The Real Secrets of Rocket Design Revealed

[@clevergirl4457]

it's a good day when a new Eager space video drops

[@keithrange4457]

Agreed. This has become one of my favorite channels

[@chrisp1601]

ULA salesman slaps rocket. “This bad boy can fit so many high energies in it!”

[@TimJSwan]

😂

[@impossiblescissors]

This video is an excellent companion to the video on Vulcan engine recovery. The higher staging altitude greatly complicates the process.

[@EagerSpace]

You just can't do propulsive landing with the Vulcan first stage even if you had a cluster of engines. Falcon 9 runs right on the edge of not getting too hot - they melted early grid fins when they were made out of aluminum - and they are still paying somewhere around 25% of their payload penalty. Vulcan is going way way faster, which means a huge amount of fuel to get it to survive reentry. I'd be surprised if the payload penalty was less than 50%.

[@plainText384]

I don't know if an inflatable heatshield + parachutes is really that much more complicated than a propulsive landing on an ocean platform. Sure, you introduce an additional staging step and inflatable heatshields are relatively new. But if you think about it, the concept isn't that crazy. NASA has been flying tech demonstrations for inflatable heatshields for a while now (LOFTID, etc.), and landing the engines seperately without the disposable tank has already been done with the Space Shuttle. The parachutes and heatshield combo is also a known, uncomplicated method for reentry. It's passively stable, it doesn't need to relight any engines and a splashdown allows for much less precision in the guidance compared to a propulsive recovery. You do need to integrate the engine section with a new rest of the booster every time, but the actual recovery else seems simpler and less complicated to me.

[@EagerSpace]

Parachutes are notoriously finicky in capsule applications, with a lot of complexity there. If you look at the amount of parachute testing that Orion, dragon, and starliner have required I do not think the word uncomplicated can be applied. Propulsive landing has turned out to be ridiculously reliable. We have very limited data on inflatable heat shields and we do know that parachutes fail. The big issue is that the reuse requires you to go back to the factory, recertify the whole engine pod, test it, attach it to a new airframe, then ship it back to the launch site. Where with propulsive landing your stage is already in the right location and your recertification work is much less.

[@Wisald]

24:25 I know I'm nitpicking but second is written as lowercase s, capital S stands for Siemens (unit of conductance) in my trade.

[@EagerSpace]

Thanks.

[@robberbarron7602]

Great video! I am very grateful that I stumbled upon this channel

[@EagerSpace]

Thanks.

[@firefly4f4]

I think it was Scott Manley who pointed in his video on the two engine centaur for Starliner that the reason that Atlas staged so late and high was because with the RL10 being efficient but low thrust meant the centaur needed that extra height & velocity or it would just fall back into the atmosphere before it got up to orbital velocity.

[@EagerSpace]

I talk about this a bit more in my Vulcan video. Atlas V ended up with that architecture because there wasn't any real choice - ULA needed an upper stage engine and it was either the RL-10 or maybe try to get somebody to build a version of the J-2X for them.

[@toddwerme121]

Where is the link to the paper? Want to read the paper, but I don't see a link.

[@lanzer22]

Just Google the title of the paper, add in "tory bruno" for good measure and you'll see the article on Medium.

[@EagerSpace]

It's there now.

[@toddwerme121]

@@EagerSpace Thank you!

[@bmobert]

Right on target. Both accurate an concise.

[@musicaldev5644]

🎉 Thank you for the regular video uploads

[@steamfire]

Link is missing in the description

[@EagerSpace]

The most useful comment I've read... Fixed.

[@donjones4719]

Nobody does this stuff better than you, Eric. You make your arguments and nail them down with a big hammer. Btw, one bit is especially funny. 25:15 If I tell my brother Sam I'll pay for nearly all of the gasoline for a long trip and I only pay for about half of it, I will quote Tory. I'm sure Sam will be satisfied.

[@807800]

Have you been blocked by Tory, yet?

[@EagerSpace]

No. I have had a couple of interactions where we were having a discussion and he didn't respond after a certain point, but he's a CEO with a lot of balls in the air and I'm a retired dude who does space videos.

[@TotallyNoAim]

@@EagerSpace really good space videos!

[@Jason-gq8fo]

@@EagerSpaceyou sound younger 🤔

[@Ormusn2o]

This explains so much. No wonder Tony plans on reusing the engines from such a high attitude, he just does not understand you need to make your rocket from first principles, it can't be just an afterthought.

[@807800]

@@Ormusn2o It's indeed an afterthought, but that's just how it is when you have to deal with what you got, just like how it's already being explained in the video.

[@gavinregier6177]

Who's Tony Bruno? Lol jk, great video as always, keep up the good work.

[@gasdive]

He's the guy who's committed to social media engagement. The one who blocks everyone who comments on any of his posts, and blocks anyone who comments on any posts that are from someone who commented on his posts.

[@tygerbyrn]

@@gasdive Aha! Revenge of the Meta-Poster!

[@dancingdog2790]

He's seeing a man about a horse 😎

[@TimothyLipinski]

Great Comment ! He had a write-up in the AIAA magazine in October 2019 issue ! tjl

[@opcn18]

Were these calculations for Starship/Superheavy delivering 20 tons to GEO done before the payload to LEO was revised from 150 tonnes to N/A?

[@EagerSpace]

I used the ones I did because 150 tons to LEO is what ULA chose to use in their charts, so the GTO (not GEO) numbers are in line with that capability. The point was to show that if starship does 150 tons to LEO this assumption that it can't get to GTO is flawed. Capabilities for Starship have squishy numbers because of the nature of the program. By starship, do you mean OFT-3? OFT-4? One of the starship 2 proposals? Where they will be when they first start launching Starlink? Where they will be when they launch commercial payloads? You can make arguments for all of them, so I choose what I think makes the most sense for the context, talk about my caveats, and figure that people understand that Starship is still in development and it's a weird project because it's going to change a lot before it's done.

[@opcn18]

@@EagerSpace Using the assumptions that ULA did seems justified, but why then are you using numbers for "probably a one way trip" instead of the reusable capacity?

