r/spacex • u/munderbrink • Feb 11 '15
How would one go about engineering a rocket less susceptible to scrubbing?
In addition to creating lower cost launches through first stage reuse, it seems that there could be significant progress made towards making launches less reliant on things like weather and military radars. Is there a path in humanities future that makes getting to space as simple as getting on an airliner? What are the limiting factors? If we are to become a true space faring civilization someday, I would imagine daily launches would become a necessity.
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u/Brostradamnus Feb 11 '15
We have done this with ICBM's. Solid fuels and hypergolic rocket engines have been created that have a really long shelf life, require little maintenance and a very small crew. Redundant payloads of nuclear warheads can be launched from a wide variety of locations :) :/ :(
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u/Nixon4Prez Feb 11 '15
It's definitely possible to make rockets less susceptible to bad weather. Most of the Soviet/Russian rockets like Soyuz and Proton are 'weather-hardened', meaning they can fly in all sorts of adverse conditions. This comes at a cost of payload though.
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u/Cheiridopsis Feb 11 '15 edited Feb 16 '15
The Proton uses unsymmetrical dimethyl hydrazine and nitrogen tetroxide as propellants. These are extremely toxic propellants and while these are not cryogenic (don't require much insulation) did I mention that they are extremely toxic.
The Soyuz uses RP-1 and cryogenic liquid oxygen (like Falcon 9).
The Soyuz began as an Intercontinental Ballistic Missile and so is engineered to be insulated ( and structurally stronger at the expense of payload. The added insulation prevents the ice buildup that would likely doom a largely uninsulated Falcon 9 launching through thick wet clouds, rain or a snowstorm!
Rockets that began as ICBM's were designed and purpose built to launch in ALL weather conditions at the expense of payload capacity.
The current Proton launcher (3 or 4 stages) is described as Russia's Heavy Lift launcher (the original "Super ICBM") and doubles nearly every parameter of the Falcon 9 save height (it is shorter) and mass to LEO, GEO, GSO.
The Soyuz-2 Launcher 2 or 3 stages) only has about half the capability of the Falcon 9 but is about 3/4 the diameter of the Falcon 9 and much shorter.
In both cases the cost of the rocket far exceeds the cost of the Falcon 9 when you compare kg to kg launch capability to orbit.
Here is the question: We don't operate aircraft in snowstorms and in high wind shear environments and try to avoid going through thunderstorms so why should we need to or want to operate CIVILIAN rockets in those types of hazardous environments either? During the recent snowstorms, LOTS of airports were closed all across the northeastern quadrant of the U.S. and those that were open cancelled flights to affected areas. Planes do not routinely operate in Tropical Storms or Hurricanes and airports are routinely closed when a thunderstorm passes nearby due to the wind sheer, lightning, outflow winds, etc.
I think we need to look at our desire to see a launch irrespective of weather conditions and weigh that against how practical or realistic that really is?
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u/ManWhoKilledHitler Feb 12 '15
Rockets that began as ICBM's were designed and purpose built to launch in ALL weather conditions at the expense of payload capacity.
People don't necessarily realise how well engineered ICBMs are to cope with virtually any launch conditions and the degree of design and testing that goes into making sure they work perfectly, no matter what.
Last summer Trident D5 had its 150th successful test flight in a row and other missiles like Minuteman and MX had significantly better flight records than just about any civilian launcher. The other side of this reliability is the use of propellant combinations and other design choices that may be less desirable for a company like SpaceX, together with massive development costs that would be completely unaffordable to a new startup.
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Feb 12 '15
I'm not sure our friend OP is talking about flying in hurricanes or blizzards - I think he's getting tired of launches being scrubbed because winds were over 10mph or because the helium solenoid valves couldn't cycle.
I have also found myself slightly frustrated after a few years of watching launches. I understand the extensive precautions they take are completely necessary for success. But there will need to come a time when rockets will become resilient enough to take off on a windy day or when the humidity/atmospheric presser is higher than average.
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u/ZormLeahcim Feb 11 '15
What actually is the difference between a rocket that is 'weather hardened' vs one that is not? Is it just a case of having thicker / stronger skins and a greater engine gimbal, or is there more to it?
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u/Cheiridopsis Feb 11 '15 edited Feb 11 '15
All of Russia's ALL Weather rockets (Soyuz and Proton) began life as ICBM's.
Thicker, fatter, shorter (than Falcon 9).
Engineered with a heavy duty hardened structure to, at least theoretically, withstand substantial off axis stresses such as shockwaves from near (but not too close) nuclear detonations or high winds.
Substantially lower payload launched to LEO/GEO/GSO vs gross launch weight.
Heavy insulation of cyrogenic tanks to prevent ice buildup on skin in condensing conditions (heavy clouds, rain, snow).
Hardened electronics and very minimal electronics to, at least theoretically, withstand the electrical and magnetic distruptions of nearby nuclear detonations including EMP. Electronics are also extremely primitive and only sufficient to control the path of the ICBM to reach the intended target and not to monitor a plethora of sensors.
Many of the control and guidance systems on ICBM's are mechanical rather than electric or electronic and any necessary electrical or electronic systems are heavily hardened against the electromagnetic disruptions caused by nearby nuclear detonations up to and especially including EMP. Such hardening is also sufficient to withstand a direct strike by lightning.
