SpaceX Launches CRS12 Mission
SpaceX Launches Cargo Resupply Mission to the Space Station (With multiple videos)
“Experiments seeking a better understanding of Parkinson’s disease and the origin of cosmic rays are on their way to the International Space Station aboard a SpaceX Dragon spacecraft following today’s 12:31 p.m. EDT launch.”
“Carrying more than 6,400 pounds of research equipment, cargo and supplies, the spacecraft lifted off on a Falcon 9 rocket from Launch Complex 39A at NASA’s Kennedy Space Center in Florida on the company’s 12th commercial resupply mission. It will arrive at the space station Wednesday, Aug. 16, at which time astronauts Jack Fischer of NASA and Paolo Nespoli of ESA (European Space Agency) will use the space station’s robotic arm to capture it.”
So much has been said about these launches here on Nasawatch and elsewhere, about how terrific it is, it’s a game changer, yada yada.
Repetition doesn’t take away from the magic of an orbital-class booster returning to earth, asking “what’s next?”
14 returned boosters out of 19 attempts. 40 launches, 1 explosion, 1 failed to reach orbit, 1 failed secondary payload. Make it 74% for the booster and 93% for the payloads. And 100% since CRS-7.
It never, ever gets old for me. It’s like seeing something crazy from Kerbal Space Program actually happening.
And a question of the smart people: just what velocity is needed before atmospheric heating is an issue? The booster achieves 4400 km/hr± on the decent, for instance, according to my eye as I watched the replay. The bottom end of the rocket is composed of all sorts of exposed parts.
I suppose the engine nozzles are immune from heating effects, and possibly the engine environment is hardened in some way. But are re-entry class speeds needed before heat shields are required? I was thinking specifically about the steering vanes, exposed as they are and being comprised of (what appears to be) thin waffle-like metal. They appear to be awfully insubstantial, although of course they are not.
Titanium now because the Al ones melted enough to be replaced after each flight. Mr. Musk tweeted after the first use of the new grid fins that they’d be good for many flights. Ablata on the legs I believe, don’t know about the rest.
Amazing to watch descent all the way down to the Cape from 95 km. Looked like a Chesley Bonstell painting.
The original waffle fins on the first stage were aluminum. But, they have since been changed to titanium.
I’ve heard that this last launch used aluminum fins, possibly to use up stock on low energy returns.
Does not the re-entry burn help serve in part (if not completely) as a means of helping to shield the vehicle from atmospheric entry heating? This idea is not new; way back when with Boeing’s proposal for a ‘ballute’ on Orbital Transfer Vehicles part of the design included an engine firing to create a shielding slipstream over the ballute’s surface.
I vaguely recall that Peter Hyams grabbed this idea and used it in his often-atrocious rendering of Clarke’s 2010.
I think the rocket exhaust does shield the booster from re-entry and is one of the biggest innovations from SpaceX. NASA imaged areturning F9 booster during its re-entry burn and I think that effort was associated with possible use for Mars re-entry. If this works at Mars, it could provide a means for landing large craft on Mars.
The obviousness of the innovation—that is, allowing a very small amount of fuel that is used to slow the now-quite light booster— really sticks out.
Decades of Flash Gordon, and nobody ever thought of returning a rocket to earth? It is so obvious— I suppose that there must be an enabling technology previously missing, but what? GPS, perhaps? [ed.: radio beacons would work just as well].
Why have we assumed, until SX, that boosters would be splashed? Why hasn’t the industry looked to returning boosters before?
I wouldn’t be surprised to learn it needed some deep learning algorithms to perfect it, but that’s speculation.
They are using convex optimization techniques to control the landing burns. The algorithms for this didn’t exist in the 1970s (nor flight computers powerful enough to run them, I strongly suspect.)
Convex optimization.
In the past all these rocket companies made enough money, they didn’t have the need to develop fly-back boosters.
Also, I think when Elon started hiring his rocket engineers they told them it really could be done. He said the only profit he can make is along the margins..he crunched the numbers and realized that eventually, after A LOT of flights that this will pay off.
And I thought that I was skeptical!!
All kidding aside, this explanation just doesn’t wash. There are simply too many very smart and very creative engineers, many of who read this site, and thee words. And to brush off this obvious Big Leap because it’s not “needed”? Just doesn’t make sense.
I think I’m on to something here.
Perhaps splashing simply became the modus operandi in the industry? No.
Or perhaps the really creative engineers were all enamored of the winged approach, thinking rockets to be “old hat”, so why even think about developing them? No.
Maybe the community was focusing on SSTO, seeing vertical rockets as “yesterday”? No.
Or perhaps the rocket equation, brutal as she is, precluded forward thinking? No.
I’m out of ideas here. Elon did something very simple, as it appears in hindsight; he created a rocket with sufficient capacity to allow a modest reserve for landing. Maybe the answer lies in the steps taken by SX to achieve the extra lift authority? This would mean that the enabling tech wasn’t a single thing; rather, many things have a part, including super-cooling, the use of lighter weight tanks and other components, and other improvements very far in the weeds and out of my personal reach.
