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The reason Falcon Heavy was delayed is because it is based on Falcon 9 which was still rapidly evolving. They couldn't decide on a spec to freeze it on and begi

The reason Falcon Heavy was delayed is because it is based on Falcon 9 which was still rapidly evolving. They couldn't decide on a spec to freeze it on and begin serious development because of how much F9 was improving. By the time it slowed down enough to begin work on FH, F9's performance and started to cover some of FH's originally envelope. I don't think it was really a case of Elon time as much as F9 proved to have a lot more room for development than they thought. Starship is a different can of worms. Its radical and innovative in many ways so there are a lot of work that needs to be done. This is definitely where Elon mis estimated how long it would take. It took them nearly a year to get the fuel tanks right. Then it took them a few prototypes to prove the belly flop concept. I wouldn't be surprised if the same proves to be true for the heat shield. The easiest part about Starship is the booster because its not doing anything F9 isn't already. Just at a much larger scale. That of course isn't easy either. But it does but things into perspective somewhat. And after all of that, my money is still on it beating SLS to orbit. Starship may be audacious but SLS's goal was never to get into space. In fact the longer they can drag it out the better it serves its purpose as a social welfare program.

hutzlibu 5y ago
Naive question: "The easiest part about Starship is the booster because its not doing anything F9 isn't already. Just at a much larger scale." Why is it in general required, to design a new, more heavy rocket - and not "just scale" up an existing design? I mean, "just scaling up" means a different build process and this alone could probably prevent it when, using off the shelf solutions and not build everything yourself (screws and cables included), but are there other fundamental reasons, why usually a redesign is required?
- ceejayoz 5y ago
  > Why is it in general required, to design a new, more heavy rocket - and not "just scale" up an existing design? Because defense contractors make a lot more money for the new one.
  - mcguire 5y ago
    Do you apply this sort of thinking to your job?
    - ceejayoz 5y ago
      I wish I got cost-plus contracting at my job.
  - greedo 5y ago
    One of the criticisms of the SLS program is it's re-use of Shuttle Engine technology, so your point is a bit off the mark.
- DisjointedHunt 5y ago
  Because the assumptions made for one class of payload don't apply to another class of payload with vastly different mission specifications. A great place to start is this amazing video by The Everyday Astronaut: https://www.youtube.com/watch?v=LbH1ZDImaI8 https://www.youtube.com/watch?v=LbH1ZDImaI8 Notice how the type of fuel used itself is a consideration for the type of rockets we may send to Mars if we're considering In-Situ refueling.
- funcDropShadow 5y ago
  I am not a mechanical engineer, but my general understanding is even mammals cannot be scaled up arbitrarily. I've read that elephants are more or less the maximal size of land-based mammals because of heat transport. The surface is not large enough to transport all the heat away from the body. I could imagine that similar effects limit mechanical designs.
  - emteycz 5y ago
    The height of trees is limited by the physical limits of water transport.
  - pyuser583 5y ago
    “The surface is not large enough to transport all the heat away from the body” Can you explain that a bit more? I don’t understand.
    - cmyr 5y ago
      As a body increases in size, the surface area increases as a square but volume increases as a cube. The more volume, the more heat, and after a certain point your available surface area is no longer adequate to vent that heat. Another example of a similar principle applies to insects: they don’t have lungs, and absorb oxygen directly through their skin. In earlier eras of earth’s history, there was much more oxygen in the air, and so insects could be much larger, because the same amount of surface area could absorb enough oxygen to fuel a larger number of cells.
    - ncmncm 5y ago
      Look up "square-cube law". It governs everything about animal size. But not vehicles, so much. The principle is that 2x size, i.e. 2x length, 2x width, 2x height, gives you 8x volume and, for animals, mass. All that mass has to be kept fed and aerated, and produces heat. But the surface area didn't go up by 8x. It only went up 4x unless you changed the shape a lot. You probably can't get skin to shed heat 2x as well, so you have to be careful not to produce 8x as much heat, instead. This is all fine up to, say, the size of a giraffe or elephant. But an elephant that runs for five minutes is in for a bad time. Vehicles are mostly empty space and skin, so they have different sorts of scaling problems.
- xoa 5y ago
