Open Loan Account to Feed Thrift Savings Program type account?

I have an opportunity to put away close to $50K into a 401K type account for gov't employees called TSP in 2009. The deposits would also be tax-exempt.

I was pondering whether getting a loan that would enable me to do this next year is a good move. I still have about 20-25 years until I could/would tap into this TSP account for money.

Thanks