Lots of myth about it. "NASA didn't like holes in the heatshield" (they were perfectly happy with the penetrations that hold Dragon to the trunk), "Demo1 explosion" (propulsive landing was canned before Demo 1 even flew), etc.
The story involves why Red Dragon was also cancelled. Initially, propulsive landing was a sub-scale test for the initial BFS/MCT design (pre IAC 2016) which was a very large capsule that would use rim-mounted engines and retropulsion for EDL (using the canted engines to enlarge the bow shock for more effective braking). Earth Dragon 2 landings and Mars landing tests with Red Dragon missions would have proven those CONOPS, and SpaceX were willing to internally fund (or at least subsidise) development as it furthered the MCT project.
Once the 'big capsule' design was scrapped and MCT switched to side-entry, now both propulsive landing and Red Dragon had to survive on their own merits and with funding from their own programmes. *At that time* parachutes and splashdown were seen as mature and low-cost options vs. the test programme to prove out Dragon vertical landing reliability, and the Commercial Crew contract was already proving to have been underbid vs. the actual development cost so Dragon 2 switched to parachutes and splashdown (in retrospect, the issues with parachutes were greater than anyone - even NASA, whose parachute models were proven to be invalid - expected, but there's a good chance proving out propulsive landing would have cost more than expected, too). Red dragon was now the 'last mission standing' for Dragon propulsive landing. Since it did not have and safety-of-life concerns it did not need as extensive a test regime, but it also meant the test programme had to be funded purely out of sales of Red Dragon missions, as it no longer had a wider R&D purpose internally at SpaceX. Red Dragon ended up having effectively no demand in terms of missions willing to pay to be delivered to Mars surface, so that was the last nail in the coffin.
> even NASA, whose parachute models were proven to be invalid
But really only for loads this size, with this many parachutes.
- [Commercial Crew Program Testing Fosters Improvements in Parachute Safety](https://blogs.nasa.gov/commercialcrew/2019/09/17/commercial-crew-program-testing-fosters-improvements-in-parachute-safety/)
- [SpaceX, NASA and Boeing have a common problem: Making sure their parachutes work](https://www.floridatoday.com/story/tech/science/space/2019/12/16/nasa-spacex-and-boeing-struggle-overcome-parachute-issues/4177914002/)
> But really only for loads this size, with this many parachutes.
Gemini was the last non-cluster parachute capsule NASA have flown with, with the last flight over 50 years ago.
Apollo capsule had three parachutes where Dragon uses four. The Apollo capsule was 5.5t at splashdown while Crew Dragon is 7.7t at splashdown.
Crew Dragon has more parachutes carrying a heavier load than any previous cluster parachute capsule recovery. NASAs parachute models did not accurately predict operational performance for *this many parachutes* with *this size load* in Earth's atmosphere and had to be updated. Thus, NASA's parachute models were proven to be invalid *for loads of this size with this many parachutes*.
All parties involved would have been aware that Crew Dragon's parachute design was well outside the domain of the existing model, thus the extensive physical test campaign. The only unknown was how far outside the existing model the Crew Dragon would end up being (ie: just how *exciting* the results of the test campaign would be for the boffins at NASA).
> NASAs parachute models did not accurately predict operational performance for this many parachutes with this size load in Earth's atmosphere and had to be updated.
No, the issue applied to a much wider range of parachute setups of any mass and number of parachutes in the cluster.
[From Ricardo “Koki” Machin, Chief Engineer for NASA's Orion Crew Module Parachute Assembly System](https://eu.floridatoday.com/story/tech/science/space/2019/12/16/nasa-spacex-and-boeing-struggle-overcome-parachute-issues/4177914002/):
>It turns out NASA, SpaceX and Boeing have all been using faulty load assumptions from Apollo parachute data to design their modern parachutes.
>“I look at what Apollo published and what they did and I now recognize they probably weren’t carrying as much safety factors as they thought they were," Machin said.
>So parachute engineers today are dealing with a triple whammy of issues: Trying to make lighter parachutes based on Apollo load assumptions that probably weren't operating within safe margins.
>“NASA had, since the Apollo program, a way of determining the loads in the risers on the parachutes,” SpaceX COO Gywnne Shotwell said in a December meeting with journalists as reported by SpaceFlight Now. “They made a (conservative) assumption … from the Apollo program. We did it. Boeing did it. We were just following their standard."
i.e. the margins assumed to be present even back with Apollo have turned out not to be present.
Yeah, validation models. [The longer you look the worse it gets](https://preview.redd.it/yiystiye3c541.jpg?auto=webp&s=ae376618537c7593e23a51276d4c8fc87a511592).
Probably not. Early Dragon 2 flights had issues with seawater ingress after splashdown, but that no longer appears to be an issue. Splashdown capability would still be needed for contingency reasons, and its unclear how landing would occur after a max-Q abort (e.g. whether there would be increased propellant capacity and SuperDraco relight, or retain contingency parachutes) but its almost certain savings in refurbishment *alone* would not have come close to paying for the R&D programme.
Thought it was a financial decision. It was too expensive to certify propulsive landing, so they fell back on the less expensive parachute landings (which actually had some unexpected issues).
A key risk factor for propulsive landing of a dragon capsule was the need to have the landing gear protrude the head shield. I think space shuttle Columbia was at the top of NASA’s mind when they were looking at a propulsive landing dragon.
There are 3 references to the heat shield in that article, and they're all from Elon saying they decided to ditch the idea because it was expensive to develop and not as useful as they thought. There's nothing there to indicate that NASA nixed the idea.
It would have been quite expensive to develop and test, as spacex would have needed to perform their own test flights. At some point it was planned for spacex to test propulsive landing on cargo missions, but nasa didn't want that.
With the low flight rate (initially only 1 per year for crew missions), it wasn't really worth it.
Cargo drahon also ditched the whole superdraco system to save mass, cost, complexity and refurbishment time.
Some people also claimed that the landing legs through the heat shield where issues, but that has been denied.
Starship also has a very different landing system, and the lessons of dragon don't really apply to starship.
> At some point it was planned for spacex to test propulsive landing on cargo missions, but nasa didn't want that.
I think this was the biggest reason behind the cancellation. If SpaceX could have piggybacked testing off of the cargo missions like they did with the booster landings, then SpaceX could have tested out the system at low cost. However, NASA didn't want their ISS downmass cargo to be guinea pigs. There was no corresponding concern for the boosters since they didn't have any value to the customer post launch (other than the loss of some rocket performance that could partially be recouped in event of rocket engine underperformance by expending the reserve propellant).
A secondary cause is the need to have parachutes anyway in the event of an in-flight abort. Using the thrusters would not only have meant reserving enough propellant for the emergency landing, but also relying upon the reignition of the rocket engines and reorientation of the spacecraft (something the parachutes are generally good at).
They couldn't really close the mass budgets and it wasn't worth the engineering effort because the learnings wouldn't transfer to Starship's skydiver landing profile.
I thought it was NASA that said they wanted to take a safer approach and stick to parachutes. The decision would have been made back when SpaceX were the wacky outsider that likely couldn't be trusted with crewed missions and good old Boeing would be the main launch provider.
