7 ms·
It helps enormously that unlike Falcon-9 this rocket can dial down the thrust of its engines low enough to be able to actually hover or to move arbitrarily slow
by generuso 2y ago
It helps enormously that unlike Falcon-9 this rocket can dial down the thrust of its engines low enough to be able to actually hover or to move arbitrarily slowly in the final meters before touchdown.
It can arrive to the designated intermediate point with some already good accuracy, and then take some time to trim the remaining errors to the noise level more slowly, possibly with feedback from the ground sensors.
The chopsticks also include rails with shock absorbers, the action of which can be seen in the view from the tower during the landing [1], so the required accuracy is probably relatively modest, provided one plans the maneuver carefully.
[1] https://youtu.be/Ysx4t7ICO58?t=678 https://youtu.be/Ysx4t7ICO58?t=678
- TechDebtDevin 2y agoThe main takeaway from Scott's commentary is that the chopsticks allow the ommission of landing legs and all their subsequent systems and saves a ton of weight. The added risk to dial this technique in is likely worth it in the long run from a sustainability stand point.
- kibwen 2y agoExcept that the landing legs allow you to land anywhere with a flat pad of concrete, whereas this requires comparatively enormous infrastructure investment.
- sagarm 2y agoYou'd still have to recover the rocket. I imagine the number of places you could land and economically recover the rocket is pretty small.
- swagasaurus-rex 2y agounless it can be refueled from a truck and reused without inspection.
- ang_cire 2y agoThat is so many iterations in the future, it's not really meaningful to design for now.
- m4rtink 2y agoSuper Heavy and its 33 raptor engines really needs a specific launch pad - on the first launch they tried to see what happens when they just fire it over a regular concrete slab (but still way above in a launch mount) and ended up with a massive crater. While Starship might be able to hop from unimproved landing sites, that is not really an option for Super Heavy, even with low fuel and short hops IMHO.
- cma 2y agoThat's why it is good in the long run, assuming the infrastructure can't get annihilated in a crash.
- Cthulhu_ 2y agoThere's always a risk, but at the same time, they've designed the infra now, they can rebuild it from the plans (and iterate on any flaws). There's a (imo unnecessary) idea of doing a lot of launches, for which you'd need multiple liftoff and landing sites.
- JacobThreeThree 2y ago>comparatively enormous infrastructure investment Any infrastructure that can remain on the ground and doesn't have to be on the rocket is worth whatever the investment cost.
- avmich 2y agoYou note of course that instead of legs, which have mass and have to have a structure in the stage which distributes the loads the SH has those parts with pins which were locked eventually with Mechazilla's arms, and those parts also have mass and need to have corresponding distribution of loads. How different those consoles with pins are from possible landing legs, and how much savings they provide is an interesting question. It's quite possible they provide some savings - but it would be nice to know some details.
- tempestn 2y agoIt seems pretty likely that those pins are going to save considerable mass and volume compared to articulating landing legs.
- avmich 2y agoWhy so? Pin parts need to withstand similar loads - and if amortizing rails of Mechazilla may soften the contact, the direction of loads for pin parts is less favorable than for legs. Legs don't need to be big or too numerous - effectively legs are those pin parts moved to the engine compartment and turned for an angle.
- krisoft 2y agoBecause the pins can be much shorter. Take a look at the falcon 9 legs. They are enermous both in absolute terms and relative to the whole rocket. They need to be that long to provide a stable platform and enough clearance for the nozzles and the residual plume as the engines shut down.
- jessriedel 2y agoThe booster is always returning to the general vicinity of the launch tower (either the tower itself or a barge). It isn’t used anywhere unimproved, and in particular is not used on Mars. So what scenario would it be helpful to be able to land the booster on a flat concrete pad?
- Cthulhu_ 2y agoIt sounds like sci-fi thinking tbh, but at the same time, Musk has hinted at using rockets for intercontinental travel. But even then, it wouldn't be just a concrete pad, it'd need disaster recovery systems and infrastructure in place.
- Tepix 2y agoYou're talking about Starship, not the booster. Starship will get landing legs.
- nkoren 2y agoOnly for Moon & Mars landings. The plan is to use the catch tower, Same as the booster, when landing on Earth.
- mavhc 2y agoJust build another tower, like you build another airport
- jfoster 2y agoNot just a hint. Here's a 2 minute video produced by SpaceX called "Earth to Earth". https://www.youtube.com/watch?v=zqE-ultsWt0 https://www.youtube.com/watch?v=zqE-ultsWt0
- jessriedel 2y agoThe booster does not travel more than ~50 miles.
- deleted 2y ago[deleted]
- neilquinn 2y ago[dead]
- starspangled 2y agoThe first stage doesn't really need to land anywhere, it launches from a known location that already has a comparatively enormous infrastructure investment. The second stage might want to land in other places. Not as a satellite launching bus or fuel truck though, that just wants to go up and down in an uncomplicated and unsurprising way, and that's where the vast majority of their launches will come from. For inter-planetary missions yes, but they have different second stage designs for those that aren't made for tower landings. If it gets used as a military transport, then similarly it will be a different second stage design.
- echelon 2y agoThe military transport option is going to provide so much capital. It's the C5 Galaxy, but with only a couple of hours needed to deploy into any theater in the world.
- Gravityloss 2y agoThere's some work needed to have the launch flexibility though. Ie lead time to launch, multiple launch locations. In comparison, simplified, if you have a bunch of things you need to send somewhere, you can go to the nearest airstrip and call a bunch of C5:s from somewhere a couple of hours away.
- adastra22 2y agoIf we’re talking about sending equipment / supplies, you can prelaunch into orbit and then re-enter on demand.
- Gravityloss 2y agoThat could actually probably be worse as the orbital path would not likely go near the wanted landing site, potentially in days. And anyway how do you know in advance what you are going to need (if it's not a nuke)? Instead, with a near-future rocket, you could have some sort of assortment of "most likely stuff needed" stored near a launch site and be ready to pack and launch in an hour.
- boxed 2y agoLanding legs are out of the question for Super Heavy anyway. If the engines come that close to the ground, the reflected sound from the ground will tear the engines apart.
- ayewo 2y agoThat's fascinating! Do you have a source for this where I can read more?
- bitwidget 2y agoThe 3 RS-25 (1860 kN each)[1] used for the Space Shuttles had 300,000 Gallons of water output per 41 seconds [2] when it launched. On landing, the Falcon Super Heavy used 5 or so [3] of the Raptor Engines (2750 kN each [4]). I'm making a few assumptions based on Napkin Math, but the parent comment seems about right since the engineering required (and the payload weight lost due to the weight/space requirements of landing feet for the FSH), would be too high to withstand the vibration reflection of landing on solid landing pad. [1]https://en.wikipedia.org/wiki/RS-25 https://en.wikipedia.org/wiki/RS-25 [2]https://en.wikipedia.org/wiki/Sound_suppression_system#NASA https://en.wikipedia.org/wiki/Sound_suppression_system#NASA [3]https://www.youtube.com/watch?v=pIKI7y3DTXk&t=6850s https://www.youtube.com/watch?v=pIKI7y3DTXk&t=6850s [4]https://www.spacex.com/vehicles/starship/ https://www.spacex.com/vehicles/starship/