: The crew is going to need somewhere a bit more spacious than Dragon to live, plus life support, power and supplies, and possibly a tether for artificial gravity but that's possibly a big ask given a 15.6t mass budget. Assume anything consumed gets replaced by payload from the Martian surface This and Dragon are the only bits that come back to earth. That's about 27.6t, which will take 3x 15.6t propulsion modules for Trans Earth Injection. Mars Lander: To land takes ~1km/s to descend and 3.8km/s to get back up. A single stage lander weighing 15.6t in Martian orbit would weigh just 2.8t with 0.5t of payload. That's probably not enough. Doubling up 31.2t allows an ascent module of 5t with 1.5t payload. Mass for Mars Insertion: Crew Module, Dragon, 3 propulsion modules for return, and the 2-stage lander. That's 105.6t. Mars Insertion takes~ 1440m/s. So that'll take 5x 15.6t propulsion modules. 183.6t total. Mass for TMI: TMI takes about 4270m/s. To push 183.6t through TLI would take 62x 15.6t propulsion modules. That's 62+5+3 propulsion modules. 2 part lander. Crew module. Dragon. 7 Flights to pre-position the Hab. 81x Falcon 9 flights. That's not completely impossible, but it's definitely in the high end of infeasible, all for a pretty lightweight mission with 5-6 crew for 30-40 days on the surface and 1.5 tonnes return payload. The F9 flights alone would retail for ~$5Bn, which is actually quite reasonable. The multiple common elements would probably be pretty cheap as well. The expensive bits would be the lander, Hab and crew compartment.