Houston founder shares how he's using tech to make digital media more effective and equitable

houston innovators podcast episode 173

This month, Mark Walker is celebrating his company's one year anniversary of going public — only the ninth Black-founded business to accomplish this feat on a U.S. stock exchange. Photo courtesy

After working in both sides of the advertising world, Mark Walker thought he could reimagine a platform that would be more efficient and equitable.

Walker co-founded his company, Direct Digital Holdings, an adtech platform, after serving in several roles — from an early hire at Houston digital media startup Questia to business development director at NRG Energy and COO of EBONY Media. He shares on the Houston Innovators Platform how he took this experience in tech, advertising, and media to create his company's platform.

"NRG Energy gave me a top-down view of the value chain, and Ebony gave me a bottoms-up view of the value chain of how media is purchased," Walker says on the show. "At Direct Digital Holdings, we help companies buy and sell media — and we leverage technology to do it. It's really the culmination of both of those experiences."

With over 30,000 publishers on its platform, Direct Digital makes it easier for its core customers — middle market companies looking to buy into the digital media ecosystem — to tap into these opportunities without the tech know-how they might otherwise need. Walker explains that at EBONY, he saw how small to midsize publications — especially the multicultural ones — were being left out on the ad selling side of the equation. The Direct Digital platform bridges the gap on each end.

Founded in 2018 in partnership with Keith Smith, who went through similar professional experiences, Direct Digital went public exactly one year ago after growing the company through strategic M&A activity. Walker says the decision to IPO made the most sense for his company — though it wasn't an easy process. Direct Digital is only the ninth company founded by a Black entrepreneur to go public on a US stock exchange.

"If you think the process is hard — it actually is," Walker says on the journey to IPO. "We were a privately held company, and we knew we had a good growth trajectory and we looked a couple different options. We decided to go public in a very traditional way."

Walker explains there were some risks involved, but the co-founders ultimately decided to shy away from adding in investors who might not have the same ideas for the company's future.

Direct Digital has been a Houston company from the star — despite the city not being home to a booming adtech ecosystem. Instead, Houston — with its collection of Fortune 500 companies and rich diversity — has allowed the business to stand out.

"If you look at and reflect on how our company has been built — from our board of directors to our leadership and management team — we're a majority minority organization all the way across the board," Walker says. "Diversity is very important to us. It's the lifeblood of our business — especially because we're serving publishers in those communities in big way. And moreso, we think you get the best product, thoughts, and ideas from a diverse workforce, and Houston fits right into that mold for us."

Walker shares more about his company's future, advice on IPO, and what all he's watching in adtech — from AI to streaming — on the podcast. Listen to the interview below — or wherever you stream your podcasts — and subscribe for weekly episodes.


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Abbott assembles expert team to help lure U.S. Space Academy to Texas

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State Rep. Greg Bonnen of Friendswood has been tapped to lead a new team that will promote Texas as the future home of the U.S. Space Academy.

Bonnen, a neurosurgeon, chairs Houston Physicians’ Hospital and the powerful Texas House Appropriations Committee. His House district is close to NASA’s Johnson Space Center.

Gov. Greg Abbott appointed the seven-member team. Last month, President Trump signed an executive order establishing the Presidential Commission on the U.S. Space Academy. Commission members, who held their first meeting this month, will recommend a permanent location for the academy.

Texas officials are pushing a site near Johnson Space Center to host the academy. Alabama, Colorado and Florida are among Texas’ competitors.

In a joint statement, U.S. Sen. Ted Cruz and U.S. Rep. Brian Babin, both of Texas, issued a statement backing the state’s bid for the academy. Cruz lives in Houston. Babbin lives in Woodville, about 55 miles south of Beaumont.

“America’s space program is built across the country, but Texas is where the pieces come together,” the lawmakers said. “We are ready to lead the next generation of space pioneers and look forward to showing why Texas is the right home for the U.S. Space Academy.”

The academy’s curriculum will include technical education, leadership development and public service components. Graduates will be set up for careers in the U.S. military, civil service, and aerospace sectors.

The Abbott-appointed team will work with the Texas Space Commission to prepare the state’s proposal for the academy.

In addition to Bonnen, team members with ties to Houston include:

  • Robert Ambrose, who grew up in Houston. He worked at Johnson Space Center before becoming associate director of the Texas A&M Space Institute.
  • Former NASA astronaut Nancy Curry-Gregg, director of the Texas A&M Space Institute. She earned a doctoral degree from the University of Houston and previously worked at Johnson Space Center.
  • Former NASA astronaut Jack Fischer, senior vice president of Houston-based Intuitive Machines. The company builds spacecraft, delivers payloads to the moon and launches satellites.

“Texas is the home of America’s human spaceflight program,” Abbott said in a release. “No state can match what Texas brings to this mission.”

“NASA’s Johnson Space Center, world-class universities, a premier commercial space industry, major military installations, and an unmatched aerospace workforce give Texas every asset the United States Space Academy requires,” the governor added.

Houston university named No. 10 in nation and more top innovation news

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Editor's note: September sees a flurry of news for the innovation community, with one Houston university topping a nationwide ranking and one Houston-area NASA contractor poised to go public. Here are the five most-read Houston innovation headlines published September 1-15, 2026:

Houston university ranks No. 10 best in the U.S. in new 2027 report

Education ranking and review website Niche has released its 2027 rankings of the best colleges in the U.S., and Rice University leads as the No. 1 best university in Texas, and No. 10 best nationwide. Rice University ranked 10th in three national lists: Best Colleges in America, Top Private Universities, and Colleges with the Best Professors. Continue reading.

