23 thoughts on “RIP, Escape Dynamics”

  1. “DARPA/NASA should be doing, but the latter has to waste money on a giant rocket.”

    In any contest to waste money, I’d bet on DARPA every time.

  2. I guess we’ll have to rely on staged combustion first stages and solar-electric for the other stages for the foreseeable future. Seems like nothing else is getting investment. TAN, solar-thermal, beamed propulsion, it’s better not even to think about nuclear either.

    Propulsion and reentry still have a lot of room for improvement. At least with what SpaceX has been doing and their known development plans our space future at least seems more bearable than it was, say, 10 years ago.

    1. Why staged combustion for first stages? The first stage is where Isp matters the least. Staged combustion engines are more expensive and have lower T/W ratio than gas generator cycle engines. The Falcon’s Merlins are gas generator cycle engines, as well as using pintle injectors that slightly reduce Isp but are much easier to make than conventional injectors.

        1. I’ve heard Russian estimates on the cost of staged combustion and they claim it isn’t that high. People keep banging answers using SSME data but the Russians have developed quite a lot more staged combustion engines than that. The SSME isn’t a normal engine to begin with.

          Soyuz (R-7) uses staged combustion on the upper stage engines and I have never heard anyone claim that Soyuz launches were expensive.

          2. I have never heard anyone claim that Soyuz launches were expensive.

            Really? How many people have you asked?

            Even the NASA Administrator says that Soyuz launches are expensive, and he has an $18-billion annual budget. Mere millionaires like Sarah Brightman find them prohibitively expensive.

        2. Soyuz 2 is a cheap launcher. One of the cheapest in the market for its payload class. The astronaut launcher isn’t the same version as the other one. Also the price the market is willing to bear for astronaut transport is a lot higher : there is no competition whatsoever at the moment. So it is hardly surprising the Russians keep increasing the price.

          1. So, how many Soyuzes have you bought? If it’s so cheap, why don’t you buy them by the dozen?

            The people who say it’s “cheap” all have one thing in common: they’re spending someone else’s money.

            Also the price the market is willing to bear for astronaut transport is a lot higher

            Obviously, it is not, or Robert Bigelow, Dennis Tito, Sarah Brightman, etc. would be buying them right now.

            You’re apparently confusing the market with the government.

      2. I’m not a rocket engineer. But what I’ve heard is that with staged combustion you can increase the chamber pressure and that results in higher performance in the atmosphere as well.
        For some reason both Blue Origin and SpaceX are working on LOX/LCH4 staged combustion engines right now.

        Heck even ESA was supposed to be working on that before they decided to blow the space launcher budget on solids to emulate the US Ares program.

        1. Chamber pressure is like boiler pressure in a steam engine and nozzle back pressure is like, well, exhaust pressure in a steam engine.

          The ultimate in thermodynamic efficiency requires both a very high boiler pressure and a very low exhaust pressure, such as the near-vacuum at the inlet to the steam condenser. Steam electric power plant efficiency is sensitive to the temperature of the river or lake water they use to cool the condensers because the lower the temperature, the lower the condenser inlet pressure.

          You can get reasonably efficient steam-cycle efficiency with modest boiler pressure if you expand to a low enough condenser inlet pressure. Likewise, you can get pretty good results with a low chamber pressure rocket engine if you expand to vacuum conditions with a huge nozzle.

          On the other hand, if you are expanding to atmospheric pressure (kind of like the steam locomotive without a sub-atmospheric condenser inlet), you need high chamber pressure to get good conversion of chemical energy to work and hence good specific impulse with the short nozzle compared to a vacuum rocket engine. That is what the SSME did — it used insane chamber pressure with an expand-to-atmospheric pressure nozzle to get really good performance (with a fixed nozzle) from ground to near orbit.

          You certainly cannot achieve high chamber pressure with an “expander cycle” (the RL-10 that boils the LH2 fuel and runs that through a turbine to power the turbo pumps). I don’t see why you couldn’t achieve high pressure with the gas-generator cycle (that dumps the turbo-pump drive-turbine exhaust out the side). On the other hand, the higher the chamber pressure, the more reaction mass you are wasting to drive pumps — the staged-combustion engine feeds the turbine-drive exhaust into the main chamber and uses it as reaction mass.

          Hence the performance penalty for the gas-generator cycle goes up with chamber pressure. YMMV

          2. An alternative sometimes discussed is a gas generator with a higher exhaust pressure and afterburning in a second chamber. In effect, a small staged combustion chamber at 200 or so psi and a main chamber at 4,000+ psi. No dumped gas, and the Isp hit is on the lower chamber pressure of the smaller staged combustion side.

            It has been called a dual chamber cycle, and probably other names I’ve not heard of.

  3. I sincerely hope the first SLS launch ends in a glorious non-recoverable accident with flaming debris scattered across the Atlantic.

    1. If that happens, it’ll be hailed as a very successful launch due to the vehicle exceeding exceptions in several key parameters, including the number of simultaneous independent trajectories.

  4. Rand,

    They were microwave thermal, not laser thermal, but yeah it’s sad to see them go. I got a tour of their shop about a year ago (they were just up the hill from us at the Jeffco airport). They had a big team and some cool technology, but it looked like they had a high financial burn rate, and weren’t able to get to a point that could convince investors to keep funding them. I like microwave thermal rockets, so hopefully someone else can pick up the torch. IIRC Kevin Parkin is still working the idea.

    ~Jon

  5. Speaking of, what do you guys think the point is at which you can “convince investors to keep funding”. Xcor was able to do it with a low and slow flying vehicle, while SpaceX had to make orbit. On the other hand, Armadillo had vehicles making it to high altitude and didn’t make it financially. Masten is still going (flying vehicle to high altitude), but doesn’t seem to be getting outside investment, just surviving on government flights.

    If you had a space launch company, and wanted a wide investment pool, what is the minimum goal? Any thoughts?

  6. The advantages of high pressure engines on first stages is both decent Isp with a sea level nozzle, and high thrust per unit area, as first stages tend to have diameters defined by the need to get the thrust in (hence the flared base of Saturn V, or the shape of Soyuz)

    1. High thrust per unit THROAT area, but if the higher pressure engine is still expanding down to 1 bar then the throat area will be smaller. There’s an overall increase in thrust/nozzle exit area, but it’s not proportional to the chamber pressure. The relevant “thrust coefficient” increases modestly with chamber pressure, I think.

      You could have the staged combustion engine expand less, to an exit pressure greater than 1 bar, trading a bit of the Isp gain for higher thrust/nozzle exit area.

  7. Can’t help but wonder if these technologies are ultimately flight rate driven? I can see a point in time where further cost reductions based on flight rates exceeding the tens decile into the 100s decile would drive this type of technology forward. Until then a solution in search of a problem?

    1. I think this sort of technology could make sense if there was a market for a large number of small launches. Propellant for delivery to a propellant farm, for example, Unfortunately that market is not here.

      I imagine they may also have been hit by the success of SpaceX. It’s a property of technology that different solutions to a problem tend not to survive in the same market segment. This is much like the “one species per niche” principle of ecology.

      https://en.wikipedia.org/wiki/Niche_differentiation

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