Category Archives: Mathematics

Business, Economics, Mathematics, Media Criticism, Political Commentary, Science And Society, Technology and Society

The 97% Number That Won’t Die

40 Comments

The problem is that the issue is not whether or not “humans are causing global warming.” I can concede that there is a good possibility of that, and it still has zero implications for policy, absent quantification with sufficient confidence levels, which remain lacking.

[Afternoon update]

“Climatologists will say that the way the question is worded depends on whether they are included,” Morano said. “We have many skeptical scientists included as the 97 percent because of the way the questions [in surveys] are asked are so vague and broadly worded.”

Yup.

Administrative, Mathematics, Technology and Society

Email Issue

24 Comments

I’m trying to send myself email from my own Linux machine, via SMPT. I’ve written the following Python program:

#!/usr/bin/env python3

# Import smtplib for the actual sending function
import smtplib

# Import the email modules we’ll need
from email.mime.text import MIMEText

# Open a plain text file for reading. For this example, assume that
# the text file contains only ASCII characters.
with open(“test.txt”) as fp:
# Create a text/plain message
msg = MIMEText(fp.read())

# me == the sender’s email address
# you == the recipient’s email address
msg[‘Subject’] = “Test”
msg[‘From’] = “simberg@interglobal.org”
msg[‘To’] = “simberg@interglobal.org”

# Send the message via our own SMTP server.
s = smtplib.SMTP(‘localhost’)
print(“s has been opened”)
s.send_message(msg)
print(“after send_message”)
s.quit()
print(“End script”)

It runs with no errors, prints the statements to the terminal, but no email appears. How do I diagnose this?

[Update a while later]

Thanks for the help in comments. Still haven’t solved it, but the need for the application that I needed it for has gone away. Nonetheless, it would be good in general to know how to email from a Python script.

Business, Economics, Education, Mathematics, Media Criticism, Political Commentary, Science And Society, Technology and Society

Bill Nye The Fascist Guy

56 Comments

And NASA isn’t covering itself in glory here, either.

I was in the same room with Nye a couple nights ago, at a reception. I felt like I needed a safe space.

Mathematics, Space, Technology and Society

Europa With Falcon Heavy

12 Comments

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.

Europa Reference Table

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]