Quote from: HMXHMX on 12/16/2016 04:28 pmToday, turbopumps are getting ridiculously cheap, so there is little reason to go pressure-fed. If I was to embark upon another LV project, it'd be pump-fed.One thing I've been wondering about is compressed-air (or compressed Helium) turbopumps. That sounds low-tech and cheap, and still more efficient and lighter than pressure-fed. Yet nobody uses them, why is that? I know they were briefly used by the Russians in the forties in their early rocketry experiments, but nothing since. Couldn't this have been better than pressure-fed for say the Lunar Lander Challenge?
Today, turbopumps are getting ridiculously cheap, so there is little reason to go pressure-fed. If I was to embark upon another LV project, it'd be pump-fed.
Nowadays, electric pumps look really good for small efforts. Rocketlab uses this approach (but they weren't the first to consider it). For a variety of reasons (especially because battery tech is ~an order of magnitude better/cheaper), this was not an attractive choice in the 80s and early 90s but is today.And for small motors, being able to 3D print means it's really easy to make a rocket with regen channels built-in. But there's a limit to this, and 3D printing big motors becomes prohibitively expensive.Guidance is also something much easier today than in the 80s/90s, and FAR easier than in the olden times before cheap ICs. A smartphone has basically everything you need (at least generally speaking hardware-wise... The gyros are not built to the right range, and the GPS stops working at very high speeds due to arms control concerns).Both Rotary Rocket and XCOR (technically late 90s) assumed the use of a person for guidance. Computer tech was more expensive and less developed. And landing especially seemed a hard problem at the time best left to people. But nowadays there's no reason to do this. Making every rocket stage crewed greatly increases the minimum size, besides it's risky and encourages you to either take potentially fatal risks or to avoid flight tests.So there's actually a whole lot of ways that starting a rocket startup is easier technically today than it was in the 80s/90s. Even amateurs with ramen-level funding can build a rocket with some sort of guidance and stabilization.One thing I'd like to see someone try is to use one of those human-carrying drones (or maybe an uncrewed electric motorglider) to haul a peroxide mono propellant rocket to a higher altitude for launch. I bet you could get to 30000ft, which might give you enough of an Isp boost to get to the Karman line.
A couple of years ago there was talk that automotive laser ignition systems might prove useful for rocketry as well. Are there any signs this is happening?
Quote from: Robotbeat on 01/03/2017 06:38 pmNowadays, electric pumps look really good for small efforts. Rocketlab uses this approach (but they weren't the first to consider it). For a variety of reasons (especially because battery tech is ~an order of magnitude better/cheaper), this was not an attractive choice in the 80s and early 90s but is today.And for small motors, being able to 3D print means it's really easy to make a rocket with regen channels built-in. But there's a limit to this, and 3D printing big motors becomes prohibitively expensive.Guidance is also something much easier today than in the 80s/90s, and FAR easier than in the olden times before cheap ICs. A smartphone has basically everything you need (at least generally speaking hardware-wise... The gyros are not built to the right range, and the GPS stops working at very high speeds due to arms control concerns).Both Rotary Rocket and XCOR (technically late 90s) assumed the use of a person for guidance. Computer tech was more expensive and less developed. And landing especially seemed a hard problem at the time best left to people. But nowadays there's no reason to do this. Making every rocket stage crewed greatly increases the minimum size, besides it's risky and encourages you to either take potentially fatal risks or to avoid flight tests.So there's actually a whole lot of ways that starting a rocket startup is easier technically today than it was in the 80s/90s. Even amateurs with ramen-level funding can build a rocket with some sort of guidance and stabilization.One thing I'd like to see someone try is to use one of those human-carrying drones (or maybe an uncrewed electric motorglider) to haul a peroxide mono propellant rocket to a higher altitude for launch. I bet you could get to 30000ft, which might give you enough of an Isp boost to get to the Karman line.If I may, I'd like to refine Robotbeat's the comment about Rotary. We assumed a person-in-the-loop for orbital missions, but not for guidance or navigation – only for "flight management" and secondarily for "control." The human manages the decision-making (when time permits) and in the case of landing can hand fly the vehicle if required. But generally the Roton would have been flown under autopilot at all times in routine flight, even for landing. What I know of the XCOR approach is that Lynx would always be hand flown, both on ascent and reentry/landing.
Quote from: mmeijeri on 01/03/2017 06:42 pmA couple of years ago there was talk that automotive laser ignition systems might prove useful for rocketry as well. Are there any signs this is happening?KbKHA has tested RD-0146D with laser ignition, Vulcain 2 prototype has been tested with multiple different laser igniters.
A similar but disposable technology (the pneumatic match) was developed by NASA in the early 70's for sounding rocket ignition using an air stirrup pump.
Quote from: john smith 19 on 01/04/2017 05:06 pm A similar but disposable technology (the pneumatic match) was developed by NASA in the early 70's for sounding rocket ignition using an air stirrup pump.What are your sources?.
The first hit on Google for "NASA pneumatic match":https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19740000202.pdf
Quote from: ringsider on 01/04/2017 06:55 pmThe first hit on Google for "NASA pneumatic match":https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19740000202.pdfThere was a full report on NTRS describing the whole thing. I may have a copy of the report somewhere but it looks like it's been purged from NTRS.
One thing I'd like to see someone try is to use one of those human-carrying drones (or maybe an uncrewed electric motorglider) to haul a peroxide mono propellant rocket to a higher altitude for launch. I bet you could get to 30000ft, which might give you enough of an Isp boost to get to the Karman line.
Quote from: john smith 19 on 01/04/2017 10:02 pmQuote from: ringsider on 01/04/2017 06:55 pmThe first hit on Google for "NASA pneumatic match":https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19740000202.pdfThere was a full report on NTRS describing the whole thing. I may have a copy of the report somewhere but it looks like it's been purged from NTRS. Is this it?Development and demonstration of flueric sounding rocket motor ignitionhttps://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19740020110.pdf
Resonance ignitor is safe for handeling, but very slow and not reliable. Up to now it is an alternative technology, absense from major use.
Quote from: Robotbeat on 01/03/2017 06:38 pmOne thing I'd like to see someone try is to use one of those human-carrying drones (or maybe an uncrewed electric motorglider) to haul a peroxide mono propellant rocket to a higher altitude for launch. I bet you could get to 30000ft, which might give you enough of an Isp boost to get to the Karman line.This might interest you on towed launch:https://www.nasa.gov/sites/default/files/files/FS_TGLAS_150129-1.pdf?linkId=14885220Met one of the self-proclaimed gray beards of the project last year. Got me excited.
Nope. And hydrogen peroxide isn't that hot if you run low concentration. And to get anywhere close to decent performance with a compressed gas turbopump, you need to heat it with a heat exchanger anyway, which adds complexity and means you need to withstand hot temperatures anyway.Copenhagen Suborbitals built a hydrogen peroxide driven turbopump, so it is feasible for amateurs. And it's used on the R7 rocket, so it's good enough for serious rocketry.
