…dodged a bullet on the Cygnus launch last week. If it had been a mission failure, it would have been its first.
Category Archives: Technology and Society
Europa With Falcon Heavy
I was running some numbers, and just got a surprising result. I’m wondering if someone can check my work.
The AIAA paper by Boeing, presented in Pasadena last fall, has a reference mission of 8.3 MT thrown at Jupiter for the fast trip with no gravity assists with the Block 2 cargo version. They specify a C3 of about 85 km^2/s^2. Here’s the table I’m looking at.
When I back that out, I end up with a departure velocity from LEO of about 6.5 km/s. With a stage fraction of 0.1 (that is, the ratio of the stage dry weight to loaded weight) and an Isp of 465 (referencing RL-10), and sixty tonnes in LEO (that’s the latest I’m hearing for FH with the upgraded cores), I can do that mission with a single flight. If we do two flights, I can throw 24 MT. Here’s my spreadsheet. Am I getting something wrong? Because that implies that they could do an even bigger mission with a 130 MT SLS. Here’s my spreadsheet.
[Update a few minutes later]
OK, I do see one slight problem, but I don’t think it affects my results much. I sized the “rubber” stage to the 2nd-stage requirement, so it’s probably a little undersized for the first stage. That is, when I change the payload mass, I get a slightly different propellant load in the first stage, though in actuality it should be independent of that.
[Update a few minutes later]
I’m wondering if the problem they have is that the EUS is oversized for the mission, so it wastes a lot of propellant shoving the parasitic stage mass? If so, that would be kind of hilarious.
But it is also possible that I’ve done the calculation wrong, which is why I’d like more eyes on my work.
[Update a couple minutes later]
D’oh!!
I do see an error. I double the potential energy as well as the kinetic when solving for departure velocity in line 13. BRB.
[Update a few minutes later]
OK, I guess I was wrong when I said I was wrong. Still not seeing the problem, if there is one.
[Update a while later]
I should note that the numbers don’t look obviously wrong, or bother me intuitively. I’m just trying to understand the disparity with the SLS mission, which supposedly has twice the throw weight.
[Late-afternoon update]
Looking at the Wikipedia page for EUS (I know, but it’s usually not a bad source for things like this), mass properties are pretty scarce. All it says is that it can carry 129,000 MT of propellant, which makes no sense, since that’s the throw weight of the SLS, and leaves no margin for structure. So huh. It’s almost like the whole program is a Bravo Sierra jobs program.
[March 28th update]
I just had an email exchange with one of the paper’s authors. They are using the Block 1B configuration, which only has 105 tonne capability. So my numbers seem to be right.
[Bumped]
Mojave
The Economist pays a visit.
Space Property Rights
A (relatively) new paper. If the space-settlement bill has hearings and is discussed on the floor, this will become a key issue.
Ancient Warfare
I’m always amused by things like this:
Before the 1990s, “for a long time we didn’t really believe in war in prehistory,” DAI’s Hansen says. The grave goods were explained as prestige objects or symbols of power rather than actual weapons. “Most people thought ancient society was peaceful, and that Bronze Age males were concerned with trading and so on,” says Helle Vandkilde, an archaeologist at Aarhus University in Denmark. “Very few talked about warfare.”
Because they bought into Rousseau’s “noble savage” BS.
I suspect there’s still a lot more that we don’t know about human history than we do.
TSA Pre-Check
I’ve been getting randomly assigned it on my boarding passes for years, but I’d never understood why. For instance, I got it on my flight back from IAD this week, but not on my flight out from LAX. So here’s the story, sort of.
Anyway, they say it’s going to end, so if I want to get it, I have to actually sign up and pay the 85 bucks. So I decided to finally do it. I have to go to LAX with my passport and fingers on Monday morning to complete the process.
Lipidophobia
Nina Teicholz, author of The Big Fat Surprise
Ivanpah’s Problems
…could end concentrated solar in the US.
And the birds and pilots rejoiced.
The Lone Wolf Era Of ISIS
…is over.
Goody.
STS-93
A rocket-geek recollection on stoichiometry and flight-propellant reserve from Wayne Hale. The other day he tweeted that he’d been looking through his old files from Shuttle days and was wondering if there’d be a market for a book. I think there would be.