Even that doesn’t really make sense. How often, before SX, did anyone ever talk about the criticality of returning boosters? I listen to a lot of space-blowhards, some serious, some not so much, and can’t recall anyone speaking about it.
But there it is.
From what I remember, NASA engineers worked real hard on flyback boosters for the Shuttle way back in the 70’s. It proved to be too expensive(there’s the $ popping up it’s ugly head again) and they dropped it.
Heck, I don’t know how SpaceX even does it. How do they get the booster to take a sharp turn just after separation? How do they know when to stop the boostback burn? Is all this preprogrammed or is there some person on the ground sending signals back and forth? I’m really impressed by the re-entry burn, who figured that one out? How does it find the landing pad?
Maybe it’s just that people like Elon Musk are willing to take risks that other people aren’t. We do live in a risk averse society.
Falcon 9 uses cold gas thrusters to do the flip. Big ones.
No one on the ground is controlling the landing – it’s all automated from liftoff to touchdown.
Look up a guy named Lars Blackmore, who SpaceX spirited away from JPL – along with about half a dozen others. He’s SpaceX’s Principle Rocket Landing Engineer/Wizard.
https://www.technologyrevie…
Quartz article
https://qz.com/915702/the-s…
Michael,
I feel that you are looking backward into history from the present with too many presumptions, some seemingly colored strongly by your adulation for the basic idea of propulsive stage return, to properly put ‘the innovation’ into context’.
As others have noted, a lot of engineers over decades (especially in the 70s) explored the possibility of reusing booster stages. Prior to that, getting the payload into orbit was everything and (as you hinted) the weight margins were tight enough that everything had to go towards going up, not bringing anything down for reuse. VTVL was in fact considered with some monster SSTO booster ideas, but these never got far beyond the viewgraph stage.
For shuttle, many configurations were explored but one might say that the engineering community at that time viewed fly-back as the most elegant means of bringing a liquid booster back from the dynamic circumstance of staging to the landing site. Frankly (and, again, restartable & throtteable main booster engines had not yet been developed…the SSME was blazing a trail first of reusability, not re-startability), the challenges they were grappling with were sufficient for the then-industry’s capacity. Even the idea of having something fly back by itself (winged or otherwise) was on the edge of the technology at the time; remember that most of the early shuttle thinking had a manned flyback booster, and that was even abandoned in part because the complexity of the manuever to separate from the ascending orbiter and fly the booster back to the Cape was a daunting control-systems & thermo-aerodynamic challenge. Even the accepted/approved shuttle RTLS abort mode (executing a portion of what the Falcon 9 booster does to return) was viewed by many in the program as very, very dicey…an ‘I really really really hope we never have to do this’ sort of thing.
If you’re looking for ‘the reason’ (I would offer that there are many, some of which you have identified) that the innovation didn’t come sooner was because a number of the technologies (control systems, materials, restartable booster engines) weren’t mature enough to give engineers ‘the idea playground’ to be able to say comfortably to themselves ‘You know, this IS achievable’. I would offer that SpaceX’s achievement in this regard is that they were open-eyed enough at the right time to recognize that the technologies were indeed finally there (or nearly there)…and they pushed those not quite there where needed to bring them into workable hardware & ops.
But as noted already, every engineering choice is a trade-off: they are sacrificing payload capacity to do it, which is something that was anathema to ‘rocket science’ for a very long time. Shuttle was the first program to fully embrace this sort of cost as acceptable for the sake of pushing forward partial reusability with hopes of reducing cost.
Major innovation is rarely a single Eureka moment; the writings of James Burke and Henry Petroski do a fine job of exploring & highlighting that engineering advancements are woven into the complex evolutionary history (technical, social, political) that produces them. I highly recommend their writings.
Too many presumptions? You are absolutely correct about that!
Thanks for the thoughtful response, as this question has been on my mind for some time. The explanation that many technologies approached maturation at the same time is indeed compelling. But there is something about the ⅓ penalty, and the “fuel is cheap” phrase that need exploring.
I’ll need to think more about this, and continue the discussion in a future thread; I’m packing for a trip to St. Louis for the Big Event on Monday.
It’s been a standard idea for a long time. The vertical landing is new, the prior assumption was horizontal landing. But the idea of returning first stages, mainly boosters, has been around for a long time.
For example, Russia’s Baikal boosters for Angara. Proposed flyback liquid-booster replacements for the US Shuttle. (Hell, there was even a proposal to equip the SRBs with twin parafoils and fly them back to land.) Russia proposed a flyback main booster as part of Energia-2. Buzz Aldrin’s Star Booster concept. And going back to the original Shuttle concept by North American.
Plus things like the Zenit boosters were reusable, but not fly-back. (They descended by parachute and were recovered down-range.)
To answer some of your question, there is a tendency in aerospace to focus on extracting the last ounce of performance from a system regardless of cost. “Low cost” is just not baked into the zeitgeist. SpaceX’s design loses around third of its payload to LEO, and 2/3rds to GEO/BEO because of its version of reusability. Musk’s reasoning? “Fuel is cheap”. But that loss is an anathema to most aerospace engineers and their managers and funders. If you’re comparing two proposals, and one gets three times the performance of the other, with no other hardware changes, which one do you pick?