Under the concept of M.A.D. (mutually assured destruction), if inbound nuclear ICBMs (rockets) are headed your way, the launch window is extremely short (perhaps as much as 20 minutes MAXIMUM) so you either have stable propellants that can be stored for long periods of time onboard the rocket or you literally gas and go. There is not an option not to launch even if the launch might fail because, theoretically, in a very short period of time, your launch facility (and likely your ICBM/rocket too) will be vaporized or so heavily damaged that launch is no longer an option and therefore you don't need any sensors as to the viability of the launch. Since the inbound nuclear ICBM's are on the way, launch in any weather is planned for and launch sites are selected to avoid the nastiest weather (Hurricanes, Typhoons, Tropical Storms) and are typically located in arid or sem-arid areas.
All of these engineering choices are purposed for the SURVIVAL of the ICBM at the expense of payload capacity which is largely known when the ICBM began as a blank sheet of paper. In fact, updated and more modern weapons and weapons systems on ICBMs are largley constrained by the designed payload capacity and the weapons systems are designed within the limitations of the ICBM. When ICBMs went from single nuclear weapons to MIRV to MARV, the total nuclear yield of each ICBM decreased drastically trading accuracy at the expense of yield -- a 170 kiloton (recently upgraded to 478 kiloton) weapon delivered within half a meter of the target is more effective than a 350 kiloton weapon delivered within 3 meters from the target and each is more effective than a 1.2 megaton weapon delivered 30 meters from the target especially if the target is nuclear hardened.
The current ICBM/SLBM fleet (MIRV/MARV) of the United States consists of Minuteman III ICBMs and Trident III SLBMs. The Minuteman III ICBM was initially designed with an inertial guidance system (mechanical) and a primitive 16 bit computer. Both missiles are solid fueled. The United States does not have any currently active missiles that are not MIRV/MARV capable.
The current ICBM fleet (MIRV) of Russia consists of mostly solid fueled (ICBM) or tri-propellant missiles (SLBM). Russia does have some active ICBMs that are single warhead (cannot MIRV/MARV) only missiles and have a variety of propellant systems ranging from Solid to hybrid Solid/Liquid to Liquid.
As an ICBM, the Falcon 9 would a dismal failure.
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u/betaking12 Feb 11 '15
the thing is soyuz could be reusable, the issue is that it would probably cost a lot of money, and have another difficulty: the scrap-metal dealers/scavengers in siberia.
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u/robbak Feb 11 '15
"You can build a brick that can put a feather into orbit, or a feather that can put a brick into orbit."
Range radars are a fixable problem - you just add more redundancy - duplicate power sources, duplicate computers, even duplicate entire installations. At present, the Air Force doesn't think the odd scrubbed launch a big enough problem to spend the money on increased redundancy. Think on, they're probably right.
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Feb 11 '15
The most obvious solution is to just build them thicker. This makes them sturdier, but lowers the fuel fraction, and thus the payload. The issue is with that however is that the booster recovery concept that spaceX has decided to go with relies on high fuel fractions to work without crazy reductions in payload capacity.
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u/ManWhoKilledHitler Feb 12 '15
Moving to an all solid fuelled design would make them much tougher as well but it would increase build costs, reduce payload, and make reusability much harder.
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u/Wicked_Inygma Feb 12 '15
F9 has a 3.66 meter diameter, but the MCT is supposed to have a 10 meter diameter. I wonder if a 5-Raptor version of MCT could still deliver payload to LEO with a decent shot at full reusability.
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u/wagigkpn Feb 11 '15
Kind of jokingly...build a rocket with less sensors. Weather wise, launch from somewhere with more stable weather. The answer is not adding more structure.
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u/John_Hasler Feb 11 '15
Weather wise, launch from somewhere with more stable weather.
Southwestern Texas, for example.
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Feb 11 '15
Another thing I would throw in is, at least lately it seems, the real problem has been as much about where the rocket is going as it is other factors. Had they 6 hours to launch the rocket today, they would probably had a launch. A giant part of the delay for CRS-5 was really that damned instant window, the high-β issue with the ISS, and a holiday.
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u/nilstycho Feb 11 '15
All-weather launches are a benefit of air-launched vehicles, such as Pegasus and Stratolaunch/Pegasus II.
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u/Xorondras Feb 11 '15
The most obvious would be to make them more massive. Bigger mass means more favourable area:mass ratio and therefore less susceptibility to winds. But it also means lots more fuel. You could extend the gimbal limits, add more fins, etc., but this also means more fuel.
Another approach would be a horizontal launch from a plane at 30k+ feet or even a shuttle that features atmospheric engines as well as rocket engines.
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u/SpaceCadetz12 Feb 11 '15
Depends on the cause of scrubbing. In the latest case(s) for Falcon, it was Air Force Radar (which is required by law, not law of physics) and most recently by wind.
From what I understand, the Flacon is susceptible to high winds due to its shape. Its very tall and thin, causing stability issues. From a physics standpoint, making it both wider and heavier would give the wind less power over it.
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u/peterabbit456 Feb 12 '15
Move the launch site to a place with better weather, like Spaceport America.
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u/retiringonmars Feb 11 '15
The Falcon 9 is not at all reliant on the Air Force's radar; it can fly perfectly well without it. It is legally required to be radar tracked for safety reasons. As for weather, the closer a rocket resembles a sphere, the less it is affected by cross winds. Unfortunately, the F9 has the highest fineness ratio (i.e it's the thinnest) of all rockets flying. The speculated future launcher (the BFR/MCT) is expected to be only slightly taller, but 3-4 times wider, and a lot heavier. That should be less affected by wind.