[@Yrouel86]

Always questioning only one side. Have you asked TF why he's still claiming Starlink is subsidized even after he was corrected multiple times? Have you asked why he's claiming Soyuz seats are cheaper than Crew Dragon using price tags from decades ago and for tourist flights?

[@EagerSpace]

I probably wasn't clear on that. Take the reusable payload to Leo as a baseline. Figure out how much the payload would be reduced if you go to GTO. This is still assuming the heavy reusable starship and fuel for landing. My one way comment is because you may need more fuel to get starship back into a survivable re-entry trajectory.

[@clipwhatcherdude]

This channel is amazing

[@noname117spore]

Good video, exactly what I’ve been saying for awhile, about how ULA’s architecture was defined by engine availability. I do think a really in-depth comparison, in cost, efficiency, payload retention, and etc, for various forms of reusable vs expendable rockets would be cool at some point. Like, do “stage low” and “stage high” strategies, when efficiently designed, each have areas where they’re best, or does “stage low” win out for practically all non-interplanetary-space missions? No refueling, although I’d be curious to see how kick stages influence things there too.

[@xponen]

High staging is standard in rocketry because upper-stage engines, which have high impulse, typically have a low thrust-to-weight ratio. This means they need to be staged at a high altitude to have enough time to reach orbital speed.

[@Freak80MC]

I know KSP isn't anywhere near close to accurate real life, at least in terms of engineering, but it's funny how I sorta came to that stage low vs stage high conclusion myself when I was making my own reusable rockets. I didn't want to stage my rocket so quickly that the first stage would be coming back in too quickly and burn up or be unable to slow down enough.

[@EagerSpace]

It's a challenging question and the only real answer is to do actual trade studies. SpaceX knows the answer to this question but it took a lot of engineering time to get there. I do have a few thoughts... Staging early wins for reuse because a) you spend to get back to a drone ship or RTLS and b) the less velocity & distance you have, the better. This is especially true for RTLS and it's not surprising that starship is moving to have super heavy do less work - the less work it does, the less RTLS costs. The countering force is that a rocket where both stages do 5000 m/s of delta v is easier to build and has a higher payload than one where it's imbalanced - 2000 m/s in the booster and 8000 m/s in the second stage. The low delta v part is easy to build, the high one is really hard to build as it needs to be very light and that's expensive. The limiting case is obviously a SSTO which is a bad idea in my book. It is *very* interesting that SpaceX seems to be moving starship to as close to the an SSTO as practical to get the RTLS costs down as low and to get the booster back as soon as possible. If you want to do reusable, I don't think it's worthwhile to consider any approach where you don't get the first stage back intact, and from what we see, that seems to be the conclusions of everybody except ULA. I don't see a lot of reason to design towards "stage high" and trying to get a ton of delta-v out of the booster as a principle - you are carrying more mass higher and accelerating it more and that's an energy loss. I do want to note that delta-v is one way of looking at things but it ignores gravity losses and they turn out to be quite important. For boosters, thrust is really a dominant factor because you are paying gravity losses during the whole launch.

[@EagerSpace]

Yes. Or to look at it another way, you need a big beefy booster to give them enough vertical acceleration so that they don't just fall back to earth.

[@rockapedra1130]

Wow! Great video!

[@marksinclair701]

Very good explanation. I wonder for how much longer it will be acceptable to deliberately dump spent dirty solid and first stage rocket boosters in the ocean? They were all given a pass when no other option existed, but with booster reuse proven viable I think SpaceX could reasonably try to make this an issue. It also seems like a strategic blunder to rely on BE4 engines when they will be presumably be preferentially allocated to New Glenn when that starts flying. Why didn't they produce their own engine? And what happened to ULA's reuse plans?

[@jamskinner]

Maybe ULA should have used BE4 temporarily while designing their own engine for later use.

[@Shrouded_reaper]

It will be acceptable as long as it needs to be. Note the outcry from the media about some metal scraps at Boca Chica but total silence on everyone else dropping whole stages into the ocean. Pretty obvious agenda.

[@SpaceAdvocate]

@@jamskinner Changing the engine generally means making changes to the entire rocket. Very few engines are interchangeable. All the required effort that would go towards redesigning the rocket could be dispensed with if they just went straight to designing their own engines. But ULA hasn't shown any interest in designing their own engines.

[@benjaminmeusburger4254]

tbh that would be a weak argument Falcon 9 first stage is ~25t Fully stacked a Falcon 9 + fuel weights about ~550 tons Therefore they burn fuel+2nd stage in the atmosphere and only reuse 5% hell, in their final constellation for Stalink with 42,000 satelites they plan to deorbit them after 5 years = 23 satelites per day

[@EagerSpace]

Engine development is hard and time consuming and ULA doesn't have expertise there; they would have to spin it up and it's not clear that the money invested would produce a better result. The BE-4 contract they have with Blue Origin puts them at the front of the line for engines.

[@snapshuttre]

that's real detailed explaination

[@gasdive]

Even if refilling never happens, SX can fit an entire fully fuelled F9 second stage and payload into the cargo bay of Starship and take it *ALL* the way to LEO. They can, and do build 3 of these a week, and they obviously cost less than 70 million. They have in flight restart capacity and so can take more mass to GEO than Vulcan can take to GTO.

[@sidharthcs2110]

Starship can barely put 60 tons to LEO and doesn't have enough room for a Falcon 9

[@gasdive]

@@sidharthcs2110 the Starship payload bay is 22m long, 8m wide. An F9 upper is 12m long and 3.6m wide. Maximum payload for Starship isn't yet known, but the test articles are lifting 60 tonnes, which means a half full F9 upper stage, so still much more mass to GTO than Vulcan (the first half of the propellant burn provides much less Delta V than the second half for obvious reasons. Clearly the final design will lift more than the current test articles.

[@SpaceAdvocate]

@@gasdive With the current Starship, you'd probably be better served delivering a full Falcon 9 second stage to *near* orbit, and then landing the Starship in Africa or on a barge. It means you are on a timer for releasing the Falcon 9 stage from the Starship, but you should still have several minutes before the Starship would start to reenter. But I don't think solutions using the current Starship are very relevant. SpaceX has already started building the version that is supposed to be able to do 100 tons to LEO.