It’s why even the “reusable” proposals from ESA and ULA to compete with Falcon only recover an engine module. Either runway landing (ESA) or mid-air recovery (ULA). Both hideously convoluted and complex, and therefore inevitably expensive. But they will get more performance than Falcon per ton of wet-vehicle mass.
Interestingly, the fly-back booster for that NAR Shuttle concept was piloted.
“The vertical landing is new, the prior assumption was horizontal landing. “
Vertical landing isn’t a new idea. In fact, that idea was successfully proven by DC-X decades ago. NASA, however, abandoned that landing mode when it chose the “winner” for X-33.
Henry Spencer used to say something like, there is nothing magic about wheels on a runway that reduces launch costs.
MS’s comment was “Why hasn’t the industry looked to returning boosters before?” and I responded to that; boosters and first stages.
I know MacDAC and Masten both played with VTOL vehicles. But when you look at actual reusable booster proposals, they are almost exclusively VTHL or HTOL. The exceptions are SpaceX and BO. (AIUI, BO and Masten both picked up ex-DC-X alumni.)
DC-X as a tech maturation for fly-back boosters and first-stages would have been interesting. But it was conceived solely as an SSTO (another corrupting obsession), even though the VTOL demonstration was the only useful thing it would ever do, even if it had been allowed to continue.
Agreed. In hindsight, there was a lack of vision by the “fly back booster” crowd following the success of DC-X. In hindsight, the cost of converting an expendable booster to a vertically landing one was minimal compared to the projected development costs of building a horizontally landing booster.
If all goes well, we should finally see a test flight of fly back “strap-on” boosters this year, but they’ll attempt a vertical landing on simple concrete pads.
Random aside:
I just noticed that the Fastrac engine program started just one year after DC-X was killed. Imagine an RP-1/LOx VTOL test vehicle built around the 270kN Fastrac engine. In 2001.
(Of course when the Fastrac team actually proposed a test vehicle for Fastrac before it too was cancelled, they picked… an air-launched wing’n’wheel HL spaceplane. D’oh!)
It does, yes; watch the velocity of the returning vehicle as it zooms up, then way down after the burn. But it returns to the neighborhood of 4400 km/hr or so.
Terrifying speeds that exemplify the very high—and contained—energies involved in space flight.
Even so, I should add parenthetically, the energies we will need to achieve any sort of mastery over space and spaceflight will exceed these huge amounts by several orders of magnitude.
That’s not an easy question to answer. Heating depends on atmospheric density as well as velocity. But at the same altitude, 4400 km/h (1.2 km/s) would produce about half a percent of the heating experienced by something at orbital velocity (I used 7.5 km/s.) All other things being equal, drag is proportional to the square of the speed, and heating proportional to the cube of the speed.
But something at orbital velocity would probably slow down significantly before it got too deep in the atmosphere. So, if you’re thinking of a Falcon 9 second stage recovery, and how it would compare to a first stage recovery, that would depend on the trajectory (speed versus altitude in particular.)
I believe they do have TPS on the bottom and on grid fins, it’s not the strong stuff used on Dragon, but it’s there. You can see some part of the TPS layer peeled off in close up shots of the returned booster (the best photos are taken when booster is on the barge or in the port area), and you can see ablatives on the aluminum grid fins burning off when booster flies back from GTO launch.
Nice video of the return and landing.I hope NASA has checked what follows. Here is my new theory on why the F-9 blew up on the pad. Metal fatigue or metal stretching. They found cavities between the carbon fiber and metal liner. The carbon would not deform. The metal liner had to have a dimple in it. The only way it could form is if there was not 5000 psi in the helium tank. The LOX was loaded with no pressure in the helium tank. The LOX tank self pressured and the presssure got to the liner causing dimples. This may have stretched the metal making it weak or several loading cycles caused metal fatigue and it cracked. When they found the helium tank there was the dimples since there was never full pressure in the helium tank to push the dimples out. They then started helium flow and it went through the crack and pressurized the LOX tank blowing it out. If the carbon fiber had burned there would not be any dimples since the 5000 psi would have straighten them out. I started thinking, what did the cavities have to do with it? NASA gave a vague answer to a reporter and Space-X said nothing when asked to explain what happened.
Who else noticed two interesting things about this launch? Watch the video “CRS-12 Launch Webcast” on youtube. 1 – You can see the 1st stage booster beginning it’s burn from the camera on the 2nd stage at 16:19 as it moves under the 2nd stage engine nozzle and again at 16:25 where it emerges from under the nozzle. And 2 – It almost looks like a spider or bug crawling across the Dragon right as the first SA is deployed. Go to 26:42 on the video, and watch the lower left corner for a black “ball” roll across the body of the dragon towards the base of the SA. Probably just a video anomaly but it is odd.
https://www.youtube.com/wat…