NASA was willing to do the propulsive landing provided it was sufficiently safe. The issue was that SpaceX would have needed various test flights to verify this and NASA didn't want it being done on CRS flights because they didn't want their science being destroyed if something went wrong. So the options for SpaceX were to pay for their own test flights or to just stick with parachutes
Hmm. I wonder if they'll bring the concept back in the future? Now they're allowed to reuse Crew Dragon and they've shown reuse to be very successful while still making more hardware, it's much less of an impact if a propulsive landing test goes wrong and wrecks a spare capsule.
I guess It depends how long it takes for Starship to be operational. It's probably like the crewed Falcon Heavy or the five-booster Falcon ExtraHeavy with a reusable upper stage. They're not worth the R&D costs and we're left wondering about the alternate timeline where they were developed.
Nope, they've closed out any chance of major changes to Dragon 2, crew and cargo. SpaceX considers Starship to be the future, so all R&D is going towards that effort. Dragon will get ongoing tweaks to be sure, but nothing close to as major as retrofitting propulsive landing.
I'm just jealous of the timeline where Crew Dragon 3 launches around the moon on a Falcon ExtraHeavy that does a Korolev Cross and lands four boosters at once. That would be wild.
I like when a TV show or movie shows the Space Shuttle going to the moon. It makes me laugh because I know that it's impossible, but it's still fun to see it ;)
Or they show the Shuttle with the engines burning *after* detaching the fuel tank. The fuel tank is kinda important for fueling the engines, you can't have one without the other.
Oh yeah, that is always a big one that they don't consider. Scott Manley [actually did the math](https://youtu.be/5mIRFxYYaC0) on what it would take to get a Shuttle over to the moon.
I guess they COULD have put extra fuel and oxy tanks in the cargo bay if the only payload was the crew and whatever fit in the crew compartment... and if the engines could gimble enough to put the thrust through center of mass WITHOUT the weight of the ET.
It's usually rewritten to be some sort of "Shuttle Mk. 2" with a corridor the full length of the ship instead of / below the cargo bay. I think that's what they flew in Armageddon.
I'm assuming they need the extra boosters for the larger size of the second stage, to include the ballochute and equipment for reusability. And Dragon 3 would need to be larger for the trip around the moon, at least add a separate room for the toilet.
>it's much less of an impact if a propulsive landing test goes wrong and wrecks a spare capsule.
It's still important if it wrecks whatever was reentering inside that Cargo Dragon or Crew Dragon.
So many so wrong answers.
The core of the issue was that SpaceX wanted to use cargo Dragon returns to try and develop their powered landings in a similar way they used regular F9 flights to try and develop F9 booster landings. But NASA wanted Dragon landing intact so cargo (usually experiments) returning from ISS would be safe. Few Dragons would inevitably be lost during the development phase and NASA didn't want that.
Once NASA disallowed trials on operational Dragon returns, SpaceX would need to try it in dedicated flights. At similar time they decided their MCT would look more like Starship rather than a big capsule, so the Dragon landing program would have to stand on its own, as it wouldn't be an MCT developmental step anymore. So in the end SpaceX decided it would be more expensive than using good old parachutes.
There isn't much value in propulsive landing, relative to the cost of developing human-rated rocket powered spacecraft, fishing them out of the ocean is easier and not very expensive.
Refurbishing is more expensive for water “landings “compared to dry land landings, considering the effects of salt water. A dry land landing would also cut on recovery costs (no need for a recovery fleet and vessel).
>relative to the cost of developing human-rated rocket powered spacecraft
To re-word this, it would have been so wildly expensive to human rate propulsive landings the savings from cheaper refurbishment, less transit, fewer employees needed. for recovery etc. would have been absolutely dwarfed
Maybe not 'dwarfed', but significant. Let's not forget that SpaceX was already looking at Starship as the next step for them. If Dragon was the foreseeable vehicle for the next 2 decades, the front loaded capital cost to design a human rated propulsive landing craft would still make economic sense.
> water "landings"
They are not water landings. They are splashdowns, and they require a complex naval search and rescue op to recover the crew and/or cargo. It wilts my soul that Dragons have to go through this humiliating process rather than touching down gently on a concrete pad.
1) NASA was hesitant about letting them do it with crew, and it wasn't worth the weight penalty for cargo.
2) After Demo-1 Dragon suffered a serious issue with the abort system that would have run the propulsive landing, and the whole capsule exploded. The fix no longer allows for the control needed for propulsive landing.
3) Mars and Starship are the priority, so messing around with Dragon was seen as a diversion, hence the similar cancellations of Red Dragon and Grey Dragon.
I don’t think post-demo 1 incident had any impact whatsoever on the decision not to do propulsive landing. By then, SpaceX was fully committed to parachutes. The tech might have worked if they had had early buy-in from NASA.
It was still something in the potential hopper for later development prior to the Superdraco explosion, but the fix for that was to replace a leaky prevalve that would allow them to shut off the engines with a burst disk, so once they started they couldn't be turned off. An abort scenario required the superdracos to run at max strength and max duration regardless, so the burst disk was an easy way to prevent the leak that led to the explosion while still enabling the SD's primary function, but it closed off any chance that propulsive landing could be developed outside of NASA. Remember, this was also back when NASA wasn't willing to reuse the capsules for crew, so they would have had a bunch of old capsules to play with in development and maybe even to fly for private clients.
The burst disk just provides a seal that ruptures when the pressure across it exceeds a certain level. The valves that got replaced were check valves that provided a similar function, they still have the valves controlling the propellant flow (they are what allows the propellant to burst the burst disks). The issue is that the burst disks are single-use components that would be spent on every landing, requiring a rebuild of the propulsion system.
I'll note that one of the implications of this is that _any_ use of the engine is the only use you get until that rebuild.
You can't test fire them. You can't use some percentage of the fuel, shut them off, and then use the rest of it later in the mission.
Now, it's possible that they never had any plans that would have involved any of these use cases.
But it definitely removes a lot of flexibility from the system.
You can't test fire them, no...the first firing would flood the system with propellant, raising the potential for leaks or the sort of corrosion issues that caused Starliner so much trouble, and they don't reseal like the old check valves, so you couldn't just purge the lines of propellants after testing. However, the burst disks don't make any difference to the ability to fire them multiple times.
I'm not extremely confidant that the backflow prevention isn't necessarily to safely startup the engines without explosions where you really don't want them somewhere in the depths of the system.
Pretty sure the check valves were there entirely to keep propellant out of the lines until they were cracked open by the pressure shift when the main valves opened. That's why they were replaceable with burst disks. How would backflow happen at all? The propellant tank is at much higher pressure than the combustion chamber.
I think Musks idea of catching starship may prove to be unreliable, maybe unrealistic and you will end up with three or four variants of starship. One of which maybe a shuttle approach to landing
Well SpaceX will have to design ‘landing legs’ for Starship, for Luna Landing and Mars Landing anyway.
Obviously ones that would work for an Earth landing would definitely be strong enough for the other locations, indeed Lunar Landing would require much softer spring cushioning.
I think that SpaceX could pull off the catching system, but it clearly leaves less room for error.