  >Why is it in general required, to design a new, more heavy rocket - and not "just scale" up an existing design? I'm not a rocket designer, just someone who has really enjoyed following it for a long time. Someone in the industry could give more specifics, but the basics are straight forward. Everything about a specific rocket is tightly coupled, from material factors to engines and everything that goes into that. To take an obvious one, how do you drive the bigger rocket? If you choose bigger engines, then you need entire new engines (and there are scaling issues there too). If you choose to use more smaller engines, you need brand new plumbing to feed all those engines (a very complex thing itself, last I checked each Raptor engine consumers nearly 800 kilograms of fuel PER SECOND), you need to deal with harmonics and control of more engines, different fluid mechanics, etc. Even merely construction changes with scale. For example scaling up carbon fiber to huge sizes is incredibly hard and expensive, one of a number of reasons SpaceX dropped it in favor of steel instead. Rocket volume obviously scales with the cube compared to surface area with the square of size, material properties change with thickness of various walls, and on and on. All of this also impacts aerodynamics, center of gravity and a host of other things. So yeah! Knowledge and expertise from existing rocket designs is absolutely very useful in designing a new one, Starship directly comes out of a ton of things SpaceX learned from F9, which itself took important lessons from F1 (and "F9" is a much bigger range much faster then typical rockets, from version 1.0 to Full Thrust Block 5, the current one, they changed more and gained more power then entire new rockets sometimes have). A much bigger Starship v2 may take much more from v1 then typical because they now do have something with more scaling potential (steel construction in particular). And a lot of the software no doubt will be directly evolved, Starship landing of course used F9 landing software and hardware lessons. But still, cannot just "scale up", even without things like completely changing fuel. Edit: In reply, jmyeet points out that I glossed over the manufacturing bit too much as well. There is a huge amount of expertise and institutional knowledge in going from a general design of any big complex machine to actually manufacturing it in a reliable fashion. People and the machines that make the machines and all the processes that go into that is a whole 'nother ball of wax. Can find plenty of stories on HN and elsewhere about merely duplicating "the same thing", like trying to manufacture an aircraft in a different factory. Or the level of work in "simply" copying a fab and the lengths that are gone to in order to try to make sure everything is exactly the same.
- mcguire 5y ago
  Not necessarily directly related to your question, but a conversation I had with a friend who was an aerospace engineer, and who worked on solid rocket design: Remember the Ares I/V designs? They theoretically were claimed to use what were "essentially" shuttle solid rocket boosters (SRBs), but scaled up. In fact, much of the chatter in general forums was that the Ares boosters were shuttle SRBs with an extra segment on top. (SRBs are built of several independent segments of propellant with the external structure wrapped around them. When they're assembled, they segments are stacked with, among other things, o-rings between them---that is what failed in Challenger.) Ok, so you can just stack another segment on top for more power, right? Well, no. SRBs don't burn from the bottom to the top; there is a hole from the bottom of the propellant to the top, and when ignited it is the propellant on the surface of this hole that burns. This hole up the propellant (remember, it's a solid) is not just a round cylinder. If it were, when you lit it on fire, it would start out at a minimum thrust and the thrust would increase as the hole got larger in diameter. This is not so much what you want a rocket engine to do. So the hole is actually a weird star shape that maintains the same surface area as it burns, which requires a bunch of strange parameters known only to the initiates of aerospace engineering magic. (This is what my friend did in grad school. Now he's an enterprise webby project manager thingy.) If you just stack another segment on a SRB, it will burn for the same amount of time with more thrust, which may not be a good idea---remember, this is a mechanical structure that is mechanically connected to whatever you want to lift and the whole thing may not like higher g-loads. So, to just "add another segment" you have to redesign the propellant entirely, then look at the structures and connectors that may not be designed for the new loads, and so on. Scaling up isn't easy. If I remember correctly (See the book Ignition!), one of the major problems for the Saturn V's F-1 engine was the design of the engine injector plate, the thing that sprays fuel and oxygen into the combustion chamber. It had dramatic effects on the stability of the burn (they can and will go BOOM!), the vibration and other aspects of the engine. And that was basically determined experimentally. Also, keep in mind that the big design problem for a liquid-fuel engine is how to feed as much liquid propellant and oxidizers into the engine at the rate necessary for the thrust. They use burning rocket propellant to drive turbine pumps to feed propellant into the combustion chamber, and those pumps are the cutting edge of high-temperature, high-pressure pump design. "Just scaling it up" can be a completely new research and development project.
- Aloha 5y ago
  The N-1 Moon Rocket indicates that scaling up by putting more of your existing rocket motor on a vehicle may not always been as easy as it appears. As other parallel posters have commented, mechanical devices do not always squish or stretch with ease.
  - soperj 5y ago
    Which engine was the NK33 used on previously? It is currently used on a newer version of Soyuz, but I'm pretty sure that it was originally built for the N-1.
- giantrobot 5y ago
