There is no guarantee that Houston Consulate does same day visas.
Their site states this:
"After all application requirements are met, the processing time is:

D.1) During an Appointment:

On the same day* or up to 4 working days for Tourist, Business, Temporary Special and Official/Courtesy/Diplomatic Visas.
On the same day* or up to 5 working days for all other types of visas
Visa Submission: from 9:00 am to 12:00 pm BY APPOINTMENT ONLY
Visa Pick-Up:from 12:00pm to 1:00pm
*Only at the time of your appointment you will be informed if your visa will be issued on the same day or not.
The Consulate does not promise same day visas.
Applicants should be prepared for maximum processing time.
If issued on the same day, tourist and business visas will be ready within 30 minutes after the appointment time; other visa types should be ready within 60 minutes after the appointment time.
If the visa is not issued on the same day, you will be issued a receipt stating the date the visa will be ready for pick up. Anyone can pick up the visa from that date on by presenting the receipt."


Chicago Consulate does not use the online appointment system, and are still using one old system of first come/first served during very limited hours (which used to mean you could show up and not be attended to, and have to return another day), while experimenting temporarily with a new system of online uploading of documents and photos.