[@robertbackhaus8911]

If you were going to put a third stage in Starship, you wouldn't make it a F9 second stage. The reason is, well, this video. The F9 second stage is a heavy stage with a big engine. You would want a very lightweight stage with a small engine. It would be a perfect application for a nuclear thermal rocket, if you want to wander off the sharp edge of the tech readiness index.

[@Niosus]

@@SpaceAdvocate Honestly, I think that it makes sense for SpaceX to develop an expendable upper stage at some point. The Falcon 9 model works really well. Instead of having to do all the refueling flights, I think in some cases it might make sense to have a classic second stage (with almost surely a third as well) that's nice and light that can really throw a heavy payload far in a single shot. They pay a huge cost due to all that dry mass. Convert a large chunk of that to fuel, get rid of the landing margin, and suddenly you have an architecture that can lift entire space stations at once. I'm not saying Starship doesn't have a place. I just think there is probably room for both.

[@Yrouel86]

ULA marketing spiel of "low energy" vs "high energy" has the same vibe of "It's Toasted" from Mad Man (it was an actual ad): Highlight something irrelevant about your product to wow the less knowledgeable people, like politicians for example... As being toasted is irrelevant in the context of discussing health issues of smocking, being high or low energy is irrelevant in the context of discussing the ability of either provider to actually complete missions. And being both contracted to launch NSSL launches means by definitions they both are equally able to complete such missions indeed making high vs energy somewhat disingenuous marketing bs

[@EagerSpace]

ULA isn't doing these papers for us, they are doing them to try to influence decision makers in the space force, DoD, and Congress. Differentiation is a tried and true marketing technique, but it's hard for ULA because the SpaceX holds most of the cards and Vulcan still isn't certified yet. So we end up with stuff like this. My big complaint isn't that they are trying to differentiate, it's that they do it so poorly.

[@zeevtarantov]

@@EagerSpace But surely decision makers in Space Force, DoD, NRO, Congress, etc. have qualified staffers who can tell them it bullshit and "just look at price per mission" ?

[@plainText384]

In a speech at the SpaceCom conference in late January of this year Tory Bruno claimed “We run about 34% cheaper on a high-energy mission than the other one, SpaceX, does,”. That's what this is about. ULA has identified a specific category of mission requirements, where they could outcompete SpaceX's Falcon Heavy (probably because SpaceX needs to expend the core stage to complete the mission) and they which think will take up an increasing share of the NSSL market. Yes, this isn't a new capability. Delta IV Heavy was also able to complete such missions, but Vulcan is not just able to do these missions, it's good at them. So it's not just meaningless marketing BS, like "It's Toasted", it's marketing BS based on a real advantage (for a certain subset of customers), like "gluten free" (important if you have gluten intolerance, not so much for other people).

[@SpaceAdvocate]

@@plainText384 A fully expended Falcon Heavy likely has a cost in the area of $80 million ($20 million per core, plus $20 million in upper stage, fairing, ground systems, etc). A Vulcan Centaur VC6 likely has a cost in the area of $110 million ($6 million per GEM-63XL, $8 million per BE-4, $20 million per RL10, $18 million in structures, ground systems, etc). The rest is marketing and pricing strategy for maximizing profits. I don't think SpaceX would get out of bed for less than a 50% gross margin. They're just too busy with other stuff.

[@Yrouel86]

@@plainText384 But their high energy vs low energy marketing does not advertise they are cheaper it implies that only they are qualified for/capable of those high energy launches, that''s the bs. The only launches that SpaceX can't do (yet) are for payloads that require vertical integration (which might not be that many anyway) but again this is not what they talk about. Also I wouldn't blindly believe Bruno on being cheaper on those high energy missions because it could very well be some accounting "trick" (like when they got paid for development but was separate from launch per se while SpaceX had to tack on extra infrastructure money to a launch task order) or some other not exactly fair/honest comparison

[@zeevtarantov]

It's clear, but you don't actually say that Falcon 9 and Falcon Heavy are more efficient and more optimized for Vulcan's target missions that Vulcan itself. Vulcan does not beat a rocket that flew before it was designed. SpaceX can either beat Vulcan on price by a huge margin or collect a lot more profit than Vulcan by a huge margin, or be visibly cheaper than Vulcan while collecting the same amount of profit.

[@EagerSpace]

I'm not a big fan of words like "efficient" or "optimized" because they aren't well defined. As for price, I do think there's great evidence that SpaceX bumped up their prices for NSSL 2 considerably because otherwise they would be leaving money on the table, and similarly for NASA. SpaceX is doing extra work for the gateway launch for NASA, but they're getting paid $330 million for a Falcon Heavy launch.

[@zeevtarantov]

@@EagerSpace I meant "efficient" and "optimized" in terms of bang for buck. We can go by price to customer or by estimated cost to SpaceX which sets price floor in case of competition which is cheaper than ULA or Ariane.

[@plainText384]

@@zeevtarantov I don't think we have particularly reliable sources on internal costs or profit margins on these launches, and comparing prices is sort of pointless since if they feel like putting in a competitive bid, they both end up at very similar prices (that's just the nature of markets and bidding). Pretty much the only thing we know is that unlike with Delta IV heavy, ULA is able to make bids with Vulcan Centaur that are competitive to (and in some cases even cheaper than) comparable launches on a Falcon variant. Whether that's because SpaceX doesn't want to go lower, SpaceX can't go lower, or because ULA can't or doesn't want to go lower, we don't know. The market isn't that competitive, so if ULA and SpaceX wanted to raise prices and milk profits while their duopoly lasts, there's nothing really forcing them to race to the bottom.

[@EagerSpace]

Exactly. With a duopoly, we would expect the two companies to end up roughly at the same prices and that's what we get.

