With the long time delay it looks like the government is dragging its feet waiting for commercial launch vehicles to become available. Commercial has the potential to reach the Lunar surface and mars surface before SLS.The economics with SLS are not there and now even more with 1st stage reuse. Congress and NASA needs to face reality !
*Conspiracy hat onNASA is aware we aint going to Mars under current budgets. Deep Space Gateway is the nice way to do something in cislunar space while still plausibly pretending that it is all about going to Mars. Otherwise we risk being stuck in LEO for another several decades.*Conspiracy hat off
NASA is aware we aint going to Mars under current budgets. Deep Space Gateway is the nice way to do something in cislunar space while still plausibly pretending that it is all about going to Mars. Otherwise we risk being stuck in LEO for another several decades.
But SEP transfers cannot make use of the Oberth effect as they have too little thrust at perigee. They need to do a chemical burn at perigee, then use the SEP, but that just complicates things.
And just now we have yet another reminder of how insanely expensive SLS is: Bezos just announced that BO expects to spend about $2.5 billion developing the 45-tonne New Glenn. That's only a bit more than NASA spends on SLS every year! Suppose Bezos has got the cost wrong by a factor of two, and suppose that BO's cost to develop a launch vehicle twice the size were twice as much again (unlikely). BO would then be able to produce an SLS-class rocket for less than 6 years' worth of SLS spending. That means BO could develop an SLS-class lifter for less than will be spent on SLS just between now and the first flight of Block 1B!
Quote from Gerst: "From our standpoint in HEOMD, it’s real important that we get some solid understanding of what the budget is." Considering they want to launch a large SEP module in 5 years, am I wrong in believing they should have figured out the budget part already, especially since the SEP itself is pointless without the money to build something for it to push?
If a commercial crew capable of reaching DSG comes available, then there is possibility of extra crew or private missions each year.
AFAIK the next biggest PLF is on the DIV H with 5m in dia by 60m long.
Quote from: john smith 19 on 04/07/2017 10:37 amAFAIK the next biggest PLF is on the DIV H with 5m in dia by 60m long. I think, 60m is a bit exaggerated.According to ULA's user guide, it's 19.1m, which happens to be 62.7 ft. Still big, but not as long as falcon 9 (70m length).
Quote from: envy887 on 04/06/2017 11:49 pmQuote from: shooter6947 on 04/06/2017 11:04 pmWell: it's a plan.But why again put a Deep Space Gateway in lunar orbit? Without an Oberth Effect it takes hardly less delta-V to get to Mars from there than it does from LEO. Why not just start in LEO instead of getting everything out there to the Moon in the first place?I do understand the (perhaps excessively cautious) desire for the shakedown cruise in Lunar orbit. But then why a gateway again? I think that I'm missing a link in the logic chain . . .The Oberth assist from L2/NRO/DRO is actually better than in LEO. The first maneuver to insert to a Earth transfer with a low perigee, where the velocity is over 3 km/s greater than LEO and already near escape. At perigee the Mars transfer burn is performed. It's not as efficient as a direct transfer out of LEO, but high staging has a lot advantages for SEP transfers.But SEP transfers cannot make use of the Oberth effect as they have too little thrust at perigee. They need to do a chemical burn at perigee, then use the SEP, but that just complicates things.
Quote from: shooter6947 on 04/06/2017 11:04 pmWell: it's a plan.But why again put a Deep Space Gateway in lunar orbit? Without an Oberth Effect it takes hardly less delta-V to get to Mars from there than it does from LEO. Why not just start in LEO instead of getting everything out there to the Moon in the first place?I do understand the (perhaps excessively cautious) desire for the shakedown cruise in Lunar orbit. But then why a gateway again? I think that I'm missing a link in the logic chain . . .The Oberth assist from L2/NRO/DRO is actually better than in LEO. The first maneuver to insert to a Earth transfer with a low perigee, where the velocity is over 3 km/s greater than LEO and already near escape. At perigee the Mars transfer burn is performed. It's not as efficient as a direct transfer out of LEO, but high staging has a lot advantages for SEP transfers.
Well: it's a plan.But why again put a Deep Space Gateway in lunar orbit? Without an Oberth Effect it takes hardly less delta-V to get to Mars from there than it does from LEO. Why not just start in LEO instead of getting everything out there to the Moon in the first place?I do understand the (perhaps excessively cautious) desire for the shakedown cruise in Lunar orbit. But then why a gateway again? I think that I'm missing a link in the logic chain . . .
I would have wished that NASA would have put the requirements out to the private sector for them to provide what they think the best solutions would be, and that way we'd also have the ability to assess what the cost trade-offs were for the different approaches. But alas, we live in a different reality...
True. But if SEP is used for any leg of the trip than staging in cislunar space can be advantageous. E.g. using a SEP tug to bring a chemical departure stage up to L2, which can then do an Oberth-assisted departure burn and fast transit. Or using chemical rockets to quickly launch crew through the Van Allen belts, then using slower SEP to do the (non-Oberth) departure.
Boeing are saying SLS can offer a 10m Dia by 31m long PLF. with a volume of 1800 m^3. Only LH2 would not be mass limited for carrying as a propellant. All others would comfortably fit in the fairing up to the full payload of the vehicle.
Quote from: RocketmanUS on 04/06/2017 11:35 pmWith the long time delay it looks like the government is dragging its feet waiting for commercial launch vehicles to become available. Commercial has the potential to reach the Lunar surface and mars surface before SLS.The economics with SLS are not there and now even more with 1st stage reuse. Congress and NASA needs to face reality !And just now we have yet another reminder of how insanely expensive SLS is: Bezos just announced that BO expects to spend about $2.5 billion developing the 45-tonne New Glenn. That's only a bit more than NASA spends on SLS every year! Suppose Bezos has got the cost wrong by a factor of two, and suppose that BO's cost to develop a launch vehicle twice the size were twice as much again (unlikely). BO would then be able to produce an SLS-class rocket for less than 6 years' worth of SLS spending. That means BO could develop an SLS-class lifter for less than will be spent on SLS just between now and the first flight of Block 1B!
Does anyone have a guess as to how long transit times from L2 to Mars might be with the DST and SEP?