  The thrust to weight ratio of a cluster of rocket engines is not a linear relationship. Adding one more engine might add N+1 thrust but it also adds at least N+1 mass. So you have more thrust but now more mass to lift and a worse mass ratio (the ratio of fuel to non-fuel). To scale your engine cluster you want to add an engine worth of thrust but not an engine worth of mass. To that end you reduce the mass of your piping or use one pump for multiple engines. All those changes require engineering and testing because the dynamics of the system have changed. For instance a fuel pipe of X thickness and Y material may have some weird failure mode if you make it just a little thinner to save mass.
- mr_toad 5y ago
  A couple of crucial design elements for Starship are a metholox engine (the idea being to make the fuel on Mars), and a reusable second stage. You couldn’t achieve those goals by scaling up a falcon.
DisjointedHunt 5y ago
It didn't take them a year to "get fuel tanks right", they were building while iterating on the upper stage design. ie, the manufacturing of an initial design that was evolving was being built at the SAME TIME. Think about that for a second. For an orbital class upper stage larger than any ever built, it took shorter than ever for it to be designed AND manufactured through multiple iterative designs and manufacturing techniques than either the design stage or the manufacturing stage for ANY OTHER ROCKET. All this while they continue to churn out and iterate on heatshield material and design at the "Bakery" which is another manufacturing facility they spun up from scratch in record time, manufacturing nearly a new rocket engine every DAY and that which has been flown and tested to demonstrate higher chamber pressures than ANY full flow staged combustion rocket engine in the history of mankind. They're much further along than any comment in this thread indicates.
- foxyv 5y ago
  I think SpaceX's efforts have highlighted the huge amount of talent that is languishing in the United States right now. Engineering and operations budgets have been cut so much in US companies that we have engineers and trained professionals like welders, aircraft mechanics, and construction workers stuck in underpaid and underutilized roles. Elon seems to be dedicated to focusing on Engineering and Operations and it's resulting in the full potential of those engineers and professionals being explored. Instead of focusing exclusively on market capture, lobbying and new marketing strategies, SpaceX is focused on actually getting something done. I've been nothing but impressed with them so far. While not nearly as financially successful as Tesla, I think SpaceX is closer to reaching Mars than Tesla is to reaching sustainable transportation and power.
  - DisjointedHunt 5y ago
    There is inherent value stored in all of Spacexs accomplishments thus far that is very, very hard to place financial value on simply because it is the only asset in the world with the capability. A reusable rocket? How much would China pay for that capability? Don't worry about ITAR rules, it's a hypothetical question to understand the value of having such an asset available for defense or aerospace contracting purposes. The centuries prior to the digital age, whole private empires were built on the back of shipping and transport. Spacex is presently sitting on the largest payload capability fleet in the world, by tonnage to orbit. Yes, including China. Yes, including Russia, Yes, we're not even counting one single Starship here yet. The alloy itself that allows their turbines to run as hot as they have demonstrated to achieve such insane chamber pressures. What is that worth? No one else in the World has been able to do that in the history of mankind (In the unclassified realm atleast) The thing i love about the company that you allude to as well is they're running a ship that converts these "ideas" into tangible business value quicker than anyone we've seen in classic space industries.
iab 5y ago
Socially Laundering Securities
enragedcacti 5y ago
> The easiest part about Starship is the booster because its not doing anything F9 isn't already. Just at a much larger scale. It's possible that its easier than the other challenges starship faces, but everything I've read seems to suggest the raptor engine underpinning the entire project is massively behind schedule and over budget to the point of putting SpaceX at risk of bankruptcy (according to Elon).[1] It's also burning a completely different fuel and has numerous other massive changes so a booster leveraging it isn't really just F9 at a larger scale. [2] [1] https://spacenews.com/spacex-grapples-with-raptor-production-problems/ https://spacenews.com/spacex-grapples-with-raptor-production... [2] https://en.wikipedia.org/wiki/SpaceX_Raptor https://en.wikipedia.org/wiki/SpaceX_Raptor
- beambot 5y ago
  Can get the latest updates directly from horse's mouth: https://www.youtube.com/watch?v=3N7L8Xhkzqo https://www.youtube.com/watch?v=3N7L8Xhkzqo TLDR: Delay at this point is mostly regulatory (environmental study approvals) to launch out of Boca Chica. If they have to move to the Cape, then there will be delays.
  - purpleidea 5y ago
    Not true. Musk said they weren't ready to launch yet anyways, and that they expected to be ready around the same time they expected to get FAA clearance. So it's not holding things up yet. And it might never.
    - beambot 5y ago
      OK, let me be more clear: The gating factor is FAA clearance, but it's not a delay yet. More specifically: Nominal date for FAA clearance is X. Actual clearance will be >X (these agencies are never complete early; it's already been delayed twice). SpaceX readiness date will be <= X. Therefore FAA clearance is the program bottleneck.
      - ncmncm 5y ago
chasd00 5y ago