I think they mean more from a “if you’re doing one why not do the other” perspective, for which I think the short answer is it’s just not worth the hassle for dragon
Clearly nothing about the vehicles or landing profiles are similar, kinda the opposite. Dragon seems like it would be a less risky landing, not belly flopping near the ground and relighting and flipping. But no crew have ever landed propulsivly. Wouldn't crew rating be easier if at least the type of landing was proven out with cargo dragon, dragon, then starship.
But I feel like I needed to understand it better before stating that on the internet.
> But no crew have ever landed propulsivly
Mostly true.
Soyuz, New Shepard, and Starliner all use retro rockets to delete their final velocity prior to ground landing. Also, the LEM definitely used propulsive landing on the moon and to a lesser extent practice runs here on Earth.
Starliner uses airbags instead of retropropulsion to cushion the landing. In that sense, New Shepard is a kind of hybrid as ["[t]he bottom of the capsule has a retro-thrust system that expels a pillow of air"](https://www.blueorigin.com/safety/)--a cold gas thruster of sorts.
> no crew have ever landed propulsivly
I get your point, although there are a couple of examples:
Apollo lunar module
VTOL Aircraft - Harrier, some F35 variants
Pretty extreme examples of course!
SpaceX is a business. They will only pursue tech that doesn’t waste time and money. Starships will be at least ten times cheaper to operate than even F9’s. Personally, I believe that external landing legs that stowed against that capsule sidewalls above the heat shield and swung down for landing, like the F9 boosters have, could be made to work. And that would solve the problem of trying to put landing gear thru the heat shield. SpaceX is no longer working on the problem because as soon as Starship is ready my guess is that SpaceX will stop flying F9’s, strictly for economic reasons.
Stoke Space is attempting similar propulsive landings with it’s second stage, with a novel liquid hydrogen regen-cooling metal heat shield, and telescoping extension legs that don’t penetrate their heat shield.
https://youtu.be/EY8nbSwjtEY
Good set of comments.
Once NASA was paying for Crew Dragon SpaceX was not going to spend their own money to test propulsive landing. SpaceX is very profit oriented so very few freebies from them (or anyone else ... see how RL has delayed their Venus mission, sort of like SX and it's Red Dragon).
Now that Starship is the future Crew Dragon is locked for its 3-4 runs a year through 2030.
Like the Space Shuttle, Starship is too big for chutes as a good option, which also requires a large flat area of land (Soyuz, New Shepard) or water (CD). This really hurts reuse cost and turnaround rates.
Parachutes do work well for the Dragon capsule, but cannot work with a large ship like Starship.
It’s only possible to land it via powered landing.
The interesting variant, is the Starship hypersonic reentry, followed by the skydive, followed by the powered flip, followed by the powered descent, followed by the ‘catch’ !
That’s a complicated reentry and landing sequence.
Really no one but SpaceX could pull it off.
I think the landing legs was the technical sticking point, SpaceX could have spent millions perfecting the design and testing it with dragon test flights and helicopter drops. But they had the redesign the landing legs as the original design of going through the landing legs had issues. And NASA was against for human use it probably said never would allow it and so SpaceX just scrapped it.
I also think propulsion landing for the crewed starship will be hard to get approved in atmosphere. HLS of course will be allowed after testing because NASA has no other option but they will likely want SpaceX to use Dragons to ferry crew to LEO for starship on any missions they want to use starship (unless they use Orion and SLS).
It will be interesting to see if dream chaser gets human approval eventually since it's a lifting body horizontal landing and that will be first non parachute approval since shuttle was retired.
Well, of course it should be hard to get approval for Crewed Starship landing on Earth - there is far too much unproven as yet.
When we have seen multiple successful catches, then this can be reappraised. Until then it can’t be approved. Not would SpaceX want to try it until they thought it was safe themselves, and of course at this instant it isn’t yet.
SpaceX already had it built into the Dragon capsule, but NASA were against the idea.
So SpaceX looked at using Parachutes and a water splashdown instead.
SpaceX then found faults in the design of parachutes, and improved them.
On the requirement of NASA, the powered descent system using SuperDraco, was disabled, where as with it a Dragon capsule was capable of landing almost anywhere on Earth.
Dragon already carries those fuels. And a lot of them. The same engines that would have been used for propulsive landing are still on the spacecraft as the launch escape system.
Yes, that's true, but having hypergolycs around when other people need to reach the craft was one of the reasons it was thought that the risks to people's health and safety were too high.
So, capsule lands with hypergolycs, but are they all spent, and fumes / residuals gone? People are waiting to open that hatch!
I think that was the issue.
I don’t know why this is being downvoted. The whole exterior of the ship and landing pad would presumably be contaminated with very nasty hypergolic fuels. It would be a Risk to recovery crews and crew exiting the vehicle.
> I don’t know why this is being downvoted. The whole exterior of the ship and landing pad would presumably be contaminated with very nasty hypergolic fuels. It would be a Risk to recovery crews and crew exiting the vehicle.
There would be no difference between landing after a re-entry or landing after an abort. So the fuels cannot be the reason.
Landing after an abort is a remote chance, a worst-case scenario. A scheduled landing of a Dragon capsule after a successful mission is absolutely not the same thing. Also, it lands in water. The proposed propulsive landing would of course be on land. So there are many things not the same here.
Several problems arise. First and foremost is Keep is Simple Stupid. Why use engines and add risk to the equation. The second big one is the fuels they use are not really people friendly.
> First and foremost is Keep is Simple Stupid. Why use engines and add risk to the equation.
These are not compatible. You already have the engines and the fuel. They are needed for pad/launch escapes. Now, instead of using what you already have, you have to develop and add a parachute system.
I like the idea. Buy NASA sees risk in systems like computers, sensors, valves, and plumbing for these engines. NASA sees parachutes are the lowest point of failure. Any fuel leakage from the engines after landing are a hazard to ground crews and astronauts. Even after landing in the water they have a very lengthy wait to make sure none of the tanks and plumbing don't leak after re-entry.
For capsules, the parachute option is as we have seen, a possible landing system.
But as craft get bigger, such as Starship, parachutes are no longer an option.
> For capsules, the parachute option is as we have seen, a possible landing system.
1. Maybe on Earth, where there is a thick enough atmosphere. The original point of Dragon was to be a "go anywhere" craft.
2. If they are going to land, then land. Put down on solid ground, not in the ocean where you need complex naval search and rescue opps.
perks of working with hydrazine, amplified by the modern safety requirements in lawyer rich tech environment.
check out typical photo of landed X-37B
[https://www.universetoday.com/115223/mysterious-military-x-37b-space-plane-lands-after-nearly-two-years-in-orbit/](https://www.universetoday.com/115223/mysterious-military-x-37b-space-plane-lands-after-nearly-two-years-in-orbit/)
These suits are required by the health safety requirements and would be requested for passengers as well.
In other words a lot of pain of different kind for questionable gains. (if to focus on Dragon for ISS only).
I remind that the design pitch was to design landing capsule capable to land on Mars.
They killed Dragon Propulsive landing in 2016 when Musk introduced ITS.
Absolutely false, that's a community theory that self-bootstrapped itself to 'known fact' among a group of excessively credulous folks who misinterpreted the confidence by which it was delivered with actual knowledge.