[@billhamill]

@@EagerSpace Bumping up prices to match the competition especially when the customer preferred the competition on volume = smart business by SpaceX

[@plainText384]

27:16 that's not really how gravity losses work though. Gravity losses aren't an on-off switch that are constant until they stop when the spacecraft enters a stable orbit. Gravity losses are related to the radial-out component of the engines thrust. If the engine is pointed nearly parallel to the earths surface (like it would during the later parts of the ascent) you have basically no gravity losses. If the engine is pointing straight up (like it would at liftoff) you are losing a full g of accelleration to gravity losses. That is also why TWR is so important on a first stage, but not on an upper stage. With that in mind it's not obvious which one of these two rockets has more gravity losses based on the time to orbit alone, as the inital portion of the flight (when the rocket is pointed more upwards) will have a greater impact. You would probably need to have additional information (attitude, thrust, etc.) to make such an analysis. The right side graph is slower up until ~T+450s, and T+450s is probably late enough in the mission that the rocket is oriented horizonally and there are no more gravity losses. BUT at the same the left side may also have required a steeper ascent profile to enable the low TWR upper stage, which would have caused more gravity losses early in the flight, so it's not possible for me to easily conclude that the left side (AtlasV) had lower gravity losses either. Again, I just don't think these give two graphs give you enough data to make that determination.

[@EagerSpace]

I have a full video on gravity losses that I probably should have linked to. Gravity losses are roughly proportional to the angle of the velocity vectory; if you are travelling straight up your gravity loss is G while if you are travelling at orbital velocity to the side, the earth is curving away from you at the same rate you are falling towards it, so your gravity losses are zero. To figure this out you need to walk the trajectory path and figure out the gravity loss at each point, then the sum is the full gravity loss. It does depend on the trajectory that is flown and the thrust/weight ratios of the stages. But the Falcon 9 is in orbit in about 490 seconds, and the Atlas V requires about 650 seconds. Seems pretty hard to spend 160 seconds more in a gravity field and have lower gravity losses, especially since you are flying a more lofted trajectory to compensate for the low thrust/weight ratio of the second stage.

[@plainText384]

@EagerSpace I think you misunderstood something. Gravity losses are NOT proportional to the angle of the velocity vector, and you are still in the gravity field after entering orbit. If you are in a highly elliptical orbit, your velocity vector will be pointing up/out at certain points in the orbit, yet you don't have gravity losses on every single orbit. No, gravity losses are proportion to the angle of the THRUST vector (really the up/outward component of the acceleration from the engine). Early in the flight, when you are trying to get out of the atmosphere, this thrust vector will be pointing almost straight up. But if you look at the graphs, Atlas V actually has a higher thrust to weight ratio at this point in the flight and will therefore have lower gravity losses here. Falcon 9 only has a higher thrust to weight after about 250-300s, when the vehicles will have already pitched over significantly and will be accelerating largely parallel to earth's surface, so gravity losses are strongly suppressed. So, at first glance, it seems like Falcon 9 is likely to have more gravity losses. But that's only if we, I the absence of more data, assume both perform the same pitch-over maneuvering and attitude is the same function of speed for both vehicles. It is possible that the lower TWR of the second stage forces ULA to take a somewhat steeper ascent, which would cause higher gravity losses early on in the flight. But without the attitude data and some actual math, it's just not possible to definitively say which one has higher gravity losses, as there is a lot more to gravity losses than just time to orbit.

[@SpaceAdvocate]

@@plainText384 Centaur has to keep the thrust vector pointed at a significant angle towards the ground for quite a while. This is to keep it in space long enough to actually get to orbital speeds. The Falcon upper stage doesn't really have to do this - it reaches orbital speed before reentry is an issue. It's very obvious if you look at the animations from ULA launches.

[@EagerSpace]

Gravity losses are based on the velocity vector. Go straight up 10km, aim your thrust fully horizontal, and you will drop our of the sky because gravity will pull you down. Orbit is all about having enough horizontal velocity so that the acceleration of gravity is matched by the curvature of the earth, and you didn't have gravity losses in orbit. At least for circular orbits - elliptical orbits are more complicated.

[@plainText384]

@@SpaceAdvocate I looked at the "Atlas V GOES-S Mission Profile" animation and there was almost no pitching up shown by the Centaur upper stage.

[@king_br0k]

25:25 not the best choice of colors, they look almost identical with a blue light filter A black line at the transition would help

[@andreasboe4509]

Great video. Thanks.

[@timjones102]

I really appreciate the thoughfulness and nuance but all these videos end up at the same (correct) conclusion which is that Falcon is so goated lmao

[@Freak80MC]

I really don't think once Starship is operational that you would pay per flight. I think SpaceX will just list a certain payload mass to whichever orbits and the cost of refueling flights will be built into that. So the customer just pays and then SpaceX handles whether they need to refuel anything or not. Also thinking about it, doesn't the fact that fuel depots exist mean they can tune their costs very finely? Like you don't need to *completely* refuel the rocket for certain orbits, whereas other orbits might be refueled all the way. So on certain missions that might visit a depot with the payload, slightly refuel, and then go to that orbit and then come back to Earth. Also listened to part of this while I did my daily walk, definitely works as a pure audio experience too!

[@EagerSpace]

I don't have any real insight into how the market will shake out with starship flying. SpaceX has flown a lot of transporter missions but their bread and butter is still conventional missions, and I'm not sure that Starship changes that. And yes, there are many scenarios where you might do a partial refuel.

[@stug77]

By my math centaur V has more delta-v than falcon 9 upper stage (in a vacuum at least), so I assume by "beefy" you mean higher thrust to weight, not energy contributed?

[@SpaceAdvocate]

What numbers are you using? With zero payload, I arrive at Centaur V having around 10.6 km/s of delta v (59.5 ton wet, 5.5 ton dry, 454s), and Falcon having 11.3 km/s of delta v (111 ton wet, 4 ton dry, 348s). With 15 tons of payload, it drops to 4.7 km/s for Centaur V and 6.0 km/s for Falcon.

[@EagerSpace]

To what orbit with how much payload? And what numbers are you using for centaur v? If you load a stage with a lot of propellant you can improve your Delta v but end up with a poor thrust to mass, which means you have to stage late. You can

[@stug77]

​@@SpaceAdvocateYou're completely right, I messed up calculating exhaust velocity. And this in a vacuum still so the long burn time of centaur V doesn't help out with gravity loses any.

