Black smoke rises from the spot where a Ukrainian army helicopter was shot down outside Slovyansk, Ukraine, on Thursday. Rebels shot the craft down amid heavy fighting around the eastern city. Alexander Zemlianichenko/AP hide caption

itoggle caption Alexander Zemlianichenko/AP

Coal miners rally in Donetsk, Ukraine, Wednesday. The miners have gone on strike to demand Ukrainian troops and other forces leave the region, where fighting has left dozens dead this week. Ivan Sekretarev/AP hide caption

itoggle caption Ivan Sekretarev/AP

A pro-Russian fighter takes position behind a car as a truck full of rebel fighters heads toward a battle with Ukrainian forces near the airport in Donetsk Monday. The rebels say more than 30 of their number were killed in the violence. Fabio Bucciarelli/AFP/Getty Images hide caption

itoggle caption Fabio Bucciarelli/AFP/Getty Images

A typical Russian kitchen inside an apartment built during the early 1960s, when Nikita Khrushchev led the Soviet Union — what later became known as Khrushchev apartments. Courtesy of The Kitchen Sisters hide caption

itoggle caption Courtesy of The Kitchen Sisters

Russia's President Vladimir Putin speaks during a session of the St. Petersburg International Economic Forum 2014 in St. Petersburg on Friday. He told the audience that he would respect Sunday's presidential vote in Ukraine. Sergei Karpukhin/Reuters/Landov hide caption

itoggle caption Sergei Karpukhin/Reuters/Landov

Ukrainian soldiers inspect the site of a gunfight near the village of Blahodatne in eastern Ukraine Thursday. At least 11 Ukrainian troops were killed and about 30 others were wounded when Pro-Russians attacked a military checkpoint. Ivan Sekretarev/AP hide caption

itoggle caption Ivan Sekretarev/AP

A worker turns a valve at an underground gas storage facility near Striy on Wednesday. Russia has said state-controlled exporter Gazprom will supply China with natural gas via a Siberian pipeline beginning in 2018. Gleb Garanich/Reuters/Landov hide caption

itoggle caption Gleb Garanich/Reuters/Landov

NASA Administrator Charles Bolden speaks during a news conference in Berlin on Monday. Bolden said no single country was indispensable to the International Space Station's success. Michael Sohn/AP hide caption

itoggle caption Michael Sohn/AP

Workers of the Ukrainian company Metinvest clear away debris in a government building in the eastern Ukrainian city of Mariupol on Friday. Local patrols by steelworkers have forced pro-Russia separatists to retreat from the government buildings they occupied. Evgeniy Maloletka/AP hide caption

itoggle caption Evgeniy Maloletka/AP

A woman casts her ballot at a polling station on May 11 in Hartsizk, Ukraine. Pro-Russian separatists are claiming independence after the referendum in cities across eastern Ukraine. Brendan Hoffman/Getty Images hide caption

itoggle caption Brendan Hoffman/Getty Images

Orbital Sciences Corp.'s Antares rocket lifts off at Wallops Island, Va., in April of last year. The Antares uses a pair of Russian-made NK-33 rocket engines that Moscow says it will stop supplying for military launches. Steve Helber/AP hide caption

itoggle caption Steve Helber/AP