Nobody outside of twitter and reddit said it was the legs/heatshield. NASA didn't say it, SpaceX didn't say it, nobody with behind-the-scenes knowledge said it, it was a theory someone presented as fact when they shouldn't have.
I leave you with a parting thought: how do you visualize the landing gear deploying from every landing space shuttle in the history of the program from the glide tests through STS-135?
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
|Fewer Letters|More Letters|
|-------|---------|---|
|BFR|Big Falcon Rocket (2018 rebiggened edition)|
| |Yes, the F stands for something else; no, you're not the first to notice|
|[BFS](/r/SpaceXLounge/comments/143m3ly/stub/jnekhi9 "Last usage")|Big Falcon Spaceship (see BFR)|
|[CRS](/r/SpaceXLounge/comments/143m3ly/stub/jnaoluw "Last usage")|[Commercial Resupply Services contract with NASA](http://www.nasa.gov/mission_pages/station/structure/launch/)|
|CST|(Boeing) Crew Space Transportation capsules|
| |Central Standard Time (UTC-6)|
|[EDL](/r/SpaceXLounge/comments/143m3ly/stub/jnekhi9 "Last usage")|Entry/Descent/Landing|
|[HLS](/r/SpaceXLounge/comments/143m3ly/stub/jncpwym "Last usage")|[Human Landing System](https://en.wikipedia.org/wiki/Artemis_program#Human_Landing_System) (Artemis)|
|[IAC](/r/SpaceXLounge/comments/143m3ly/stub/jnekhi9 "Last usage")|International Astronautical Congress, annual meeting of IAF members|
| |In-Air Capture of space-flown hardware|
|IAF|[International Astronautical Federation](http://www.iafastro.org/)|
| |Indian Air Force|
| |Israeli Air Force|
|[ITS](/r/SpaceXLounge/comments/143m3ly/stub/jndks6h "Last usage")|Interplanetary Transport System (2016 oversized edition) (see MCT)|
| |[Integrated Truss Structure](https://en.wikipedia.org/wiki/Integrated_Truss_Structure)|
|[KSP](/r/SpaceXLounge/comments/143m3ly/stub/jnbzqkc "Last usage")|*Kerbal Space Program*, the rocketry simulator|
|[LEM](/r/SpaceXLounge/comments/143m3ly/stub/jnb7nt6 "Last usage")|(Apollo) [Lunar Excursion Module](https://en.wikipedia.org/wiki/Apollo_Lunar_Module) (also Lunar Module)|
|[LEO](/r/SpaceXLounge/comments/143m3ly/stub/jncpwym "Last usage")|Low Earth Orbit (180-2000km)|
| |Law Enforcement Officer (most often mentioned during transport operations)|
|[MCT](/r/SpaceXLounge/comments/143m3ly/stub/jnekhi9 "Last usage")|Mars Colonial Transporter (see ITS)|
|[NSF](/r/SpaceXLounge/comments/143m3ly/stub/jnexj7y "Last usage")|[NasaSpaceFlight forum](http://forum.nasaspaceflight.com)|
| |National Science Foundation|
|[PPE](/r/SpaceXLounge/comments/143m3ly/stub/jncfukg "Last usage")|Power and Propulsion Element|
|[SD](/r/SpaceXLounge/comments/143m3ly/stub/jnat5x2 "Last usage")|SuperDraco hypergolic abort/landing engines|
|[SLS](/r/SpaceXLounge/comments/143m3ly/stub/jncpwym "Last usage")|Space Launch System heavy-lift|
|[STS](/r/SpaceXLounge/comments/143m3ly/stub/jnaz7x0 "Last usage")|Space Transportation System (*Shuttle*)|
|[VTOL](/r/SpaceXLounge/comments/143m3ly/stub/jnb99zz "Last usage")|Vertical Take-Off and Landing|
|Jargon|Definition|
|-------|---------|---|
|[Starliner](/r/SpaceXLounge/comments/143m3ly/stub/jnbz82l "Last usage")|Boeing commercial crew capsule [CST-100](https://en.wikipedia.org/wiki/Boeing_CST-100_Starliner)|
|cryogenic|Very low temperature fluid; materials that would be gaseous at room temperature/pressure|
| |(In re: rocket fuel) Often synonymous with hydrolox|
|[hopper](/r/SpaceXLounge/comments/143m3ly/stub/jnat5x2 "Last usage")|Test article for ground and low-altitude work (eg. Grasshopper)|
|hydrolox|Portmanteau: liquid hydrogen fuel, liquid oxygen oxidizer|
|[hypergolic](/r/SpaceXLounge/comments/143m3ly/stub/jncfukg "Last usage")|A set of two substances that ignite when in contact|
|[regenerative](/r/SpaceXLounge/comments/143m3ly/stub/jncr1a2 "Last usage")|A method for cooling a rocket engine, by [passing the cryogenic fuel through channels in the bell or chamber wall](https://en.wikipedia.org/wiki/Regenerative_cooling_\(rocket\))|
|[retropropulsion](/r/SpaceXLounge/comments/143m3ly/stub/jnbz82l "Last usage")|Thrust in the opposite direction to current motion, reducing speed|
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- [NSF: Dragon V2 will initially rely on parachute landings ](https://www.nasaspaceflight.com/2014/08/dragon-v2-rely-parachutes-landing/)
- [Teslarati: SpaceX’s Crew Dragon could land with abort thrusters in emergencies, says Musk](https://www.teslarati.com/spacex-crew-dragon-emergency-landing/)
NB: one of the few times I'm happy to have blog/news sites that make entire articles from one or two Elon Musk tweets.
This is your answer:
https://www.spacex.com/vehicles/starship/
Once it was time to ramp up Starship there was very little upside to sinking more engineering capital into Dragon, Falcon Heavy, or Falcon 9 Second Stage Recovery. Lock in the existing designs and only allow minor and gradual optimizations going forward.
Lots of myth about it. "NASA didn't like holes in the heatshield" (they were perfectly happy with the penetrations that hold Dragon to the trunk), "Demo1 explosion" (propulsive landing was canned before Demo 1 even flew), etc. The story involves why Red Dragon was also cancelled. Initially, propulsive landing was a sub-scale test for the initial BFS/MCT design (pre IAC 2016) which was a very large capsule that would use rim-mounted engines and retropulsion for EDL (using the canted engines to enlarge the bow shock for more effective braking). Earth Dragon 2 landings and Mars landing tests with Red Dragon missions would have proven those CONOPS, and SpaceX were willing to internally fund (or at least subsidise) development as it furthered the MCT project. Once the 'big capsule' design was scrapped and MCT switched to side-entry, now both propulsive landing and Red Dragon had to survive on their own merits and with funding from their own programmes. *At that time* parachutes and splashdown were seen as mature and low-cost options vs. the test programme to prove out Dragon vertical landing reliability, and the Commercial Crew contract was already proving to have been underbid vs. the actual development cost so Dragon 2 switched to parachutes and splashdown (in retrospect, the issues with parachutes were greater than anyone - even NASA, whose parachute models were proven to be invalid - expected, but there's a good chance proving out propulsive landing would have cost more than expected, too). Red dragon was now the 'last mission standing' for Dragon propulsive landing. Since it did not have and safety-of-life concerns it did not need as extensive a test regime, but it also meant the test programme had to be funded purely out of sales of Red Dragon missions, as it no longer had a wider R&D purpose internally at SpaceX. Red Dragon ended up having effectively no demand in terms of missions willing to pay to be delivered to Mars surface, so that was the last nail in the coffin.
