Over-the-air programming (OAP) is a fundamental service in sensor networksthat relies upon reliable broadcast for efficient dissemination.??As such,existing OAP protocols become decidedly inefficient (with respect toenergy, communication or delay) in unreliable broadcast environments, suchas those with relatively high node density or noise.??In this paper, weconsider OAP approaches based on rateless codes, which significantlyimprove OAP in such environments by drastically reducing the need forpacket rebroadcasting.??We thus design and implement two rateless OAPprotocols, rateless Deluge and ACKless Deluge, both of which replace the datatransfer mechanism of the established OAP Deluge protocol with ratelessanalogs.??Experiments with Tmote Sky motes on single-hop networks withpacket loss rates of 7\% show these protocols to save significantly incommunication over regular Deluge (roughly 15-30\% savings in the dataplane, and 50-80\% in the control plane), and multi-hop experimentsreveal similar trends.??Simulations further shows that our newprotocols scale better than standard Deluge (in terms of communication and energy) tohigh network density.??TinyOS code for our implementation can be found at http://nislab.bu.edu.