iirc Starship was conceived before Falcon Heavy was finished as well. So, to me, Falcon Heavy would seem like a solution in search of a problem. There are some commercial flights for Falcon Heavy planned but as soon as Starship comes online it's obsolete. I don't know how much money the Falcon Heavy program will make but I would consider it paying for the R/D before being retired (just breaking even) a success.
- jve 5y ago
  Elon wanted to cancel FH according to the following article. > Years earlier, Musk ordered Falcon Heavy canceled, forcing Shotwell, who’d been tipped off by another SpaceX employee, to sprint to a conference room and remind him that the U.S. Air Force, a critical customer, had already purchased a launch https://www.bloomberg.com/news/features/2018-07-26/she-launches-spaceships-sells-rockets-and-deals-with-elon-musk https://www.bloomberg.com/news/features/2018-07-26/she-launc...
- MPSimmons 5y ago
  FH was first mentioned in 2003 (https://hobbyspace.com/AAdmin/archive/Interviews/Systems/ElonMusk.html https://hobbyspace.com/AAdmin/archive/Interviews/Systems/Elo...), when it was going to be made of Falcon 1s. Not saying there was any engineering done there, but it was an idea that he wanted, so he could increase payload to orbit.
- emteycz 5y ago
  I always thought they did it purely for the show - and now even my mom is a big fan of SpaceX, so they were very successful.
  - simonh 5y ago
    What a show. I could watch the twin booster landings all day. Not that I have or anything...
XorNot 5y ago
The big problem with Starship right now looks to be the heat tiles - I don't think they've had a single test where they haven't had some pop off, and I'd be willing to bet the internal redesign that was announced is to stiffen up the hill to deal with flex (since it seems to be trading a little of internal diameter to do it - willing to bet that's too deepen some bracing members).
- chasd00 5y ago
  As soon as I saw the tiles I thought “oh no”. They’re so fragile, they have to be a major hurdle for reusability. During the everyday astronaut interview Elon is talking and then looks over at a worker smacking a tile trying to get it to stay in place. Elon whips out his cellphone and then the interview cuts to a different scene. I imagine the amount of curse words being yelled into that cellphone would not pass YouTube’s guidelines. The heat tiles suck.
- ncmncm 5y ago
  The main problem with the tiles is that they are the same design as on the space shuttle, which had to all be individually rejiggered on each flight: take it off, squirt in some fresh goo, stick it back on. They won't be making any 8-hour turnarounds doing that. The tiles they have are a design that is known to work, and will suffice to prove that the vehicle can get to orbit and come back in one piece. So they will need a new design that doesn't need so much detailed attention after every flight. They have years to work out what that will be, because they are much farther from ready than some, apparently many, imagine. The gross, visible, easy stuff is mostly in place. The hard stuff you can't see is still to come.
  - KiwiJohnno 5y ago
    Not quite. Each tile has a socket in the middle of the back, which goes over a mounting post which is welded to the steel hull of starship. Also, there are very few different shapes of heat tiles, and the vast majority of the heat tiles are of exactly the same design and shape. On the space shuttle few, if any heatshield tiles were the same. They were individually manufactured, instead of bulk manufactured to a common specification as SpaceX are doing. Obviously that is going to be far, far more efficient. Yeah, they have had problems with tiles coming off during static fires. Although this seems to have been getting better, and it remains to be seen how bad an issue losing a few patches of single tiles actually is. Under the tiles the structure is stainless steel, while with the space shuttle it was aluminum which is clearly not as tolerant of the extreme heating of re-entry.
beerandt 5y ago
>The easiest part about Starship is the booster because its not doing anything F9 isn't already. Just at a much larger scale. That of course isn't easy either. Scaling up in this context isn't simple at all. For all the recognition of the complexity of rocket science, structural engineering is perhaps the most underappreciated. Scaling up in multiple dimensions often means different things need to be scaled at different rates. Hydraulic and atmospheric modeling is similar in this respect. You pick the variable(s) that you want to scale linearly, and then have to resolve all the other variables in terms of what you've fixed. Lots of dimensional analysis, and then experiments to calibrate the results to be meaningful. For instance, max ultimate moment loading is generally the controlling factor for determining beam strength, which in turn determines the required beam cross section and weight/span. However, as beam span length increases linearly, moment increases exponentially for the same load. And scaling up likely increases the external loading, such that moment increases to the 4th power as base dimensions increase linearly. And then needing a bigger/stronger beam cross-section increases the self-weight that also needs to be supported. Things can quickly runaway in certain configurations, when you start to account for volumetric increases in fuel capacity, and dynamic loadings like impact forces on fuel tank baffles, which themselves are often scaled to the 3rd or 4th power of the fuel weight, and 2nd or 3rd power wrt to the relative change in velocity. And finally there's the structural harmonics and vibration, which all increase in force faster than linear increases in span, and affect structural serviceability (lifetime loading cycles).