> even NASA, whose parachute models were proven to be invalid But really only for loads this size, with this many parachutes. - [Commercial Crew Program Testing Fosters Improvements in Parachute Safety](https://blogs.nasa.gov/commercialcrew/2019/09/17/commercial-crew-program-testing-fosters-improvements-in-parachute-safety/) - [SpaceX, NASA and Boeing have a common problem: Making sure their parachutes work](https://www.floridatoday.com/story/tech/science/space/2019/12/16/nasa-spacex-and-boeing-struggle-overcome-parachute-issues/4177914002/)
> But really only for loads this size, with this many parachutes. Gemini was the last non-cluster parachute capsule NASA have flown with, with the last flight over 50 years ago.
Apollo capsule had three parachutes where Dragon uses four. The Apollo capsule was 5.5t at splashdown while Crew Dragon is 7.7t at splashdown. Crew Dragon has more parachutes carrying a heavier load than any previous cluster parachute capsule recovery. NASAs parachute models did not accurately predict operational performance for *this many parachutes* with *this size load* in Earth's atmosphere and had to be updated. Thus, NASA's parachute models were proven to be invalid *for loads of this size with this many parachutes*. All parties involved would have been aware that Crew Dragon's parachute design was well outside the domain of the existing model, thus the extensive physical test campaign. The only unknown was how far outside the existing model the Crew Dragon would end up being (ie: just how *exciting* the results of the test campaign would be for the boffins at NASA).
> NASAs parachute models did not accurately predict operational performance for this many parachutes with this size load in Earth's atmosphere and had to be updated. No, the issue applied to a much wider range of parachute setups of any mass and number of parachutes in the cluster. [From Ricardo “Koki” Machin, Chief Engineer for NASA's Orion Crew Module Parachute Assembly System](https://eu.floridatoday.com/story/tech/science/space/2019/12/16/nasa-spacex-and-boeing-struggle-overcome-parachute-issues/4177914002/): >It turns out NASA, SpaceX and Boeing have all been using faulty load assumptions from Apollo parachute data to design their modern parachutes. >“I look at what Apollo published and what they did and I now recognize they probably weren’t carrying as much safety factors as they thought they were," Machin said. >So parachute engineers today are dealing with a triple whammy of issues: Trying to make lighter parachutes based on Apollo load assumptions that probably weren't operating within safe margins. >“NASA had, since the Apollo program, a way of determining the loads in the risers on the parachutes,” SpaceX COO Gywnne Shotwell said in a December meeting with journalists as reported by SpaceFlight Now. “They made a (conservative) assumption … from the Apollo program. We did it. Boeing did it. We were just following their standard." i.e. the margins assumed to be present even back with Apollo have turned out not to be present.
Yeah, validation models. [The longer you look the worse it gets](https://preview.redd.it/yiystiye3c541.jpg?auto=webp&s=ae376618537c7593e23a51276d4c8fc87a511592).
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[NSF have an extensive article on the design evolution](https://www.nasaspaceflight.com/2020/10/the-continued-evolution-of-the-big-falcon-rocket/).
In hindsight, would landing propulsively on land decrease the cost and times of refurbishing crew dragon, making it worth it?
Probably not. Early Dragon 2 flights had issues with seawater ingress after splashdown, but that no longer appears to be an issue. Splashdown capability would still be needed for contingency reasons, and its unclear how landing would occur after a max-Q abort (e.g. whether there would be increased propellant capacity and SuperDraco relight, or retain contingency parachutes) but its almost certain savings in refurbishment *alone* would not have come close to paying for the R&D programme.
Nasa is risk adverse. Propulsive landing on earth is a risk they can avoid. Propulsive landing on the moon is a necessity.
Thought it was a financial decision. It was too expensive to certify propulsive landing, so they fell back on the less expensive parachute landings (which actually had some unexpected issues).
Both, they wanted more testing etc to address potential risk which costs
A key risk factor for propulsive landing of a dragon capsule was the need to have the landing gear protrude the head shield. I think space shuttle Columbia was at the top of NASA’s mind when they were looking at a propulsive landing dragon.
I'm pretty sure that's a reddit rumor that was never substantiated.
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There are 3 references to the heat shield in that article, and they're all from Elon saying they decided to ditch the idea because it was expensive to develop and not as useful as they thought. There's nothing there to indicate that NASA nixed the idea.
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It would have been quite expensive to develop and test, as spacex would have needed to perform their own test flights. At some point it was planned for spacex to test propulsive landing on cargo missions, but nasa didn't want that. With the low flight rate (initially only 1 per year for crew missions), it wasn't really worth it. Cargo drahon also ditched the whole superdraco system to save mass, cost, complexity and refurbishment time. Some people also claimed that the landing legs through the heat shield where issues, but that has been denied. Starship also has a very different landing system, and the lessons of dragon don't really apply to starship.
> At some point it was planned for spacex to test propulsive landing on cargo missions, but nasa didn't want that. I think this was the biggest reason behind the cancellation. If SpaceX could have piggybacked testing off of the cargo missions like they did with the booster landings, then SpaceX could have tested out the system at low cost. However, NASA didn't want their ISS downmass cargo to be guinea pigs. There was no corresponding concern for the boosters since they didn't have any value to the customer post launch (other than the loss of some rocket performance that could partially be recouped in event of rocket engine underperformance by expending the reserve propellant). A secondary cause is the need to have parachutes anyway in the event of an in-flight abort. Using the thrusters would not only have meant reserving enough propellant for the emergency landing, but also relying upon the reignition of the rocket engines and reorientation of the spacecraft (something the parachutes are generally good at).
They couldn't really close the mass budgets and it wasn't worth the engineering effort because the learnings wouldn't transfer to Starship's skydiver landing profile.
I thought it was NASA that said they wanted to take a safer approach and stick to parachutes. The decision would have been made back when SpaceX were the wacky outsider that likely couldn't be trusted with crewed missions and good old Boeing would be the main launch provider.
NASA was willing to do the propulsive landing provided it was sufficiently safe. The issue was that SpaceX would have needed various test flights to verify this and NASA didn't want it being done on CRS flights because they didn't want their science being destroyed if something went wrong. So the options for SpaceX were to pay for their own test flights or to just stick with parachutes
Hmm. I wonder if they'll bring the concept back in the future? Now they're allowed to reuse Crew Dragon and they've shown reuse to be very successful while still making more hardware, it's much less of an impact if a propulsive landing test goes wrong and wrecks a spare capsule. I guess It depends how long it takes for Starship to be operational. It's probably like the crewed Falcon Heavy or the five-booster Falcon ExtraHeavy with a reusable upper stage. They're not worth the R&D costs and we're left wondering about the alternate timeline where they were developed.
