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Over 47% of 2003 income taxes will be spent to pay interest on the debt..

http://encyclopedia.thefreedictionary.com/U.S.%20national%20debt

U.S. national debt The U.S. public debt is the amount of money that the United States federal government (not the states or banks or corporations or individuals) owes.

The calculation of the debt is subject to political manipulation and creative accounting, but the accounting assumptions behind any specific set of numbers can be made clear. As these are often also political assumptions, they form an important role in debates on U.S. fiscal policy, the most important of which is the U.S. budget deficit. Any budget deficit must be made up for by deficit spending, which increases the debt. A budget surplus, by U.S. law, must be used to pay down the debt. So these cannot be discussed separately.
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The deepening crisis: The real score on deficits, public debt

By EMMANUEL S. DE DIOS, BENJAMIN E. DIOKNO, EMMANUEL F. ESGUERRA, RAUL V. FABELLA, MA. SOCORRO GOCHOCO-BAUTISTA, FELIPE M. MEDALLA, SOLITA C. MONSOD, ERNESTO M. PERNIA, RENATO E. RESIDE JR., GERARDO P. SICAT AND EDITA A. TAN.

Unsustainability: the simple arithmetic
The deepening crisis: The real score on deficits, public debt - ABS CBN News - Aug 24, 2004
"This late in the day, staving off a full-blown fiscal crisis really boils down to attaining one goal: stopping the growth of the government debt as proportion of GDP. In other words, maintain it indefinitely at its current level of 78 percent, or lower. In the end, any combination of measures that falls short of accomplishing this goal cannot be regarded as serious."

There are two potential problems with our national debt:

The interest payments on the debt redistribute income from taxpayers to bondholders. This redistribution is potentially regressive since wealthier households hold Treasury bonds. So all taxpayers pay debt interest but mostly wealthier taxpayers receive that interest. However, higher income households also bear a larger tax burden than low- and middle-income households: In 1999 the top 1% of household in terms of income paid over 30% of all income taxes.
Large debts may produce the crowding out effect. Large debt levels by the U.S. government increase the demand for loanable funds, which increases interest rates and reduces the amount of private borrowing for investment spending. The size of this effect is a subject of debate among economists.

Federal Deficit A Nightmare For Our Children

www.panettainstitute.org/Commentaries/020804.htm

U.S. National Debt Clock
A Stronger Economy Balancing Budget Deficit - JohnKerry.com
Balancing our budget takes a leader - read about John Kerry's plan