hutzlibu 5y ago

Naive question: "The easiest part about Starship is the booster because its not doing anything F9 isn't already. Just at a much larger scale." Why is it in general required, to design a new, more heavy rocket - and not "just scale" up an existing design? I mean, "just scaling up" means a different build process and this alone could probably prevent it when, using off the shelf solutions and not build everything yourself (screws and cables included), but are there other fundamental reasons, why usually a redesign is required?

ceejayoz 5y ago
> Why is it in general required, to design a new, more heavy rocket - and not "just scale" up an existing design? Because defense contractors make a lot more money for the new one.
- mcguire 5y ago
  Do you apply this sort of thinking to your job?
  - ceejayoz 5y ago
    I wish I got cost-plus contracting at my job.
- greedo 5y ago
  One of the criticisms of the SLS program is it's re-use of Shuttle Engine technology, so your point is a bit off the mark.
DisjointedHunt 5y ago
Because the assumptions made for one class of payload don't apply to another class of payload with vastly different mission specifications. A great place to start is this amazing video by The Everyday Astronaut: https://www.youtube.com/watch?v=LbH1ZDImaI8 https://www.youtube.com/watch?v=LbH1ZDImaI8 Notice how the type of fuel used itself is a consideration for the type of rockets we may send to Mars if we're considering In-Situ refueling.
funcDropShadow 5y ago
I am not a mechanical engineer, but my general understanding is even mammals cannot be scaled up arbitrarily. I've read that elephants are more or less the maximal size of land-based mammals because of heat transport. The surface is not large enough to transport all the heat away from the body. I could imagine that similar effects limit mechanical designs.
- emteycz 5y ago
  The height of trees is limited by the physical limits of water transport.
- pyuser583 5y ago
  “The surface is not large enough to transport all the heat away from the body” Can you explain that a bit more? I don’t understand.
  - cmyr 5y ago
    As a body increases in size, the surface area increases as a square but volume increases as a cube. The more volume, the more heat, and after a certain point your available surface area is no longer adequate to vent that heat. Another example of a similar principle applies to insects: they don’t have lungs, and absorb oxygen directly through their skin. In earlier eras of earth’s history, there was much more oxygen in the air, and so insects could be much larger, because the same amount of surface area could absorb enough oxygen to fuel a larger number of cells.
  - ncmncm 5y ago
    Look up "square-cube law". It governs everything about animal size. But not vehicles, so much. The principle is that 2x size, i.e. 2x length, 2x width, 2x height, gives you 8x volume and, for animals, mass. All that mass has to be kept fed and aerated, and produces heat. But the surface area didn't go up by 8x. It only went up 4x unless you changed the shape a lot. You probably can't get skin to shed heat 2x as well, so you have to be careful not to produce 8x as much heat, instead. This is all fine up to, say, the size of a giraffe or elephant. But an elephant that runs for five minutes is in for a bad time. Vehicles are mostly empty space and skin, so they have different sorts of scaling problems.
xoa 5y ago
>Why is it in general required, to design a new, more heavy rocket - and not "just scale" up an existing design? I'm not a rocket designer, just someone who has really enjoyed following it for a long time. Someone in the industry could give more specifics, but the basics are straight forward. Everything about a specific rocket is tightly coupled, from material factors to engines and everything that goes into that. To take an obvious one, how do you drive the bigger rocket? If you choose bigger engines, then you need entire new engines (and there are scaling issues there too). If you choose to use more smaller engines, you need brand new plumbing to feed all those engines (a very complex thing itself, last I checked each Raptor engine consumers nearly 800 kilograms of fuel PER SECOND), you need to deal with harmonics and control of more engines, different fluid mechanics, etc. Even merely construction changes with scale. For example scaling up carbon fiber to huge sizes is incredibly hard and expensive, one of a number of reasons SpaceX dropped it in favor of steel instead. Rocket volume obviously scales with the cube compared to surface area with the square of size, material properties change with thickness of various walls, and on and on. All of this also impacts aerodynamics, center of gravity and a host of other things. So yeah! Knowledge and expertise from existing rocket designs is absolutely very useful in designing a new one, Starship directly comes out of a ton of things SpaceX learned from F9, which itself took important lessons from F1 (and "F9" is a much bigger range much faster then typical rockets, from version 1.0 to Full Thrust Block 5, the current one, they changed more and gained more power then entire new rockets sometimes have). A much bigger Starship v2 may take much more