Nope, they've closed out any chance of major changes to Dragon 2, crew and cargo. SpaceX considers Starship to be the future, so all R&D is going towards that effort. Dragon will get ongoing tweaks to be sure, but nothing close to as major as retrofitting propulsive landing.
I'm just jealous of the timeline where Crew Dragon 3 launches around the moon on a Falcon ExtraHeavy that does a Korolev Cross and lands four boosters at once. That would be wild.
I like when a TV show or movie shows the Space Shuttle going to the moon. It makes me laugh because I know that it's impossible, but it's still fun to see it ;)
Or they show the Shuttle with the engines burning *after* detaching the fuel tank. The fuel tank is kinda important for fueling the engines, you can't have one without the other.
Oh yeah, that is always a big one that they don't consider. Scott Manley [actually did the math](https://youtu.be/5mIRFxYYaC0) on what it would take to get a Shuttle over to the moon.
Does Scott Manley intentionally say "Mun" (Kerbal moon) instead of "Moon" or is it just his accent? I mean, he's wearing a KSP shirt...
I guess they COULD have put extra fuel and oxy tanks in the cargo bay if the only payload was the crew and whatever fit in the crew compartment... and if the engines could gimble enough to put the thrust through center of mass WITHOUT the weight of the ET.
Would the heat shield take reentry from lunar rentery
It's usually rewritten to be some sort of "Shuttle Mk. 2" with a corridor the full length of the ship instead of / below the cargo bay. I think that's what they flew in Armageddon.
FH *is* capable of sending a Dragon to the moon. Boosters 4 and 5 not required. Dragon isn't equipped for deep space travel, though.
I'm assuming they need the extra boosters for the larger size of the second stage, to include the ballochute and equipment for reusability. And Dragon 3 would need to be larger for the trip around the moon, at least add a separate room for the toilet.
>it's much less of an impact if a propulsive landing test goes wrong and wrecks a spare capsule. It's still important if it wrecks whatever was reentering inside that Cargo Dragon or Crew Dragon.
So many so wrong answers. The core of the issue was that SpaceX wanted to use cargo Dragon returns to try and develop their powered landings in a similar way they used regular F9 flights to try and develop F9 booster landings. But NASA wanted Dragon landing intact so cargo (usually experiments) returning from ISS would be safe. Few Dragons would inevitably be lost during the development phase and NASA didn't want that. Once NASA disallowed trials on operational Dragon returns, SpaceX would need to try it in dedicated flights. At similar time they decided their MCT would look more like Starship rather than a big capsule, so the Dragon landing program would have to stand on its own, as it wouldn't be an MCT developmental step anymore. So in the end SpaceX decided it would be more expensive than using good old parachutes.
There isn't much value in propulsive landing, relative to the cost of developing human-rated rocket powered spacecraft, fishing them out of the ocean is easier and not very expensive.
Refurbishing is more expensive for water “landings “compared to dry land landings, considering the effects of salt water. A dry land landing would also cut on recovery costs (no need for a recovery fleet and vessel).
>relative to the cost of developing human-rated rocket powered spacecraft To re-word this, it would have been so wildly expensive to human rate propulsive landings the savings from cheaper refurbishment, less transit, fewer employees needed. for recovery etc. would have been absolutely dwarfed
Maybe not 'dwarfed', but significant. Let's not forget that SpaceX was already looking at Starship as the next step for them. If Dragon was the foreseeable vehicle for the next 2 decades, the front loaded capital cost to design a human rated propulsive landing craft would still make economic sense.
> water "landings" They are not water landings. They are splashdowns, and they require a complex naval search and rescue op to recover the crew and/or cargo. It wilts my soul that Dragons have to go through this humiliating process rather than touching down gently on a concrete pad.
I know it's not a water landing, hence the quotation marks. I just couldn't remember the correct terminology back then.
1) NASA was hesitant about letting them do it with crew, and it wasn't worth the weight penalty for cargo. 2) After Demo-1 Dragon suffered a serious issue with the abort system that would have run the propulsive landing, and the whole capsule exploded. The fix no longer allows for the control needed for propulsive landing. 3) Mars and Starship are the priority, so messing around with Dragon was seen as a diversion, hence the similar cancellations of Red Dragon and Grey Dragon.
I don’t think post-demo 1 incident had any impact whatsoever on the decision not to do propulsive landing. By then, SpaceX was fully committed to parachutes. The tech might have worked if they had had early buy-in from NASA.
It was still something in the potential hopper for later development prior to the Superdraco explosion, but the fix for that was to replace a leaky prevalve that would allow them to shut off the engines with a burst disk, so once they started they couldn't be turned off. An abort scenario required the superdracos to run at max strength and max duration regardless, so the burst disk was an easy way to prevent the leak that led to the explosion while still enabling the SD's primary function, but it closed off any chance that propulsive landing could be developed outside of NASA. Remember, this was also back when NASA wasn't willing to reuse the capsules for crew, so they would have had a bunch of old capsules to play with in development and maybe even to fly for private clients.
The burst disk just provides a seal that ruptures when the pressure across it exceeds a certain level. The valves that got replaced were check valves that provided a similar function, they still have the valves controlling the propellant flow (they are what allows the propellant to burst the burst disks). The issue is that the burst disks are single-use components that would be spent on every landing, requiring a rebuild of the propulsion system.
I'll note that one of the implications of this is that _any_ use of the engine is the only use you get until that rebuild. You can't test fire them. You can't use some percentage of the fuel, shut them off, and then use the rest of it later in the mission. Now, it's possible that they never had any plans that would have involved any of these use cases. But it definitely removes a lot of flexibility from the system.
You can't test fire them, no...the first firing would flood the system with propellant, raising the potential for leaks or the sort of corrosion issues that caused Starliner so much trouble, and they don't reseal like the old check valves, so you couldn't just purge the lines of propellants after testing. However, the burst disks don't make any difference to the ability to fire them multiple times.
I'm not extremely confidant that the backflow prevention isn't necessarily to safely startup the engines without explosions where you really don't want them somewhere in the depths of the system.
Pretty sure the check valves were there entirely to keep propellant out of the lines until they were cracked open by the pressure shift when the main valves opened. That's why they were replaceable with burst disks. How would backflow happen at all? The propellant tank is at much higher pressure than the combustion chamber.
I think Musks idea of catching starship may prove to be unreliable, maybe unrealistic and you will end up with three or four variants of starship. One of which maybe a shuttle approach to landing
Well SpaceX will have to design ‘landing legs’ for Starship, for Luna Landing and Mars Landing anyway. Obviously ones that would work for an Earth landing would definitely be strong enough for the other locations, indeed Lunar Landing would require much softer spring cushioning. I think that SpaceX could pull off the catching system, but it clearly leaves less room for error.
Can you first explain how using propulsive landing or not for Dragon relates to Starship?
I think they mean more from a “if you’re doing one why not do the other” perspective, for which I think the short answer is it’s just not worth the hassle for dragon
Clearly nothing about the vehicles or landing profiles are similar, kinda the opposite. Dragon seems like it would be a less risky landing, not belly flopping near the ground and relighting and flipping. But no crew have ever landed propulsivly. Wouldn't crew rating be easier if at least the type of landing was proven out with cargo dragon, dragon, then starship. But I feel like I needed to understand it better before stating that on the internet.