Houston-area NASA contractor plans Nasdaq IPO

Webster-based NASA contractor Rothe Development Inc. has filed paperwork with the U.S. Securities and Exchange Commission to go public. Rothe, a minority- and woman-owned business, hasn’t yet identified how many shares it will sell and how much money its IPO might raise. Rothe plans to offer Class B common stock on the Nasdaq exchange. Continue reading.

10+ can't-miss Houston business and innovation events for September

The energy transition and AI will be the talk of this town this month, thanks to a packed calendar of Houston events. September brings the return of Houston Energy and Climate Startup Week and some of its signature anchor events, plus AI conferences and talks exploring how the technology is impacting everything from healthcare to leadership. Here’s what not to miss and how to register. Continue reading.

Amazon's robotaxi service Zoox rolls out in 'sprawling' Houston market

Amazon-owned robotaxi ride-hailing service Zoox is zooming into Houston in September, becoming the latest robotaxi operator jockeying for local riders. Initially, self-driving retrofitted SUVs with safety drivers on board will serve downtown Houston, centrally located tourist hotspots, and certain residential neighborhoods. The SUVs will test Houston roads before Zoox rolls out autonomous robotaxis here, the company says. Continue reading.

10 Houston billionaires land on Forbes' 2026 list of richest Americans

The richest billionaires in America have a collective worth of $8 trillion in 2026, a staggering $1.4 trillion increase since last year, says Forbes. American billionaires are so wealthy that it now takes an unprecedented $4.4 billion net worth to be considered one of the richest people in the country. And one local billionaire has regained the title as Houston's wealthiest resident. Oil tycoon Jeffery Hildebrand, 67, now reigns as the No. 1 richest Houstonian, the 9th richest Texan, and the 88th richest person in America for 2026. Continue reading.

Houston space companies take off with new tech, deals and contracts

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Space City has had a busy month.

Houston-based aerospace institutions Venus Aerospace, Axiom Space, and Aegis Aerospace have each recently announced advancements in their respective fields that include expansions and new contracts from U.S. and international government agencies.

Here’s the latest:

Venus launches new test stand

Earlier this month, Venus Aerospace added infrastructure to support the ongoing progress of its Rotating Detonation Rocket Engine (RDRE) with the opening of its new propulsion test stand at the Houston Spaceport.

The Texas Space Commission's Space Exploration and Aeronautics Research Fund is funding the test stand, which is part of a larger effort from the state to increase investments in the aerospace economy. The ribbon-cutting event on Sept. 10 welcomed officials from Venus Aerospace, the Texas Space Commission, the Houston Spaceport, Houston business and local community leaders.

With the new stand, Venus will be able to test at higher thrust and for longer durations, which will allow the company to better replicate real-life conditions.

"Building and testing propulsion systems at this pace requires the right infrastructure around the technology," Sassie Duggleby, CEO and co-founder of Venus Aerospace, said in a news release. "We're grateful to the Texas Space Commission and the State of Texas for investing alongside companies like Venus. Public investment like this helps companies move faster and keeps critical aerospace capability growing here in Texas."

Venus closed a $91 million Series B in July and expanded its leadership team.

Axiom partners in Europe

Axiom Space has signed a memorandum of understanding with the European Space Agency for “sustained European access to low-Earth orbit (LEO)” following the retirement of the International Space Station, according to a news release from the company.

Under the agreement, Axiom and the ESA agreed to explore future astronaut missions on the ISS and Axiom Station, research, transportation and spacesuit partnerships. The organizations will explore using the ESA’s European Cargo Return service and potentially a future European crew vehicle to support operations at Axiom Station, the company's forthcoming commercial space station. The partnership could also involve Axiom's AxEMU spacesuit for orbital and lunar applications, according to the release.

“With the upcoming de-orbitation of the ISS, it is our duty to anticipate and prepare future solutions to ensure our access to low-Earth orbit,” Daniel Neuenschwander, director of human and robotic exploration at ESA, said in the release. “The two documents signed today underline both our commitment to safeguard our ability to pursue in-orbit science and to keep offering flight opportunities to our European astronaut corps, as well as the growing interest of international partners for our ongoing project to develop an autonomous European cargo vehicle.”

The announcement comes as Axiom has made several international moves this year. The company shared plans to establish Axiom Space Switzerland this summer and launched Axiom Space Japan in July.

"The path to a sustainable human presence in space runs through international collaboration — reliable supply chains, shared innovation, and partners who bring real capability," Jonathan Cirtain, CEO and President of Axiom Space, said in the release. "Europe's contributions to microgravity science and deep space technology make ESA exactly that kind of partner. This MoU strengthens our work together, and we look forward to ESA and its member states joining us as customers for future astronaut missions."

Aegis expands DoW deal

Webster, Texas-based Aegis Aerospace announced that it has won a new task order to continue supporting the U.S. Space Force’s Space Test Program.

The contract starts in October and covers designing, building, testing and operating Department of War payloads or equipment on NASA, government, and commercial launch vehicles and platforms. The contract was issued by the USSF Space Systems Command, Space Test Program under NASA Johnson Space Center’s Research, Engineering, and Mission Integration Services 2 (REMIS 2).

Currently, the company is working on three payload facilities on the ISS and has plans for two more in development.

“Aegis Aerospace is grateful to continue our exceptional payload integration support to the USSF and the STP to meet their critical mission objectives,” President Matt Ondler added in the release. “This work is more important than ever to maintain U.S. superiority in space. This new contract will take us beyond the current life of the ISS and see us integrate and test payloads on commercial space stations, free-flyers, and cislunar missions.”

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