from v1 then typical because they now do have something with more scaling potential (steel construction in particular). And a lot of the software no doubt will be directly evolved, Starship landing of course used F9 landing software and hardware lessons. But still, cannot just "scale up", even without things like completely changing fuel. Edit: In reply, jmyeet points out that I glossed over the manufacturing bit too much as well. There is a huge amount of expertise and institutional knowledge in going from a general design of any big complex machine to actually manufacturing it in a reliable fashion. People and the machines that make the machines and all the processes that go into that is a whole 'nother ball of wax. Can find plenty of stories on HN and elsewhere about merely duplicating "the same thing", like trying to manufacture an aircraft in a different factory. Or the level of work in "simply" copying a fab and the lengths that are gone to in order to try to make sure everything is exactly the same.
mcguire 5y ago
Not necessarily directly related to your question, but a conversation I had with a friend who was an aerospace engineer, and who worked on solid rocket design: Remember the Ares I/V designs? They theoretically were claimed to use what were "essentially" shuttle solid rocket boosters (SRBs), but scaled up. In fact, much of the chatter in general forums was that the Ares boosters were shuttle SRBs with an extra segment on top. (SRBs are built of several independent segments of propellant with the external structure wrapped around them. When they're assembled, they segments are stacked with, among other things, o-rings between them---that is what failed in Challenger.) Ok, so you can just stack another segment on top for more power, right? Well, no. SRBs don't burn from the bottom to the top; there is a hole from the bottom of the propellant to the top, and when ignited it is the propellant on the surface of this hole that burns. This hole up the propellant (remember, it's a solid) is not just a round cylinder. If it were, when you lit it on fire, it would start out at a minimum thrust and the thrust would increase as the hole got larger in diameter. This is not so much what you want a rocket engine to do. So the hole is actually a weird star shape that maintains the same surface area as it burns, which requires a bunch of strange parameters known only to the initiates of aerospace engineering magic. (This is what my friend did in grad school. Now he's an enterprise webby project manager thingy.) If you just stack another segment on a SRB, it will burn for the same amount of time with more thrust, which may not be a good idea---remember, this is a mechanical structure that is mechanically connected to whatever you want to lift and the whole thing may not like higher g-loads. So, to just "add another segment" you have to redesign the propellant entirely, then look at the structures and connectors that may not be designed for the new loads, and so on. Scaling up isn't easy. If I remember correctly (See the book Ignition!), one of the major problems for the Saturn V's F-1 engine was the design of the engine injector plate, the thing that sprays fuel and oxygen into the combustion chamber. It had dramatic effects on the stability of the burn (they can and will go BOOM!), the vibration and other aspects of the engine. And that was basically determined experimentally. Also, keep in mind that the big design problem for a liquid-fuel engine is how to feed as much liquid propellant and oxidizers into the engine at the rate necessary for the thrust. They use burning rocket propellant to drive turbine pumps to feed propellant into the combustion chamber, and those pumps are the cutting edge of high-temperature, high-pressure pump design. "Just scaling it up" can be a completely new research and development project.
Aloha 5y ago
The N-1 Moon Rocket indicates that scaling up by putting more of your existing rocket motor on a vehicle may not always been as easy as it appears. As other parallel posters have commented, mechanical devices do not always squish or stretch with ease.
- soperj 5y ago
  Which engine was the NK33 used on previously? It is currently used on a newer version of Soyuz, but I'm pretty sure that it was originally built for the N-1.
giantrobot 5y ago
The thrust to weight ratio of a cluster of rocket engines is not a linear relationship. Adding one more engine might add N+1 thrust but it also adds at least N+1 mass. So you have more thrust but now more mass to lift and a worse mass ratio (the ratio of fuel to non-fuel). To scale your engine cluster you want to add an engine worth of thrust but not an engine worth of mass. To that end you reduce the mass of your piping or use one pump for multiple engines. All those changes require engineering and testing because the dynamics of the system have changed. For instance a fuel pipe of X thickness and Y material may have some weird failure mode if you make it just a little thinner to save mass.
mr_toad 5y ago
A couple of crucial design elements for Starship are a metholox engine (the idea being to make the fuel on Mars), and a reusable second stage. You couldn’t achieve those goals by scaling up a falcon.