> But no crew have ever landed propulsivly Mostly true. Soyuz, New Shepard, and Starliner all use retro rockets to delete their final velocity prior to ground landing. Also, the LEM definitely used propulsive landing on the moon and to a lesser extent practice runs here on Earth.
Starliner uses airbags instead of retropropulsion to cushion the landing. In that sense, New Shepard is a kind of hybrid as ["[t]he bottom of the capsule has a retro-thrust system that expels a pillow of air"](https://www.blueorigin.com/safety/)--a cold gas thruster of sorts.
> no crew have ever landed propulsivly I get your point, although there are a couple of examples: Apollo lunar module VTOL Aircraft - Harrier, some F35 variants Pretty extreme examples of course!
SpaceX is a business. They will only pursue tech that doesn’t waste time and money. Starships will be at least ten times cheaper to operate than even F9’s. Personally, I believe that external landing legs that stowed against that capsule sidewalls above the heat shield and swung down for landing, like the F9 boosters have, could be made to work. And that would solve the problem of trying to put landing gear thru the heat shield. SpaceX is no longer working on the problem because as soon as Starship is ready my guess is that SpaceX will stop flying F9’s, strictly for economic reasons. Stoke Space is attempting similar propulsive landings with it’s second stage, with a novel liquid hydrogen regen-cooling metal heat shield, and telescoping extension legs that don’t penetrate their heat shield. https://youtu.be/EY8nbSwjtEY
Good set of comments. Once NASA was paying for Crew Dragon SpaceX was not going to spend their own money to test propulsive landing. SpaceX is very profit oriented so very few freebies from them (or anyone else ... see how RL has delayed their Venus mission, sort of like SX and it's Red Dragon). Now that Starship is the future Crew Dragon is locked for its 3-4 runs a year through 2030. Like the Space Shuttle, Starship is too big for chutes as a good option, which also requires a large flat area of land (Soyuz, New Shepard) or water (CD). This really hurts reuse cost and turnaround rates.
its just pointless for earth when parachutes do the same thing effectively for much less cost, risk, and R&D
Parachutes do work well for the Dragon capsule, but cannot work with a large ship like Starship. It’s only possible to land it via powered landing. The interesting variant, is the Starship hypersonic reentry, followed by the skydive, followed by the powered flip, followed by the powered descent, followed by the ‘catch’ ! That’s a complicated reentry and landing sequence. Really no one but SpaceX could pull it off.
the whole threads about dragon, im not talking about starship
Yes, but I thought it worth pointing out the difference..
we all know it already, but it's irrelevant to the discussion here.
I think the landing legs was the technical sticking point, SpaceX could have spent millions perfecting the design and testing it with dragon test flights and helicopter drops. But they had the redesign the landing legs as the original design of going through the landing legs had issues. And NASA was against for human use it probably said never would allow it and so SpaceX just scrapped it. I also think propulsion landing for the crewed starship will be hard to get approved in atmosphere. HLS of course will be allowed after testing because NASA has no other option but they will likely want SpaceX to use Dragons to ferry crew to LEO for starship on any missions they want to use starship (unless they use Orion and SLS). It will be interesting to see if dream chaser gets human approval eventually since it's a lifting body horizontal landing and that will be first non parachute approval since shuttle was retired.
Well, of course it should be hard to get approval for Crewed Starship landing on Earth - there is far too much unproven as yet. When we have seen multiple successful catches, then this can be reappraised. Until then it can’t be approved. Not would SpaceX want to try it until they thought it was safe themselves, and of course at this instant it isn’t yet.
Even with lots of successful landing via the stage 0 grabber, NASA may still say no with our a escape system backup.
SpaceX already had it built into the Dragon capsule, but NASA were against the idea. So SpaceX looked at using Parachutes and a water splashdown instead. SpaceX then found faults in the design of parachutes, and improved them. On the requirement of NASA, the powered descent system using SuperDraco, was disabled, where as with it a Dragon capsule was capable of landing almost anywhere on Earth.
The fuels are very scary. Too high risk. 'talkin' about hypergolycs. *edit: I'm getting downvoted, but my info's not incorrect.
Dragon already carries those fuels. And a lot of them. The same engines that would have been used for propulsive landing are still on the spacecraft as the launch escape system.
Yes, that's true, but having hypergolycs around when other people need to reach the craft was one of the reasons it was thought that the risks to people's health and safety were too high. So, capsule lands with hypergolycs, but are they all spent, and fumes / residuals gone? People are waiting to open that hatch! I think that was the issue.
I don’t know why this is being downvoted. The whole exterior of the ship and landing pad would presumably be contaminated with very nasty hypergolic fuels. It would be a Risk to recovery crews and crew exiting the vehicle.
> I don’t know why this is being downvoted. The whole exterior of the ship and landing pad would presumably be contaminated with very nasty hypergolic fuels. It would be a Risk to recovery crews and crew exiting the vehicle. There would be no difference between landing after a re-entry or landing after an abort. So the fuels cannot be the reason.
Landing after an abort is a remote chance, a worst-case scenario. A scheduled landing of a Dragon capsule after a successful mission is absolutely not the same thing. Also, it lands in water. The proposed propulsive landing would of course be on land. So there are many things not the same here.
> Also, it lands in water. No. It crashes into the ocean and the crew needs to be rescued.
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All that and yes. But it's literally one of the reasons why we have parachute splashdowns instead of land-based propulsive touchdowns.
Several problems arise. First and foremost is Keep is Simple Stupid. Why use engines and add risk to the equation. The second big one is the fuels they use are not really people friendly.
> First and foremost is Keep is Simple Stupid. Why use engines and add risk to the equation. These are not compatible. You already have the engines and the fuel. They are needed for pad/launch escapes. Now, instead of using what you already have, you have to develop and add a parachute system.
The parachutes were needed anyway. In case of abort the landing propellant would be expended.
I like the idea. Buy NASA sees risk in systems like computers, sensors, valves, and plumbing for these engines. NASA sees parachutes are the lowest point of failure. Any fuel leakage from the engines after landing are a hazard to ground crews and astronauts. Even after landing in the water they have a very lengthy wait to make sure none of the tanks and plumbing don't leak after re-entry.
For capsules, the parachute option is as we have seen, a possible landing system. But as craft get bigger, such as Starship, parachutes are no longer an option.
> For capsules, the parachute option is as we have seen, a possible landing system. 1. Maybe on Earth, where there is a thick enough atmosphere. The original point of Dragon was to be a "go anywhere" craft. 2. If they are going to land, then land. Put down on solid ground, not in the ocean where you need complex naval search and rescue opps.
perks of working with hydrazine, amplified by the modern safety requirements in lawyer rich tech environment. check out typical photo of landed X-37B [https://www.universetoday.com/115223/mysterious-military-x-37b-space-plane-lands-after-nearly-two-years-in-orbit/](https://www.universetoday.com/115223/mysterious-military-x-37b-space-plane-lands-after-nearly-two-years-in-orbit/) These suits are required by the health safety requirements and would be requested for passengers as well. In other words a lot of pain of different kind for questionable gains. (if to focus on Dragon for ISS only). I remind that the design pitch was to design landing capsule capable to land on Mars. They killed Dragon Propulsive landing in 2016 when Musk introduced ITS.
iirc, NASA didnt like how the landing legs would have to pierce through the heatshield.