[@xitheris1758]

Marketing people lie for a living even more than lawyers and politicians. I discovered that before going to college, for which I am grateful.

[@douginorlando6260]

The Starship is designed to meet Starlink’s requirement to launch thousands of heavier starlink satellites cost effectively. But the added twist is knowing low cost LEO payload delivery will open up the market to more customers (some identified, some anticipated, some not anticipated). A city on Mars is more an ideal down the road, realistically requiring a new design assembled in LEO built out of starships’ LEO payloads. I expect starship to be complimented by some form of cost effective LEO to high orbit delivery system (reusable space tugs or payloads which effectively include a 3rd stage). That’s when all the high orbit missions can’t compete against a Starship solution

[@Azd1r]

Damn when you mentioned homework that made me feel old I don't have that anymore..

[@Orandu]

SPX customer is primarily themselves, nasa, and commercial. ULA is primarily USG with NSSL Phase 3 Lane 2 reference orbits. Two different rockets doing two different things. It is annoying when ULA makes their rocket seem better than “the competition” but I’ve been on the Disneyland tour at the Hawthorn factory three times and SPX does the exact same thing… hey, it’s business!

[@EagerSpace]

Part of my complaint isn't that ULA is trying to differentiate their product - that's a natural thing to do - it's that they do it so poorly. There's a good argument to be made about ULA's history of high reliability and being able to do the complex missions that DoD and the Space Force want without doing this weird "high energy" stuff, especially when the rocket you're touting hasn't been certified yet. Better to act like there's a good reason so many USG payloads have been launched on ULA rockets and trade on that.

[@Orandu]

@@EagerSpace I agree; there is too much _Kool-Aid drinking_ in the rocket business these days…

[@AspynDoesStuff]

"LEO is a location aswell" he means the height of leo, not that theres some forbidden other LEO acronym somewhere.

[@TheEvilmooseofdoom]

The problem is the O. It shows he doesn't really understand what it means.

[@EagerSpace]

The height of LEO is "LEO altitude", which is what they chart uses. That's perfectly fine. LEO by itself doesn't mean that, which is pretty clear by all the other uses of LEO in the document.

[@jgottula]

The "O" means orbit. If "LEO" (just "LEO", not "LEO altitude") also means a location/altitude, then that would apparently mean that suborbital vehicles like New Shepard go to the "location" known as "low earth orbit". Which is just kinda idiotic. Using terminology in this odd, imprecise manner mainly just serves to confuse. And it does so in an area that's already confusing enough to the public: the suborbital vs orbital distinction. And this makes Bruno's double-down tweet-where rather than clarifying that "yeah the graphic title really should have said 'LEO altitude'", he instead insists that it's correct as-is and also that the purpose of all this is to help educate the public about space-frankly quite baffling.

[@Scania770V8]

I'm not sure I understand the various nuances regarding ULA's statements or their validity. However, I will agree that putting Foreigner and Captain and Tennille on the same album is pretty baffling. Strong work as always. Keep that up

[@EagerSpace]

I was very disappointed to find that this was not a mashup... kzbin.info/www/bejne/gKu2aquwfq6Sh8k

[@digitaurus]

One of Musk's most important insights has been that vertical integration confers huge advantages if you want to drive and control radical change in an industry. He has been a little less successful at consistently following a second golden rule - never allow your blueprints to end up in China, either by manufacturing there or through inadequate server security, although in the case of SpaceX he's managed to avoid the first, more egregious error.

[@TerryClarkAccordioncrazy]

Thank you, I feel less stupid than I was earlier today.

[@waldmeisterexperte]

Do you have an explanation why rocket lab isn't using srb's on their electron? I have done some (very simplified) math and came to the conclusion that they could ramp up their max. payload to orbit a lot with just a little more costs. Great video as always!

[@EagerSpace]

I don't have any particular insight. My *guess* is that a) pushing Electron to say double their payload doesn't increase their market very much and it adds quite a bit of complexity operationally and b) Neutron is a better place to spend engineering resources because Electron is not the long term plan for the company. Maybe if they had meaningful competition is small launch they'd have a different opinion.

[@redcoat4348]

Hey Eric, I want to know what you think about an article I recently read questioning the viability of Starship HLS based on an overlooked comment from Musk's last starship presentation. It's titled "Starship Faces Performance Shortfall for Lunar Missions", from AmericaSpace, though I haven't linked it because I think youtube is screening out outbound links from comments sections. Hope to see what you think and whether or not Starship might have underlooked payload capacity problems which might scuttle HLS.

[@EagerSpace]

My general opinion about starship performance numbers is that none of them are particularly trustworthy because what we see now is a developmental prototype that is changing along the way and since it's a brand new design, what we see now is not the final version. The thing to note for HLS is that the contractual amount of mass delivered to the lunar surface is much less than spacex has said they can carry, so there's a lot of margin there. Golding's testimony was self serving in my book. He's the reason Artemis looks the way it does and taking attention off of that seems a likely reason for his interest. SpaceX exists largely because his NASA could replace the cargo and crew carrying capacity of shuttle, so we should thank him for that even if his goal was the opposite. The reliability numbers on refueling are the same argument made against large clusters of engines on falcon 9, falcon heavy, and starship, and we can see how those turned out. If you can only get two nines, you aren't doing very well and there's no reason you can't have redundancy for refueling operations. Unlike launch, they are not high energy operations and while you still need to do the development work, I think worrying about refueling is like worrying about docking.

[@redcoat4348]

@@EagerSpace Alright, thank you!

[@KrKrp0n3]

I think saying the choice of rl10 over BE3U dictated the rest of the rocket undersells just how locked in ULA was into that architecture. Directly because they needed that heritage selling point to claim their 100% success streak so far has anything at all to do with Vulcan, and somewhat more indirectly because the goal was from the beginning to swap out Atlas parts until it turns into Vulcan. Funnily enough that didn't turn out to be all that useful given they do in fact now fly the new centaur from the beginning, and I think Tory even admitted that this was a bad idea, but that was the rationale back then. This leads us to an even more boring conclusion, that ULA didn't choose this architecture because of engine constraints, an at least somewhat technical reason, but because of organizational inertia and cargo culting. That's how we always did it so that's what we gonna do, so BE3U and by extension other architecture were never really in the race.