DisjointedHunt 5y ago

It didn't take them a year to "get fuel tanks right", they were building while iterating on the upper stage design. ie, the manufacturing of an initial design that was evolving was being built at the SAME TIME. Think about that for a second. For an orbital class upper stage larger than any ever built, it took shorter than ever for it to be designed AND manufactured through multiple iterative designs and manufacturing techniques than either the design stage or the manufacturing stage for ANY OTHER ROCKET. All this while they continue to churn out and iterate on heatshield material and design at the "Bakery" which is another manufacturing facility they spun up from scratch in record time, manufacturing nearly a new rocket engine every DAY and that which has been flown and tested to demonstrate higher chamber pressures than ANY full flow staged combustion rocket engine in the history of mankind. They're much further along than any comment in this thread indicates.

foxyv 5y ago
I think SpaceX's efforts have highlighted the huge amount of talent that is languishing in the United States right now. Engineering and operations budgets have been cut so much in US companies that we have engineers and trained professionals like welders, aircraft mechanics, and construction workers stuck in underpaid and underutilized roles. Elon seems to be dedicated to focusing on Engineering and Operations and it's resulting in the full potential of those engineers and professionals being explored. Instead of focusing exclusively on market capture, lobbying and new marketing strategies, SpaceX is focused on actually getting something done. I've been nothing but impressed with them so far. While not nearly as financially successful as Tesla, I think SpaceX is closer to reaching Mars than Tesla is to reaching sustainable transportation and power.
- DisjointedHunt 5y ago
  There is inherent value stored in all of Spacexs accomplishments thus far that is very, very hard to place financial value on simply because it is the only asset in the world with the capability. A reusable rocket? How much would China pay for that capability? Don't worry about ITAR rules, it's a hypothetical question to understand the value of having such an asset available for defense or aerospace contracting purposes. The centuries prior to the digital age, whole private empires were built on the back of shipping and transport. Spacex is presently sitting on the largest payload capability fleet in the world, by tonnage to orbit. Yes, including China. Yes, including Russia, Yes, we're not even counting one single Starship here yet. The alloy itself that allows their turbines to run as hot as they have demonstrated to achieve such insane chamber pressures. What is that worth? No one else in the World has been able to do that in the history of mankind (In the unclassified realm atleast) The thing i love about the company that you allude to as well is they're running a ship that converts these "ideas" into tangible business value quicker than anyone we've seen in classic space industries.

iab 5y ago

Socially Laundering Securities

enragedcacti 5y ago

> The easiest part about Starship is the booster because its not doing anything F9 isn't already. Just at a much larger scale. It's possible that its easier than the other challenges starship faces, but everything I've read seems to suggest the raptor engine underpinning the entire project is massively behind schedule and over budget to the point of putting SpaceX at risk of bankruptcy (according to Elon).[1] It's also burning a completely different fuel and has numerous other massive changes so a booster leveraging it isn't really just F9 at a larger scale. [2] [1] https://spacenews.com/spacex-grapples-with-raptor-production-problems/ https://spacenews.com/spacex-grapples-with-raptor-production... [2] https://en.wikipedia.org/wiki/SpaceX_Raptor https://en.wikipedia.org/wiki/SpaceX_Raptor

beambot 5y ago
Can get the latest updates directly from horse's mouth: https://www.youtube.com/watch?v=3N7L8Xhkzqo https://www.youtube.com/watch?v=3N7L8Xhkzqo TLDR: Delay at this point is mostly regulatory (environmental study approvals) to launch out of Boca Chica. If they have to move to the Cape, then there will be delays.
- purpleidea 5y ago
  Not true. Musk said they weren't ready to launch yet anyways, and that they expected to be ready around the same time they expected to get FAA clearance. So it's not holding things up yet. And it might never.
  - beambot 5y ago
    OK, let me be more clear: The gating factor is FAA clearance, but it's not a delay yet. More specifically: Nominal date for FAA clearance is X. Actual clearance will be >X (these agencies are never complete early; it's already been delayed twice). SpaceX readiness date will be <= X. Therefore FAA clearance is the program bottleneck.
    - ncmncm 5y ago

chasd00 5y ago

iirc Starship was conceived before Falcon Heavy was finished as well. So, to me, Falcon Heavy would seem like a solution in search of a problem. There are some commercial flights for Falcon Heavy planned but as soon as Starship comes online it's obsolete. I don't know how much money the Falcon Heavy program will make but I would consider it paying for the R/D before being retired (just breaking even) a success.