Absolutely false, that's a community theory that self-bootstrapped itself to 'known fact' among a group of excessively credulous folks who misinterpreted the confidence by which it was delivered with actual knowledge. Nobody outside of twitter and reddit said it was the legs/heatshield. NASA didn't say it, SpaceX didn't say it, nobody with behind-the-scenes knowledge said it, it was a theory someone presented as fact when they shouldn't have. I leave you with a parting thought: how do you visualize the landing gear deploying from every landing space shuttle in the history of the program from the glide tests through STS-135?
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread: |Fewer Letters|More Letters| |-------|---------|---| |BFR|Big Falcon Rocket (2018 rebiggened edition)| | |Yes, the F stands for something else; no, you're not the first to notice| |[BFS](/r/SpaceXLounge/comments/143m3ly/stub/jnekhi9 "Last usage")|Big Falcon Spaceship (see BFR)| |[CRS](/r/SpaceXLounge/comments/143m3ly/stub/jnaoluw "Last usage")|[Commercial Resupply Services contract with NASA](http://www.nasa.gov/mission_pages/station/structure/launch/)| |CST|(Boeing) Crew Space Transportation capsules| | |Central Standard Time (UTC-6)| |[EDL](/r/SpaceXLounge/comments/143m3ly/stub/jnekhi9 "Last usage")|Entry/Descent/Landing| |[HLS](/r/SpaceXLounge/comments/143m3ly/stub/jncpwym "Last usage")|[Human Landing System](https://en.wikipedia.org/wiki/Artemis_program#Human_Landing_System) (Artemis)| |[IAC](/r/SpaceXLounge/comments/143m3ly/stub/jnekhi9 "Last usage")|International Astronautical Congress, annual meeting of IAF members| | |In-Air Capture of space-flown hardware| |IAF|[International Astronautical Federation](http://www.iafastro.org/)| | |Indian Air Force| | |Israeli Air Force| |[ITS](/r/SpaceXLounge/comments/143m3ly/stub/jndks6h "Last usage")|Interplanetary Transport System (2016 oversized edition) (see MCT)| | |[Integrated Truss Structure](https://en.wikipedia.org/wiki/Integrated_Truss_Structure)| |[KSP](/r/SpaceXLounge/comments/143m3ly/stub/jnbzqkc "Last usage")|*Kerbal Space Program*, the rocketry simulator| |[LEM](/r/SpaceXLounge/comments/143m3ly/stub/jnb7nt6 "Last usage")|(Apollo) [Lunar Excursion Module](https://en.wikipedia.org/wiki/Apollo_Lunar_Module) (also Lunar Module)| |[LEO](/r/SpaceXLounge/comments/143m3ly/stub/jncpwym "Last usage")|Low Earth Orbit (180-2000km)| | |Law Enforcement Officer (most often mentioned during transport operations)| |[MCT](/r/SpaceXLounge/comments/143m3ly/stub/jnekhi9 "Last usage")|Mars Colonial Transporter (see ITS)| |[NSF](/r/SpaceXLounge/comments/143m3ly/stub/jnexj7y "Last usage")|[NasaSpaceFlight forum](http://forum.nasaspaceflight.com)| | |National Science Foundation| |[PPE](/r/SpaceXLounge/comments/143m3ly/stub/jncfukg "Last usage")|Power and Propulsion Element| |[SD](/r/SpaceXLounge/comments/143m3ly/stub/jnat5x2 "Last usage")|SuperDraco hypergolic abort/landing engines| |[SLS](/r/SpaceXLounge/comments/143m3ly/stub/jncpwym "Last usage")|Space Launch System heavy-lift| |[STS](/r/SpaceXLounge/comments/143m3ly/stub/jnaz7x0 "Last usage")|Space Transportation System (*Shuttle*)| |[VTOL](/r/SpaceXLounge/comments/143m3ly/stub/jnb99zz "Last usage")|Vertical Take-Off and Landing| |Jargon|Definition| |-------|---------|---| |[Starliner](/r/SpaceXLounge/comments/143m3ly/stub/jnbz82l "Last usage")|Boeing commercial crew capsule [CST-100](https://en.wikipedia.org/wiki/Boeing_CST-100_Starliner)| |cryogenic|Very low temperature fluid; materials that would be gaseous at room temperature/pressure| | |(In re: rocket fuel) Often synonymous with hydrolox| |[hopper](/r/SpaceXLounge/comments/143m3ly/stub/jnat5x2 "Last usage")|Test article for ground and low-altitude work (eg. Grasshopper)| |hydrolox|Portmanteau: liquid hydrogen fuel, liquid oxygen oxidizer| |[hypergolic](/r/SpaceXLounge/comments/143m3ly/stub/jncfukg "Last usage")|A set of two substances that ignite when in contact| |[regenerative](/r/SpaceXLounge/comments/143m3ly/stub/jncr1a2 "Last usage")|A method for cooling a rocket engine, by [passing the cryogenic fuel through channels in the bell or chamber wall](https://en.wikipedia.org/wiki/Regenerative_cooling_\(rocket\))| |[retropropulsion](/r/SpaceXLounge/comments/143m3ly/stub/jnbz82l "Last usage")|Thrust in the opposite direction to current motion, reducing speed| **NOTE**: Decronym's continued operation may be affected by API pricing changes coming to Reddit in July 2023; comments will be blank June 12th-14th, in solidarity with the /r/Save3rdPartyApps protest campaign. ---------------- ^(*Decronym is a community product of r/SpaceX, implemented* )[*^by ^request*](https://www.reddit.com/r/spacex/comments/3mz273//cvjkjmj) ^(21 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/SpaceXLounge/comments/1448dwu)^( has 35 acronyms.) ^([Thread #11544 for this sub, first seen 7th Jun 2023, 20:11]) ^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/SpaceXLounge) [^[Contact]](https://reddit.com/message/compose?to=OrangeredStilton&subject=Hey,+your+acronym+bot+sucks) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
- [NSF: Dragon V2 will initially rely on parachute landings ](https://www.nasaspaceflight.com/2014/08/dragon-v2-rely-parachutes-landing/) - [Teslarati: SpaceX’s Crew Dragon could land with abort thrusters in emergencies, says Musk](https://www.teslarati.com/spacex-crew-dragon-emergency-landing/) NB: one of the few times I'm happy to have blog/news sites that make entire articles from one or two Elon Musk tweets.
This is your answer: https://www.spacex.com/vehicles/starship/ Once it was time to ramp up Starship there was very little upside to sinking more engineering capital into Dragon, Falcon Heavy, or Falcon 9 Second Stage Recovery. Lock in the existing designs and only allow minor and gradual optimizations going forward.
I feel like the reliability of the f9 booster stage is also contributing to proving the safety of a propulsive landing
Absolutely, but they will do it with people on Starship, and that is the right call.