Norm,
I would like to challenge both the DIRECT group and the EELV group to respond to this speech on a point-by-point basis.
While one could definitely draw the conclusion that Griffin drew, ie. that hydrogen boiloff issues imply it would be better to launch the system in fewer pieces, one could also draw a different conclusion. The conclusion I would draw is that if cryogenic propellant storage technologies are so critical--develop them. Don't let the existing state of the art in propellant handling drive transportation system decisions for projects that won't be undertaken for 15-20 years!
There are current technologies under development that could yield very low to zero boiloff of cryogenic propellants. For a six launch architecture, especially if the LH2 is being used in some sort of nuclear or solar thermal system (where the hydrogen is used gradually over the course of the trip to and from Mars), you already need a system that can keep LH2 for months to years, so extending that technology further so that boiloff during mission assembly isn't an issue.
Is 2025-2030 really so close that we can't afford to do this right and actually develop the technologies we need instead of trying to kludge by with existing technologies?
Once you have the boiloff issue reduced or solved, that ~500klb of hydrogen ceases to be a headache, and begins to be an opportunity. That's a lot of demand for propellant in orbit, and it can be supplied commercially. You're already going to need propellant transfer technologies anyway if you have to launch the hydrogen in multiple launches, so what's to stop launching it in even smaller launches? Use a depot if you're worried about too many docking events with your mars ship.
I'm sure the DIRECT guys can bring up other points, but that's one that stuck out to me. If one of his key arguments for why you need Ares V is hydrogen boiloff, he's going about it in the wrong way.
~Jon
jongoff - 23/1/2008 10:18 AMthe control of hydrogen boiloff in space is one of the key limiting technologies for deep space exploration, the need to conduct fewer rather than more launches to LEO for early Mars missions becomes glaringly apparent.While one could definitely draw the conclusion that Griffin drew, ie. that hydrogen boiloff issues imply it would be better to launch the system in fewer pieces, one could also draw a different conclusion.
While one could definitely draw the conclusion that Griffin drew, ie. that hydrogen boiloff issues imply it would be better to launch the system in fewer pieces, one could also draw a different conclusion.
Thomas - 23/1/2008 2:46 PMI'm glad to see Griffin emphasizing that the switch to the 5 segment booster/J-2X upper stage was for the purposes of reducing the cost/development time of the Ares V and not due to any inherent weakness in the SRB or SSME. Too many Ares I detractors either don't realize this or intentionally mislead their audience.
Jon may have something here. Propellant boiloff is an issue, but it does scream out as a problem to be solved by a new technology or strategy and not by a new and expensive hulking rocket. Griffin does seem to assume that technology for various things including propellant storage will remain static. Without money they may remain static anyway, but if there's no money then it's a moot point IMO.
Tim S - 23/1/2008 2:39 PMWell said Mr Griffin.We're not talking about U-Haulers for cargo here. We're talking manned space flight. EELV folks on here need to stick to what they know.
Tim S - 23/1/2008 3:39 PMWell said Mr Griffin.We're not talking about U-Haulers for cargo here. We're talking manned space flight. EELV folks on here need to stick to what they know.
Tim S - 23/1/2008 12:39 PMWell said Mr Griffin.We're not talking about U-Haulers for cargo here. We're talking manned space flight. EELV folks on here need to stick to what they know.
Chris Bergin - 23/1/2008 11:30 AMhttp://www.nasa.gov/pdf/208916main_Space_Transportation_Association_22_Jan_08.pdfHere's the part that will make many a coffee be spat over screens in Denver etc. snipThe Ares I lift requirement is 20.3 mT for the ISS mission and 23.3 mT for the lunar mission. EELV lift capacity for both the Delta IV and Atlas V are insufficient, so a new RL-10 powered upper stage would be required, similar to the J-2X based upper stage for Ares I. We considered using additional strap-on solid rocket boosters to increase EELV performance, but such clustering lowers overall reliability.ship
Norm Hartnett - 23/1/2008 1:57 PMNot the Moon and not Mars but beyond, in other words a system that has the versatility to go to any place in space that is reasonable within the framework of the next thirty years.
As to the Constellation architecture looking better cost-wise than any alternative for Mars IMO Ross has already addressed this in the DIRECT discussion. And to address your question, if it is not used for Mars there are still the NEOs, Mars' moons, and Venus.
Danny Dot - 23/1/2008 3:21 PMQuoteChris Bergin - 23/1/2008 11:30 AMhttp://www.nasa.gov/pdf/208916main_Space_Transportation_Association_22_Jan_08.pdfHere's the part that will make many a coffee be spat over screens in Denver etc. snipThe Ares I lift requirement is 20.3 mT for the ISS mission and 23.3 mT for the lunar mission. EELV lift capacity for both the Delta IV and Atlas V are insufficient, so a new RL-10 powered upper stage would be required, similar to the J-2X based upper stage for Ares I. We considered using additional strap-on solid rocket boosters to increase EELV performance, but such clustering lowers overall reliability.shipWhat is the lift capability of Delta and Atlas heavy? I am certain Atlas Heavy can lift this much and it is already at CDR with a very low risk to first flight.Danny Deger
Thomas - 23/1/2008 3:38 PMWhy do people seem so surprise that the ARES (hello!!!!!!) series of vehicles have Mars as an ultimate destination?
edkyle99 - 23/1/2008 4:43 PMQuoteThomas - 23/1/2008 3:38 PMWhy do people seem so surprise that the ARES (hello!!!!!!) series of vehicles have Mars as an ultimate destination? Then why is NASA betting its foreseeable future on lunar exploration? - Ed Kyle
A bigger launch vehicle is always going to cost less on a $/kg payload basis when it is compared to a smaller launch vehicle if the payload requirements are large enough or the program time frame is long enough, or both. Ares V outhauls Direct, and so will always beat it at that cost-comparison game when it comes to Mars missions that start in 2030, require a million pounds of payload in LEO for each mission, and are part of a Mars exploration program that continues forever.
edkyle99 - 23/1/2008 4:38 PMQuoteDanny Dot - 23/1/2008 3:21 PMQuoteChris Bergin - 23/1/2008 11:30 AMhttp://www.nasa.gov/pdf/208916main_Space_Transportation_Association_22_Jan_08.pdfHere's the part that will make many a coffee be spat over screens in Denver etc. snipThe Ares I lift requirement is 20.3 mT for the ISS mission and 23.3 mT for the lunar mission. EELV lift capacity for both the Delta IV and Atlas V are insufficient, so a new RL-10 powered upper stage would be required, similar to the J-2X based upper stage for Ares I. We considered using additional strap-on solid rocket boosters to increase EELV performance, but such clustering lowers overall reliability.shipWhat is the lift capability of Delta and Atlas heavy? I am certain Atlas Heavy can lift this much and it is already at CDR with a very low risk to first flight.Danny DegerMy recollection is that NASA's study showed that the EELVs couldn't lift the payload when restricted to the low-loft ascent profiles. They would also carry a lot of LAS mass, etc., that would limit them compared to a typical satellite in a shroud type payload. Together, these factors dramatically cut the EELV mass delivery capabilities for a CEV. - Ed Kyle
jongoff - 23/1/2008 11:50 AMFor existing, very low launch rate vehicles (EELV, SDVs, etc), you might have a point, but I'd be careful with generalities like that.