That’s… not exactly true. The rocket equation looks like this for a two-stage rocket:
dV = Ve0ln(m0/m1) + Ve1ln(m2/m3)
That’s a lot of inputs, but one thing you can read clearly from it is that if the mass fractions (m0/m1 and m2/m3) are the same between stages, then it doesn’t matter if you swap Ve0 and Ve1. You get the same result in both cases.
It’s true that low-Isp solids do tend to be used on lower stages. But the benefit is mostly related to their high thrust to weight ratio. To reduce gravity losses, you don’t want to spend a lot of time barely rising from the launch pad. And you don’t necessarily want to add more liquid fuel engines because they tend to be heavy and they’ll have to be throttled down later in flight anyway. A solid booster is a (relatively) cheap and easy way to get some early velocity at a time when the rocket weighs the most.
All of which has basically nothing to do with using solids on upper stages. There, storability and reliability are bigger concerns.
I don’t like solids as main rocket engines for reusability, safety, and control concerns. But these things don’t matter as much for an expendable cargo rocket.
Incidentally, Antares uses a Castor 30 upper stage, manufactured by… ATK. You know, the same guys (modulo their acquisition of Thiokol) that built the Shuttle boosters. They aren’t some salvage ICBM parts.
You get better mass fractions with upper stages because upper stage burns do not need as much acceleration, and because the upper stage doesn’t have to include the mass of the whole stage above it in the final mass. This is why you want to stick your more efficient engine on the upper stage if you have a choice.
The correct formulation of your equation looks like : dV = Ve0ln((m0+payload)/(m1+payload)) + Ve1ln((m2+stage 2+payload)/(m3+stage 2+payload))
Also, the Castor 30 is apparently yanked off a SAM, not an ICBM. Still a missile.
The mX values in my formulation had the payload and stage masses folded into them. The point is that you said “it’s always more efficient”, and that is false. There is some mass ratio where it does not matter, and a range of ratios where putting the low-Isp stage on top is superior.
Also, engines are not infinitely variable in their performance and that imposes some constraints on mass ratios. You cannot put 2.37 engines on a vehicle to hit the optimal point. A clean-sheet design can reap some of these gains, but Orbital didn’t have that option.
Uh, no. The Castor line is derived from earlier motors. That does not mean they are the same. They’re new parts, unlike the modded NK-33s or Minotaur line.
C’est n’importe quoi! The Castor 30 is not a motor off of a SAM, or ICBM, or any other kind of surplus. It is a modern commercial motor designed expressly for upper stage launch vehicle applications such as Antares, Athena, and Minotaur V+. That it is propulsively less efficient than a liquid propellant engine of comparable size and mass is not the issue; it is designed for applications where the simplicity and robustness trump absolute maximum mass performance, e.g. applications for delivering payloads to a Low Earth Orbit like cargo deliveries to the ISS. Again, the same reason that upper stages powered by motors such as the Star-48 and Orbus-21 motors are used on EELV and STS launches. This particular Antares launch was actually the debut of the Castor 30XL, a slightly more efficient and capable version of the previous Castor 30A/B motor.
Really, you could find this out for yourself by searching on Castor 30 or going to the ATK website and downloading their AATK Space Propulsion Products Catalog.
Presumably they will build more, or contract with someone to have them built. That shouldn’t be too hard if the plans still exist. If the plans don’t exist, then I’m not sure what they were smoking when they decided to use something that they didn’t understand.
The problem is, apparently, this engine is inherently very expensive to manufacture, and too expensive for Orbital to continue launching using it at the current prices.
Probably not. There are supposedly a bunch more of the engines still stockpiled, but they’re in Russia and availability is up to Putin’s whims (not to mentioned the undetermined quality). Aerojet has a license to produce more, but from what I understand it would be cheaper to just build a new engine. The metallurgy still isn’t fully understood and the designs tend to require a lot of man-hours.
Nearly the same problem exists with the RD-180 engines on Atlas V, but at this point no one is talking about trying to reproduce the engine. Instead, ULA has contracted with Blue Origin to produce a semi-equivalent methalox design. Aerojet has their own replacement proposal in the AR-1 design, but it’s not a direct copy of either NK-33 or RD-180.