[@EagerSpace]

Love to have comments from the business side.. I agree that organizational inertia plays a big role. And initially with Vulcan one of his big goals was to get out from under having two rockets including the really poor delta IV, and it has/will do that pretty well. I don't think beating SpaceX was ever in the cards, and I don't think LM and Boeing would pony up the money to try to do so. And that's probably the right business decision - it's not clear that they'd ever make the money back. Same problem with reuse. Kuiper is the wild-card here - Vulcan could fly a lot if that actually goes forward but there's been so little happening that it's hard to predict.

[@donjones4719]

All good points. And I think at some point during Vulcan's development, when F9 showed showed how successful it was, ULA decided it didn't have to shift course and try to make a reusable rocket because they didn't have to compete for 1st place, competing for 2nd place would be the most profitable way to go. That's because NSSL and NASA policy mandates two launchers. Another reason for ULA's approach is put best by a quote from Dirty Harry; "A man's got to know his limitations." SpaceX could make F9, and make it work, because they were a lean vertically integrated company with a rocket engine engineering team.

[@EagerSpace]

Yes. I think ULA is behaving in a rational way given their current position.

[@TomatOgorodow]

The real secrets of rocket design revealed

[@sirmicro]

The real secret is designing your own rocket engine with the thrust levels you need.

[@EagerSpace]

That certainly helps.

[@TheJazzbandit13]

Seeing Tory get into the weeds and argue with people on X about LEO is quite amusing. The fact of the matter remains that no matter what your launch vehicle architecture is, the true deliverables are how big of a payload can you yeet into a given orbit, how cheaply can you do it (factoring in reuse of course), and how frequently. I doubt Vulcan can compete with rival launch provider(s) without artificial undercutting. Fixed prices for things like SRB's and expended fairings cant be ignored. Too, the reuse of the thrust structure/BE-4's of Vulcan is still a pipe dream. The amount of engineering work and unknown refurb costs of this mechanism is probably higher than ULA can afford currently. All we've seen so far is an inflatable heatshield demo, nothing much of substance. They really need to remain focused on getting as many NSSL missions as possible and start recieving some kuiper money to stay out of the red and have enough cash to build enough vulcans/centaurs and make the proper investments in facilities and reuse tech.

[@EagerSpace]

The prices of the engines and the solid rockets are essentially fixed, and since the engines are a big part of the price it's very hard to reduce the price. Reuse could help the booster price but a) you still have solid boosters to buy and b) I agree with you that they are drastically underrepresenting the difficulty of the engine pod concept.

[@SpaceAdvocate]

@@EagerSpace Even with 100% success with SMART, ULA is still throwing away two very expensive RL10 engines on every flight. The BE-4 engines aren't even that big a percentage of the total cost of flying Vulcan Centaur. At something like $20 million per RL10, even a flight with no boosters would likely be north of $50 million. That's a less capable vehicle than Falcon 9 at probably around three times the cost.

[@EagerSpace]

I agree with your basic point. There is no list price for the rl10 and the numbers I give are likely examples of what has been paid. Supposedly ULA ordered a bunch for the kuiper ramp up, but if course we don't know the price or conditions of that order.

[@xponen]

SpaceX's design excludes using a highly efficient second-stage engine like the Centaur. The Centaur is the most efficient upper stage globally, but Falcon 9 stages too low altitude for it. At this low altitude, the Centaur can't have enough burn time to reach orbital speed and would crash instead. Centaur carries more energy than Falcon 9's upper stage but needs a longer burn time, so it must be staged at a higher altitude for more air-time.

[@SpaceAdvocate]

The design doesn't exclude using a highly efficient engine like the Centaur (RL10). But it would need more thrust than the RL10 can provide. One option would be the BE-3U. It's similar to the RL10, but it has 6.5 times the thrust. This allows for staging lower. This is the engine used on the New Glenn second stage, and New Glenn also stages fairly low, allowing for booster landings.

[@xponen]

@@SpaceAdvocate They likely traded efficiency for thrust, as the specific impulse of the BE-3 engine hasn't been publicly disclosed.

[@SpaceAdvocate]

@@xponen It's probably around 440 seconds. Though it's not the only option for a higher thrust high efficiency engine. Another option would be to design a new staged combustion cycle vacuum hydrolox engine. That should enable pushing the specific impulse up towards 460 seconds or more.

[@xponen]

@@SpaceAdvocateThe theoretical maximum specific impulse for a hydrolox engine is 460 seconds. To increase thrust or approach this maximum, trade-offs are necessary, such as making the engine heavier or more expensive, like the Space Shuttle's RS-25. Therefore, we should be skeptical of the BE-3U's performance until detailed specifications are published.

[@SpaceAdvocate]

@@xponen The absolute theoretical maximum for a hydrolox engine is more like 530 seconds, using only the energy of the propellant. The RL10 is at 465 seconds, but you could increase this by increasing the chamber pressure. The RL10 has a chamber pressure of 44 bar, while if you used a staged combustion cycle engine, 200+ bar is achievable.

[@GlutenEruption]

I agree with your assessment overall and I definitely think that graphic was very misleading but I do somewhat agree with his point with LEO being used both as an orbit and a location - people use "above LEO" or "lower than LEO" etc like they do with the Karman line as a shorthand for altitude. It's misleading and technically incorrect but it IS a common usage.

[@EagerSpace]

Can you give me references for people doing this?