jve 5y ago
Elon wanted to cancel FH according to the following article. > Years earlier, Musk ordered Falcon Heavy canceled, forcing Shotwell, who’d been tipped off by another SpaceX employee, to sprint to a conference room and remind him that the U.S. Air Force, a critical customer, had already purchased a launch https://www.bloomberg.com/news/features/2018-07-26/she-launches-spaceships-sells-rockets-and-deals-with-elon-musk https://www.bloomberg.com/news/features/2018-07-26/she-launc...
MPSimmons 5y ago
FH was first mentioned in 2003 (https://hobbyspace.com/AAdmin/archive/Interviews/Systems/ElonMusk.html https://hobbyspace.com/AAdmin/archive/Interviews/Systems/Elo...), when it was going to be made of Falcon 1s. Not saying there was any engineering done there, but it was an idea that he wanted, so he could increase payload to orbit.
emteycz 5y ago
I always thought they did it purely for the show - and now even my mom is a big fan of SpaceX, so they were very successful.
- simonh 5y ago
  What a show. I could watch the twin booster landings all day. Not that I have or anything...

XorNot 5y ago

The big problem with Starship right now looks to be the heat tiles - I don't think they've had a single test where they haven't had some pop off, and I'd be willing to bet the internal redesign that was announced is to stiffen up the hill to deal with flex (since it seems to be trading a little of internal diameter to do it - willing to bet that's too deepen some bracing members).

chasd00 5y ago
As soon as I saw the tiles I thought “oh no”. They’re so fragile, they have to be a major hurdle for reusability. During the everyday astronaut interview Elon is talking and then looks over at a worker smacking a tile trying to get it to stay in place. Elon whips out his cellphone and then the interview cuts to a different scene. I imagine the amount of curse words being yelled into that cellphone would not pass YouTube’s guidelines. The heat tiles suck.
ncmncm 5y ago
The main problem with the tiles is that they are the same design as on the space shuttle, which had to all be individually rejiggered on each flight: take it off, squirt in some fresh goo, stick it back on. They won't be making any 8-hour turnarounds doing that. The tiles they have are a design that is known to work, and will suffice to prove that the vehicle can get to orbit and come back in one piece. So they will need a new design that doesn't need so much detailed attention after every flight. They have years to work out what that will be, because they are much farther from ready than some, apparently many, imagine. The gross, visible, easy stuff is mostly in place. The hard stuff you can't see is still to come.
- KiwiJohnno 5y ago
  Not quite. Each tile has a socket in the middle of the back, which goes over a mounting post which is welded to the steel hull of starship. Also, there are very few different shapes of heat tiles, and the vast majority of the heat tiles are of exactly the same design and shape. On the space shuttle few, if any heatshield tiles were the same. They were individually manufactured, instead of bulk manufactured to a common specification as SpaceX are doing. Obviously that is going to be far, far more efficient. Yeah, they have had problems with tiles coming off during static fires. Although this seems to have been getting better, and it remains to be seen how bad an issue losing a few patches of single tiles actually is. Under the tiles the structure is stainless steel, while with the space shuttle it was aluminum which is clearly not as tolerant of the extreme heating of re-entry.

beerandt 5y ago

>The easiest part about Starship is the booster because its not doing anything F9 isn't already. Just at a much larger scale. That of course isn't easy either. Scaling up in this context isn't simple at all. For all the recognition of the complexity of rocket science, structural engineering is perhaps the most underappreciated. Scaling up in multiple dimensions often means different things need to be scaled at different rates. Hydraulic and atmospheric modeling is similar in this respect. You pick the variable(s) that you want to scale linearly, and then have to resolve all the other variables in terms of what you've fixed. Lots of dimensional analysis, and then experiments to calibrate the results to be meaningful. For instance, max ultimate moment loading is generally the controlling factor for determining beam strength, which in turn determines the required beam cross section and weight/span. However, as beam span length increases linearly, moment increases exponentially for the same load. And scaling up likely increases the external loading, such that moment increases to the 4th power as base dimensions increase linearly. And then needing a bigger/stronger beam cross-section increases the self-weight that also needs to be supported. Things can quickly runaway in certain configurations, when you start to account for volumetric increases in fuel capacity, and dynamic loadings like impact forces on fuel tank baffles, which themselves are often scaled to the 3rd or 4th power of the fuel weight, and 2nd or 3rd power wrt to the relative change in velocity. And finally there's the structural harmonics and vibration, which all increase in force faster than linear increases in span, and affect structural serviceability (lifetime loading cycles).