First, what do you need? Looking at the numbers for Apollo 12, we see 3150 m/s for TLI, 880 m/s to enter lunar orbit, and 923 m/s to return to Earth. So we need 4953 m/s delta-V from LEO orbit.To get this, we can use the second stage engine (ISP=348) and the super Dracos (vacuum ISP roughly 240). The division of labor helps even with the SuperDraco's worse ISP, since they don't need to push the empty second stage. To make this work, we'll need about 4 tonnes of Dragon fuel. This is more than they normally carry (1.3 tonnes) but they are only carrying two people. This gives a total Dragon mass of 11 tonnes.
Assuming the empty Dragon + occupants = 7 tonnes, the Dragon adds 240*9.8*ln(11/7) = 1063 m/s. That's a total of 4953 m/s, just what is needed. The Dragon now needs to land in the ocean since there is no delta-V left for a propulsive landing, or even an assist.
So Elon was being disingenuous when he said no one from Hollywood?
It's likely easier to add tanks mounted on hard points in the trunk, and run plumbing to Dragon's service section. Using Dracos instead of SuperDracos would help as well, they appear to have a specific impulse of 300 seconds. Dragon 2 looks to have 8 forward-pointing Dracos, which could fire simultaneously to get 3.2 kN of thrust.
Quote from: envy887 on 03/07/2017 05:09 pmIt's likely easier to add tanks mounted on hard points in the trunk, and run plumbing to Dragon's service section. Using Dracos instead of SuperDracos would help as well, they appear to have a specific impulse of 300 seconds. Dragon 2 looks to have 8 forward-pointing Dracos, which could fire simultaneously to get 3.2 kN of thrust. Note that there is a constraint on the engines on CPS for the SLS (IIRC) that the thrust could not be too high for certain manoeuvres, as the short burn time, and uncertainty in exact residual thrust after shutdown cause too large large uncertainties in the resulting orbit.
Dracos are a better choice for this application.
The problem with a trunk mounted propulsion system is what happens in the event of launch abort.Can a trunk payload be reliably jettisoned or left behind?Has a figure been published for maximum trunk payload on a crewed launch?
The RED is smaller, but is prone to artifacts caused by cosmic radiation. A recent IMAX documentary was shot on Station with the RED, but needed a ton of post production cleanup to deal with the cosmic radiation noise that was present in the footage. On a trip to the Moon the problem will be worse.
“You can see missing pixels in the footage,” Ivins says. “They’re like stars. Particularly in a low-light image, you can look at a frame and I can tell you pretty much to the month how old the camera is.”
Quote from: craigcocca on 03/07/2017 06:02 amThe RED is smaller, but is prone to artifacts caused by cosmic radiation. A recent IMAX documentary was shot on Station with the RED, but needed a ton of post production cleanup to deal with the cosmic radiation noise that was present in the footage. On a trip to the Moon the problem will be worse. I think watching the film with cosmic radiation artifacts would be pretty cool.
So let's save the snark until there's a reason to be snarky. Be snarky instead about the less-smart people who want to go to space but can't afford to pay for it. Like most NASA Astronauts.
(Snip)I'd think a broad definition makes the most sense. Part of me would want to not include suborbital flights at all, but then Alan Shepard ceases to be an astronaut---this becomes a Pluto-like discussion at some level, someone might have to have a status change to secure a more useful definition.
I'd think a broad definition makes the most sense. Part of me would want to not include suborbital flights at all, but then Alan Shepard ceases to be an astronaut--
Quote from: tater on 03/10/2017 01:34 pm(Snip)I'd think a broad definition makes the most sense. Part of me would want to not include suborbital flights at all, but then Alan Shepard ceases to be an astronaut---this becomes a Pluto-like discussion at some level, someone might have to have a status change to secure a more useful definition.And down the rabbit hole we go.....Alan Shepard went to the moon.😜But in general I agree. Let's call them all astronauts and get back to discussing the mission.
Jim Lovell comments on the SpaceX mission and comparisons with Apollo 8:http://www.collectspace.com/news/news-030817a-spacex-moon-lovell-apollo8.html