[@GlutenEruption]

@@EagerSpace KZbin doesn't allow links but "altitude chart sea level to geo stationary" on Wikipedia commons is a good example. Note how it uses low earth orbit, and medium earth orbit solely in reference to altitude ranges, with no mention of orbital velocity. I totally agree that LEO has a well defined technical meaning which by definition includes both altitude and velocity vector, and no aerospace engineer would misuse it to refer to altitude or location only in any technical context but I think it's important to remember this was in the context of an advertising graphic intended for the general public and non-technical audiences, and in that context, it definitely does get used to reference altitude/location alone fairly regularly. Now I think the argument definitely can and should be made that it's still wrong and misleading and someone with his expertise and knowledge shouldn't be continuing to perpetuate that usage to general audiences but it does get used like that unfortunately.

[@EagerSpace]

A) the graphic in the paper isn't intended for the general public, it's intended for the very small subset of people that might but ULA launches. B) the graphic very clearly says LEO altitude.

[@GlutenEruption]

@@EagerSpace wow, KZbin deleted my reply even without a link. This is really getting ridiculous... okay, I thought the graphic was something he posted to twitter or had on a public facing page, so maybe general public isn't the best term but still they're directed at audiences who have a very poor understand rocket science - if they had any basic understanding, there would be no reason for an incredibly overly simplistic graphic to advertise, he could just put the actual specs without explanation and they would understand the benefits. The purpose was to convince the bean counters why they should choose ULA, and to make Vulcan sound more impressive to people who have no concept of orbital mechanics. And as far as b) exactly, LEO *altitude*, not LEO referring to the orbital state. Again, I totally agree, you are 100% right from a technical perspective: it is a total misuse of a very well defined term and extremely misleading at minimum but the point I was making is that there is at least some precedent for that use for non-technical, very general knowledge audiences which certainly includes the politicians, bean counters, and military brass that was aimed at, and all companies stretch the benefits of their products in sales literature like this. Again, I agree with you, but I can see what he was saying too.

[@GuardsmanBass]

I understand it would have been embarrassing, but could ULA have opted to buy Merlin engines from SpaceX instead of relying on Blue Origin or Aerojet? That would obviously force a change away from the "hefty first stage" approach, but . . .

[@EagerSpace]

I've sometimes said that the only engine that was the right size for Vulcan is named Merlin, but afaik spacex didn't put in a bid to sell Merlin to ula, so it wasn't a real option.

[@williamthomas5788]

Thank you. I think the (then Orbital, now NG) Antares design was more closely tailored to NASA's cargo transport needs than Falcon 9 was. I think it's pretty clear that SpaceX was looking to build a rocket that could cover a lot of the commercially addressable satellite launching market, and using NASA's funds to help develop it. Sure, it had to also fulfill NASA's needs, but that was part of the goals of the design, not the whole or greatest goal. Whereas, Antares was never seriously intended to do anything much other than launch cargos for NASA.

[@EagerSpace]

Antares was very clearly a one trick pony, and my guess is it made NASA happy to have a more established company join the program when Kistler dropped out, but one of NASA's goals is to foster new commercial capabilities and the contract to Antares did nothing in that realm. I talk a lot about Falcon 9 development in my recent Falcon Heavy video. They certainly had their eyes on commercial launch because Ariane 5 was so expensive and Proton was so explosive, but they were focused on NASA because it was clear that whoever got the contract would likely be flying cargo for as long as ISS is around. And it gave them a possible gateway to carrying crew, also lucrative and a capability in their long-term plans. But I think that SpaceX is generally pretty good at not getting ahead of themselves.

[@r-saint]

This video probably needs a better name :D

[@GovernmentFails]

Why not use NASAs Launch Vehicle Performance Website?

[@EagerSpace]

It's fairly widely believed that the numbers of the launch vehicle performance website are outdated. For Falcon 9 they list the Full Thrust version which was superceded by block 5 quite a few years ago. The Vulcan numbers are lower than the ones in the Vulcan user's guide. Falcon Heavy Expendable on a cheap launch to Mars (C3 = 8) gives a payload of 12,850 kg. SpaceX says 16,800 kg. ULA says Vulcan does less to Mars than the NASA site does.

[@adamgrundy4327]

another great thing of making your own engine is improvements. SpaceX has increased merlin by i think double on the version today vs when they started. This allow them to make small increase in payload over time which ula would have to get a new rocket engine to do.

[@googlespamversuch4940]

Greetings from Germany. During IAC 2024 in Milan, Italy we will give a lecture on the Sea Dragon. For this, I like to come into contact with you. What is an appropiate way / E-Mail to reach you directly? Thank you so much and please, keep up the fantastic work you do.

[@EagerSpace]

Sounds fun. My contract info on Twitter and Reddit is in the video description - you can send me a private message there.

[@googlespamversuch4940]

@@EagerSpace I registered at reddit but there private messaging is not enabled with your account.

[@tomporter8849]

Even with refuelling in orbit, Starship seems very oversized to deliver a satellite of say 10 tons to GEO. I'm wondering if it would be a good idea for SpaceX to develop an internal third stage to allow Starship to deliver relatively small payloads to high energy orbits.

[@EagerSpace]

Impulse aerospace is already doing this.

[@pc_screen5478]

It doesn't matter if it's oversized if it does the job at a lower price than the competition. From the perspective of the customer they want the cheapest launcher that can get their payload to the orbit they want with other details being irrelevant, and starship is supposed to be cheap enough where it'll become the default choice for most customers even if they underuse its payload capacity. A non reusable third stage for a payload starship can do without refueling would certainly be more expensive than doing it with just starship, no customer would ever choose it just because it looks wrong to use a massive ship for a small-ish payload

[@tomporter8849]

@ That’s a valid point, if starship’s ‘cost per flight’ is low enough then its better to have lots of flights than to expend even a small piece of hardware. Although I still think it remains to be seen which approach would be cheaper overall.

[@concretedonkey4726]

I'm finding surprising paralells with game development, both in technical constrains and CEOs that talk too much :).

[@Wisald]

Expandable Starship version and/or third stage deployed by Starship is only a matter of time, no launch system comes anywhere close to the C3 of this kind of Starship.

[@EagerSpace]

Impulse aerospace is the obvious near-term choice for a lot of payloads.