I hope that more indigenous designs are produced, but there are a lot of proposals flying around and they all seem to involve “old space” prices. That is, billions in development costs and tens of millions in unit costs. In comparison, SpaceX developed the Merlin engine for $100M or so and they probably don’t cost more than $1M each.
The engineering data package (“plans” as you colloqually refer to them) are not everything needed to construct a complex system such as a rocket engine. You also need all of the supplier specifications, access to the materials and test data, and the necessary manufacturing infrastructure to actually fabricate and assemble the engine. The “special sauce” such as so-called tribal knowledge, special tooling and fixtures, measurement and test data and appliances, et cetera are all critical to being able to build a qualified propulsion system or other complex device.
With regard to the use of the AJ-26 (refurbished and modified NK-33) engines on Antares, they never planned for a flight rate exceeding four or five flights a year, and therefore a stockpile of 40 available flight units at two engines per vehicle gave a four or five year run. Orbital is reported to have an “Antares II” vehicle in the work albeit with an unspecified configuration. Orbital isn’t trying to develop a reusable vehicle, or achieve production line rates, or go to Mars. They’re were trying to build a Delta II-class vehicle using known and previously used propulsion systems without investing the cost into developing all new propulsion technology. The general, rule-of-thumb cost for developing a new, high performance and high thrust staged combustion engine like the NK-33 is on the order of a billion dollars US, which is about twice as much as Orbital put into developing the entire Antares vehicle. (This estimate, while conservative, is within a close order of magnitude to what I’ve actually seen in engine development studies.)
Note that Orbital is not the first or only company to consider use of the NK-33 for this type of application; Rocketplane Kistler planned to use the NK-33 and NK-43 for their reusable K-1 two stage vehicle and Aerojet did extensive testing to qualify the engine for this reuseable application. Lockheed considered use of the NK-33 for a proposed vehicle. And the Soyuz-2.1v uses teh NK-33 on the first stage (instead of the RD-117 and RD-0124 used on the 2.1a and 2.1b vehicles respectively); their plan is to eventually replace it with the RD-191, which is a derivative of the RD-170 used on the Zenit and RD-180 used on Atlas V. So this is hardly just one company making an obtuse choice of propulsion system.
sigh The Merlin 1 engine development and evolution cost considerably more than $100m; that was just the money the government provided to SpaceX to develop the Merlin 1c and 1d engines. And this was a relatively simple gas generator engine (with considerable heritage to the TR-107 engine developed by TRW for the Space Launch Initiative program) with unimpressive propellant mass effiicency (I[SUB]sp[/SUB] = 311 s (vacuum) compared to I[SUB]sp[/SUB] = 338 s (vacuum) for the staged combustion RD-180 or I[SUB]sp[/SUB] = 331 s (vacuum) for the NK-33.
Interestingly, Tom Markusic (former head of McGreggor operations and now founder of the Firefly smallsat SLV) reported back in 2010 a ~US$1B development cost for the Merlin 2 LOX/RP-1 gas generator cycle engine that was to be used on the proposed Falcon X and XX vehicles. SpaceX hasn’t discussed the anticipated development cost for the staged combustion CH[SUB]4[/SUB]/LOX engine but given the novel fuel (no one has yet developed a methane engine of anywhere near this size) and the staged combustion cycle a ROM of US$1B development cost is probably a reasonable first estimate.
This entire “New Space” versus “Old Space” dichotomy is largely a bunch of horseshit. There are certainly bloated and regressive companies which have discovered that the way to make a profit in the aerospace industry isn’t by innovation but rather manipulation of contract scope (e.g. ULA), and companies that do try to innovate and advance the state of the art through various methods of varying efficacy, but the distinction isn’t always as clear cut as “New Space” advocates would like to promote. Great innovaction can be found within the aerospace giants (viz. TRW developing the LCPE and TR-107 that went on to flow into the original Merlin engines, or the Lockheed-developed Linear Aerospike Engine intended for use on the X-33), but while they have the means to develop they don’t see the market to manufacture at profit. (And sadly, they’re probably correct, at least in a near term application.) And the upstarts have innovation but not enough money to go through a rigorous and thorough devleopment and qualification process which often results in dramatic failures that end up stalling development for everyone.
