Lugging groceries and supplies to the astronauts on the International Space Station may not be as cool as ferrying the astronauts themselves into orbit. But the NASA contract to fly cargo to the station in unmanned rocket ships has attracted bids from high-profile companies in what analysts say is another indication of commercial spaceflight’s recent renaissance.

It appears that at least five space firms have submitted proposals for the work, including giants such as Boeing and Lockheed Martin, which didn't bother to bid on the work the last time. In a new sort of space race, the contract has touched off an intense competition between stalwart defense contractors and new space start-ups that have, in just a few years, shown they can compete.

Years ago, NASA implemented a plan to outsource transportation to the space station in low Earth orbit, saying that, with a tight budget, it needed to be focused on bigger targets, such as Mars.

Some members of Congress and others criticized the decision, saying that private industry could not be trusted with such high-stakes work and that the business of spaceflight should be left to NASA. But in the years since, NASA’s decision to rely on commercial companies helped ignite the commercial space industry, which, backed by new infusions of cash and with more launches to its credit, has grown more robust.

For the past few years, two companies have been resupplying the space station, taking supplies and experiments to the orbital laboratory. Billionaire entrepreneur Elon Musk’s SpaceX won a $1.6 billion contract, and so far has had five successful trips, and is scheduled for a sixth in April.

The other company to win the cargo contract, Orbital Sciences, now Orbital ATK, had its unmanned rocket explode shortly after takeoff last year. That raised questions about whether NASA should be relying on the commercial sector so heavily.

But at NASA, the explosion did not dampen enthusiasm for outsourcing the work. That’s in part because of SpaceX’s success. But also because given the NASA’s tight budgets, it doesn’t really have a choice but to hire contractors to do the work for it, analysts said.

The private space industry has been buoyed by billionaires, such as Musk, Richard Branson, who owns Virgin Galactic, and Jeff Bezos, the founder who owns Blue Origin (as well as the Washington Post).

But now others are looking to invest in space as well. On a recent trip to Silicon Valley, Eric Stallmer, the president of the Commercial Spaceflight Federation, said many other investors had a palpable fear-of-missing-out vibe.

“Tell me the companies I need to be looking out for,” he said they asked. “Never have we seen this level of investment come in.”

In January, SpaceX announced it had received a $1 billion infusion from Google and Fidelity. Planet Labs, which builds and operates satellites, also announced this year that it had received $95 million in funding.

The money, or interest, in space wasn’t there just a few years ago.

At the time of the last cargo contract, “the environment looked different,” said Marco Caceres, an analyst with the Teal Group. “It wasn’t clear that this new paradigm shift was going to work. A lot of people were saying this is wrong; NASA has to have its own rocket.”

SpaceX’s successful launches not only propelled the once obscure start-up into the mainstream but demonstrated, even to the large, traditional defense contractors, that there is money to be made in space.

“We’re really moving quickly away from that old paradigm where NASA dominates,” Caceres said.

Last year, NASA awarded contracts to SpaceX and Boeing, worth a total of $6.8 billion, to take astronauts to the space station. Now, in the coming months, it is expected to award another contract for cargo resupply, which could also be worth billions.

This time, the big players are lining up for a piece of the action.

Fresh off its win to take astronauts to the space station, Boeing thinks it has a good shot. Its CST-100 capsule, originally designed for astronauts, could be easily reconfigured to handle cargo, said John Mulholland, a Boeing vice president in its space programs.

Unlike some space vehicles that plop down in the sea, the CST-100 can land on land, with a combination of parachutes and air-bag like balloons that deploy under the capsule to ensure a soft landing.

The company didn’t bid on the last cargo contract but isn’t surprised so many are now.

“What you’re seeing now is more recognition that there is a near- and long-term market for commercial access to low Earth orbit, and that is why you see more competition emerging,” Mulholland said.

Despite the explosion in October, Orbital ATK said its experience delivering cargo to the space station successfully gives it an edge. “We’ve proven the system works and works extremely well,” said spokesman Barron Beneski. “NASA knew we were a partner they could rely on.”

On its next resupply mission this fall, the company will use a United Launch Alliance Atlas V while it continues to develop its new Antares rocket. The new rocket should be ready in March 2016 in time for the following cargo launch, he said.

A spokesman for SpaceX wouldn’t confirm whether it is bidding, but analysts think that after its recent successes it wouldn’t pass up the opportunity.

The world’s largest defense contractor, Lockheed Martin, is in as well, promising to unveil “an innovative, reliable solution” at an invitation-only cocktail reception at D.C.'s Union Station later this week. Lockheed makes the Orion space capsule, which late last year NASA launched on a historic mission, sending the unmanned spacecraft farther than any human-rated vehicle had gone in 40 years.

Then there is the Sierra Nevada Corporation. It made it to the final round of the contract to take astronauts to the space station but ultimately lost. Still, NASA has invested more than $363 million in its Dream Chaser space plane, which looks like a miniature version of the space shuttle and can land on commercial runways.

It’s an entirely different approach than the other companies’ offerings, which is in part why it “can’t be counted out,” said Caceres, the space analyst. “It will once again put pressure on NASA to make a tough call.”