[@meinking_sensei3807]

A Kickstage for Starship (internal on the payload adapter) makes so much sense

[@TimothyLipinski]

Great Video ! Went to ISDC 2001 in Albuquerque, NM were the one BIG topic was Single Stage To Orbit (SSTO) and the back up design was Two Stage to Orbit (TSTO) ! NASA and other agencies worked on the Delta Clipper (DC/DC-X/DC-XA) a reusable rocket and maybe SSTO (X-33) ! The Delta Clipper made about a dozen flights when one landing leg failed to deploy and the rocket tipped over... ! Someone wrote a book "Half Way to Any Where", where the energy to get to LEO, that same energy will get you anywhere in the Solar System ! The paper "Moon Direct" by Robert Zubrin said a 6.1 km/sec delta-V can take a rocket from LEO to the Lunar Surface (LS) ! Then you can fuel up at a LS Fuel Depot and return to LEO ! Also I think a 6.1 km/sec delta-V can take you from LEO to GEO and return to LEO to be serviced ! A new low inclination LEO CSS heading East from the KSC with a Fuel Depot nearby is needed ! This can then bring down the cost of travel in Cis-Lunar Space ! The Tech developed to return to the moon to stay, can take US and the world to Mars and beyond ! tjl

[@donjones4719]

30:00 The projected GTO capacity of Starship is a surprise to me, it's often been said (not just by Tory) that Starship can't get something to GTO without refilling or by carrying a transfer stage along with the satellite. If it can actually get 20t to GTO if expendable then hopefully it can get a ~quarter of that there and still have enough propellant to drop down to a LEO-velocity reentry. ~5t is a sizable satellite. IIRC, geo sats tend to be beefy. For example, Viasat 3s have a 6.4t wet mass per Gunter's Space Page. If these assumptions work out then Starship can make very inexpensive (zero-tankers) launches for the majority of geostationary satellites, the ones that go via GTO. Of course the big NRO birds aren't included in this.

[@EagerSpace]

My model said the low 20s, I've seen others that say mid 20s. They all depend on mass numbers for starship and those of course aren't trustworthy right now. Shuttle was stuck in LEO because it was (from memory) 27 tons to a very low LEO orbit plus about 136 tons of orbiter + tank, and that gave it a very low payload ratio, maybe 17% Any credible numbers for Starship put it *way* above that. Even if it does 100 tons with a 150 ton stage, that puts it up at 40%. But the GTO numbers are one-way. My guess is that it's going to be a lot more economical to take a kick stage from Impulse and use that on a geo satellite from LEO.

[@debott4538]

I would expect Starship to survive re-entry from GTO. They want to go interplanetary with it after all. No need to slow down to LEO before re-entry.

[@Zorba-Ivy]

​@@debott4538I'm in no position to absolutely agree or disagree, but reentry from GTO will probably be a LOT faster than reentry from LEO (you might be able to estimate reentry speed with vis viva equation? I don't know how much delta v starship would have or where it would make the deceleration burn though (apoapsis?)).

[@SpaceAdvocate]

@@Zorba-Ivy If you reenter from geostationary orbit, you'd be going at around 10.3 km/s. If you reenter from the ISS, you'd be going at around 8 km/s. Given that heating increases with the cube of the velocity, reentering from GEO would see over twice the heating.

[@Zorba-Ivy]

@@SpaceAdvocate i wasn't aware of reentry heating working like that. I would certainly rather use a kick stage than subject a reusable launcher to that. Or maybe go Kerbal and aerobrake?

[@dancingdog2790]

Sleepy SpaceX and their low-energy rockets -- SAD 🤣🤣🤣/s

[@s0mar885]

Says that "The article is linked in the video description" and then doesn't link the article in the video description. Amazing😂

[@EagerSpace]

Maybe it was a test to see how many people would actually go read it... Or maybe I just forgot. Fixed now.

[@RogerM88]

So you are a critic about Bruno's claims for Vulcan Centaur, but not the over optimistic Musk's claims about Starship? Which clearly look to be having gross weight issues? Let's start being less biased.

[@Neront90]

I think this is because SpaceX already managed to demonstrate their approach and their capabilities when they optimized Falcon 9, by incresing its max payload from 9000 to 22800kg (+153%) In order for the Starship to live up to its promises and do 100t reusable, they only need to increase its max payload by 66% and figure out landing on a tower

[@EagerSpace]

Whenever I talk about Starship I say that it's hard to do analysis because there are no good numbers out there. All I can do now is project based on the numbers that are out there. Will they reach those numbers? I don't know, but SpaceX is in a better position to know than anybody outside.

[@RogerM88]

@@Neront90 Falcon 9 is a different type of rocket than Starship. Many hyping Starship are still relying on F9 development trajectory.

[@donjones4719]

Eric's main aim here is to critique Tory's specific claims in his "The Secret's of Rocket Design Revealed" article by showing how the claims don't stand up. In fact, it turns out Tory did't make a rather poor case - he made a very poor case. Eric's refutation could stand on its own but the references to Falcon 9 are made for illustration about the paths of rocket design. Starship is a pretty minor point in all of this, and Eric makes it clear those are rough estimates with a foundation on shifting sand.

[@TheEvilmooseofdoom]

@@EagerSpace Roger isn't the sharpest or even most honest person there is. When he talks about bias he has a tendency to ignore his regular his own (anything elon=bad) bias to the point where he is more ridiculous than anything.

[@PeteSty]

You must be a REAL rocket Scientist. Or.........

[@Shrouded_reaper]

Useless Legacy Aerospace

[@firefly4f4]

It's hard to take you seriously when you can't even say his name correctly in the first 5 seconds. To be clear, the analysis is good, but using the wrong name isn't helping you.

[@kaltenstein7718]

I just have to say, your habit to omit the unit of specific impulse (seconds with the numbers you use, although it really should be Ns/kg) in your videos strikes me as very wierd and unnecessary.

[@EagerSpace]

Seconds is the unit when used in rocketry. It's not a unit based on Newtons because not all rocket research has been done with the metric system, and one of the points of specific impulse is to normalize across those two systems. I do have a video that talks about specific impulse in more detail for those who want to know, but my opinion is that using the unit seconds doesn't increase the explanatory value of the discussion and instead confuses people.