There are certainly inefficiencies and excessive costs, often driven by the fact that this is the way to maximize profit on poorly written government contracts, which can be reduced to reduce the cost for space access, but there are minimum thresholds to the amount of cost required to develop and mature technologies for reliable space access. Using existing and proven (e.g. qualified) technology is one way of reducing development costs. In other words, not reinventing the wheel.
I don’t understand the 3-stooges reference to Russian rocket engines. We’ve been using the RD-180 in the Atlas V for years. They’re apparently more reliable than anything in US inventory.
I wasn’t talking about the evolution cost. Just from time 0 to the first Merlin engine on a successful orbital flight.
Figures are hard to come by but it’s clear that the Falcon 1 cost no more than a couple hundred million to develop (Musk was not that rich, and there was not that much other funding), and that included engine development up to the 1C. Since the Falcon 1 itself and another, simpler engine (Kestrel) were also designed, I think $100M is a perfectly reasonable estimate if we exclude the further Falcon 9 work (1D and the vacuum models).
No doubt. But while SpaceX may have a monopoly on Tom Mueller, they don’t have a monopoly on heritage knowledge. As you said yourself, propulsion programs are being left to atrophy. The knowledge and personnel are out there but simply decaying at the moment.
And I believe it. As you say, no one has done a full-size methalox engine before, and not a full-flow staged combustion of any kind (beyond prototypes). It will be an impressive achievement in any case, and especially so if they can keep it within projected costs.
To be clear, I was comparing against Aerojet’s proposed AR-1 engines. They anticipate development costs of $800M to $1B. That seems outrageous to me for what appears to be a fairly conventional, and not too large, kerolox design.
And this is exactly it. “New” vs. “old” space is just a piece of shortcut linguistics that can only be an approximation. But I think that old space is characterized by stagnancy related to their way of interacting with the government. From the cost-plus model to the way NASA has traditionally subcontracted work, it means that really innovative stuff never really goes anywhere. There’s obviously lots of talent within the companies that is simply hamstrung because management won’t spend a dime if there is the tiniest risk that they won’t get it back.
We need scrappy upstarts to try (and fail). I want to see stuff blow up as long as something new was tried. Most ideas are bad ones, but you don’t know which ones upfront.
NASA independently verified SpaceX’s total development costs of both the Falcon 1 and Falcon 9 at approximately $390 million in the aggregate ($300 million for Falcon 9; $90 million for Falcon 1). NASA, Falcon 9 Launch Vehicle NAFCOM Cost Estimates, August 2011.
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It bears noting that the Falcon 9’s development included designing, building and testing SpaceX’s Merlin engine, the first new all- American hydrocarbon engine for an orbital booster in forty years.
They don’t give a breakdown of the costs, but for $390M they got two vehicles and two engines (three if you count the vacuum model separately). Again, I think “$100M or so” is a perfectly reasonable estimate for 1C development.
We’re gonna need to see an actual cite on that ~$1B cost to develop the Merlin1. A powerpoint presentation with one slide about a non-existent engine that is not even being planned for doesn’t count as a cite.
Eh, it still doesn’t say that the engine is at fault. A turbopump failure could mean that the engine sucked down a wrench that some technician left in the RP1 tank. And even if the engine was at fault, it’s not necessarily related to the age or their Russian origin–it could have been an unrelated design defect or something to do with the Aerojet retrofit.
I’d still give odds that it was age-related, either directly or indirectly (including certain aspects of their modernization), but the current press release doesn’t yet prove that at all.
I do wonder who the winner is. ULA is expensive. SpaceX would be… funny, since they already have a launch contract and a pretty full manifest. Ariane could make sense, I suppose, though if it were on a Soyuz rocket I think the negative press about being dependent on Russian aerospace would continue.
looks like Stranger is correct or almost correct in all these cites. Do you have any cites where he has been shown to be wrong?
Can you reference any of your posts where you contribute technical information to the discussion? I can’t find any.